Schwefel(IV)‐Verbindungen als Liganden, XIII. Schwefeldioxid als Brückenligand in unsymmetrischen Zweikernkomplexen

Abstract

Sulfur(IV) Compounds as Ligands, XIII. – Sulfur Dioxide as a Bridging Ligand in Unsymmetrical Dinuclear ComplexesA series of known or newly synthesized dinuclear complexes with the following combinations of elements: Mo/Ir, Mo/Pd, W/Pd, Mn/Pd, Fe/Rh, Rh/Pt, Ir/Pd, and Ir/Pt has been treated with sulfur dioxide. Only electron‐rich systems are capable of taking up SO2 into a bridging position. [Mo(CO)3(η2‐dppe) (η1‐dppm)] (2) reacts with [PdCl2(C8H12)] to form [MoPdCl2(CO)3(dppe)(μ‐dppm)] (3), which is unstable and does not take up SO2. However, the complexes [FeRhCl(CO)4(μ‐SO2)(μ‐dppee)] (5), [MoIr(μ‐Cl)(CO)3(μ‐SO2)(μ‐dppm)2] (8), and [MnPdBr(CO)2(μ‐SO2)(μ‐dppm)2] (14) have been obtained. Reactions of fac;‐[M(CO)3(η2‐dppm)(η1‐dppm)] (MMo: 6a, W: 6b) or the corresponding mer‐isomers 10a, b with [PdCl2;‐(C8H12)] give the dinuclear complexes [MPdCl(μ‐Cl)(CO)2(μ‐CO)(μ‐dppm)2] (11a, b). From [Ir(CO)(dppm)2]Cl and [Pd(dba)2] in the presence of CO [IrPdCl(CO)2(μ‐dppm)2] (16) is obtained, whereas in dichloromethane under an inert gas the oxidation product [IrPdC]3(CO)(μ‐dppm)2] (17) is formed. 11a, b, 16, and 17 apparently are too electron‐poor to form stable adducts with SO2. However, from 17 and (Me3Si)2S the sulfur‐bridged complex [IrPdCl(μ‐S)(CO)(μ‐dppm)2] (18) is obtained. The alkynyl complexes [MPtCl(CCPh)2(μ‐dppm)2] (M  Rh: 19, Ir: 21) readily add SO2, reversibly in the case of 19. From [IrPtCl‐(C  CPh)2(μ‐SO2)](μ‐dppm)2] (22) the salt [IrPt(C  CPh)2(SO2) (μ‐dppm)2]PF6 (23) is formed by Cl abstraction. 23 is one of the rare examples of terminal coordination of SO2 in a dinuclear complex.