Synthesis, Reactivity and Coordination Chemistry of Group 9 PBP Boryl Pincer Complexes: [(PBP)M(PMe)] (M = Co, Rh, Ir; = 1, 2).

The unsymmetrical diborane(4) derivative [(d(CHP(Pr))abB)-Bpin] () proved to be a versatile PBP boryl pincer ligand precursor for Co(I) (, ), Rh(I) (-) and Ir(I/III) (-, -) complexes, in particular of the types [(d(CHP(Pr))abB)M(PMe)] (-) and [(d(CHP(Pr))abB)M-PMe] (-). Whilst similar complexes have been obtained before, for the first time, the coordination chemistry of a homologous series of PBP pincer complexes, in particular the interconversion of the five- and four-coordinate complexes -/-, was studied in detail. For Co, instead of the mono phosphine complex , the dinitrogen complex [(d(CHP(Pr))abB)Co(N)(PMe)] () is formed spontaneously upon PMe abstraction from in the presence of N. All complexes were comprehensively characterised spectroscopically in solution via multinuclear (VT-)NMR spectroscopy and structurally in the solid state through single-crystal X-ray diffraction. The unique properties of the PBP ligand with respect to its coordination chemical properties are addressed.