Stopping Hydrogen Migration in Its Tracks: The First Successful Synthesis of Group Ten Scorpionate Complexes Based on Azaindole Scaffolds.

The first successful synthesis and characterization of group 10 complexes featuring flexible scorpionate ligands based on 7-azaindole heterocycles are reported herein. Addition of 2 equiv of either K[HB(azaindolyl)3] or Li[HB(Me)(azaindolyl)2] to [M(μ-Cl)(η,1η2-COEOMe)]2 leads to the formation of 2 equiv of the complexes [M{κ3- N,N,H-HB(azaindolyl)3}(η,1η2-COEOMe)] and [M{κ3- N,N,H-HB(Me)(azaindolyl)2}(η,1η2-COEOMe)] (where M = Pt, Pd; COEOMe = 8-methoxycyclooct-4-en-1-ide), respectively. In these reactions, the borohydride group is directed toward the metal center forming square based pyramidal complexes. In contrast to analogous complexes featuring other flexible scorpionate ligands, no hydrogen migration from boron is observed in the complexes studied. The fortuitous line widths observed in some of the 11B NMR spectra allow for a closer inspection of the B-H···metal unit in scorpionate complexes than has previously been possible.