Abstract:
This thesis describes the synthesis, structural studies, and stoichiometric and catalytic
reactivity of novel Mo(IV) imido silylamide (R'N)Mo(R2)(173_RIN-SiR32-H)(PMe3)n (1:
Rl = tBu, Ar', Ar; R2 = Cl; R32 = Me2, MePh, MeCl, Ph2, HPh; n = 2; 2: R' = Ar, R2 =
SiH2Ph, n = 1) and hydride complexes (ArN)Mo(H)(R)(PMe3)3 (R = Cl (3), SiH2Ph (4».
Compounds of type 1 were generated from (R'N)Mo(PMe3)n(L) (5: R' = tBu, Ar', Ar; L =
PMe3, r/- C2H4) and chlorohydrosilanes by the imido/silane coupling approach, recently
discovered in our group. The mechanism of the reaction of 5 with HSiCh to give
(ArN)MoClz(PMe3)3 (8) was studied by VT NMR, which revealed the intermediacy of
(ArN)MCh(172
-ArN=SiHCl)(PMe3)z (9). The imido/silyl coupling methodology was
transferred to the reactions of 5 with chlorine-free hydrosilanes. This approach allowed
for the isolation of a novel ,B-agostic compound (ArN)Mo(SiHzPh)(173
-NAr-SiHPhH)(PMe3) (10). The latter was found to be active in a variety of hydrosilation processes,
including the rare monoaddition of PhSiH3 to benzonitrile. Stoichiometric reactions of 11
with unsaturated compounds appear to proceed via the silanimine intermediate
(ArN)M(17z-ArN=SiHPh)(PMe3) (12) and, in the case of olefins and nitriles, give
products of Si-C coupling, such as (ArN)Mo(R)(173
-NAr-SiHPh-CH=CHR')(PMe3) (13: R
= Et, R' = H; 14: R = H, R' = Ph) and (ArN)Mo(172-NAr-SiHPh-CHR=N)(PMe3) (15).
Compound 13 was also subjected to catalysis showing much improved activity in the
hydrosilation of carbonyls and alkenes.
Hydride complexes 3 and 4 were prepared starting from (ArN)MoCh(PMe3)3 (8). Both
hydride species catalyze a diversity of hydrosilation processes that proceed via initial
substrate activation but not silane addition. The proposed mechanism is supported by stoichiometric reactions of 3 and 4, kinetic NMR studies, and DFf calculations for the
hydrosilation of benzaldehyde and acetone mediated by 4.
