trans-Chlorido[6-chloro-4-(4-methoxy-benz-yl)-3-oxo-3,4-dihydro-pyrazin-2-yl]-bis-(triphenyl-phosphine)palladium(II).

The title compound, [Pd(C(12)H(10)ClN(2)O(2))Cl(C(18)H(15)P)(2)], is the inter-mediate of the reduction of a 3,5-dichloro-pyrazinone [Loosen, Tutonda, Khorasani, Compernolle & Hoornaert (1991 ▶). Tetra-hedron, 47, 9259-9268]. This species is formed by oxidative addition of coordinatively unsaturated Pd(0) to the reactive 3-position of the heterocycle. The coordination around the Pd atom is square planar, with two trans PPh(3) ligands. π-π inter-actions are observed between the centroid of the pyrazinone ring and planes of two adjacent phenyl rings, one from each PPh(3) group (3.25 and 3.078 Å), stabilizing the inter-mediate structure. This could explain the reduced reactivity towards substitution of the Cl atom by the formate anion, resulting in poor yield of the reduced compound. 3-Substituted pyrazinones are important precursors in the synthesis of 5-amino-piperidinone-2-carboxyl-ate (APC) systems.