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RESEARCH PRODUCT

Structural studies on 2-pyridyl complexes of the platinum triad metals. The crystal and molecular structure of the 2-pyridylium derivative trans-[PdCl(C5H5NC2)(PMe2Ph)2]ClO4

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Abstract In solution, the complex trans -[PdCl(C 5 H 4 N C 2 )(PMe 2 Ph) 2 ] ( 1 ) is in equilibrium with a small amount of the binuclear species [{PdCl(μ-C 5 H 4 N C 2 , N )(PMe 2 Ph)} 2 ] ( 2 ), which can be isolated upon recrystallization. The compound 1 is easily N-protonated by HClO 4 to the 2-pyridylium product trans -[PdCl(C 5 H 5 N C 2 )(PMe 2 Ph) 2 ]ClO 4 ( 3 ), which crystallizes in the orthorhombic space group P2 1 2 1 2 1 , with cell parameters a =15.761(3), b =14.369(2), c =11.132(2) A and Z =4. The X-ray crystal structure analysis of 3 , using 3744 observed reflections in the refinement and resulting in a final R value of 0.0298, shows that the coordination around palladium is essentially square-planar with PdC=1.970(5), PdCl=2.368(2), PdP(1)=2.317(1) and PdP(2)=2.318(1) A. The planar pyridine ring is perpendicular to the coordination plane, and the NH group is involved in hydrogen bonding with an oxygen of the perchlorate anion, at a contact distance of 2.08(6) A. Extensive hydrogen bonding occurs also in dichloromethane solution and accounts for the hindered rotation of the 2-pyridylium ligand around the PdC 2 bond.