Thiourea monoanion and dianion complexes of rhodium(III) and ruthenium(II)

Abstract

The versatility of deprotonated thioureas as ligands is shown by the synthesis and characterisation of a range of rhodium(III) complexes of substituted thioureas, with support from a ruthenium(II) analogue in one case. Reaction of the complexes [LMCl(μ-Cl)]2 [M=Rh, L=η5-C5Me5 (Cp*); M=Ru, L=η6-p-cymene] with Na[MeNHC(S)NCN] and excess trimethylamine base gives the dinuclear complexes [LM{SC(=NCN)NMe}]2 containing chelate-bridging thiourea dianion ligands. The Ru complex was characterised by an X-ray diffraction study. The mononuclear complexes [Cp*Rh{SC(=NCN)NMe}(PPh3)] and [Cp*Rh{SC(=NPh)NPh}(PPh3)], containing chelating thiourea dianion ligands, were prepared by analogous reactions in the presence of triphenylphosphine. Reaction of [Cp*Rh{SC(=NCN)NMe}(PPh3)] with HCl, or [Cp*RhCl(μ-Cl)]2 with 2 equiv. of PPh3 and Na[MeNHC(S)NCN] (with no added base) gave the complex [Cp*RhCl{SC(=NCN)NHMe}(PPh3)], containing a (monodentate) S-bonded thiourea monoanion ligand, which was characterised by an X-ray diffraction study. The AsPh3 and SbPh3 analogues of this complex were also prepared and characterised. Reaction of [Cp*RhCl(μ-Cl)]2 with 2 equiv. of PPh3 or SbPh3 and PhNHC(S)NHPh or various trisubstituted thioureas PhNHC(S)NR1R2, triethylamine and NaBPh4 gave a range of cationic complexes [Cp*Rh{SC(=NR1R2)NPh}(EPh3)]+ (E=P, Sb), as their tetraphenylborate salts, in which the thiourea is bonded as a monoanion through the S and the NPh group. The corresponding reaction utilising 1,6-bis(diphenylphosphino)hexane (dpph) gave the dinuclear complex [Cp*Rh{SC(=N(CH2CH2)2O)NPh}]2(μ-η2-dpph) (BPh4)2.