SYNTHESIS AND REACTIVITY OF MANGANESE(II) DIALKYLAMIDO COMPLEXES - CRYSTAL AND MOLECULAR-STRUCTURE OF (MN3(MU-NET2)6-(MU-CL)2(LI(THF)2)2).C7H16 (THF = TETRAHYDROFURAN) AND (MN2(MU-NPRI2)2(NPRI2)2)

By reaction of MnCl2 with LiNR2 (R = Me, Et or Pr(i)) the corresponding dialkylamido complexes were prepared. The compounds [Mn3(mu-NEt2)6(mu-Cl)2{Li(thf)2}2] 1 (thf = tetrahydrofuran), [Mn2(mu-NPr(i)2)2-(NPr(i)2)2] 2 and [Mn2(NMe2)4(LiCl)] 3 were isolated, and the molecular and crystal structures of 1 and 2 determined by single-crystal X-ray diffraction methods. Crystal data: 1, monoclinic, space group C2/c, a = 18.81(1), b = 20.45(2), c = 18.15(2) angstrom, beta = 113.31(8)-degrees, R = 0.063; 2, monoclinic, space group P2(1)/c, a = 9.361(2), b = 9.724(2), c = 16.883(2) angstrom, beta = 100.91(1)-degrees, R = 0.046. The pentanuclear compound 1 consists of a trinuclear Mn3(NEt2)6Cl2 core, built up by edge-sharing of the three co-ordination tetrahedra, which are connected by four bridging diethylamido ligands, and terminally bonded to the Li(thf)2 moieties via chloride and amido bridges. The homoleptic compound 2 contains two three-co-ordinated manganese atoms, joined by two bridging dialkylamido groups, with an overall planar arrangement of the Mn2N4 skeleton. Both 1 and 2 react with CO2 to give the expected dialkylcarbamato complexes. The reactions of 1-3 with CO result in reductive carbonylation to [Mn(CO)5]-. The compounds also catalyse the selective carbonylation of secondary amines to dialkylformamides, a 87% yield of Et2NC(O)H being obtained from NHEt2 and CO at atmospheric pressure, in 24 h, in the presence of 1, at room temperature.