Palladium(II) Complexes of N,N-Co-ordinating Arylazouracil Ligands: Infrared Spectroscopy, Thermal Properties, and X-Ray Crystal Structure of trans-Bis(6-amino-1,3-dimethyl-5-phenylazouracilato)palladium(II)

Article abstract of DOI:10.1039/DT9900002747

Palladium(II) forms the complexes (1) - (4) on reaction of tetrachloropalladate(II) with 6-amino-5-arylazouracil derivatives (uracil=pyrimidine-2,4-dione) in ethanolic media, with the exception of 6-amino-5-(2'-chlorophenylazo)-3-methyluracil (HL⁵) which leads to the complex 5)2Cl2> (5).The crystal structure of the complex bis(6-amino-1,3-dimethyl-5-phenylazouracilato)palladium(II), 12> (1), was determined by X-ray crystallography.The complex crystallizes in the monoclinic system, space group P2¹/c, with a = 7.404(2), b = 9.537(1), c = 17.420(4) Angstroem, β = 99.38(2) deg, Z = 2, and R = 0.043.The sructure consists of discrete 12> molecules (L¹ = 6-amino-1,3-dimethyl-5-phenylazouracilate), in which L¹ acts as a bidentate ligand through the nitrogen atom of the deprotonated amino group and the nitrogen atom of the azo group bonded to the phenyl ring, to give a square-planar PdN4 geometry with palladium(II) at the inversion centre.The entire molecule is planar with the exception of the phenyl rings which are twisted by 84.4(2) deg about the C-N bond away from the co-ordination plane in order to overcome interligand steric crowding.On the basis of i.r. and thermal data a trans-square-planar structure is proposed for (5), the ligand being co-ordinated through the nitrogen atom of the 6-amino group.In the temperature range 230-320 deg C this complex eliminates two molecules of HCl to give 52> (6).The solid-state parameters and mechanism for this reaction were determined.

Full text of DOI:10.1039/DT9900002747

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