Synthesis and Structure of Copper(II) Phosphonodithioite Complexes

Abstract

A series of new complexes of CuBr with phosphonodithioites were prepared and characterized by NMR and IR spectroscopy. As shown by single crystal X-ray diffraction, diethyl tert-butylphosphonodithioite forms with CuBr a tetrameric cubane-like complex with the monodentate coordination of the organophosphorus ligand via the P atom.Our previous studies [137] showed that complexes formed by phosphorothoite with transition metals are more diverse in the structure and coordination mode than complexes formed by other trivalent phosphorus compounds, in particular, phosphines, phosphites, and amides [8313]. This is due to the specific electronic structure of the ligand molecules containing P3S ambident systems [14]. It can be expected that the replacement of one of the SR groups in a phosphorothoite molecule by an alkyl group will alter the donor properties of the P and S atoms and hence the coordination properties of the ligand. A search in the Cambridge Structural Database [15] revealed no data on the crystal structure of phosphorothoite complexes. Copper(I) phosphorothoite complexes, in which the ligand molecule contains a P3C bond along with two P3S bonds, are of interest from the viewpoint of ligand reactivity in the metal coordination sphere. Our previous studies of copper thiophosphite complexes revealed such phenomena as ligand exchange, disproportionation, ligand transformation, and formation of ligands of a new structure in the metal coordination sphere [2,5,16,17].Here we report on the complexation of CuBr with a series of diethyl phosphonodithioites containing ethyl, phenyl, and tert-butyl substituents at the P atom. Thiophosphonites Ia3Ic readily react with CuBr. Complexes IIb and IIc are colorless crystalline substances. According to elemental analysis, the reaction products have 1 : 1 composition. Complexes IIb and IIc are formed in fairly high yields (80 385%).Compound IIb is soluble in the majority of organic solvents. Complex IIc is insoluble in organic solvents, RP(SEt) 2 + CuBr 76 RP(SEt) 2 .CuBr,including DMSO and DMF. Complex IIa was isolated as an oily precipitate; it rapidly darkens, which suggests its instability and possible decomposition. Products of its secondary transformations were not studied.Complexes IIa3IIc were studied by IR spectroscopy (solid samples). According to the IR data, the P3C stretching frequency does not noticeably change upon complexation and remains about 750 cm !1 . At the same time, the P3S bands in the spectra of the complexes become more intense compared to the free ligands and are shifted toward higher frequencies bỹ 20 cm !1 . To compare, in the case of bidentate coordination of triethyl phosphorotrithioite, the shift is toward lower frequencies and is larger in the absolute value (~30 3 40 cm !1 ) [2].In the 31 P NMR spectra, the complexation exerts a weaker effect on the phosphorus chemical shift, compared to the complexation with trialkyl phosphorotrithioites [2,3]. The most significant upfield shift of the P signal upon complexation is observed in IIb: from 112 ...

Synthesis and Some Properties of Transition Metal Complexes Based on the Octathiophophetane Ammonium Salts

“…Because of the disproportionate transformations of ligands ranging from the monodentate type of coordination via the P atom to the bidentate type via P and S atoms in one molecule as well as via S atoms only, different types of structure and coordination modes were found in complexes with Cu(I) halides . Therefore, ammonium salts of cyclic octathiotetraphosphetanes represent such type of novel heterocyclic ligands.…”