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 Mo^II 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 CNBu^t (4 equiv.) affording the Mo^IV complex [2,2,2,2-(CNBu^t)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-(CNBu^t)₃-2-CO-2-I-closo-2,1-WCB₁₀H₁₁] and [2,2-(CNBu^t)₂-2,2-(CO)₂-2-I-closo-2,1-WCB₁₀H₁₁]. Treatment of 1 with iodine in tetrahydrofuran yields the Mo^II 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.