Synthesis, reactivity and catalytic activity in transfer hydrogenation of ketones of ruthenium(II) and ruthenium(IV) complexes containing the novel N-thiophosphorylated iminophosphorane-phosphine ligands Ph2PCH2P{=NP(=S)(OR)2}Ph2 (R = Et, Ph)

Article abstract of DOI:10.1039/b305520e

Iminophosphorane-phosphines Ph₂PCH₂P{=NP(=S)(OR)₂}Ph₂ (R = Et 1a, Ph 1b) have been prepared by treatment of bis(diphenylphosphino)methane with an equimolar amount of thiophosphorylated azides (RO)₂P(=S)N₃. Dimers [{Ru(η⁶-p-cymene)(μ-Cl)Cl}₂] and [{Ru(η³:η³-C₁₀H₁₆) (μ-Cl)Cl}₂] react with a two-fold excess of 1a,b yielding the neutral complexes [Ru(η⁶-p-cymene)Cl₂ (κ¹-P-Ph₂PCH₂P{=NP(=S)(OR)₂} Ph₂)] (R = Et 2a, Ph 2b) and [Ru(η³:η³- C₁₀H₁₆)Cl₂(κ¹-P- Ph₂PCH₂P{=NP(=S)(OR)₂}Ph₂)] (R = Et 5a, Ph 5b), respectively. Treatment of 2a,b and 5a,b with one equivalent of AgSbF₆ affords the cationic species [Ru(η⁶-p-cymene) Cl(κ²-P,S-Ph₂PCH₂P{=NP(=S) (OR)₂}-Ph₂)][SbF₆] (R = Et 3a, Ph 3b) and [Ru(η³:η³-C₁₀H₁₆)Cl (κ²-P,S-Ph₂PCH₂P{=NP(=S) (OR)₂}Ph₂)][SbF₆] (R = Et 6a, Ph 6b), respectively. The structure of the cation of complex 6a has been confirmed by X-ray crystallography. The preference observed for the κ²-P,S- vs. κ²-P,N- coordination of 1a,b seems to be sterically controlled since theoretical calculations on the models [Ru(η⁶- C₆H₆)Cl(κ²-P,N-H₂ PCH₂P{=NP(=S)(OH)₂} H₂)]⁺ A and [Ru(η⁶-C₆H₆)Cl(κ²- P,S-H₂PCH₂P{=NP(=S)(OH)₂} H₂)]⁺ B show that isomer A is ca. 5.0 kcal mol^-1 more stable than B. Dicationic complexes [Ru (η⁶-p-cymene)(κ³-P,N,S-Ph₂PCH ₂P{=NP(=S)(OR)₂}Ph₂)] [SbF₆]₂ (R = Et 4a, Ph 4b) and [Ru(η³:η³-C₁₀ H₁₆)-(κ³-P,N,S-Ph₂PCH₂ P{=NP(=S)(OR)₂}Ph₂)][SbF₆]₂ (R = Et 7a, Ph 7b) have been obtained by treating 2a,b and 5a,b, respectively, with two equivalents of AgSbF₆. The reactivity of [Ru(η⁶-p- cymene)(κ³-P,N,S-Ph₂PCH₂P{=NP(=S)- (OEt)₂}Ph₂)][SbF₆]₂ 4a towards neutral and anionic ligands has been explored allowing the synthesis of complexes [Ru(η⁶-p-cymene)(L)(κ²-P,S- Ph₂PCH₂P{=NP(=S)(OEt)₂}Ph₂)] [SbF₆]₂ (L = N≡CMe 8, PMe₃ 9, PMe₂Ph 10, PMePh₂ 11) and [Ru(η⁶-p- cymene)X(κ²-P,S-Ph₂PCH₂P{=NP(=S) (OEt)₂}Ph₂)][SbF₆] (X = Br 12, I 13, N₃ 14), respectively. The catalytic activity of complexes 2-7a,b in transfer hydrogenation of ketones by propan-2-ol has been also studied.