SYNTHESIS AND STRUCTURES OF BIS(TETRAMETHYLPIPERIDINO)ALUMINUM HALIDES X-RAY CRYSTAL-STRUCTURES OF TMP(2)ALX (X=CL, BR, I) AND [TMP(2)AL(MU-F)](2)

N-Lithio-2,2,6,6-tetramethylpiperidine [Li(tmp)] reads with AlX3 (X = Cl, Br) in diethyl ether/n-hexane solution to generate the products of substitution and ether cleavage, [tmpAl(X)(mu-OEt)](2) (1a, X = Cl; 1 b, X = Br). However, when the reaction is allowed to proceed in n-hexa ne alone, an almost quantitative yield of compounds tmp(2)AlX (2a, X = Cl; 2b, X = Br; 2c, X = I) is obtained. According to Al-27-NMR spectr oscopy, mass spectroscopy, cryoscopy, and X-ray crystal structure dete rminations, these compounds are monomeric in the solid state, in solut ion, and in the gas phase. 2b reacts with AgBF4 yielding the fluoride- bridged dimer (tmp(2)AlF)(2), 2d, as shown by X-ray crystal structure determination.