摘要:
Transition metal dihaloboryl complexes of the types [(eta(5)-C5R5)Fe(CO)(2)BX2] (R = H, Me; X = F, Cl, Br), [(eta(5)-C5H4Me)Ru(CO)(2)BX2] (X = Cl), and [(OC)(5)MnBX2] (X = Cl, Br) were prepared via salt elimination reactions. Comparison of the CO stretching frequencies indicates a higher degree of Fe- B d(pi)-p(pi) back-bonding in the dibromoboryl complexes [(eta(5)-C5R5)Fe(CO)(2)BBr2] with respect to their -BCl2 and -BF2 analogues. This finding is constistent with the p(pi)-p(pi) back-bonding abilities of the halides (F > Cl > Br). Reactions of [(eta(5)-C5Me5)Fe(CO)(2)BX2] (X = Cl, Br) with 4-methylpyridine were performed, leading to the formation of the corresponding Lewis-base adducts and, with base in excess, to the first metal-substituted boronium cation [(eta(5)-C5Me5)Fe(CO)(2)BBr(NC5H4-4-Me)(2)](+).