Maximum spin cyclopentadienyl complexes of 3d transition metals
Identifieur interne : 000392 ( Istex/Corpus ); précédent : 000391; suivant : 000393Maximum spin cyclopentadienyl complexes of 3d transition metals
Auteurs : H. SitzmannSource :
- Coordination Chemistry Reviews [ 0010-8545 ] ; 2000.
English descriptors
- KwdEn :
- 3d Transition metals, Cyclopentadienyl complexes, Maximum spin, Me, methyl, Mes, mesityl, VE, valence electrons, acac, acetylacetonate, dme, 1,2-dimethoxyethane, dmpe, 1,2-bis(dimethylphosphino)ethane, dppe, 1,2-bis(diphenylphosphino)ethane, thf, tetrahydrofuran, tmeda, 1,2-bis(dimethylamino)ethane, μB, Bohr magnetons, μeff, effective magnetic moment.
Abstract
For decades maximum spin behavior of transition metal cyclopentadienyl complexes seemed to be limited to a small set of 3d central atoms in certain oxidation states such as V(II), V(III), Cr(III), Mn(II), and nickelocenes. The observation of four unpaired electrons for the Fe(II) central atoms of the tetraisopropylcyclopentadienyliron bromide dimer in 1996 erased such limitations. High spin behavior has then also been observed for chromocenes and nickel(II) half sandwich complexes. Many of these species are easily accessible, highly reactive and serve as versatile starting compounds for a broad range of follow-up products.
Url:
DOI: 10.1016/S0010-8545(01)00298-3
Links to Exploration step
ISTEX:F1D1A8D5253BECD81B79DE0D04D3ADB0E1471573Le document en format XML
<record><TEI wicri:istexFullTextTei="biblStruct"><teiHeader><fileDesc><titleStmt><title xml:lang="en">Maximum spin cyclopentadienyl complexes of 3d transition metals</title><author><name sortKey="Sitzmann, H" sort="Sitzmann, H" uniqKey="Sitzmann H" first="H." last="Sitzmann">H. Sitzmann</name><affiliation><mods:affiliation>FB Chemie der Universitat, Erwin-Schroedinger Strasse, 67663 Kaiserslautern, Germany</mods:affiliation></affiliation><affiliation><mods:affiliation>E-mail: sitzmann@chemie.uni-kl.de</mods:affiliation></affiliation></author></titleStmt><publicationStmt><idno type="wicri:source">ISTEX</idno><idno type="RBID">ISTEX:F1D1A8D5253BECD81B79DE0D04D3ADB0E1471573</idno><date when="2001" year="2001">2001</date><idno type="doi">10.1016/S0010-8545(01)00298-3</idno><idno type="url">https://api.istex.fr/document/F1D1A8D5253BECD81B79DE0D04D3ADB0E1471573/fulltext/pdf</idno><idno type="wicri:Area/Istex/Corpus">000392</idno></publicationStmt><sourceDesc><biblStruct><analytic><title level="a" type="main" xml:lang="en">Maximum spin cyclopentadienyl complexes of 3d transition metals</title><author><name sortKey="Sitzmann, H" sort="Sitzmann, H" uniqKey="Sitzmann H" first="H." last="Sitzmann">H. Sitzmann</name><affiliation><mods:affiliation>FB Chemie der Universitat, Erwin-Schroedinger Strasse, 67663 Kaiserslautern, Germany</mods:affiliation></affiliation><affiliation><mods:affiliation>E-mail: sitzmann@chemie.uni-kl.de</mods:affiliation></affiliation></author></analytic><monogr></monogr><series><title level="j">Coordination Chemistry Reviews</title><title level="j" type="abbrev">CCR</title><idno type="ISSN">0010-8545</idno><imprint><publisher>ELSEVIER</publisher><date type="published" when="2000">2000</date><biblScope unit="volume">214</biblScope><biblScope unit="issue">1</biblScope><biblScope unit="page" from="287">287</biblScope><biblScope unit="page" to="327">327</biblScope></imprint><idno type="ISSN">0010-8545</idno></series><idno type="istex">F1D1A8D5253BECD81B79DE0D04D3ADB0E1471573</idno><idno type="DOI">10.1016/S0010-8545(01)00298-3</idno><idno type="PII">S0010-8545(01)00298-3</idno></biblStruct></sourceDesc><seriesStmt><idno type="ISSN">0010-8545</idno></seriesStmt></fileDesc><profileDesc><textClass><keywords scheme="KwdEn" xml:lang="en"><term>3d Transition metals</term><term>Cyclopentadienyl complexes</term><term>Maximum spin</term><term>Me, methyl</term><term>Mes, mesityl</term><term>VE, valence electrons</term><term>acac, acetylacetonate</term><term>dme, 1,2-dimethoxyethane</term><term>dmpe, 1,2-bis(dimethylphosphino)ethane</term><term>dppe, 1,2-bis(diphenylphosphino)ethane</term><term>thf, tetrahydrofuran</term><term>tmeda, 1,2-bis(dimethylamino)ethane</term><term>μB, Bohr magnetons</term><term>μeff, effective magnetic moment</term></keywords></textClass><langUsage><language ident="en">en</language></langUsage></profileDesc></teiHeader><front><div type="abstract" xml:lang="en">For decades maximum spin behavior of transition metal cyclopentadienyl complexes seemed to be limited to a small set of 3d central atoms in certain oxidation states such as V(II), V(III), Cr(III), Mn(II), and nickelocenes. The observation of four unpaired electrons for the Fe(II) central atoms of the tetraisopropylcyclopentadienyliron bromide dimer in 1996 erased such limitations. High spin behavior has then also been observed for chromocenes and nickel(II) half sandwich complexes. Many of these species are easily accessible, highly reactive and serve as versatile starting compounds for a broad range of follow-up products.</div></front></TEI><istex><corpusName>elsevier</corpusName><author><json:item><name>H. Sitzmann</name><affiliations><json:string>FB Chemie der Universitat, Erwin-Schroedinger Strasse, 67663 Kaiserslautern, Germany</json:string><json:string>E-mail: sitzmann@chemie.uni-kl.de</json:string></affiliations></json:item></author><subject><json:item><lang><json:string>eng</json:string></lang><value>Maximum spin</value></json:item><json:item><lang><json:string>eng</json:string></lang><value>Cyclopentadienyl complexes</value></json:item><json:item><lang><json:string>eng</json:string></lang><value>3d Transition metals</value></json:item><json:item><lang><json:string>eng</json:string></lang><value>acac, acetylacetonate</value></json:item><json:item><lang><json:string>eng</json:string></lang><value>dme, 1,2-dimethoxyethane</value></json:item><json:item><lang><json:string>eng</json:string></lang><value>dmpe, 1,2-bis(dimethylphosphino)ethane</value></json:item><json:item><lang><json:string>eng</json:string></lang><value>dppe, 1,2-bis(diphenylphosphino)ethane</value></json:item><json:item><lang><json:string>eng</json:string></lang><value>Me, methyl</value></json:item><json:item><lang><json:string>eng</json:string></lang><value>Mes, mesityl</value></json:item><json:item><lang><json:string>eng</json:string></lang><value>thf, tetrahydrofuran</value></json:item><json:item><lang><json:string>eng</json:string></lang><value>tmeda, 1,2-bis(dimethylamino)ethane</value></json:item><json:item><lang><json:string>eng</json:string></lang><value>VE, valence electrons</value></json:item><json:item><lang><json:string>eng</json:string></lang><value>μeff, effective magnetic moment</value></json:item><json:item><lang><json:string>eng</json:string></lang><value>μB, Bohr magnetons</value></json:item></subject><language><json:string>eng</json:string></language><abstract>For decades maximum spin behavior of transition metal cyclopentadienyl complexes seemed to be limited to a small set of 3d central atoms in certain oxidation states such as V(II), V(III), Cr(III), Mn(II), and nickelocenes. The observation of four unpaired electrons for the Fe(II) central atoms of the tetraisopropylcyclopentadienyliron bromide dimer in 1996 erased such limitations. High spin behavior has then also been observed for chromocenes and nickel(II) half sandwich complexes. Many of these species are easily accessible, highly reactive and serve as versatile starting compounds for a broad range of follow-up products.</abstract><qualityIndicators><score>6.104</score><pdfVersion>1.2</pdfVersion><pdfPageSize>536 x 684 pts</pdfPageSize><refBibsNative>true</refBibsNative><keywordCount>14</keywordCount><abstractCharCount>630</abstractCharCount><pdfWordCount>13750</pdfWordCount><pdfCharCount>83219</pdfCharCount><pdfPageCount>41</pdfPageCount><abstractWordCount>92</abstractWordCount></qualityIndicators><title>Maximum spin cyclopentadienyl complexes of 3d transition metals</title><pii><json:string>S0010-8545(01)00298-3</json:string></pii><genre><json:string>review-article</json:string></genre><host><volume>214</volume><pii><json:string>S0010-8545(00)X0156-7</json:string></pii><pages><last>327</last><first>287</first></pages><issn><json:string>0010-8545</json:string></issn><issue>1</issue><genre><json:string>Journal</json:string></genre><language><json:string>unknown</json:string></language><title>Coordination Chemistry Reviews</title><publicationDate>2001</publicationDate></host><categories><wos><json:string>CHEMISTRY, INORGANIC & NUCLEAR</json:string></wos></categories><publicationDate>2000</publicationDate><copyrightDate>2001</copyrightDate><doi><json:string>10.1016/S0010-8545(01)00298-3</json:string></doi><id>F1D1A8D5253BECD81B79DE0D04D3ADB0E1471573</id><score>1</score><fulltext><json:item><original>true</original><mimetype>application/pdf</mimetype><extension>pdf</extension><uri>https://api.istex.fr/document/F1D1A8D5253BECD81B79DE0D04D3ADB0E1471573/fulltext/pdf</uri></json:item><json:item><original>true</original><mimetype>text/plain</mimetype><extension>txt</extension><uri>https://api.istex.fr/document/F1D1A8D5253BECD81B79DE0D04D3ADB0E1471573/fulltext/txt</uri></json:item><json:item><original>false</original><mimetype>application/zip</mimetype><extension>zip</extension><uri>https://api.istex.fr/document/F1D1A8D5253BECD81B79DE0D04D3ADB0E1471573/fulltext/zip</uri></json:item><istex:fulltextTEI uri="https://api.istex.fr/document/F1D1A8D5253BECD81B79DE0D04D3ADB0E1471573/fulltext/tei"><teiHeader><fileDesc><titleStmt><title level="a" type="main" xml:lang="en">Maximum spin cyclopentadienyl complexes of 3d transition metals</title></titleStmt><publicationStmt><authority>ISTEX</authority><publisher>ELSEVIER</publisher><availability><p>ELSEVIER</p></availability><date>2001</date></publicationStmt><notesStmt><note type="content">Fig. 1: Two MO diagrams for transition metal complexes. The diagram on the left illustrates the situation encountered in most organotransition metal complexes, where strong σ donation of the ligands into suitable metal orbitals is synergetically enhanced by strong π back donation from filled metal orbitals into empty ligand orbitals of π symmetry. This provides for a large energy gap between metal–ligand back bonding and metal–ligand antibonding orbitals of the complex. If π acceptor orbitals of the ligand set are missing or too high in energy, the diagram on the right side is valid, where metal–ligand back bonding is absent and the metal orbitals not engaged in ligand–metal σ interaction remain essentially non bonding. In this case the energy gap between these non bonding metal orbitals and the metal–ligand antibonding orbitals is relatively small. It can be even smaller, if filled π donor orbitals of the ligands are available to shift this non bonding set of metal orbitals to higher energy (not shown here).</note><note type="content">Fig. 2: Complexes with unpaired electrons in the non bonding orbitals only. In the bis(alkynyl)vanadium complex the ligand set provides seven filled donor orbitals shifting seven metal orbitals up in energy. The two remaining metal orbitals are singly occupied with the two d electrons of the V(III) central atom. The second example shows a V(II) methyl complex with a d3 configuration and six electron pairs of the ligand set engaged in ligand–metal σ donation. The three remaining metal d orbitals hold three unpaired electrons.</note><note type="content">Fig. 3: Hypothetical complexes with four of five unpaired electrons in non bonding d orbitals. This figure shows two hypothetical examples for complexes, which can be predicted to exhibit maximum spin: if a cyclopentadienylchromium(II) complex possesses only two donor ligands without significant π acceptor properties in addition to the cyclopentadienyl ring, four non bonding d orbitals should contain four unpaired electrons. The manganese(II) central atom of the second example shown possesses five approximately non bonding d orbitals, which should contain five unpaired electrons. Both types of complexes are yet unknown and require sufficient steric bulk of both the cyclopentadienyl derivative and the additional ligand(s) in order to prevent dimerization.</note><note type="content">Fig. 4: Examples, which seem to contradict the principles outlined here. The diamagnetic butadiene complex [(C5Me5)Ti(η4-C4H6)(η3-C4H7)] has 16 VE and may be regarded as a Ti(II) species with a d2 configuration. In this case the ligand set donates seven electron pairs to the central ion and leaves two approximately non bonding d orbitals, which should contain two unpaired electrons in contrast to experimental observation. In fact, butadiene acts as a strong π acceptor, receives both electrons from the metal and forms a metallacyclopentene complex containing Ti(IV) with a d0 configuration, which must be diamagnetic. Likewise, the V(II) complex [(C5H5)V(BH4)(dmpe)] has only one unpaired electron, although its d3 electron configuration should give rise to a spin quartet with three unpaired electrons. The η2-BH4− anion occupies two metal orbitals, however, and therefore the ligand set leaves only two approximately non bonding metal d orbitals. The energy gap to the orbital next in energy is large enough to enforce spin pairing.</note><note type="content">Fig. 5: MO digram for nickelocene. In nickelocene the two cyclopentadienyl anions donate six electron pairs to the central atom and shift six metal orbitals of suitable symmetry to high energy. The e2g set (dxy and dx2−y2) and the a1g MO (dz2) are approximately non bonding and fully occupied with six electrons, the remaining two d electrons populate the e1g* set (dxz and dxz) with parallel spin at high energy. The electron count amounts to 20 VE.</note><note type="content">Fig. 6: Paramagnetic scandium complexes with di- or triphosphacyclopentadienide ligands. Complex 1 exhibits four unpaired electrons and with a total VE count of 22 marks the lower limit known for such triple decker complexes. The sandwich complex 2 is a unique example of a Sc(II) metallocene derivative.</note><note type="content">Fig. 7: Instead of octamethyltitanocene the mixed-valent dinuclear titanium hydride 3 has been obtained by reduction of the dichloride precursor.</note><note type="content">Fig. 8: Removal of an alkyne ligand results in formation of hydride-bridged Ti(III) fulvalene complexes with a variety of methylated cyclopentadienyl ligands carrying at least two ring protons.</note><note type="content">Fig. 9: With tetramethylcyclopentadienyl ligands a similar procedure (cf. Fig. 8) gives the diamagnetic complexes 5a and 5b with 16 valence electrons shown.</note><note type="content">Fig. 10: By methane or benzene elimination from Ti(III) precursors dinuclear complexes with bridging η5:η1-C5Me4 ligands can be generated.</note><note type="content">Fig. 11: The Ti(III) hydride shown undergoes spontaneous reduction with formation of 7 when dinitrogen is admitted.</note><note type="content">Fig. 12: An equilibrium mixture of octamethyltitanocene 8 with the corresponding mono- and dihydrides reacts with N2 to form the dinuclear dinitrogen complex 7, which eliminates N2 and forms octamethyltitanocene under appropriate conditions.</note><note type="content">Fig. 13: The decamethyltitanocene 9 is a well-characterized titanocene with two unpaired electrons. It exists in an equilibrium with the fulvalene hydride complex 10.</note><note type="content">Fig. 14: bis(Dimethyl-tert-butylsilyl)octamethyltitanocene 12 is the first titanocene which could be crystallographically characterized. 12 also exhibits two unpaired electrons.</note><note type="content">Fig. 15: Structure and magnetic properties of octamethyl-bis(trimethylsilyl) derivative 13 closely resemble those of 12.</note><note type="content">Fig. 16: The open titanocenes 15 and 16 are diamagnetic in contrast to the known bis(cyclopentadienyl)titanium complexes (see text for explanation).</note><note type="content">Fig. 17: The δ type back donation into the pentadienyl LUMO stabilizes the dxy orbital and provides for an energy gap to the next MO large enough to enforce spin pairing in open titanocenes.</note><note type="content">Fig. 18: The hexaphosphatitanocene 17 is also a diamagnetic low spin complex (see text for explanation).</note><note type="content">Fig. 19: Like complexes 18–20, most vanadium(II) cyclopentadienyl complexes have three unpaired electrons.</note><note type="content">Fig. 20: Some related vanadium(II) compounds exhibit low spin behavior with only one unpaired electron like the borohydride shown in Fig. 4 and the open vanadocene derivative 21 shown here. The reasons for spin pairing have been discussed for open titanocenes and in the introduction, respectively.</note><note type="content">Fig. 21: Antiferromagnetic coupling causes complications in the trinuclear vanadium complex 22.</note><note type="content">Fig. 22: Hexa- and octaisopropylvanadocene exhibit three unpaired electrons like the parent compound.</note><note type="content">Fig. 23: Chromocenium cations are isoelectronic with vanadocenes and exhibit three unpaired electrons like these.</note><note type="content">Fig. 24: Cyclopentadienylchromium(III) half sandwich complexes may have a formal valence electron count of 17 VE (30), 15 VE (31), or 13 VE (32).</note><note type="content">Fig. 25: The chromium(II) complexes 40–42 display variations of structure and spin state (see text).</note><note type="content">Fig. 26: The chromocenes 43–47 have been structurally characterized recently. Remarkable is the pair of bis(1,3-dialkylindenyl)chromium complexes 46 and 47, where the bulkier ligand creates the shorter Cr–C distances (see Table 1).</note><note type="content">Fig. 27: The MnC10 skeleton of decamethylmanganocene (55) is nearly identical with that of hexaisopropylmanganocene (57) and even the six α carbon atoms both molecules have in common show little deviation.</note><note type="content">Fig. 28: The different behavior of ferrocene and manganocene under steric congestion is illustrated by superimposition of octa- (56) and hexaisopropylmanganocene (57) on the left side and hexa- (58) and octaisopropylferrocene (59) on the right side. The two manganocene derivatives show a dramatic difference in Mn–C bond length, whereas the impact of steric bulk on the iron sandwich is visible, but not comparable to the manganese example.</note><note type="content">Fig. 29: Manganocenes with increasing steric bulk from right to left show a variation of their magnetic behavior ranging from pure low spin (right) to pure high spin behavior even at very low temperatures (left). The derivatives with intermediate bulk show spin transitions (see text).</note><note type="content">Fig. 30: The χT vs. T plot of the magnetic susceptibility data of hexaisopropyltetramethyl-manganocene 64 shows an abrupt spin transition with hysteresis at 167 K.</note><note type="content">Fig. 31: Donor adducts of manganocene show very long Mn–C distances. Therefore the diphosphane chelate 65 should not be regarded as a 21 VE complex, but as an ionic compound. The tmeda adduct 66 shows almost equal C–C distances within the upper cyclopentadienyl ring, which is therefore not regarded as an η1 cyclopentadienyl ligand, but rather as a loosely coordinated counterion.</note><note type="content">Fig. 32: Mn(II) half sandwich complexes 69 display a low spin configuration with one unpaired electron.</note><note type="content">Fig. 33: The chloro-bridged dimer 70 is shown as an example for a class of high spin Mn(II) half sandwich complexes, which displays high spin behavior and has been investigated by 13C- and 1H-NMR spectroscopy.</note><note type="content">Fig. 34: In both 73 and 74 the Mn atom(s) showing π-coordination to the open pentadienyl ligand can be regarded as the center of a diamagnetic anion with 18 VE coordinated to high spin Mn(II) with or without an additional cyclopentadienyl ligand.</note><note type="content">Fig. 35: The reversible reaction of the cyclopentadienyliron halide 76 with donor solvents and the irreversible addition of carbon monxide are shown above. Reduction of the dicarbonyl halide 77 gives the only known cyclopentadienyliron dicarbonyl radical which does not dimerize in solution (78).</note><note type="content">Fig. 36: The bromide-bridged complex 76 shows ferromagnetic coupling within the dimeric molecules. The maximum below 50 K corresponds to saturation effects, not to antiferromagnetic interaction. The χT vs. T plot has been reproduced with permission from WILEY-VCH (see Ref. [116]).</note><note type="content">Fig. 37: The acetone complex shown here is a unique example of a cyclopentadienyliron(II) complex with two unpaired electrons, a paramagnetic 18 VE complex. For a d6 configuration this represents an intermediate spin situation.</note><note type="content">Fig. 38: The nickel(III) half sandwich complexes 80 and 81 shown here are both low spin complexes with one unpaired electron.</note><note type="content">Fig. 39: The dimer 86 shows a puckered four-membered Ni2Br2 ring and a non bonding Ni⋯Ni distance, for details see text.</note><note type="content">Fig. 40: 86 is highly reactive and can be converted to the diamagnetic dichalcogenides 87 easily.</note><note type="content">Fig. 41: With extremely bulky phenoxides the deep purple, monomeric cyclopentadienylnickelphenoxide derivatives 88 and 89 have been obtained from 86 as sublimable complexes.</note><note type="content">Fig. 42: The orange dimer 90 was formed with 2,6-dimethylphenolate. Its partial hydrolysis product 91 could also be crystallographically characterized. Both complexes are paramagnetic like the monomers shown before.</note><note type="content">Table 1: Structural parameters of chromocenes with bulky cyclopentadienyl or indenyl ligands</note></notesStmt><sourceDesc><biblStruct type="inbook"><analytic><title level="a" type="main" xml:lang="en">Maximum spin cyclopentadienyl complexes of 3d transition metals</title><author><persName><forename type="first">H.</forename><surname>Sitzmann</surname></persName><email>sitzmann@chemie.uni-kl.de</email><note type="biography">Tel.: +49-631-2054399; Fax: +49-631-2054676</note><affiliation>Tel.: +49-631-2054399; Fax: +49-631-2054676</affiliation><affiliation>FB Chemie der Universitat, Erwin-Schroedinger Strasse, 67663 Kaiserslautern, Germany</affiliation></author></analytic><monogr><title level="j">Coordination Chemistry Reviews</title><title level="j" type="abbrev">CCR</title><idno type="pISSN">0010-8545</idno><idno type="PII">S0010-8545(00)X0156-7</idno><imprint><publisher>ELSEVIER</publisher><date type="published" when="2000"></date><biblScope unit="volume">214</biblScope><biblScope unit="issue">1</biblScope><biblScope unit="page" from="287">287</biblScope><biblScope unit="page" to="327">327</biblScope></imprint></monogr><idno type="istex">F1D1A8D5253BECD81B79DE0D04D3ADB0E1471573</idno><idno type="DOI">10.1016/S0010-8545(01)00298-3</idno><idno type="PII">S0010-8545(01)00298-3</idno></biblStruct></sourceDesc></fileDesc><profileDesc><creation><date>2001</date></creation><langUsage><language ident="en">en</language></langUsage><abstract xml:lang="en"><p>For decades maximum spin behavior of transition metal cyclopentadienyl complexes seemed to be limited to a small set of 3d central atoms in certain oxidation states such as V(II), V(III), Cr(III), Mn(II), and nickelocenes. The observation of four unpaired electrons for the Fe(II) central atoms of the tetraisopropylcyclopentadienyliron bromide dimer in 1996 erased such limitations. High spin behavior has then also been observed for chromocenes and nickel(II) half sandwich complexes. Many of these species are easily accessible, highly reactive and serve as versatile starting compounds for a broad range of follow-up products.</p></abstract><textClass xml:lang="en"><keywords scheme="keyword"><list><head>Keywords</head><item><term>Maximum spin</term></item><item><term>Cyclopentadienyl complexes</term></item><item><term>3d Transition metals</term></item></list></keywords></textClass><textClass xml:lang="en"><keywords scheme="keyword"><list><head>Abbreviations</head><item><term>acac, acetylacetonate</term></item><item><term>dme, 1,2-dimethoxyethane</term></item><item><term>dmpe, 1,2-bis(dimethylphosphino)ethane</term></item><item><term>dppe, 1,2-bis(diphenylphosphino)ethane</term></item><item><term>Me, methyl</term></item><item><term>Mes, mesityl</term></item><item><term>thf, tetrahydrofuran</term></item><item><term>tmeda, 1,2-bis(dimethylamino)ethane</term></item><item><term>VE, valence electrons</term></item><item><term>μeff, effective magnetic moment</term></item><item><term>μB, Bohr magnetons</term></item></list></keywords></textClass></profileDesc><revisionDesc><change when="2000-12-19">Registration</change><change when="2000-11-22">Modified</change><change when="2000">Published</change></revisionDesc></teiHeader></istex:fulltextTEI></fulltext><metadata><istex:metadataXml wicri:clean="Elsevier, elements deleted: ce:floats; body; tail"><istex:xmlDeclaration>version="1.0" encoding="utf-8"</istex:xmlDeclaration><istex:docType PUBLIC="-//ES//DTD journal article DTD version 4.5.2//EN//XML" URI="art452.dtd" name="istex:docType"><istex:entity SYSTEM="gr1" NDATA="IMAGE" name="gr1"></istex:entity><istex:entity SYSTEM="gr2" NDATA="IMAGE" name="gr2"></istex:entity><istex:entity SYSTEM="gr3" NDATA="IMAGE" name="gr3"></istex:entity><istex:entity SYSTEM="gr4" NDATA="IMAGE" name="gr4"></istex:entity><istex:entity SYSTEM="gr5" NDATA="IMAGE" name="gr5"></istex:entity><istex:entity SYSTEM="gr6" NDATA="IMAGE" name="gr6"></istex:entity><istex:entity SYSTEM="gr7" NDATA="IMAGE" name="gr7"></istex:entity><istex:entity SYSTEM="gr8" NDATA="IMAGE" name="gr8"></istex:entity><istex:entity SYSTEM="gr9" NDATA="IMAGE" name="gr9"></istex:entity><istex:entity SYSTEM="gr10" NDATA="IMAGE" name="gr10"></istex:entity><istex:entity SYSTEM="gr11" NDATA="IMAGE" name="gr11"></istex:entity><istex:entity SYSTEM="gr12" NDATA="IMAGE" name="gr12"></istex:entity><istex:entity SYSTEM="gr13" NDATA="IMAGE" name="gr13"></istex:entity><istex:entity SYSTEM="gr14" NDATA="IMAGE" name="gr14"></istex:entity><istex:entity SYSTEM="gr15" NDATA="IMAGE" name="gr15"></istex:entity><istex:entity SYSTEM="gr16" NDATA="IMAGE" name="gr16"></istex:entity><istex:entity SYSTEM="gr17" NDATA="IMAGE" name="gr17"></istex:entity><istex:entity SYSTEM="gr18" NDATA="IMAGE" name="gr18"></istex:entity><istex:entity SYSTEM="gr19" NDATA="IMAGE" name="gr19"></istex:entity><istex:entity SYSTEM="gr20" NDATA="IMAGE" name="gr20"></istex:entity><istex:entity SYSTEM="gr21" NDATA="IMAGE" name="gr21"></istex:entity><istex:entity SYSTEM="gr22" NDATA="IMAGE" name="gr22"></istex:entity><istex:entity SYSTEM="gr23" NDATA="IMAGE" name="gr23"></istex:entity><istex:entity SYSTEM="gr24" NDATA="IMAGE" name="gr24"></istex:entity><istex:entity SYSTEM="gr25" NDATA="IMAGE" name="gr25"></istex:entity><istex:entity SYSTEM="gr26" NDATA="IMAGE" name="gr26"></istex:entity><istex:entity SYSTEM="gr27" NDATA="IMAGE" name="gr27"></istex:entity><istex:entity SYSTEM="gr28" NDATA="IMAGE" name="gr28"></istex:entity><istex:entity SYSTEM="gr29" NDATA="IMAGE" name="gr29"></istex:entity><istex:entity SYSTEM="gr30" NDATA="IMAGE" name="gr30"></istex:entity><istex:entity SYSTEM="gr31" NDATA="IMAGE" name="gr31"></istex:entity><istex:entity SYSTEM="gr32" NDATA="IMAGE" name="gr32"></istex:entity><istex:entity SYSTEM="gr33" NDATA="IMAGE" name="gr33"></istex:entity><istex:entity SYSTEM="gr34" NDATA="IMAGE" name="gr34"></istex:entity><istex:entity SYSTEM="gr35" NDATA="IMAGE" name="gr35"></istex:entity><istex:entity SYSTEM="gr36" NDATA="IMAGE" name="gr36"></istex:entity><istex:entity SYSTEM="gr37" NDATA="IMAGE" name="gr37"></istex:entity><istex:entity SYSTEM="gr38" NDATA="IMAGE" name="gr38"></istex:entity><istex:entity SYSTEM="gr39" NDATA="IMAGE" name="gr39"></istex:entity><istex:entity SYSTEM="gr40" NDATA="IMAGE" name="gr40"></istex:entity><istex:entity SYSTEM="gr41" NDATA="IMAGE" name="gr41"></istex:entity><istex:entity SYSTEM="gr42" NDATA="IMAGE" name="gr42"></istex:entity></istex:docType><istex:document><converted-article version="4.5.2" docsubtype="rev" xml:lang="en"><item-info><jid>CCR</jid><aid>9842</aid><ce:pii>S0010-8545(01)00298-3</ce:pii><ce:doi>10.1016/S0010-8545(01)00298-3</ce:doi><ce:copyright type="full-transfer" year="2001">Elsevier Science B.V.</ce:copyright></item-info><head><ce:title>Maximum spin cyclopentadienyl complexes of 3d transition metals</ce:title><ce:author-group><ce:author><ce:given-name>H.</ce:given-name><ce:surname>Sitzmann</ce:surname><ce:cross-ref refid="CORR1">*</ce:cross-ref><ce:e-address>sitzmann@chemie.uni-kl.de</ce:e-address></ce:author><ce:affiliation><ce:textfn>FB Chemie der Universitat, Erwin-Schroedinger Strasse, 67663 Kaiserslautern, Germany</ce:textfn></ce:affiliation><ce:correspondence id="CORR1"><ce:label>*</ce:label><ce:text>Tel.: +49-631-2054399; Fax: +49-631-2054676</ce:text></ce:correspondence></ce:author-group><ce:date-received day="24" month="8" year="2000"></ce:date-received><ce:date-revised day="22" month="11" year="2000"></ce:date-revised><ce:date-accepted day="19" month="12" year="2000"></ce:date-accepted><ce:abstract><ce:section-title>Abstract</ce:section-title><ce:abstract-sec><ce:simple-para>For decades maximum spin behavior of transition metal cyclopentadienyl complexes seemed to be limited to a small set of 3d central atoms in certain oxidation states such as V(II), V(III), Cr(III), Mn(II), and nickelocenes. The observation of four unpaired electrons for the Fe(II) central atoms of the tetraisopropylcyclopentadienyliron bromide dimer in 1996 erased such limitations. High spin behavior has then also been observed for chromocenes and nickel(II) half sandwich complexes. Many of these species are easily accessible, highly reactive and serve as versatile starting compounds for a broad range of follow-up products.</ce:simple-para></ce:abstract-sec></ce:abstract><ce:keywords class="keyword"><ce:section-title>Keywords</ce:section-title><ce:keyword><ce:text>Maximum spin</ce:text></ce:keyword><ce:keyword><ce:text>Cyclopentadienyl complexes</ce:text></ce:keyword><ce:keyword><ce:text>3d Transition metals</ce:text></ce:keyword></ce:keywords><ce:keywords class="abr"><ce:section-title>Abbreviations</ce:section-title><ce:keyword><ce:text>acac, acetylacetonate</ce:text></ce:keyword><ce:keyword><ce:text>dme, 1,2-dimethoxyethane</ce:text></ce:keyword><ce:keyword><ce:text>dmpe, 1,2-bis(dimethylphosphino)ethane</ce:text></ce:keyword><ce:keyword><ce:text>dppe, 1,2-bis(diphenylphosphino)ethane</ce:text></ce:keyword><ce:keyword><ce:text>Me, methyl</ce:text></ce:keyword><ce:keyword><ce:text>Mes, mesityl</ce:text></ce:keyword><ce:keyword><ce:text>thf, tetrahydrofuran</ce:text></ce:keyword><ce:keyword><ce:text>tmeda, 1,2-bis(dimethylamino)ethane</ce:text></ce:keyword><ce:keyword><ce:text>VE, valence electrons</ce:text></ce:keyword><ce:keyword><ce:text><ce:italic>μ</ce:italic><ce:inf>eff</ce:inf>, effective magnetic moment</ce:text></ce:keyword><ce:keyword><ce:text><ce:italic>μ</ce:italic><ce:inf>B</ce:inf>, Bohr magnetons</ce:text></ce:keyword></ce:keywords></head></converted-article></istex:document></istex:metadataXml><mods version="3.6"><titleInfo lang="en"><title>Maximum spin cyclopentadienyl complexes of 3d transition metals</title></titleInfo><titleInfo type="alternative" lang="en" contentType="CDATA"><title>Maximum spin cyclopentadienyl complexes of 3d transition metals</title></titleInfo><name type="personal"><namePart type="given">H.</namePart><namePart type="family">Sitzmann</namePart><affiliation>FB Chemie der Universitat, Erwin-Schroedinger Strasse, 67663 Kaiserslautern, Germany</affiliation><affiliation>E-mail: sitzmann@chemie.uni-kl.de</affiliation><description>Tel.: +49-631-2054399; Fax: +49-631-2054676</description><role><roleTerm type="text">author</roleTerm></role></name><typeOfResource>text</typeOfResource><genre type="review-article" displayLabel="Review article"></genre><originInfo><publisher>ELSEVIER</publisher><dateIssued encoding="w3cdtf">2000</dateIssued><dateValid encoding="w3cdtf">2000-12-19</dateValid><dateModified encoding="w3cdtf">2000-11-22</dateModified><copyrightDate encoding="w3cdtf">2001</copyrightDate></originInfo><language><languageTerm type="code" authority="iso639-2b">eng</languageTerm><languageTerm type="code" authority="rfc3066">en</languageTerm></language><physicalDescription><internetMediaType>text/html</internetMediaType></physicalDescription><abstract lang="en">For decades maximum spin behavior of transition metal cyclopentadienyl complexes seemed to be limited to a small set of 3d central atoms in certain oxidation states such as V(II), V(III), Cr(III), Mn(II), and nickelocenes. The observation of four unpaired electrons for the Fe(II) central atoms of the tetraisopropylcyclopentadienyliron bromide dimer in 1996 erased such limitations. High spin behavior has then also been observed for chromocenes and nickel(II) half sandwich complexes. Many of these species are easily accessible, highly reactive and serve as versatile starting compounds for a broad range of follow-up products.</abstract><note type="content">Fig. 1: Two MO diagrams for transition metal complexes. The diagram on the left illustrates the situation encountered in most organotransition metal complexes, where strong σ donation of the ligands into suitable metal orbitals is synergetically enhanced by strong π back donation from filled metal orbitals into empty ligand orbitals of π symmetry. This provides for a large energy gap between metal–ligand back bonding and metal–ligand antibonding orbitals of the complex. If π acceptor orbitals of the ligand set are missing or too high in energy, the diagram on the right side is valid, where metal–ligand back bonding is absent and the metal orbitals not engaged in ligand–metal σ interaction remain essentially non bonding. In this case the energy gap between these non bonding metal orbitals and the metal–ligand antibonding orbitals is relatively small. It can be even smaller, if filled π donor orbitals of the ligands are available to shift this non bonding set of metal orbitals to higher energy (not shown here).</note><note type="content">Fig. 2: Complexes with unpaired electrons in the non bonding orbitals only. In the bis(alkynyl)vanadium complex the ligand set provides seven filled donor orbitals shifting seven metal orbitals up in energy. The two remaining metal orbitals are singly occupied with the two d electrons of the V(III) central atom. The second example shows a V(II) methyl complex with a d3 configuration and six electron pairs of the ligand set engaged in ligand–metal σ donation. The three remaining metal d orbitals hold three unpaired electrons.</note><note type="content">Fig. 3: Hypothetical complexes with four of five unpaired electrons in non bonding d orbitals. This figure shows two hypothetical examples for complexes, which can be predicted to exhibit maximum spin: if a cyclopentadienylchromium(II) complex possesses only two donor ligands without significant π acceptor properties in addition to the cyclopentadienyl ring, four non bonding d orbitals should contain four unpaired electrons. The manganese(II) central atom of the second example shown possesses five approximately non bonding d orbitals, which should contain five unpaired electrons. Both types of complexes are yet unknown and require sufficient steric bulk of both the cyclopentadienyl derivative and the additional ligand(s) in order to prevent dimerization.</note><note type="content">Fig. 4: Examples, which seem to contradict the principles outlined here. The diamagnetic butadiene complex [(C5Me5)Ti(η4-C4H6)(η3-C4H7)] has 16 VE and may be regarded as a Ti(II) species with a d2 configuration. In this case the ligand set donates seven electron pairs to the central ion and leaves two approximately non bonding d orbitals, which should contain two unpaired electrons in contrast to experimental observation. In fact, butadiene acts as a strong π acceptor, receives both electrons from the metal and forms a metallacyclopentene complex containing Ti(IV) with a d0 configuration, which must be diamagnetic. Likewise, the V(II) complex [(C5H5)V(BH4)(dmpe)] has only one unpaired electron, although its d3 electron configuration should give rise to a spin quartet with three unpaired electrons. The η2-BH4− anion occupies two metal orbitals, however, and therefore the ligand set leaves only two approximately non bonding metal d orbitals. The energy gap to the orbital next in energy is large enough to enforce spin pairing.</note><note type="content">Fig. 5: MO digram for nickelocene. In nickelocene the two cyclopentadienyl anions donate six electron pairs to the central atom and shift six metal orbitals of suitable symmetry to high energy. The e2g set (dxy and dx2−y2) and the a1g MO (dz2) are approximately non bonding and fully occupied with six electrons, the remaining two d electrons populate the e1g* set (dxz and dxz) with parallel spin at high energy. The electron count amounts to 20 VE.</note><note type="content">Fig. 6: Paramagnetic scandium complexes with di- or triphosphacyclopentadienide ligands. Complex 1 exhibits four unpaired electrons and with a total VE count of 22 marks the lower limit known for such triple decker complexes. The sandwich complex 2 is a unique example of a Sc(II) metallocene derivative.</note><note type="content">Fig. 7: Instead of octamethyltitanocene the mixed-valent dinuclear titanium hydride 3 has been obtained by reduction of the dichloride precursor.</note><note type="content">Fig. 8: Removal of an alkyne ligand results in formation of hydride-bridged Ti(III) fulvalene complexes with a variety of methylated cyclopentadienyl ligands carrying at least two ring protons.</note><note type="content">Fig. 9: With tetramethylcyclopentadienyl ligands a similar procedure (cf. Fig. 8) gives the diamagnetic complexes 5a and 5b with 16 valence electrons shown.</note><note type="content">Fig. 10: By methane or benzene elimination from Ti(III) precursors dinuclear complexes with bridging η5:η1-C5Me4 ligands can be generated.</note><note type="content">Fig. 11: The Ti(III) hydride shown undergoes spontaneous reduction with formation of 7 when dinitrogen is admitted.</note><note type="content">Fig. 12: An equilibrium mixture of octamethyltitanocene 8 with the corresponding mono- and dihydrides reacts with N2 to form the dinuclear dinitrogen complex 7, which eliminates N2 and forms octamethyltitanocene under appropriate conditions.</note><note type="content">Fig. 13: The decamethyltitanocene 9 is a well-characterized titanocene with two unpaired electrons. It exists in an equilibrium with the fulvalene hydride complex 10.</note><note type="content">Fig. 14: bis(Dimethyl-tert-butylsilyl)octamethyltitanocene 12 is the first titanocene which could be crystallographically characterized. 12 also exhibits two unpaired electrons.</note><note type="content">Fig. 15: Structure and magnetic properties of octamethyl-bis(trimethylsilyl) derivative 13 closely resemble those of 12.</note><note type="content">Fig. 16: The open titanocenes 15 and 16 are diamagnetic in contrast to the known bis(cyclopentadienyl)titanium complexes (see text for explanation).</note><note type="content">Fig. 17: The δ type back donation into the pentadienyl LUMO stabilizes the dxy orbital and provides for an energy gap to the next MO large enough to enforce spin pairing in open titanocenes.</note><note type="content">Fig. 18: The hexaphosphatitanocene 17 is also a diamagnetic low spin complex (see text for explanation).</note><note type="content">Fig. 19: Like complexes 18–20, most vanadium(II) cyclopentadienyl complexes have three unpaired electrons.</note><note type="content">Fig. 20: Some related vanadium(II) compounds exhibit low spin behavior with only one unpaired electron like the borohydride shown in Fig. 4 and the open vanadocene derivative 21 shown here. The reasons for spin pairing have been discussed for open titanocenes and in the introduction, respectively.</note><note type="content">Fig. 21: Antiferromagnetic coupling causes complications in the trinuclear vanadium complex 22.</note><note type="content">Fig. 22: Hexa- and octaisopropylvanadocene exhibit three unpaired electrons like the parent compound.</note><note type="content">Fig. 23: Chromocenium cations are isoelectronic with vanadocenes and exhibit three unpaired electrons like these.</note><note type="content">Fig. 24: Cyclopentadienylchromium(III) half sandwich complexes may have a formal valence electron count of 17 VE (30), 15 VE (31), or 13 VE (32).</note><note type="content">Fig. 25: The chromium(II) complexes 40–42 display variations of structure and spin state (see text).</note><note type="content">Fig. 26: The chromocenes 43–47 have been structurally characterized recently. Remarkable is the pair of bis(1,3-dialkylindenyl)chromium complexes 46 and 47, where the bulkier ligand creates the shorter Cr–C distances (see Table 1).</note><note type="content">Fig. 27: The MnC10 skeleton of decamethylmanganocene (55) is nearly identical with that of hexaisopropylmanganocene (57) and even the six α carbon atoms both molecules have in common show little deviation.</note><note type="content">Fig. 28: The different behavior of ferrocene and manganocene under steric congestion is illustrated by superimposition of octa- (56) and hexaisopropylmanganocene (57) on the left side and hexa- (58) and octaisopropylferrocene (59) on the right side. The two manganocene derivatives show a dramatic difference in Mn–C bond length, whereas the impact of steric bulk on the iron sandwich is visible, but not comparable to the manganese example.</note><note type="content">Fig. 29: Manganocenes with increasing steric bulk from right to left show a variation of their magnetic behavior ranging from pure low spin (right) to pure high spin behavior even at very low temperatures (left). The derivatives with intermediate bulk show spin transitions (see text).</note><note type="content">Fig. 30: The χT vs. T plot of the magnetic susceptibility data of hexaisopropyltetramethyl-manganocene 64 shows an abrupt spin transition with hysteresis at 167 K.</note><note type="content">Fig. 31: Donor adducts of manganocene show very long Mn–C distances. Therefore the diphosphane chelate 65 should not be regarded as a 21 VE complex, but as an ionic compound. The tmeda adduct 66 shows almost equal C–C distances within the upper cyclopentadienyl ring, which is therefore not regarded as an η1 cyclopentadienyl ligand, but rather as a loosely coordinated counterion.</note><note type="content">Fig. 32: Mn(II) half sandwich complexes 69 display a low spin configuration with one unpaired electron.</note><note type="content">Fig. 33: The chloro-bridged dimer 70 is shown as an example for a class of high spin Mn(II) half sandwich complexes, which displays high spin behavior and has been investigated by 13C- and 1H-NMR spectroscopy.</note><note type="content">Fig. 34: In both 73 and 74 the Mn atom(s) showing π-coordination to the open pentadienyl ligand can be regarded as the center of a diamagnetic anion with 18 VE coordinated to high spin Mn(II) with or without an additional cyclopentadienyl ligand.</note><note type="content">Fig. 35: The reversible reaction of the cyclopentadienyliron halide 76 with donor solvents and the irreversible addition of carbon monxide are shown above. Reduction of the dicarbonyl halide 77 gives the only known cyclopentadienyliron dicarbonyl radical which does not dimerize in solution (78).</note><note type="content">Fig. 36: The bromide-bridged complex 76 shows ferromagnetic coupling within the dimeric molecules. The maximum below 50 K corresponds to saturation effects, not to antiferromagnetic interaction. The χT vs. T plot has been reproduced with permission from WILEY-VCH (see Ref. [116]).</note><note type="content">Fig. 37: The acetone complex shown here is a unique example of a cyclopentadienyliron(II) complex with two unpaired electrons, a paramagnetic 18 VE complex. For a d6 configuration this represents an intermediate spin situation.</note><note type="content">Fig. 38: The nickel(III) half sandwich complexes 80 and 81 shown here are both low spin complexes with one unpaired electron.</note><note type="content">Fig. 39: The dimer 86 shows a puckered four-membered Ni2Br2 ring and a non bonding Ni⋯Ni distance, for details see text.</note><note type="content">Fig. 40: 86 is highly reactive and can be converted to the diamagnetic dichalcogenides 87 easily.</note><note type="content">Fig. 41: With extremely bulky phenoxides the deep purple, monomeric cyclopentadienylnickelphenoxide derivatives 88 and 89 have been obtained from 86 as sublimable complexes.</note><note type="content">Fig. 42: The orange dimer 90 was formed with 2,6-dimethylphenolate. Its partial hydrolysis product 91 could also be crystallographically characterized. Both complexes are paramagnetic like the monomers shown before.</note><note type="content">Table 1: Structural parameters of chromocenes with bulky cyclopentadienyl or indenyl ligands</note><subject lang="en"><genre>Keywords</genre><topic>Maximum spin</topic><topic>Cyclopentadienyl complexes</topic><topic>3d Transition metals</topic></subject><subject lang="en"><genre>Abbreviations</genre><topic>acac, acetylacetonate</topic><topic>dme, 1,2-dimethoxyethane</topic><topic>dmpe, 1,2-bis(dimethylphosphino)ethane</topic><topic>dppe, 1,2-bis(diphenylphosphino)ethane</topic><topic>Me, methyl</topic><topic>Mes, mesityl</topic><topic>thf, tetrahydrofuran</topic><topic>tmeda, 1,2-bis(dimethylamino)ethane</topic><topic>VE, valence electrons</topic><topic>μeff, effective magnetic moment</topic><topic>μB, Bohr magnetons</topic></subject><relatedItem type="host"><titleInfo><title>Coordination Chemistry Reviews</title></titleInfo><titleInfo type="abbreviated"><title>CCR</title></titleInfo><genre type="Journal">journal</genre><originInfo><dateIssued encoding="w3cdtf">20010401</dateIssued></originInfo><identifier type="ISSN">0010-8545</identifier><identifier type="PII">S0010-8545(00)X0156-7</identifier><part><date>20010401</date><detail type="volume"><number>214</number><caption>vol.</caption></detail><detail type="issue"><number>1</number><caption>no.</caption></detail><extent unit="issue pages"><start>1</start><end>334</end></extent><extent unit="pages"><start>287</start><end>327</end></extent></part></relatedItem><identifier type="istex">F1D1A8D5253BECD81B79DE0D04D3ADB0E1471573</identifier><identifier type="DOI">10.1016/S0010-8545(01)00298-3</identifier><identifier type="PII">S0010-8545(01)00298-3</identifier><accessCondition type="use and reproduction" contentType="">© 2001Elsevier Science B.V.</accessCondition><recordInfo><recordContentSource>ELSEVIER</recordContentSource><recordOrigin>Elsevier Science B.V., ©2001</recordOrigin></recordInfo></mods></metadata><enrichments><istex:catWosTEI uri="https://api.istex.fr/document/F1D1A8D5253BECD81B79DE0D04D3ADB0E1471573/enrichments/catWos"><teiHeader><profileDesc><textClass><classCode scheme="WOS">CHEMISTRY, INORGANIC & NUCLEAR</classCode></textClass></profileDesc></teiHeader></istex:catWosTEI></enrichments><serie></serie></istex></record>Pour manipuler ce document sous Unix (Dilib)
EXPLOR_STEP=$WICRI_ROOT/Ticri/CIDE/explor/HapticV1/Data/Istex/Corpus
HfdSelect -h $EXPLOR_STEP/biblio.hfd -nk 000392 | SxmlIndent | more
Ou
HfdSelect -h $EXPLOR_AREA/Data/Istex/Corpus/biblio.hfd -nk 000392 | SxmlIndent | more
Pour mettre un lien sur cette page dans le réseau Wicri
{{Explor lien
|wiki= Ticri/CIDE
|area= HapticV1
|flux= Istex
|étape= Corpus
|type= RBID
|clé= ISTEX:F1D1A8D5253BECD81B79DE0D04D3ADB0E1471573
|texte= Maximum spin cyclopentadienyl complexes of 3d transition metals
}}
| This area was generated with Dilib version V0.6.23. |  |