Organometallic imido complexes - higher valent derivatives of the d-metal acids. 3. Synthesis and reactions of pentamethylcyclopentadienyl imido complexes of molybdenum and tungsten and an efficient strategy for the synthesis of the organometallates

Abstract

A convenient and new entry into the chemistry of highvalent pentamethylcyclopentadienyl halfsandwich complexes of molybdenum and tungsten is described. The reaction of Mo-(NtBu)$_2$Cl$_2$ or W(NtBu)$_2$Cl$_2$(py)$_2$ with Cp*Li (Cp* = $\eta^5$-C$_5$Me$_5$) provides a high-yield route to new complexes Cp*Mo-(NtBu)$_2$CI (la) and Cp*W(NtBu)$_2$Cl (1 b) which are converted into a variety of diimido, monoimido, and oxo derivatives. Treatment of 1 a, b with MeLi yields the highly volatile methyl derivatives Cp*Mo(NtBu)$_2$Me (2a) and Cp*W(NtBu)$_2$Me (2b), while protolysis of 1 a, b with an excess of HCI gas leads to selective cleavage of only one imido function with formation of Cp*Mo(NtBu)Cl$_3$ (3a) and Cp*W(NtBu)Cl$_3$ (3b). In contrast, protolysis of 1 a, b with aqueous HCI provides a high-yield route to the well-known organometallic oxides [Cp*MoO$_2$](μ-0) (4a) and [Cp*WO$_2$]($\mu$-0) (4b). These two key compounds are easily converted into the organomolybdate and organotungstate salts NBu$_4$[Cp*MoO$_3$] (5a) and NBu$_4$[Cp*WO$_3$] (Sb) by cleavage of the M - 0 - M bridge with NBu$_4$[OH]. The Xray structure of 3a is reported