Synthesis and crystal structure of the unique chiral anion [Re2Cl7PBzMePh]− and the direct determination of its δ-bond energy by molecular modelling

The quadruply bonded chiral anion [Re2Cl7PBzMePh]− (Bx = Ch2Ph) was synthesized and its crystal structure was determined. It crystallized in space group P1 with unit cell dimensions a = 10.677(2), b = 12.220(2), c= 18.220(4) A, α = 85.66(2), β = 75.98(2) and γ = 80.07(2)°. The ReRe distance was 2.2196(8) A. The average twist angle χ was 11.6°. The δ-bond energy was determined by molecular modelling to be 9 kcal mol−1 and 5% greater than the energy required to eclipse [Re2Cl8]2−.