Organoaluminum-phosphine chemistry. Synthesis and molecular structure of [Ph 2P(O) 2 · AlCl 2] 2 and [Ph 2P · Al(i-Bu) 2] 2

Abstract

The crystalline complex [Ph 2P(O) 2 · AlCl 2] 2 (I) was prepared by reaction of the disproportionation product of ethylaluminum sesquichloride, EtAlCl 2, or by direct reaction of EtAlCl 2 with diphenylphosphonic acid, Ph 2P(O)OH, in a heptane/toluene mixture. I crystallizes in the monoclinic space group C2/ c with unit cell parameters a 11.201(9), b 15.059(6), c 17.665(5) Å, β 105.4°(2), V 2979.7 Å 3 and D calc 1.40 g cm −3 for Z = 4. Least-squares refinement based on 1656 observed reflections led to a final R factor of 0.047 ( R 2 = 0.062). I resides about a crystallographic center of symmetry. The core of the dimer consists of a planar eight-membered (Al-O-P-O) 2 ring. The mean Al-O bond distance is 1.73(1) Å while the independent Al-Cl bond distance is 2.085(2) Å. The organoaluminum crystalline product [Ph 2P · Al(i-Bu) 2] 2 (II) was prepared by reaction of diisobutylaluminum hydride with diphenylphosphine in heptane. II crystallizes in the orthorhombic space group Pbca with unit cell parameters a 12.809(2), b 15.207(2), c 20.574(3) Å, V 4008.5 Å 3, and D calc 1.08 g cm −3 for Z = 4. Least-squares refinement based on 2111 observed reflections converged at R = 0.036, R w = 0.049. The dimeric organoaluminium compound possesses crystallographic inversion symmetry and contains a planar four-membered Al 2P 2 ring. The mean Al-P bond distance is 2.476(1) Å. The Al-P-Al bond angle in the Al 2P 2 ring is 93.8(1)° while the P-Al-P bond angle is determined to be 86.2(1)°. The Al ··· Al and P ··· P contact distances are 3.615(1) Å and 3.381(1) Å, respectively.