The crystal and molecular structures of [(η-C9H7)2M] (M = Fe, 1; Co, 2; Ni, 3) and [(η-C9Me7)2Fe], 4, are reported, along with a discussion of the correlation between hapticity and the 13C chemical shift of the indenyl ring-junction carbons (C(3a), C(7a)). Single crystals of both 1 and 2 undergo non-destructive and reversible phase changes upon cooling below ca. 240–245 K. The room-temperature structures are disordered; however, the low temperature ones (150 K) are essentially ordered. Crystals of 3 do not display this behavior on cooling to 150 K, and residual anisotropy in certain carbon atoms is ascribed to a minor twinning problem. Crystals of 4 were only examined at ambient temperature, where an ordered structure was obtained. In contrast to the analogous Cp2M series (Cp = η5-C5H5; M = Fe, Co, Ni), which display a gradual symmetric increase in MC distances in the order Fe < Co < Ni, the distortions in the indenyl series are of a fundamentally different nature. Thus, there is a gradual increase in the degree of slip-fold distortion from η5- toward η3-coordination which involves (a) slippage of the metal away from C(3a),C(7a), and (b) folding of the ring system (particularly at C(1),C(3)), in the order Fe < Co < Ni. The slip values (Δ = avg d(MC(3a),C(7a)) − avg d(MC(1),C(3)) are 0.043(4), 0.124(4), 0.418(6), and 0.030(4) Å for 1–4, respectively. For a “true η5”-complex, Δ should be ca. 0 Å, whereas values of ca. 0.69–0.79 Å have been reported for “true η3-”indenyl complexes such as [(η3-C9H7)Ir(PMe2Ph)3]. Therefore, complexes 1 and 4 are clearly η5, as predicted on the basis of the 18-electron rule, whereas 2 and 3 display increasing degrees of distortion in both rings to avoid 19- and 20-electron counts, respectively. The two indenyl rings in 3 are half-way between η5- and η3-coordination modes. Crystal data for 1 at 295 K are: monoclinic, P21 n, a 8.030(2), b 7.806(2), c 10.779(2) Å, β 107.39(1)°, V 648.9(2) Å3, Z = 2, structure not refined; at 150 K: monoclinic, Cc, a 16.021(4), b 15.510(5), c 11.187(3) Å, β 115.53(2)°, V 2509(1) Å3, Z = 8, R = 0.0306, Rw = 0.0332. For 2 at 295 K: monoclinic, P21 n, a 8.027(2), b 7.838(2), c 10.936(3) Å, β 107.57(2)°, V 655.9(2) Å3, Z = 2, structure not refined; at 150 K: monoclinic, P21 c, a 11.258(3), b 7.824(3), c 15.256(6) Å, β 108.07(2)°, V 1277.7(7) Å3, Z = 4, R = 0.0397, Rw = 0.0447. For 3, at 150 K: monoclinic, P21 n, a 6.063(1), b 20.056(3), c 10.703(2) Å, β 94.27(1)°, V 1297.9(3) Å3, Z = 4, R = 0.0413, Rw = 0.0493. For 4, at 295 K: orthorhombic, Pbcn, a 14.211(2), b 9.284(2), c 19.289(4) Å, V 2544.8(8) Å3, Z = 4, R = 0.0410, Rw = 0.0421.

EXPLOR_STEP=$WICRI_ROOT/Ticri/CIDE/explor/HapticV1/Data/Main/Merge

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{{Explor lien
   |wiki=    Ticri/CIDE
   |area=    HapticV1
   |flux=    Main
   |étape=   Merge
   |type=    RBID
   |clé=     ISTEX:E09722F8883EFAAA12C3C0B2457E7A345AC6AF63
   |texte=   Flexible coordination of indenyl ligands in sandwich complexes of transition metals. Molecular structures of [(η-C9R7)2M] (M = Fe, R = H, Me; M = Co, Ni, R = H): Direct measurement of the degree of slip-fold distortion as a function of d -electron count
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