HIGHLY SELECTIVE MONO-ALKYLATION AND DI-ALKYLATION OF THE BACKBONE OFCOMPLEXES OF TYPE O)(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, )(3){PPh(2)CH(2)C(B u(t))=N-N=C(Bu(t))CH(2)PPh(2)}] 1a with 1 equivalent of LiBu(n) select ively deprotonated the backbone to give the carbanion (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 )(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 )(3){PPh(2)CH(2)C(B u(t))=N-N=C(Bu(t))CH(2)PPh(2)}] 1b. Treatment of the tricarbonyltungst en(0) carbanion with deuterium oxide gave the monodeuteriated complex )(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 dimet hyl complex 3){PPh(2)CH(Me)C(Bu(t))=N-N=C(Bu(t))CH(Me)PPh(2)}] 5a, spe cifically as R,R and S,S isomers. Complex 5a was also prepared by depr otonating and methylating 2b. The analogous molybdenum complex 5b was similarly prepared from 1a. Proton, C-13-{H-1}, P-31-{H-1} NMR and inf rared data are reported. The crystal structures of 2a and 5a have been determined.