Pyridine-2-selenolate complexes of palladium(II) and platinum(II): Crystal structure of [(Prⁿ<inf>3</inf>P)Cl<inf>2</inf>Pd(NC<inf>5</inf>H <inf>4</inf>Se)PdCl(PPrⁿ<inf>3</inf>)]

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(μCl)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(PR 3)] 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)(PPh 3)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(NC5H 4Se)-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.