Synthesis of a bulky bis(carbene)borate ligand - Contrasting structures of homoleptic nickel(II) bis(pyrazolyl)borate and bis(carbene)borate complexes

摘要

Twofold deprotonation of the "boronium" cation H2B(tBu-ImH)(2)I-+(-) provides access to the bulky his (carbene) borate ligand H2B(tBuIm)(2)(-). Transfer of the ligand to Ni-II sources affords the square-planar, diamagnetic complex Ni[H2B-(tBuIm)(2)](2). The proper-Lies of this complex are contrasted with the related his (pyrazolyl) borate complex Ni[H2B(tBupyr)(2)](2), which is octahedral and paramagnetic. Density functional theory has been used to evaluate the reasons for the structural differences. Stabilization of the square-planar geometry by the bis(carbene)borate ligand can be ascribed to its greater donor ability. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008).