title: Conversion of (η(5)-C2B9H10R)TaX3 (X = Me, NMe2) to (η(6)-C2B9H10R)TaX' (X' = NMe2, azaallyl) in the absence of a reducing agent: synthesis and structure of tantallacarboranes incorporating an arachno-η(6)-C2B9(4-) ligand.
abstract: Heating a benzene solution of [η(5)-(Me2NCH2CH2)C2B9H10] Ta(NMe2)3 (1) in the presence of pyridine gave an unprecedented complex [η(1):η(6)-(Me2NCH2CH2)C2B9H10]Ta (NMe2)(NC5H5) (2). On the other hand, reaction of (η(5)-C2B9H11)TaMe3 with adamantly isonitrile (AdNC) in dimethoxyethane (DME) at room temperature afforded another unexpected complex (η(6)-C2B9H11)Ta[η(3)-C,C,N-CH2C(CH3)NAd](DME) (4). These results show that pyridine and DME are essential for the formation of 2 and 4, respectively. It is suggested that the nido-η(5)-C2B9H10R(2−) ligand in tantallacarboranes takes up two electrons released by reductive elimination to form an arachno-η(6)-C2B9H10R(4−) fragment via the cage C–C bond cleavage.
authors.affiliation: Department of Chemistry and State Key Laboratory of Synthetic Chemistry, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China. zxie@cuhk.edu.hk.
authors.forename: Li
authors.initials: L
authors.lastname: Xiang
authors.forename: Zuowei
authors.initials: Z
authors.lastname: Xie
mesh_terms: D001554:Benzene / Q000737:chemistry; D001880:Boranes / Q000737:chemistry*; D056831:Coordination Complexes / Q000737:chemistry*; D018360:Crystallography, X-Ray; D004583:Electrons; D008024:Ligands; D008956:Models, Chemical; D008958:Models, Molecular; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D010084:Oxidation-Reduction; D011725:Pyridines / Q000737:chemistry; D019163:Reducing Agents / Q000737:chemistry*; D013635:Tantalum / Q000737:chemistry*
chemical_list: D001880:Boranes; D056831:Coordination Complexes; D008024:Ligands; D009942:Organometallic Compounds; D011725:Pyridines; D019163:Reducing Agents; D013635:Tantalum; D001554:Benzene; C023666:pyridine