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

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.

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