PNN‐Type Pincer Imidazolylphosphine Complexes of Late Transition Metals for the Catalytic Dehydrocoupling of Amine Boranes

The catalytic dehydrocoupling of amine boranes produces well‐defined BN compounds and polymers that are isovalent electronic to hydrocarbon analogs. In this study, the synthesis and characterization of a set of Rh, Ir, and Ru complexes with tridentate imidazolylphosphine PN(H)N ligands of the type (imidazolyl)CH 2 N(H)CH 2 CH 2 PR 2 ( R = i Pr, t Bu) are presented. These complexes potentially engage in metal–ligand cooperative dehydrogenation of amine boranes, followed by BN coupling. All complexes show facial coordination of the PN(H)N ligands to the metal centers with pronounced hydrogen bonding to an outer‐sphere chloride ligand. All Rh and Ir complexes are active catalysts for the dehydrogenation of H 3 B·NMeH 2 and H 3 B·NMe 2 H, producing mainly linear and cyclic BN oligomers. Only the Ru complex [Ru(PN(H)N)(PPh 3 )(CO)(H)]Cl ( 8 ) produces low‐molecular‐weight poly(aminoboranes) from H 3 B·NMeH 2 with high activity after activation with KO t Bu, supporting metal‐ligand cooperativity during activation of the amine borane substrates.