Bonding and Activation of N2 in Molybdenum(0) Complexes Supported by Tripod Ligands with Phospholane End Groups

Tripod ligands with a neopentyl backbone and one (trpd-1 pln), two (trpd-2 pln) or three (trpd-3 pln) phospholane end groups are synthesized and used for the synthesis of MoX3 (X=Cl, Br, I) complexes supported by these ligands. NaxHg reduction of [MoBr3(trpd-3 pln)], in the presence of N-2 and the bidentate coligand dppm leads to the molybdenum(0) mono(dinitrogen) complex [Mo(N-2)(trpd-3 pln)(dppm)] with a moderately activated N-2 ligand. An attempt to further increase the activation by using dmpm as coligand leads to a mixture containing desired [Mo(N-2)(trpd-3 pln)(dmpm)], but also the bis(dinitrogen) complex [Mo(N-2)(2)(kappa(2)-trpd-3 pln)(2)] and the homoleptic complex [Mo(trpd-3 pln)(2)]. Protonation of [Mo(N-2)(trpd-3 pln)(dppm)] with [H(OEt2)(2)][Al{OC(CF3)(3)}(4)] generates the hydrazido(2-) complex [Mo(NNH2)(trpd-3 pln)(dppm)][Al{OC(CF3)(3)}(4)](2).