SYNTHESIS AND CHARACTERIZATION OF CATIONIC GOLD RHODIUM PHOSPHITE CLUSTER COMPLEXES - X-RAY CRYSTAL AND MOLECULAR-STRUCTURE OF (AU4RH(H)2[P(O-I-C3H7)3]2(PPH3)4)PF6

The reactions of Au(PPh3)NO3 with (Rh(H)[P(OR)3]2}n (R = i-C3H7, n = 2; R = CH3, n = 3) have been investigated. {Au4Rh(H)2[P(O-i-C3H7)3]2(PPh3)4}PF6 (1) and {Au5Rh(H)[P(OCH3)3]2(PPh3)5{PF6 (2) were synthesized by the reaction of Au(PPh3)NO3 and {Rh(H)[P(O-i-C3H7)3]2)2 or [Rh(H)[P(OCH3)3]2)3, respectively, with THF as solvent. {Au6Rh(H)[P-(OCH3)3]2(PPh3)6|(PF6)2 (3) was made by further reaction of Au(PPh3)NO3 and 2 with CH2Cl2 as solvent. Compound 1 was characterized by single-crystal X-ray diffraction in the solid state [1, {formula-omited} (No. 2), a = 14.38 (1) Å, b = 14.50 (2) A, c = 26.81 (2) Å, α = 101.98 (10)°, β = 89.03 (7)°, γ = 117.82 (10)°, T = -95 °C, Z = 2, R = 0.042 for 8,142 observations] and by 31P and 1H NMR spectroscopy in solution. The molecular structure of complex 1 consists of an approximately trigonal-bipyramidal (TBP) RhAu4 core with a Rh[P(O-i-C3H7)3]2 unit occupying an equatorial position. The four AuPPh3 units occupy the axial positions and the two remaining equatorial positions. The major deviation from ideal TBP geometry is reflected in the shorter Au-Rh distances (average 2.685 (1) Å) compared with the bonded Au-Au separations (average 2.904 (1) Å). The hydride ligands were not directly observed by X-ray diffraction in 1; however, spectroscopic evidence, potential energy calculations, and the solid-state structural results (average distances: axial Au-Rh = 2.717 (1) Å; equatorial Au-Rh = 2.654 (1) Å) indicate the presence of one hydride bridging each of the longer Au-Rh bonds. Compounds 2 and 3 were characterized by IR and 1H and 31P NMR spectroscopies. Compounds 2 and 3 were each determined to possess one bridging hydride ligand. © 1990, American Chemical Society. All rights reserved.