Dirhodium(II,II) tetra-acetate complexes with axially co-ordinated triphenylstibine, triphenylarsine, and dibenzyl sulphide ligands. The syntheses, properties, and X-ray crystal structures of [Rh2(O2CMe)4(SbPh3)2], [Rh2(O2CMe)4(AsPh3)2], and [Rh2(O2CMe)4{S(CH2Ph)2}2

Abstract

The triphenylstibine and dibenzyl sulphide complexes [Rh2(O2CMe)4(SbPh3)2] and [Rh2(O2CMe)4{S(CH2Ph)2}2] have been synthesised for the first time, and their electronic and Raman spectra recorded together with those of [Rh2(O2CMe)4(AsPh3)2]. The triphenylstibine complex was isolated as light brown crystals belonging to space group P, with one centrosymmetric molecule per unit cell. The structure has been refined to an R value of 0.027 for 3 608 observed intensities measured on a diffractometer. The triphenylarsine complex was isolated as maroon needles also belonging to space group P with one centrosymmetric molecule per unit cell. The structure has been refined to R 0.022 for 2 969 observed intensities. The dibenzyl sulphide complex crystallises as burgundy-coloured thin plates with two centrosymmetric molecules per unit cell, space group P21/c. The final R value was 0.056 for 2 469 observed intensities. The dirhodium tetra-acetate nuclei in the three complexes are essentially identical with each other and with the nuclei found in analogous bis adducts. The Rh–Rh bond lengths are 2.421 (4), 2.427(1), 2.406(3)A for the triphenylstibine, triphenylarsine, and dibenzyl sulphide complexes, respectively, and the Rh–Sb, Rh–As, and Rh–S bond lengths are 2.732(4), 2.576(1), and 2.561(5)A, respectively. The Rh–Sb distance is the longest (by 0.13 A) axial rhodium-to-donor-atom bond length known for a bis adduct of dirhodium tetra-acetate. The syntheses of these complexes further demonstrate the versatility of the dirhodium tetra-acetate nucleus in co-ordinating a wide variety of different axial ligands.