Solid-State ³¹P N.M.R. and Crystal Structure of Binuclear Di-μ-chloro-bis[(4-methylpyridine)(triphenyl-phosphine)copper(I)]

Abstract

The 1 : 1 : 1 adduct of 4-methylpyridine (MeC₅H₄N), triphenylphosphine and copper(I) chloride has been synthesized, and characterized by solid-state ³¹P CP-MAS n.m.r. and a single-crystal X-ray structure determination. The structure determination reveals the presence of two crystallographically independent but pseudo-symmetrically related [(PPh₃)(MeC₅H₄N) CuCl ]₂ molecules in the unit cell, with the [(MeC₅H₄N) CuCl ]₂ core and PPh₃ ligands adopting different dispositions in each dimer. Crystals of the compound are triclinic, with space group Pī , a 16.884(5), b 14.898(4), c 9.501(3)Ǻ , α 104.28(2), β 89.95(2), γ 111.25(2)°. This structure refined to a final residual of 0.041 for 3022 'observed' [I> 3σ(I)] reflections. Cu- P,Cl,Cl,N are 2.196(2), 2.395(2), 2.402(3), 2.061(5)Ǻ for molecule 1 and 2.197(2), 2.420(2), 2.386(3), 2.061(5)Ǻ for molecule 2. The n.m.r. data show quartets arising from two crystallographically independent phosphorus atoms coupled to copper(I) atoms. The chemical shift difference between the quartets is 2.5 ppm. Line spacings of 1.546-1.746 kHz are indicative of [PPh₃Cu]⁺ with the copper atoms in a tetrahedral environment. n.m.r. data have been recorded also for the analogous dimeric systems, [(PPh₃)(RC₅H₄N) CuCl ]₂ (R = H, 4-CN). Comparison of the n.m.r. data is made with analogous data for other compounds containing the [(PPh₃)Cu]⁺ molecular fragment.