Synthesis and crystal structures of novel one-dimensional polymers, [{M(bpen)X}∞][M = CuI, X = PF6–; M = AgI, X = ClO4–; bpen =trans-1,2-bis(2-pyridyl)ethylene] and [{Cu(bpen)(CO)(CH3CN)(PF6)}∞]

Abstract

The new polymeric compounds [{M(bpen)X}_∞][M = Cu^I, X = PF₆^–, 1; M = Ag^I, X = ClO₄^–, 2; bpen =trans-1,2-bis(2-pyridyl)ethylene] and [{Cu(bpen)(CO)(CH₃CN)(PF₆)}_∞]3 have been synthesised and their structures determined by X-ray crystallography: 1, monoclinic, space group P2₁/n, a= 13.653(8), b= 9.288(3), c= 11.232(3)Å, β= 96.89(3)° and Z= 4; 2, triclinic, space group P, a= 7.569(1), b= 13.253(5), c= 6.757(1)Å, α= 92.24(3), β= 104.05(1), γ= 78.41(3)° and Z= 2; 3, triclinic, space group P, a= 9.882(8), b= 12.126(9), c= 8.173(8)Å, α= 93.33(9), β= 102.10(9), γ= 106.90(7)° and Z= 2. The complexes show an infinite-chain structure of macrocations with non-interacting PF₆^– or ClO₄^– anions. Compounds 1 and 2 are unique polymers having a linear co-ordination geometry, characteristic of d¹⁰ metals. They differ in the mode of polymerization, being of rectangular and triangular wave chain types, respectively. A non-coplanar structure between the pyridyl and olefinic groups of the co-ordinated bpen is recognized, indicative of the importance of intermolecular interaction in crystal packing. Compound 3 has a tetrahedral form of copper(I) as a repeating unit, involving a single CO molecule, which exhibits a short CO distance [1.104(6)Å] irrespective of the normal ν(CO) value (2088 cm^–1). Proton NMR spectra of the copper(I)–bpen systems demonstrate that the solution species has a dimeric structure having two bridging bpen, where the olefinic moiety is co-ordinated to copper(I), dissimilar to the co-ordination mode of 1. A difference in chemical shifts between the PF₆^– and ClO₄^– salts is observed, indicative of the interaction of ClO₄^– with copper(I). The polymeric complex is predominantly obtained from the PF₆^– salt. The formation and the structure of CO or C₂H₄ adducts in solution have also been examined by ¹H NMR spectroscopy.