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

Sulfur(IV) Compounds as Ligands, XIII. – Sulfur Dioxide as a Bridging Ligand in Unsymmetrical Dinuclear Complexes A 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 SO 2 into a bridging position. [Mo(CO) 3 (η 2 ‐dppe) (η 1 ‐dppm)] ( 2 ) reacts with [PdCl 2 (C 8 H 12 )] to form [MoPdCl 2 (CO) 3 (dppe)(μ‐dppm)] ( 3 ), which is unstable and does not take up SO 2 . However, the complexes [FeRhCl(CO) 4 (μ‐SO 2 )(μ‐dppee)] ( 5 ), [MoIr(μ‐Cl)(CO) 3 (μ‐SO 2 )(μ‐dppm) 2 ] ( 8 ), and [MnPdBr(CO) 2 (μ‐SO 2 )(μ‐dppm) 2 ] ( 14 ) have been obtained. Reactions of fac ;‐[M(CO) 3 (η 2 ‐dppm)(η 1 ‐dppm)] (MMo: 6a, W: 6b ) or the corresponding mer ‐isomers 10a, b with [PdCl 2;‐ (C 8 H 12 )] 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 SO 2 . However, from 17 and (Me 3 Si) 2 S the sulfur‐bridged complex [IrPdCl(μ‐S)(CO)(μ‐dppm) 2 ] ( 18 ) is obtained. The alkynyl complexes [MPtCl(CCPh) 2 (μ‐dppm) 2 ] (M Rh: 19 , Ir: 21 ) readily add SO 2 , reversibly in the case of 19 . From [IrPtCl‐(C CPh) 2 (μ‐SO 2 )](μ‐dppm) 2 ] ( 22 ) the salt [IrPt(C CPh) 2 (SO 2 ) (μ‐dppm) 2 ]PF 6 ( 23 ) is formed by Cl abstraction. 23 is one of the rare examples of terminal coordination of SO 2 in a dinuclear complex.