The oxidative addition of diphenylphosphine and monophenylphosphine to the electron-rich rhenium-rhenium triple bond. The isolation and characterization of compounds that contain the four-center Re(?-X)(?-PR2)Re cluster (X=halide)

Abstract

Diphenylphosphine oxidatively adds to the Re≡Re bonds of Re2X4(μ-dppm)2 (X=Cl or Br; dppm=Ph2PCH2PPh2) and Re2Cl4(μ-dpam)2 (dpam=Ph2AsCH2AsPh2) to afford the dirhenium(III) complexes Re2(μ-X)(μ-PPh2)HX3(μ-LL)2. The dppm complexes have also been prepared from the reactions of Re2(μ-O2CCH3)X4(μ-dppm)2 with Ph2PH, and a similar strategy has been used to prepare Re2(μ-Cl)(μ-PPh2)HCl3(μ-dmpm)2 (dmpm=Me2PCH2PMe2) from Re2(μ-O2CCH3)Cl4(dmpm)2. Phenylphosphine likewise reacts with Re2X4(μ-dppm)2 to give Re2(μ-X)(μ-PHPh)HX3(μ-dppm)2. An X-ray crystal structure determination on Re2(μ-Cl)(μ-PPh2)HCl3(μ-dppm)2 confirms its edge-shared bioctahedral structure. This complex crystallizes in the space group\(R\bar 3\) (No. 148) witha=21.699(3) A, α=84.50(4)°,V=10084(5) A3, andZ=6. The structure was refined toR=0.049 (Rw0.069) for 5770 data withI>3.0σ(I). The Re-Re distance is 2.5918(7) A. Oxidation of the bromide complex Re2(μ-Br)(μ-PPh2)HBr3(μ-dppm)2 with NOPF6 produces the unusual dirhenium(III, II) cation [Re2(μ-H)(μ-Br)[P(O)Ph2]Br2(NO)(μ-dppm)2]+ which has been structurally characterized as its perrhenate salt, [Re2(μ-H)(μ-Br)[P(O)Ph2]Br2(NO)(μ-dppm)2]ReO4 · 2CH2Cl2. This complex crystallizes in the space group\(P\bar 1\) (No. 2) witha=14.187(7) A,b=16.419(5) A,c=16.729(5) A, α=98.76(2)°, β=110.11(3)°, γ=104.66(3)°,V=3414(6) A3,Z=2. The structure was refined toR=0.040 (Rw=0.051) for 5736 data withI>3.0σ(I). The presence of a phosphorus-bound [P(O)Ph2]− ligand, a linear nitrosyl and a bridging hydrido ligand has been confirmed. The Re-Re distance is 2.6273(8) A.