Journal of the American Chemical Society, Vol.116, No.25, 11387-11396, 1994
((Eta(5)-C(5)R(5))Crr)(N) - A New Class of Paramagnetic Alkyls and Hydrides of Divalent Chromium
[Cp*Cr-II(mu-Cl)](2) (1), prepared by reduction of [Cp*Cr-III(mu-Cl)Cl](2) with Li[HBEt(3)] or by reaction of Cr-II-Cl-2 with Cp*Li, served as the precursor for the synthesis of a series of dinuclear chromium(II) alkyls of the type [Cp*CrII(mu-R)](2)(R = Me (2), Et (3), (n)Bu (4), Ph (5), CH(2)SiMe(3) (6)). They feature short Cr-Cr distances, low magnetic moments, and attenuated reactivity, consistent with strong metal-metal banding. 3 decomposed in benzene to yield [(Cp*Cr-II)(2)(mu-Et)(mu-Ph)] (7), and 2 reacted with O-2 to give both Cp*Cr-VI(O)(2)Me and [(Cp*Cr-V(O)Me)(2)(mu-O)] (8). Hydrogenolysis of [Cp"Cr-II(mu-Me](2) (2a, Cp" = eta(5)-C(5)Me(4)Et) first yielded paramagnetic [Cp"Cr-II(mu(3)-H)](4) (9); however, pure 9 must be prepared by reaction of [Cp"Cr-II(mu-Cl)](2) (1a) with Li[HBEt(3)]. The structure of 9 has been redetermined due to a compositional disorder problem of the original determination. The identification of 9 as a tetrahydride rests on protonation experiments and the C-13 NMR observation of five isotopomers [(Cp"Cr-II)(4)(H-4-x)(D)(x)], resulting from WD exchange. The molecular structures of 1, 2, 7, 8, and 9 have been determined by X-ray diffraction.
Keywords:RAY CRYSTAL-STRUCTURES;ELECTRONIC-STRUCTURE;COMPLEXES;BOND;CHEMISTRY;CR;POLYMERIZATION;ACTIVATION;CATALYSTS;CLUSTER