Chemistry of N,S-heterocyclic carbene and metallaboratrane complexes: a new η³-BCC-borataallyl complex

A high-yielding synthetic route for the preparation of group 9 metallaboratrane complexes [Cp*MBH(L)2], 1 and 2 (1, M=Rh, 2, M=Ir; L=C7H4NS2) has been developed using [{Cp*MCl2}2] as precursor. This method also permitted the synthesis of an Rh–N,S-heterocyclic carbene complex, [(Cp*Rh)(L2)(1-benzothiazol-2-ylidene)] (3; L=C7H4NS2) in good yield. The reaction of compound 3 with neutral borane reagents led to the isolation of a novel borataallyl complex [Cp*Rh(L)2B{CH2C(CO2Me)}] (4; L=C7H4NS2). Compound 4 features a rare η3-interaction between rhodium and the B-C-C unit of a vinylborane moiety. Furthermore, with the objective of generating metallaboratranes of other early and late transition metals through a transmetallation approach, reactions of rhoda- and irida-boratrane complexes with metal carbonyl compounds were carried out. Although the objective of isolating such complexes was not achieved, several interesting mixed-metal complexes [{Cp*Rh}{Re(CO)3}(C7H4NS2)3] (5), [Cp*Rh{Fe2(CO)6}(μ-CO)S] (6), and [Cp*RhBH(L)2W(CO)5] (7; L=C7H4NS2) have been isolated. All of the new compounds have been characterized in solution by mass spectrometry, IR spectroscopy, and 1H, 11B, and 13C NMR spectroscopies, and the structural types of 4–7 have been unequivocally established by crystallographic analysis