Crystal and Molecular Structure of Dinuclear Palladium(II) Complex Containing Nitrogen and Phosphorus Donor Ligands, [Pd2(N3)4(PPh3)2(.MU.-ted)]

Abstract

Triethylenediamine (ted) is a bidentade ligand that can bind to metallic centers through two nitrogen atoms.1 Such coordination behavior is very attractive, since the triethylenediamine can be used as linear building block for constructing sophisticated metallosupramolecular architectures.2 Moreover, in environmental and military applications, ted has been impregnated on various supports in order to adsorb toxic gases, such as HCN, CNCl, SO2 and CH3I, or as a sensor to detect these gases. The pseudohalide azide (NNN -) is known to coordinate to metals in both terminal and bridging modes.Besides, 1,3-dipolar cycloaddition of multiply-bonded molecules (e.g. CS2) to coordinated azide in metal compounds is an effective method for obtaining metal-bonded heterocycles, many of which are otherwise inaccessible. 4 In the medical area, Pd(II) azido compounds have shown remarkable antitumor activity against some human cancer cell lines. 5 Focusing our interest on the coordination and supramolecular chemistry of palladium-based compounds, 6 we describe herein the synthesis and single-crystal X-ray structure of [Pd2(N3)4(PPh3)2(m-ted)] (Fig. 1). To the best of our knowledge, this is the first complex containing the ted ligand coordinated to the palladium(II) center. This compound was prepared by adding ted, PPh3 and NaN3 to an acetone solution of [PdCl2(CH3CN)2] in 1:2:4:2 molar ratio. After 1 h of stirring, the orange suspension formed was filtered off and the mother liquor was left to evaporate, yielding orange single-crystals suitable for X-ray diffraction measurements.The structure of the title compound, C42H42N14P2Pd2, was determined by single-crystal X-ray diffraction. It was solved from 8358 independent reflections [R(int) = 0.0389] and refined by full-matrix least-squares of the non-H atoms to an R1 value of 0.0339 for 7178 reflections with Fo > 4s(Fo). The H-atoms were positioned stereochemically and refined with the riding model. The locations of the methylenic hydrogen atoms were optimized during the refinement by treating them as rigid