ORGANOMETALLIC IMIDO COMPLEXES - HIGHERVALENT 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 NBU4[CP-ASTERISK-MO3] (M = MO, W)

A convenient and new entry into the chemistry of highvalent pentamethylcyclopentadienyl halfsandwich complexes of molybdenum and tungsten is described. The reaction of Mo(NtBu)2Cl2 or W(NtBu)2Cl2(py)2 with Cp*Li (Cp* = eta5-C5Me5) provides a high-yield route to new complexes Cp*Mo(NtBU)2Cl (1a) and Cp*W(NtBU)2Cl (1b) which are converted into a variety of diimido, monoimido, and oxo derivatives. Treatment of 1a,b with MeLi yields the highly volatile methyl derivatives Cp*Mo(NtBu)2Me (2a) and Cp*W(NtBu)2Me (2b), while protolysis of 1a, b with an excess of HCl gas leads to selective cleavage of only one imido function with formation of Cp*Mo(NtBu)Cl3 (3a) and Cp*W(NtBu)Cl, (3b). In contrast, protolysis of la,b with aqueous HCl provides a high-yield route to the well-known organometallic oxides [CP*MoO2](mu-O) (4a) and [CP*WO2](mu-O) (4b). These two key compounds are easily converted into the organomolybdate and organotungstate salts NBu4[CP*MoO3] (5a) and NBU4[CP*WO3] (5b) by cleavage of the M - O - M bridge with NBu4[OH]. The X-ray structure of 3a is reported.