Reactivity of the molybdenacarbaborane anion [2,2,2,2-(CO)4-closo-2,1-MoCB10H11]–: metal oxidation versus cage substitution†

Abstract

In CH2Cl2 solutions, the MoII salt [N(PPh3)2][2,2,2,2-(CO)4-closo-2,1-MoCB10H11] 1 is oxidized by iodine (1 equiv.) in the presence of CNBut (4 equiv.) affording the MoIV complex [2,2,2,2-(CNBut)4-2-I-closo-2,1-MoCB10H11], the structure of which was established by X-ray diffraction. In contrast, under similar conditions the corresponding tungsten salt yields a mixture of [2,2,2-(CNBut)3-2-CO-2-I-closo-2,1-WCB10H11] and [2,2-(CNBut)2-2,2-(CO)2-2-I-closo-2,1-WCB10H11]. Treatment of 1 with iodine in tetrahydrofuran yields the MoII species [N(PPh3)2][2,2,2-(CO)3-2-I-7-{O(CH2)4}-closo-2,1-MoCB10H10], the structure of which was also confirmed by X-ray diffraction. The latter with iodine and S(CH2)4 gives [2,2,2-(CO)3-2-I-3-{S(CH2)4}-11-{O(CH2)4}-closo-2,1-MoCB10H9]. Using CH2Cl2 as solvent, 1 reacts with thioethers L [L = S(CH2)4, cyclo-1,4-S2(CH2)4, cyclo-1,4,7-S3(CH2)6, cyclo-1,4,7,10-S4(CH2)8] and iodine to form [2,2,2-(CO)3-2,3-μ-I-n-L-closo-2,1-MoCB10H9] (isomers, n = 7 and 11) and [2,2,2-(CO)3-2-I-3,11-L2-closo-2,1-MoCB10H9] [except L = cyclo-1,4,7,10-S4(CH2)8]. The molecular structures of [2,2,2-(CO)3-2,3-μ-I-7-{cyclo-1,4,7-S3(CH2)6}-closo-2,1-MoCB10H9] and [2,2,2-(CO)3-2-I-3,11-{cyclo-1,4-S2(CH2)4}2-closo-2,1-MoCB10H9] were determined by X-ray diffraction, confirming both to have doubly B-substituted cages and the former to contain a novel iodide bridge between molybdenum and a cage-boron atom.