Diimido, Imido Oxo, Dioxo, And Imido Alkylidene Halfsandwich Compounds Via Selective Hydrolysis And Alpha-H Abstraction In Molybdenum(Vi) And Tungsten(Vi) Organyl Complexes

Organometal imides [(eta(5)-C5R5)M(NR')(2)Ph] (M = Mo, W, R = H, Me, R' = Mes, tBu) 4 - 8 can be prepared by reaction of halfsandwich complexes [(eta(5) -C5R5)M(NR')(2)Cl] with phenyl lithium in good yields. Starting from phenyl complexes 4-8 as well as from previously described methyl compounds [(eta(5)-C5Me5)M(NtBu)(2)Me] (M Mo, W), reactions with aqueous HCl lead to imido(oxo) methyl and phenyl complexes [(eta(5)-C5Me5)M(NtBu)(O)(R)] M = Mo, R = Me (9), Ph (10); M = W, R = Ph (11) and dioxo complexes [(eta(5)-C5Me5)M(O)(2)(CH3)] M = Mo (12), M = W (13). Hydrolysis of organometal imides with conservation of M-C sigma and pi bonds is in fact an attractive synthetic alternative for the synthesis of organometal oxides with respect to known strategies based on the oxidative decarbonylation of low valent alkyl CO and NO complexes. In a similar manner, protolysis of [(eta(5)-C5H5)W(NtBu)(2)(CH3)] and [(eta(5)-C5Me5)Mo(NtBu)(2)(CH3)] by HCl gas leads to [(eta(5)-C5H5)W(NtBu)Cl-2(CH3)] 14 and [(eta(5)-C5Me5)Mo(NtBu)Cl-2(CH3)] 15 with conservation of the M-C bonds. The inert character of the relatively non-polar M-C sigma bonds with respect to protolysis offers a strategy for the synthesis of methyl chloro complexes not accessible by partial methylation of [(eta(5)-C5R5)M(NR')Cl-3] with MeLi. As pure substances only trimethyl compounds [(eta(5)-C5R5)M(NtBu)(CH3)(3)] 16-18, M = Mo, W, R = H, Me, are isolated. Imido(benzylidene) complexes [(eta(5)-C5Me5)M(NtBu)(CHPh)(CH2Ph)] M = Mo (19), W (20) are generated by alkylation of [(eta(5)-C5Me5)M(NtBU)Cl-3] with PhCH2MgCl via alpha-H abstraction. Based on nmr data a trend of decreasing donor capability of the ligands [NtBu](2-) > [O](2-) > [CHR](2-) much greater than 2 [CH3](-) > 2 [Cl](-) emerges.