Ana M. López

This review analyzes the role of transition metal polyhydrides as homogeneous catalysts for organic reactions. Discussed reactions involve nearly every main organic functional group.

The silylation of a phosphine of OsH 6 (P i Pr 3 ) 2 is performed via net‐metathesis between Si−C(sp n ) and H−C(sp 3 ) σ‐bonds ( n =2, 3). Complex OsH 6 (P i Pr 3 ) 2 activates the Si−H bond of Et 3 SiH and Ph 3 SiH to give OsH 5 (SiR 3 )(P i Pr 3 ) 2 , which yield OsH 4 {κ 1 ‐P,η 2 ‐SiH‐[ i Pr 2 PCH(Me)CH 2 SiR 2 H]}(P i Pr 3 ) and R−H (R=Et, Ph), by displacement of a silyl substituent with a methyl group of a phosphine. Such displacement is a first‐order process, with activation entropy consistent with a rate determining step occurring via a highly ordered transition state. It displays selectivity, releasing the hydrocarbon resulting from the rupture of the weakest Si‐substituent bond, when the silyl ligand bears different substituents. Accordingly, reactions of OsH 6 (P i Pr 3 ) 2 with dimethylphenylsilane, and 1,1,1,3,5,5,5‐heptamethyltrisiloxane afford OsH 5 (SiR 2 R′)(P i Pr 3 ) 2 , which evolve into OsH 4 {κ 1 ‐P,η 2 ‐GeH‐[ i Pr 2 PCH(Me)CH 2 SiR 2 H]}(P i Pr 3 ) (R=Me, OSiMe 3 ) and R′−H (R′=Ph, Me). Exchange reaction is extended to Et 3 GeH. The latter reacts with OsH 6 (P i Pr 3 ) 2 to give OsH 5 (GeEt 3 )(P i Pr 3 ) 2 , which loses ethane to form OsH 4 {κ 1 ‐P,η 2 ‐GeH‐[ i Pr 2 PCH(Me)CH 2 GeEt 2 H]}(P i Pr 3 ).