HIGHLY SELECTIVE MONO-ALKYLATION AND DI-ALKYLATION OF THE BACKBONE OF COMPLEXES OF TYPE FAC-[M(CO)(3)(E,Z-PPH(2)C(BU(T))=N-N=C(BU(T))CH(2)PPH(2))] (M=MO OR W)

Treatment of the tricarbonylmolybdenum(0) complex, [Mo(CO)(3){PPh(2)CH(2)C(Bu(t))=N-N=C(Bu(t))CH(2)PPh(2)}] 1a with 1 equivalent of LiBu(n) selectively deprotonated the backbone to give the carbanion [Mo(CO)(3){PPh(2)CHC(Bu(t))=N-N=C(Bu(t))CH(2)PPh(2)}](-), which on addition of methyl iodide or allyl bromide gave the monoalkyl complexes [Mo(CO)(3){PPh(2)CH(R)C(Bu(t))=N-N=C(Bu(t))CH(2)PPh(2)}] (R = Me 2a or CH2CH=CH2 3a). The tungsten(0) analogues 2b and 3b were similarly prepared from [W(CO)(3){PPh(2)CH(2)C(Bu(t))=N-N=C(Bu(t))CH(2)PPh(2)}] 1b. Treatment of the tricarbonyltungsten(0) carbanion with deuterium oxide gave the monodeuteriated complex [W(CO)(3){PPh(2)CH(D)C(Bu(t))=N-N=C(Bu(t))CH(2)PPh(2)}] 4. Treatment of 1b with 4 equivalents of LiBu(n) followed by methyl iodide gave the dimethyl complex [W(CO)(3){PPh(2)CH(Me)C(Bu(t))=N-N=C(Bu(t))CH(Me)PPh(2)}] 5a, specifically as R,R and S,S isomers. Complex 5a was also prepared by deprotonating and methylating 2b. The analogous molybdenum complex 5b was similarly prepared from 1a. Proton, C-13-{H-1}, P-31-{H-1} NMR and infrared data are reported. The crystal structures of 2a and 5a have been determined.