Synthesis, structure and properties of new iron-molybdenum and -tungsten fulvalene-bridged heterobimetallic complexes

Reaction of Li[C5H4Fe(C5H5)] with 2,3,4,5-tetramethylcyclopent-2-enone followed by acid work-up afforded the ferrocenyl-substituted cyclopentadiene [Fe(C5H5)(C(5)H(4)C(5)Me(4)H)] 1. Lithiation of 1 with LiBu(n) in hexane gave Li[C(5)Me(4)C(5)H(4)Fe(C5H5)]. Reactions of this salt or the previously described lithium 3,4-dimethylcyclopentadienide or indenide homologues, Li[C(5)H(2)Me(2)C(5)H(4)Fe(C5H5)] or Li[C9H6C5H4Fe(C5H5)], with the allyl complexes [MoBr(MeCN)(2)(CO)(2)(eta-C3H5)] or [WCl(MeCN)(2)(CO)(2)(eta-C3H5)] led to the corresponding fulvalene (and related)-bridged, Fe-Mo or Fe-W heterobimetallic derivatives [(C5H5)Fe(C(5)H(4)C(5)Me(4))Mo(CO)(2)(eta-C3H5)] 2, [(C5H5)Fe(C(5)H(4)C(5)H(2)Me(2))M(CO)(2)(eta-C3H5)] (M = Mo 3 or W 4) and [(C5H5)Fe(C5H4C9H6)M(CO)(2)(eta-C3H5)] (M = Mo 5 or W 6). The crystal structure of 5 has been determined. Reaction of the cinnamyl complex [MoBr(MeCN)(2)(CO)(2)(eta-C(3)H(4)Ph)] with Li[C(5)H(2)Me(2)C(5)H(4)Fe(C5H5)] or Li[C9H6C5H4Fe(C5H5)] yielded [(C5H5)Fe(C(5)H(4)C(5)H(2)Me(2))Mo(CO)(2)(eta-C(3)H(4)Ph)] 7 or [(C5H5)Fe(C5H4C9H6)Mo(CO)(2)(eta-C(3)H(4)Ph)] 8 respectively, both of which exist as a mixture of isomers. Treatment of 7 with [Cr(CO)(6)] in Bu(2)(n)O-tetrahydrofuran gave the Fe-Mo-Cr heterotrimetallic complex [(C5H5)Fe(CH(4)C(5)H(2)Me(2))(OC)(2)Mo(mu-eta(3):eta(6)-C(3)H(4)Ph)Cr(CO)(3)] 9. The new monometallic analogue [Mo(CO)(2)(eta-C3H5)(eta-CMe(5))] 10 has also been prepared, Cyclic voltammetric studies of some of the new heterobimetallic complexes and of 10, [Mo(CO)(2)(eta-C3H5)(eta-C5H5)] and [Mo(CO)(2)(eta-C3H5)(eta-C9H7)] are described.