FORMATION OF NOVEL ANSA-CARBORANE-ALKOXIDE COMPLEXES BY CARBONYLATIONOF (C5ME5)(ETA(5)-C2B9H11)TIME

The reaction of Cp(eta(5)-C2B9H11)TiMe (1, Cp* = C5Me5) with CO (0.5- 1 atm) in toluene (-78 to 23 degrees C) yields a 1:4 mixture of Cp(et a(5):eta(1)-8-CHMeO-C2B9H10)Ti (6) and Cp(eta(5):eta(1)-4-CHMeO-C2B9H 10)Ti (7), in ca. 90% total NMR yield. Complexes 6 and 7 both contain a linked carborane-alkoxide ligand but differ in the site of attachmen t of the -CHMeO-linker to the carborane cage. The linker is attached a t the central boron of the C2B3 donor ring (B8) in 6 and to a lateral boron (B4 or B7) in 7. The anticipated acyl complex, Cp(eta(5)-C2B9H1 1)TiC(=O)Me (8), was not observed. However, experiments with (CO)-C-13 show that the -BCHMeO- carbon atoms in 6 and 7 originate from the CO, which implies that 8 is formed first and rearranges to 6 or 7 by net insertion of the acyl carbon into a B-H bond. The molecular structures of 6 and Cp(eta(5):eta(1)-4-CHMeO-C2B9H10)Ti(NCMe) (9) have been det ermined by X-ray crystallography.