Syntheses, Structures, and Reactions of η2-N-Acylamido-N,O Hydrido Complexes of Molybdenum(II) and Tungsten(II)

The N-acylamido complexes [MH{N(R1)COR2-N,O}(dppe)2] (M = Mo, W; R1/R2 = Me/Me, Ph/Me, Me/H, Ph/H, (CH2)3, Ph/Ph; dppe = Ph2PCH2CH2PPh2) were synthesized by photochemical or thermal reactions of [MoH4(dppe)2] or trans-[W(N2)2(dppe)2] with N-alkylamides R1NHCOR2. An X-ray study of [MoH{N(CH3)COCH3-N,O}(dppe)2] revealed a distorted-pentagonal-bipyramidal configuration with two phosphorus atoms, the nitrogen and the oxygen atoms of the amide, and a hydride lying in the equatorial plane. These complexes reacted with methanol or ethanol in toluene at ambient temperature to give the novel alkoxo hydrido complexes [MH2(OR)2(dppe)2] (R = Me, Et). The reactions apparently proceeded via a coordinatively unsaturated 16e intermediate, which is formed upon release of the N-acylamido ligand. The reactions between the amido complexes and catechols yielded the chelated catecholato complexes [MH2(catecholato-O,O‘)(dppe)2] (catecholato = O2C6H4, O2C6H3(4-Me), O2C6H3(4-But), O2C6H3(4-COOEt), and O2C10H6). The structures of catecholato complexes, determined by single-crystal X-ray diffraction studies, exhibit distorted-dodecahedral geometry.