Chiral functionalized bisphosphine ligands: Transition metal complexes of 1,2-bis(tert-Butylchlorophosphino)-1,2-dicarba-closo-dodecaborane(12)

When rac- or meso-1,2-bis(tert-butylchlorophosphino)-1,2-dicarba-closo-dodecaborane(12) (1a or 1b) is reacted with M(CO)₄(NBD)] (M = Cr, Mo, NBD = norbornadiene), Mo(CO)₄(EtCN)₂] or W(CO)₆], rac-Cr(CO)₄{1,2-(P^tBuCl)₂C₂B₁₀H₁₀}] (2), rac- or meso-Mo(CO)₄{1,2-(P^tBuCl)₂C₂B₁₀H₁₀}] (3a or 3b) and rac-W(CO)₄{1,2-(P^tBuCl)₂C₂B₁₀H₁₀}] (4) could be isolated as pure diastereomers. UV irradiation of 1 with Cr(CO)₆] in moist THF proceeds with hydrolysis and formation of Cr(CO)₄{1,2-(P(OH)^tBu)₂C₂B₁₀H₁₀}] (5) which contains the metal complex-stabilized phosphinous acid. Compounds 2–5 were characterized spectroscopically (¹H, ³¹P, ¹¹B, ¹³C NMR), by mass spectrometry and by X-ray structure determination.