Metathesis between E−C(sp( n )) and H−C(sp(3)) σ‐Bonds (E=Si, Ge; n=2, 3) on an Osmium‐Polyhydride

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)).