(Dinitrogen)molybdenum Complexes Supported by Asymmetric Silicon‐Centered Tripod Ligands: Steric and Electronic Influences on the Coordination of Mono‐ and Diphosphine Coligands

A reliable and generally applicable synthetic route for the rational synthesis of silicon‐centered tripod ligands with mixed dialkylphosphine/diarylphosphine donors is developed. On the basis of this protocol, two new asymmetric SiPPP′ ligands, SiP Me 2 P Ph and SiP Me 2 P i Pr , were prepared and employed for the synthesis of (dinitrogen)molybdenum complexes of the types [Mo(N 2 )(SiPPP′)(P 2 )] [P 2 = (diphenylphosphino)methane (dppm), (dimethylphosphino)methane (dmpm), or two PMe 2 Ph] and [Mo(N 2 ) 2 (SiPPP′)(PMe 2 Ph)]. The constitution of the complexes is elucidated by 31 P NMR spectroscopy and analyzed on the basis of steric and electronic factors. The activation of N 2 in the synthesized dinitrogen complexes is determined by IR spectroscopy and correlated with the donor/acceptor properties of the phosphine coligands.