A Spirocyclic Borate and a Dihydroborate Derived from the 1,2-Diselenolato-1,2-dicarba-closo-dodecaborane(12) Dianion [1,2-(1,2-C2B10H10)Se2]2-: Structures, NMR Spectroscopy, and DFT Calculations

The reaction of the diselenolato-1,2-dicarba-closo-dodecaborane(12) dianion with BF3-OEt2 affords selectively a spirocyclic bis(1,2-dicarba-closo-dodecaborane-1,2-diselena)borate, whereas the analogous reaction with boron trichloride leads mainly to 1,2-bis(ethylseleno)-1,2-dicarba-closododecaborane(12) through ether cleavage. The spirocyclic borate reacts with methanol by cleavage of both Se-B and Se-C bonds. With borane in THF (BH3/THF) and also with LiBH4 exchange reactions take place, which afford the 1,2-dicarba-closo-dodecaborane-1,2-diselenadihydroborate. The molecular structures of both borates as tetrabutylammonium salts were determined by X-ray analysis. In solution, the borates were characterized by multinuclear magnetic resonance spectroscopy (H-1, B-11, C-13, Se-77). The gas-phase geometries of the borate anions were optimized [RB3LYP/6-3111+G(d,p) level of theory], and the NMR spectroscopic parameters (chemical shifts and coupling constants) were calculated.