The versatility of the boronyl (BO) and fluoroborylene (BF) ligands in binuclear cyclopentadienylpalladium chemistry

The organometallic compounds Cp2Pd2(BO)2 and Cp2Pd2(BF)2 have been investigated by the MPW1PW91 and BP86 density functional methods. The potential energy surface of Cp2Pd2(BO)2 is found to be relatively complicated with 11 structures within 20 kcal/mol (MPW1PW91) or 26 kcal/mol (BP86) of the global minimum. This cornucopia of Cp2Pd2(BO)2 structures includes both perpendicular and coaxial structures exhibiting a variety of different coordination modes of the BO groups. These Cp2Pd2(BO)2 structures even include several structures with the BO group directly bonded to a Cp carbon atom. The Cp2Pd2(BF)2 potential surface is considerably simpler than that of Cp2Pd2(BO)2. Thus a coaxial Cp2Pd2(μ-BF)2 structure with bridging BF groups and a Pd–Pd single bond of ∼2.67 Å is highly favored, lying more than 18 kcal/mol below any of the next lowest energy Cp2Pd2(BF)2 structures. This Cp2Pd2(μ-BF)2 structure is closely related to the known structure of the stable compound (η5-Me5C5)2Pd2(μ-CO)2, which has been structurally characterized by X-ray crystallography.