Reactivity of the unsaturated manganese dihydrides [Mn2(μ-H)2(CO)6(μ-L2)] [L2 = (EtO)2POP(OEt)2, Ph2PCH2PPh2, Me2PCH2PMe2] toward silicon and tin hydrides

The dimanganese hydride complexes [Mn2(μ-H)2(CO)6(μ-L2)] [L2 = (EtO)2POP(OEt)2 (tedip), Ph2PCH2PPh2 (dppm)] react with primary and secondary silanes H2SiPhR (R = Ph, Me, H) to give the corresponding derivatives [Mn2(μ-H2SiPhR)(CO)6(μ-L2)] having a silane molecule displaying a relatively unusual μ-κ2:κ2 coordination mode (averaged values are ca. Mn–H = 1.59 Å, H–Si = 1.69 Å and Mn–Si = 2.381 Å, when R = Ph and L2 = tedip). These complexes display in solution cis and/or trans arrangement of the bridging silane relative to the diphosphorus ligands (and facial and/or meridional arrangements of the corresponding carbonyl ligands), depending on the bridging groups. The novel unsaturated dihydride [Mn2(μ-H)2(CO)6(μ-dmpm)] (dmpm = Me2PCH2PMe2) has been prepared through the reaction of [Mn2(μ-Cl)2(μ-dmpm)(CO)6] and 5 equiv of Li[BH2Me2] in tetrahydrofuran followed by addition of water. The dihydride complexes [Mn2(μ-H)2(CO)6(μ-L2)] (L2 = tedip, dppm, dmpm) react with HSnPh3 to give different mixtures of products strongly dependent on the particular reaction conditions. We have thus been able to isolate and characterize five new types of dimanganese-tin derivatives: [Mn2(μ-SnPh2)2(CO)6(μ-L2)], [Mn2(μ-H)(μ-Ph2SnO(H)SnPh2)(CO)6(μ-L2)] (average values are Mn–Sn = 2.54 Å, Sn–O = 2.11 Å, when L2 = tedip), [Mn2(μ-H)(μ-κ1:κ2-HSnPh2)(CO)6(μ-L2)], [Mn2(μ-H)(μ-κ1:κ1-O(H)SnPh2)(CO)6(μ-L2)], and [Mn2(μ-H)(SnPh3)(CO)7(μ-L2)] (Mn–Mn = 3.237(1) Å, Mn–Sn = 2.642(1) Å, when L2 = dppm).

The reactions of the title unsaturated dihydrides with different organosilicon- and organotin hydrides involve different elemental processes, including agostic-type E–H–Mn coordination of the reagent (E = Si, Sn), as well as dihydrogen and benzene elimination, to give electron-precise derivatives in all cases, as illustrated in the scheme (L2 represented as A2PXPA2).Figure optionsDownload as PowerPoint slideHighlights
► Silanes bind the Mn2 center through tricentric Si–H–Mn interactions.
► HSnPh3 reacts with the title hydrides eliminating H2 and C6H6.
► Novel Mn2 compounds are formed with bridging SnPh2 and HSnPh2 ligands.