Pyridine-2-selenolate complexes of palladium(II) and platinum(II): crystal structure of [(Prn3P)Cl2Pd(NC5H4Se)PdCl(PPrn3)]

Abstract

Reactions of sodium pyridine-2-selenolate with several palladium(II) and platinum(II) complexes were carried out and a variety of products isolated and characterized. Treatment of [M₂Cl₂(µ-Cl)₂(PR₃)₂] with NaSeC₅H₄N readily afforded complexes of the type [MCl(NC₅H₄Se)(PR₃)] 1 (M = Pd or Pt; PR₃ = PEt₃, PPrⁿ₃, PBuⁿ₃, PMe₂Ph, PMePh₂ or PPh₃). Some of the complexes containing trialkylphosphine existed as binuclear species, [M₂Cl₂(µ-NC₅H₄Se)₂(PR₃)₂] 2 in ≈5% concentration in solution. Reaction of [MCl(NC₅H₄Se)(PR₃)] with [M₂Cl₂(µ-Cl)₂(PR₃)₂] gave an unusual series of binuclear complexes, [(R₃P)Cl₂M(NC₅H₄Se)MCl(PR₃)] 3, in which NC₅H₄Se acts simultaneously as a Se bridging and Se,N chelating ligand. Reactions of [PtCl₂(cod)] or Na₂[PdCl₄] with NaSeC₅H₄N afforded [{M(NC₅H₄Se)₂}_n]. Similar reactions with [MCl₂(L–L)] and [MCl₂(PPh₃)₂] (L–L = dppm or dppe) gave [M(NC₅H₄Se)₂(L–L)] and [M(NC₅H₄Se)₂(PPh₃)₂], respectively. The latter complex exists in a dynamic equilibrium with [M(NC₅H₄Se)(NC₅H₄Se-N,Se)(PPh₃)₂] and PPh₃. All the complexes were characterized by elemental analyses and NMR (¹H, ³¹P, ⁷⁷Se, ¹⁹⁵Pt) spectral data. The crystal structure of [(Prⁿ₃P)Cl₂Pd(NC₅H₄Se)PdCl(PPrⁿ₃)] revealed that NC₅H₄Se acts as a triply bridging ligand. One of the palladium atoms is co-ordinated to two trans chlorine atoms, one PPrⁿ₃, and a Se atom, while the second is bound to a chelating NC₅H₄Se ligand, a chlorine atom and a PPrⁿ₃ ligand.