Monohaloboryls (BHX ~-) as bridging ligands: Observable dinuclear σ-(halo)boranyl intermediates in the synthesis of metalloborylenes

摘要

Upon treating transition-metal-dihaloboryl complexes of the form [L _nMBX _2] with K[(?· ~5-C _5H _5)MnH(CO) 2], salt elimination occurs along with a migration of the Mn-bound hydride ligand onto the boron atom, thereby forming dinuclear σ-(halo)boranyl complexes of the form [L nM(μ-BHX)Mn(CO) _2(?· ~5-C _5H _5)]. Most of these complexes react further at room temperature to lose HX and provide metalloborylene complexes [L nM-B=Mn(CO) _2(?· ~5-C _5H _5)]; however, when ML _n=Re(CO) _5 the σ-(halo)boranyl complex decomposes into unidentifiable products. We found through DFT calculations that two electronically and structurally distinct forms of the intermediate σ-(halo)boranyl complexes exist, one of which easily loses HX and one that does not.