Synthesis and solid state structure of some 2,6-diphenylphenoxide derivatives of rhodium(I) and iridium(I)

Abstract

Treatment of the carbonyl dimer Rh 2Cl 2(CO) 4 with 2 equivalents of LiOAr-2,6Ph 2 (OAr-2,6Ph 2 = 2,6-diphenylphenoxide) produces the aryloxide bridged dimer [(CO) 2Rh(μ-OAr-2,6Ph 2) 2Rh(CO) 2] ( 1) in excellent yield. Compound 1 shows two, equal intensity carbonyl stretching frequencies at 2090 and 2006 cm −1 in the IR spectrum (Nujol mull) consistent with a solid state structure consisting of two edge shared square planes. A single crystal X-ray diffraction analysis of 1 confirmed this formulation showing no evidence for Π-bonding by the side chain aryl groups to the 16-electron metal centre. Treatment of the dimer Ir 2Cl 2(COD) 2 (COD = 1,5-cyclooctadiene) with LiOAr-2,6Ph 2 yielded a mixture of products. Eventually sparingly soluble crystals of a salt [(COD)Ir(η 5-HOAr-2,6Ph 2)] +[(COD)Ir(OAr-2,6Ph 2) 2] − ( 2) were obtained in very minor yield. The presence of a 2,6-diphenylphenol ligand η 5-bound through the central phenoxy ring to the iridium metal centre was confirmed by a single crystal X-ray diffraction analysis of 2. The distances IrC to the COD ligand in the cation in 2, 2.10(2)–2.16(2) Å, are slightly shorter than the distances of 2.25(2)–2.35(2) Å to the five carbon atoms of the central phenoxy ring. The ipso carbon attached to the hydroxyl group is non-bound. The anion in 2 contains two terminal aryloxide ligands bound approximately trans to the two iridium-olefinic bonds of the COD group yielding a structure best described as square planar. Crystal data at 20°C for Rh 2O 6C 40H 26 ( 1): a = 10.750(2), b = 28.307(5), c = 11.311(2) Å, β = 96.21(1)°, Z = 4, d calc = 1.569 g cm −3 in space group P2 1/ n; for Ir 2Cl 6O 3C 72H 58 ( 2) 2CHCl 3: a = 13.428(2), b = 22.838(3), c = 20.937(2) Å, β = 92.775(9)°, Z = 4, d calc = 1.624 g cm −3 in space group P2 1/ n.