HETEROLYSIS OF H-X BONDS BY PENTAMETHYLCYCLOPENTADIENYL-AMINOBOROLE COMPLEXES OF ZIRCONIUM AND HAFNIUM

The pentamethylcyclopentadienyl-aminoborole chloro complexes Cp{eta(5 )-C4H4BN(CH-Me-2)(2)}MCl . LiCl (Cp = (eta(5)-C5Me5); M = Zr, Hf) het erolytically cleave H-X bonds to form Cp{eta(5)-C4H4BNH(CHMe2)(2)}MCl (X) (X = OR, SR, C=CR). Control experiments using deuterium-labeled su bstrates show heterolysis occurs with no incorporation of deuterium in to the 2,5 positions of the borole heterocycle. Cp{eta(5)-C4H4BNH(CHM e2)(2)} Hf(C=CSiMe3)(2) is prepared from Cp{eta(5)-C4H4BN(CHMe2)(2)}H f(eta(3)-C3H5) and 2 equiv of (trimethylsilyl)acetylene. Treatment of Cp{eta(5)-C4H4BN(CHMe2)(2)}MCl . LiCl (M = Zr, Hf) with donor ligands L yields the LiCl-free complexes Cp{eta(5)-C4H4BN(CHMe2)(2)}MCl(L) ( M = Zr, L = NMe2H; M = Hf, L = PMe3). Cp{eta(5)-C4H4BN(CHMe2)(2)}HfCl (PMe3) reacts with (trimethylsilyl)acetylene with loss of HN(CHMe2)(2) to form Cp{eta(5)-C4H4B(C=CSiMe3)}HfCl(PMe3), resulting from formal migration of acetylide from hafnium to boron. X-ray structure determin ations of Cp{eta(5)-C4H4BNH(CHMe2)(2)}HfCl(C=CSiMe3), Cp*{eta(5)-C4H4 BN(CHMe2)(2)}HfCl(PMe3), and Cp{eta(5)-C4H4B(C=CSiMe3)}HfCl(PMe3) are reported.