Investigation of Pb-B Bonding in PbB(BO) ( = 0-2): Transformation from Aromatic PbB to Pb[B(BO)] Complexes with BB Triple Bonds.

Boron has been found to be able to form multiple bonds with lead. To probe Pb-B bonding, here we report an investigation of three Pb-doped boron clusters, PbB, PbBO, and PbBO, which are produced by a laser ablation cluster source and characterized by photoelectron spectroscopy and calculations. The most stable structures of PbB, PbBO, and PbBO are found to follow the formula, [PbB(BO)] ( = 0-2), with zero, one, and two boronyl ligands coordinated to a triangular and aromatic PbB core, respectively. The PbB cluster contains a BB double bond and two Pb-B single bonds. The coordination of BO is observed to weaken Pb-B bonding but strengthen the BB bond in [PbB(BO)] ( = 1, 2). The anionic [PbB(BO)] and its corresponding neutral closed-shell [PbB(BO)] contain a BB triple bond. A low-lying Y-shaped isomer is also observed for PbBO, consisting of a central sp hybridized B atom bonded to two boronyl ligands and a PbB unit.