ORGANOALUMINUM-PHOSPHINE CHEMISTRY - SYNTHESIS AND MOLECULAR-STRUCTURE OF [PH2P(O)2.ALCL2]2 AND [PH2P.AL(I-BU)2]2

The crystalline complex [Ph2P(O)2 · AlCl2]2 (I) was prepared by reaction of the disproportionation product of ethylaluminum sesquichloride, EtAlCl2, or by direct reaction of EtAlCl2 with diphenylphosphonic acid, Ph2P(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 Å3 and Dcalc 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 (R2 = 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 [Ph2P · 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 Å3, and Dcalc 1.08 g cm-3 for Z = 4. Least-squares refinement based on 2111 observed reflections converged at R = 0.036, Rw = 0.049. The dimeric organoaluminium compound possesses crystallographic inversion symmetry and contains a planar four-membered Al2P2 ring. The mean Al-P bond distance is 2.476(1) Å. The Al-P-Al bond angle in the Al2P2 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. © 1990.