MIXED-RING AND INDENYL ANALOGS OF MOLYBDENOCENE AND TUNGSTENOCENE - PREPARATION AND CHARACTERIZATION

A stepwise route to derivatives of the molybdenocene, Cp(2)Mo, and analogue mixed-ring CpCp'Mo (Cp' = CpMe, Cp*, Ind) fragments is described. Treatment of CpMo(eta(3)-C(3)H5())(CO)(2) with HBF4 . OEt(2) and C5H6 forms [CpMo(eta(4)-C5H6)(CO)(2)][BF4], which reacts with Ph(3)CBF(4) to give [Cp(2)Mo(CO)(2)][BF4](2) and decarbonylates to [Cp(2)MoH(CO)][BF4]. These complexes are a convenient new entry into molybdenocene chemistry allowing ready access to other derivatives of the types [Cp(2)MoL(2)](2+), [Cp(2)MoXL](+), Cp(2)MoX(2), and Cp(2)Mo(CO). Use of C(5)H(5)Me instead of cyclopentadiene allows the preparation of several mixed-ring, differentially substituted analogues of molybdenocene complexes, namely, [Cp(CpMe)MoCl(CO)][BF4](2), [Cp(CpMe)Mo(CO)(2)][BF4](2), [Cp(CpMe)Mo(NCMe)(CO)][BF4](2), and [Cp(CpMe)Mo(NCMe)(2)][BF4](2). Similar transformations of IndMo(eta(3)-C3H5)(CO)(2), through [IndMo(eta(4)-C5H6)(CO)(2)][BF4], produce the indenyl substituted mixed-ring analogues of molybdenocene, [IndCpMo(CO)(2)][BF4](2) and [IndCpMoH(CO)][BF4]. Substitution reactions of these complexes produce [IndCpMo(NCMe)(Co)][BF4](2), [IndCpMO(NCMe)(2)][BF4](2), [IndCpMoCl(CO)][BF4], [IndCpMoI(CO)][BF4], [IndCpMoCl(NCMe)][BF4], IndCpMoCl(2), IndCpMoH(2), and IndCpMo(SPh)(2). The fluorenyl complex FluMo(eta(3)-C3H5)(CO)(2) does not lead to a parallel chemistry. [Cp*Mo(eta(4)C(5)H(6))(CO)(2)][BF4] reacts with Ph(3)CBF(4) to give [Cp*CpMo(CO)(2)][BF4](2) and decarbonylates slowly to [Cp*CpMoH(CO)][BF4], but [Cp*Mo(eta(4)-Cp*H)(CO)(2)][BF4] is inert with respect to both reaction pathways. Prolonged photolysis of [Cp*CpMo(CO)(2)][BF4](2) gives [Cp*CpMo(NCMe)(CO)][BF4](2) and [Cp*CpMo(NCMe)(2)][BF4](2). Deprotonation of [IndMo(eta(4)-C5H6)(CO)(2)][BF4], [CpW(eta(4)-C5H6)(CO)(2)][BF4], and [CpMo(eta(4)-C5H6)(CO)(2)][BF4] with NEt(3) gives the ring-slipped complexes CpMo(eta(3)-Ind)(CO)(2), CpW(eta(3)-Cp)(CO)(2), and CpMo(eta(3)-Cp)(CO)(2), respectively. Oxidation of CpMo(eta(3)-Ind)(CO)(2) gives the dication [IndCpMo(CO)(2)][BF4](2). Deprotonation of [CpM(eta(4)-Cp*H)(CO)(2)][BF4] occurs at one of the CH3 substituents in a terminal position of the diene to give the allylic complexes [CpM{eta(3)-C-5(CH3)(4)H(CH2)}(CO)(2)] (M = Mo, W). The X-ray crystal structures of [IndCpMo(NCMe)(CO)][BF4](2), CpMo(eta(3)-Ind)(CO)(2), and [CpMo{eta(3)-C-5(CH3)(4)H(CH2)}(CO)(2)] are presented. The latter is present in an enantiomerically pure R form in the analyzed crystals.