Reactions and Coordination Properties of the First Secondary Carbaboranyldiphosphane: 1,2-Bis(phenylphosphanyl)-1,2-dicarba-closo-dodecaborane(12)

Abstract

When a mixture of stereoisomers of rac- and meso-1,2-bis(phenylphosphanyl)-1,2-dicarba-closo-dodecaborane(12) (1a, b; 1a/1b = 3:1) is treated with [Cp2ZrMe2] in boiling toluene for 2 h, the formation of three phosphorus-containing products, namely meso-[Cp2Zr(PPh)3] (3), (PPh)4 (4) and (PPh)5 (5), ratio 2.8:1.1:1.0, was observed by 31P-NMR spectroscopy. In the 11B-NMR spectrum of the reaction mixture, only signals for 1,2-dicarba-closo-dodecaborane(12) were observed. When zirconocene, prepared in situ from [Cp2ZrCl2] and BuLi, was treated with 1a, b at low temperature and then heated to reflux in toluene for 2 h, only formation of 3 and 1,2-dicarba-closo-dodecaborane(12) was observed. The mixture of stereoisomers of 1a, b reacts with CuCl in THF to give rac- and meso-[CuCl(THF){1,2-(PHPh)2C2B10H10}] (7a, b), which is only stable in THF solution and loses THF in vacuo over several hours to yield the insoluble colorless complex [CuCl{1,2-(PHPh)2C2B10H10}]n (8). In THF solution, 7 reacts with PPh3 to give the stable isolable complex [CuCl(PPh3){1,2-(PHPh)2C2B10H10}] (9). No reaction of 1a, b is observed with [Cp′Mo(CO)3]2 (Cp′ = C5H4Me) in boiling THF, while only decomposition occurs in boiling toluene. However, [(NBD)Mo(CO)4] (NBD = norbornadiene) reacts smoothly with 1a in toluene at room temperature to give cis-rac-[Mo(CO)4{1,2-(PHPh)2C2B10H10}] (10). Compounds 7, 9, and 10 were characterized spectroscopically (1H, 31P, 11B, 13C NMR, IR), and an X-ray structure determination was carried out on 10.