Unusual cationic rhodathiaboranes: synthesis and characterization of [8,8,8-(H)(PR3)2-9-(Py)-nido-8,7-RhSB9H10]⁺ and [1,3-μ-(H)-1,1-(PR3)2-3-(Py)-isonido-1,2-RhSB9H8]⁺.

The treatment of the hydridorhodathiaboranes, [8,8,8-(H)(PR3)2-9-(Py)-nido-8,7-RhSB9H9], where PR3 = PPh3 (2), PMePh2 (3), PPh3 and PMe2Ph (4), or PMe3 and PPh3 (5), and [8,8,8-(H)(PMePh2)2-9-(PMePh2)-nido-8,7-RhSB9H9] (6), with TfOH affords [8,8,8-(H)(PR3)2-9-(Py)-nido-8,7-RhSB9H10](+) cations, where PR3 = PPh3 (12), PMePh2 (13), PPh3 and PMe2Ph (14), or PMe3 and PPh3 (15), and [8,8,8-(H)(PMePh2)2-9-(PMePh2)-nido-8,7-RhSB9H10](+) (16). Compounds 13 and 14 lose H2 to give [1,3-μ-(H)-1,1-(PR3)2-3-(Py)-isonido-1,2-RhSB9H8](+), where PR3 = PMe2Ph (18), PPh3 and PMe2Ph (21), or PMePh2 (22). Similarly, the 11-vertex rhodathiaboranes, [1,1-(PR3)2-3-(Py)-1,2-RhSB9H8], where PR3 = PPh3 (7), PMe2Ph (8), PMe3 (9), or PPh3 and PMe3 (10), react with TfOH to give the corresponding cations, [1,3-μ-(H)-1,1-(PR3)2-3-(Py)-isonido-1,2-RhSB9H8](+), where PR3 = PPh3 (17), PMe2Ph (18), PMe3 (19), or PPh3 and PMe3 (20). Four conformers of 20 are studied by X-ray diffraction methods and DFT-calculations, identifying packing motifs that stabilize different metal-thiaborane linkages, and energy variations that are involved in these conformational changes. It is demonstrated that the proton induces nonrigidity on these clusters as well as an enhancement of their Lewis acidity.