Chemistry of group 5 metallaboranes with heterocyclic thiol ligands: a combined experimental and theoretical study

Abstract

International audienceThermolysis of [(Cp*Nb)(BH)], 1b (Cp* = η-CMe), with 2-mercaptobenzothiazole, CHNSCSH (MBT), and 2-mercaptobenzoxazole, CHNOCSH (MBO), yielded hydrogen substituted compounds 2 and 3 with a general formula [(Cp*Nb)(BH)(BHL)] (2: L = CHNSCS and 3: L = CHNOCS). A similar reaction of 1b with PhSe yielded the monosubstituted derivative [(Cp*Nb)(BH){BH(PhSe)}], 4. All further efforts towards persubstitution of 1b under various drastic conditions were unfruitful. In parallel, in an effort to find a better synthetic route to the known Ta-aziridine complex [Cp*TaBH(CHNS)CHSNCH], Cp*TaCl was treated with a 2-mercaptobenzothiazolyl-based borate ligand Na[HB(CHNSCS)]. Surprisingly, the reaction led to the formation of the half-sandwich trichloroaryltantalum(v) complex [Cp*TaCl{κ-N,S-CHNSCS}], 5, containing a heterocyclic thiol ligand. Using an alternative method complex 5 was isolated in good yield when Cp*TaCl was treated with the potassium salt of 2-mercaptobenzothiazole K[CHNSCS]. All the compounds were characterized by H, B{H}, and C{H} NMR spectroscopy, and their structures were unequivocally established by crystallographic analysis