The synthesis and co-ordination chemistry of new functionalised pyridylphosphines derived from Ph2PCH2OH

Abstract

Condensation of Ph₂PCH₂OH with H₂NC₅H₃(OH)N in methanol/toluene gave the new “hybrid” ligand Ph₂PCH₂N(H)C₅H₃(OH)N Ia, which upon phosphorylation with either ClP(O)R₂ (R = Ph, OPh) or ClPR₂ afforded Ph₂PCH₂N(H)C₅H₃(X)N [X = OP(O)Ph₂II; OP(O)(OPh)₂III; OPPh₂IV]. Oxidation of Ia with aqueous H₂O₂ in thf gave Ph₂P(O)CH₂N(H)C₅H₃(OH)N V. The dichloroplatinum(II) complexes 1–4 were prepared from [PtCl₂(cod)] (cod = cycloocta-1,5-diene) and Ia, II or III (2 equiv.) or IV (1 equiv.). Reaction of [AuCl(tht)] (tht = tetrahydrothiophene) with 1 equiv. of Ia gave [AuCl(Ia)] 5. Bridge cleavage of [{RuCl(μ-Cl)(η⁶-p-cymene)}₂], [{RuCl(μ-Cl)(η⁶-C₆Me₆)}₂] or [{MCl(μ-Cl)(η⁵-C₅Me₅)}₂] (M = Rh, Ir) with Ia–IV afforded either monometallic [MCl₂(L)(PR₃)] 6–11 (M = Ru, Rh or Ir; L = η⁶-p-cymene, η⁵-C₅Me₅; PR₃ = Ia, II or III) or P,P′-bridged bimetallic [{MCl₂(L)}₂IV] 12–15 (M = Ru, Rh or Ir; L = η⁶-p-cymene, η⁶-C₆Me₆, η⁵-C₅Me₅) complexes. The neutral ruthenium(II) complexes [RuCl₂(η⁶-p-cymene){P-Ph₂PCH₂N(H)C₅H₃(X)}] (X = OH 6a; X = H 6b) undergo isomerisation in CDCl₃ to give [RuCl(η⁶-p-cymene){P,N(pyridyl)-Ph₂PCH₂N(H)C₅H₃(X)N}]Cl (X = OH 6c; X = H 6d). In contrast aged solutions (ca. 40 d) of 7–15 show no evidence (by ³¹P{¹H} NMR) for P,N(pyridyl)-chelation. The X-ray structures of representative compounds have been determined, and confirm, in the case of 6c/6d, a novel six-membered M–P–C–N–C–N metallacycle.