Molybdenum tricarbonyl complexes of 1-substituted borepins

The reaction of 1-substituted borepins C6H6BX, where X = Me, Ph, and Cl, with Py3Mo(CO)(3) and BF3 . OEt2 affords the corresponding borepin molybdenum tricarbonyl complexes. Similar reaction of 1-methoxyborepin affords (C6H6BF)Mo(CO)(3). The reaction of(C6H6BCl)Mo(CO)(3) with appropriate nucleophiles affords the boron-substituted complexes (C6H6BX)Mo(CO)(3), where X = H, OCH3, OH, O-1/2, N(iPr)(2), N(CH2)(5), N(c-C6H11)(2), and NBnMe. All complexes (C6H6BX)Mo(CO)(3) have been compared using H-1 NMR, B-11 NMR, and C-13 NMR spectroscopies. The X-ray structure of (C6H6BN(iPr)(2))Mo(CO)(3) shows that Mo is eta(6)-coordinated to the ring carbon atoms but not to B. Rates of rotation about the B-N bonds of (C6H6BN(iPr)(2))Mo(CO)(3) and (C6H6BNBnMe)Mo(CO)(3) have been measured using variable-temperature NMR spectroscopy.