Platinum-Templated Coupling of B=N Units: Synthesis of BNBN Analogues of 1,3-Dienes and a Butatriene

The 1:2 reaction of [μ-(dmpm)Pt(nbe)]2 (dmpm=bis(dimethylphosphino)methane, nbe=norbornene) with Cl2BNR(SiMe3) (R=tBu, SiMe3) yields unsymmetrical (N-aminoboryl)aminoboryl PtI2 complexes by B−N coupling via ClSiMe3 elimination. A subsequent intramolecular ClSiMe3 elimination from the tBu-derivative leads to cyclization of the BNBN unit, forming a unique 1,3,2,4-diazadiboretidin-2-yl ligand. In contrast, the analogous reaction with Br2BN(SiMe3)2 leads, via a twofold BrSiMe3 elimination, to a PtII2 A-frame complex bridged by a linear BNBN isostere of butatriene. Structural and computational data confirm π electron delocalization over the entire BNBN unit.