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

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 CNBut (4 equiv.) affording the Mo-IV complex [2,2,2,2-(CNBU)(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 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-S-2(CH2)(4), cyclo-1,4,7-S-3(CH2)(6), cyclo-1,4,7,10-S-4(CH2)(8)] and iodine to form [2,2,2-(CO)(3)-2,3-mu -I-n-L-closo-2,1-MoCB10H9] (isomers, n = 7 and 11) and [2,2,2-(CO)(3)-2-I-3,11-L-2-closo-2, 1-MoCB10H9] [except L = cyclo-1,4,7,10-S-4(CH2)(8)]. The molecular structures of [2,2,2-(CO)(3)-2,3-mu -I-7-{cyclo- 1,4,7-S-3(CH2)(6)}-closo-2,1-MoCB10H9] and [2,2,2-(CO)(3)-2-I-3,11-{cyclo-1,4-S-2(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.