Synthesis and structural study of neutral mononuclear and anionic binuclear 2,4,6-trifluorophenyl derivatives of palladium(II). Crystal structure of [P(CH2Ph)Ph3]2[(C6F3H2)2Pd(µ-SCN)(µ-NCS)Pd(C6F3H2)2]
Abstract
Arylation of K2[PdCl4] with Mg(C6F3H2)Br in tetrahydrofuran–dioxane and subsequent addition of either benzonitrile or dibenzylideneacetone (dba) in diethyl ether leads to the formation of labile complexes [Pd(C6F3H2)2(PhCN)2] or [Pd(C6F3H2)2(dba)] respectively. A number of [Pd(C6F3H2)2L2]- type complexes [L = PEt3, AsPh3, P(OMe)3, P(OEt)3, P(OPh)3, L2= cyclo-octa-1,5-diene or NNN′N′-tetramethylethylenediamine] have been prepared by addition of the corresponding neutral ligand to chloroform solutions of [Pd(C6F3H2)2(PhCN)2]. Proton, 19F, and 31P n.m.r. data for all the square-planar palladium(II) complexes have been collected and 31P-{1H} spectra show that they are the cis isomers. The complex [Pd(C6F3H2)2(PhCN)2] reacts with NMe4Cl to give [NMe4]2[Pd2(C6F3H2)4(µ-Cl)2] and treatment of this with the appropriate alkali-metal salt (KBr, NaI, or KSCN) leads to [NMe4]2[Pd2(C6F3H2)4(µ-X)2](X = Br, I, or SCN). The behaviour of the binuclear anions in the solvents acetone and dimethyl sulphoxide has been studied by 19F n.m.r. spectroscopy. The crystal structure of [P(CH2Ph)Ph3]2[(C6F3H2)2Pd(µ-SCN)-(µ-NCS)Pd(C6F3H2)2] has been solved and refined to R= 0.040 based on 3 384 observed reflections, confirming the existence of centrosymmetric binuclear anions where the Pd atoms have square-planar co-ordination [Pd-C 2.02(1) and 1.99(1), Pd–S 2.387(5), and Pd–N 2.07(1)Å].
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