New complexes of functionalised ligands bearing P/N/Se or P2Se donor sets

Abstract

The new selenoether functionalised tertiary phosphines (2-Ph₂P)C₆H₄C(H)N(CH₂)_nSePh (n = 3 1a; 4 1b) were readily prepared by condensation of (2-Ph₂P)C₆H₄C(H)O and H₂N(CH₂)_nSePh (n = 3, 4) in absolute ethanol. Reaction of two equiv. of Ph₂PCH₂OH with H₂N(CH₂)_nSePh (n = 3, 4) affords the symmetrical ditertiary phosphines (Ph₂PCH₂)₂N(CH₂)_nSePh (n = 3 2a; 4 2b). Reaction of 1a–2b with [MCl₂(cod)] (M = Pt, Pd) gave the dichlorometal(II) chelate complexes 3a–4d in which either six-membered P,P- or P,N-ligation is observed. Chloro bridge cleavage of [{RuCl₂(p-cymene)}₂] or tht (tht = tetrahydrothiophene) substitution of [AuCl(tht)] with 2a (or 2b) gave the new complexes [{RuCl₂(p-cymene)}₂{μ-(P,P′-Ph₂PCH₂)₂N(CH₂)_nSePh}] (n = 3 5a; 4 5b) or [{AuCl}₂{μ-(P,P′-Ph₂PCH₂)₂N(CH₂)_nSePh}] (n = 3 6a; 4 6b) in which the ligand P,P′-bridges two metal centres. Spectroscopic evidence suggests the pendant selenoether group in 3c undergoes further reaction with [PdCl₂(MeCN)₂] affording an unusual trinuclear palladium(II) complex 7. Furthermore reaction of 3b with 1 equiv. of Ag[BF₄] in dichloromethane gave the cationic complex [PtCl(1a)][BF₄] 8 in which 1a functions as a P,N,Se-tridentate ligand. All structures have been confirmed by a combination of spectroscopic, analytical and single crystal X-ray studies. The structure of 8 represents, to the best of our knowledge, an extremely rare example of a crystallographically characterised Group 10 metal complex with a P/N/Se/Cl coordination environment.