Tetramethylthioharnstoff als Ligand in Übergangsmetallkomplexen: Redoxsubstitutionen mit dem Dithiobis(1,1,3,3-tetramethylformamidinium)-Kation Synthese und Kristallstrukturen von [Fe(SR)L3]+BPh4 -, [FeL4]2+BPh4 -)2 und [RuCl2(CO)2L2] (R = 2,4,6-i-Pr3C6H2; L = SC(NMe2)2) / Tetramethylthiourea as Ligand in Transition Metal Complexes:. Redox Substitution Reactions with the Dithiobis(1,1,3,3-tetramethylformamidinium) Cation Synthesis and Crystal Structures of [Fe(SR)L3]+BPh4 -, [FeL4]2+(BPh4 -)2 and [RuCl2(CO)2L2] (R = 2,4,6-i-Pr3C6H2; L = SC(NMe2)2)

Abstract

The oxidation of tetramethylthiourea (SC(NMe2)2,L) with HC1/H2O2 yields dithiobis-(1,1,3,3-tetramethylformamidinium)dichloride, [{SC(NMe2)2}2]2+Cl2 (1). Anions in 1 can be easily exchanged by tetraphenylborate to give [{SC(NMe2)2}2]2+(BPh4 -)2 (2). The reaction of the neutral complex [Fe(SR)2L2] (3) (R = 2,4,6-i-Pr3C6H2) with 2 results in either partial or complete oxidation of the thiolate ligands, depending on the stoichiometric ratio of the reactants, and replacement by neutral ligands L. The cations [Fe(SR)L3]+ and [FeL 4]2+ were isolated as tetraphenylborate salts (4 and 5, respectively). [RuCl2(CO)2L2] (6) was obtained by the reaction of dodecacarbonyltriruthenium with 1. In the course of the reaction ruthenium is oxidized and CO ligands are partially replaced by L and Cl-. The structures of 4, 5 and 6 were determined from single crystal X-ray diffraction data. 4: monoclinic, P 21/n, a = 2272.1(2), b = 1009.1(1), c = 2533.4(2) pm, β = 96.96(1)°. V = 5765· 106 pm3, Z = 4, conventional R = 0.066. The cation of 4 shows a distorted tetrahedral coordination of Fe(II) with Fe–Sthiolate 229.0(2) pm and Fe–Sthiourea 237.6(2) pm (mean). 5: monoclinic, P 21/n, a = 1153.2(1), b = 2913.8(1), c = 2019.1(1) pm, β = 92.84°. V = 6776.5 • 106 pm3, Z = 4, conventional R = 0.061. The cation of 5 possesses approximate D2d symmetry with the central [FeS4] tetrahedron compressed along the two-fold axis (Fe–S: 234.2 pm (mean)). 6: orthorhombic, P bcn, a = 847.9(2), b = 1442.2(3), c = 1660.1(3) pm. V = 2030.0· 106 pm3, Z = 4, conventional R = 0.037. The neutral complex cis, cis, trans-6 exhibits a distorted octahedral coordination of Ru(II) with thiourea ligands in trans position. 6 possesses C2 symmetry. The S–Ru–Sa angle was found to be 165.0°. The deviation from linearity is probably caused by the sterically hindered tetramethylthiourea ligands. The Ru–S bond length is 241.6(1) pm. Structural studies of geometrical parameters in tmtu complexes that are related to the nature of the M–Sthiourea bond suggest, that 1,1,3,3-tetramethylthiourea (L) does not only function as a σ-donor but possibly also exhibits weak π-donor and π-acceptor properties, respectively. The exact type of bonding is determined by the nature and oxidation state of the metal centre.