Different reactivity of cyclooctadiene complexes 3,3-(cod)-8-SMe2-closo-3,1,2-RhC2B9H10 and 1,8-Me2-2,2-(cod)-11-SMe2-2,1,8-closo-RhC2B9H8 toward iodine.

Reaction of the thallium salt Tl[7,8-Me 2 -10-SMe 2 -7,8- nido -C 2 B 9 H 8 ] with [(cod)RhCl] 2 in THF furnishes new rhodacarborane 1,2-Me 2 -3,3-(cod)-8-SMe 2 -3,1,2 -closo -RhC 2 B 9 H 8 ( 1 ). The latter undergoes 1,2 → 1,7 carbon atom isomerization upon reflux in o -xylene for 5 h producing complex 1,8-Me 2 -2,2-(cod)-11-SMe 2 -2,1,8- closo -RhC 2 B 9 H 8 ( 2 ). Reaction of complex 2 with 1 equiv of I 2 in benzene results in a loss of the cod ligand and formation of product 3 , consisting of cationic [(1,8-Me 2 -11-SMe 2 - closo -2,1,8-RhC 2 B 9 H 8 ) 2 I 3 ] + ( 3a + ) and anionic [(1,8-Me 2 -11-SMe- closo -2,1,8-RhC 2 B 9 H 8 ) 2 I 3 ] − ( 3b – ) iodide species. In contrast, unisomerized analog 3,3-(cod)-8-SMe 2 - closo- 3,1,2-RhC 2 B 9 H 10 reacts with I 2 affording dimeric iodide [3,3-I 2 -8-SMe 2 - closo- 3,1,2-RhC 2 B 9 H 10 ] 2 ( 5 ). The structures of 2 and 5 were determined by a single crystal X-ray diffraction. [ABSTRACT FROM AUTHOR]