Synthesis of sulphimide complexes of palladium and platinum. Crystal and molecular structure of cis-dichloro[S,S-dimethyl-N-(2-pyrimidinyl)sulphimide](triphenyiphosphine)pailadium(II)

Abstract

Reactions of [MCl₂(PhCN)₂](M = Pd or Pt) and K₂[PtCl₄] with S,S-dimethyl-N-heteroaromatic sulphimides Me₂SNR (R = 2-pyridyl, 4-methyl-2-pyridyl, 2-pyrimidinyl, 4-methyl-2-pyrimidinyl, or 2-pyrazinyl) give 1 : 1 adducts trans-[M₂Cl₂(µ-Cl)₂(Me₂SNR)₂](1) in which the sulphimide appears to co-ordinate through the ylide nitrogen according to ¹H n.m.r. studies. Reaction of [MCl₂(PhCN)₂] with Me₂SNPh gives a bis(sulphimide) complex trans-[MCl₂(Me₂NSPh)₂](2) when M = Pd but when M = Pt a phenylnitrene derivative cis-[PtCl₂(Me₂SNPh)(NPh)](3) is obtained. Reactions of complexes (1) with phosphines L = PEt₃, PMe₂Ph, PMePh₂, or PPh₃, give 1 : 1 adducts [MCl₂L(Me₂SNR)][M = Pd; R = 2-pyridyl, L = PEt₃, PMe₂Ph, PMePh₂, or PPh₃, (4a)–(4d); M = Pt, R = 2-pyridyl, L = PEt₃(4e); M = Pd, R = 2-pyrimidinyl, L = PPh₃(4f)]. An X-ray analysis of cis-[PdCl₂(PPh₃)(Me₂SNC₄H₃N₂)]·CH₂Cl₂(4f) revealed that the pyrimidine rather than the sulphimide N atom is the point of attachment of the sulphimide ligand to Pd. Conformational energy calculations suggest that electronic rather than steric factors determine which N atom acts as donor to Pd. The crystals are monoclinic, space group P2₁/_n, with a= 17.307(6), b= 9.182(1), c= 17.960(2)Å, β= 97.15(2)°, R= 0.024 for 1 999 independent reflections with I > 3σ(I). N.m.r. studies suggest a trans structure for complex (4e) with sulphimide co-ordination via the pyridyl nitrogen. The isomerism and fluxional behaviour of (4c) and (4d) was studied by variable-temperature n.m.r. spectroscopy.