The mixed ligand P 2 CuN 2 copper() complexes [Cu(PPh 3 ) 2 (MeCN) 2 ]X have been studied by one-and twodimensional 31 P CP MAS NMR spectroscopy for X = PF 6 , BF 4 or ClO 4 and single crystal X-ray diffraction for X = PF 6 and ClO 4 , completing availability of precise structural data for this isomorphous series. The compounds crystallise as discrete cations and anions in space group P2 1 /n with a ≈ 15, b ≈ 27, c ≈ 9 Å, β = 95Њ, Z = 4. The anion is located ca. 6 Å from the copper atom and adjacent to a cleft formed between the acetonitrile ligands and phosphine ligand 2 while the crystallographically independent PPh 3 ligands adopt staggered three-bladed propeller-type conformations of opposite chirality. The geometric symmetry of the P 2 CuN 2 co-ordination sphere is low with Cu᎐P(1) 2.276(4)-2.287(2), Cu᎐P(2) 2.258 J( 31 P᎐ 31 P) 75 Hz. The copper quadrupolar induced distortion of the line spacings is different for the two sites and is postulated to be a consequence of variation in the angle between the Cu᎐P vectors and the z axis of the electric field gradient tensor. The magnitude of the distortion is relatively small and consistent with small copper quadrupolar coupling constants for the compounds and a balanced electronic charge distribution about the copper() site in spite of the low geometric symmetry of the P 2 CuN 2 co-ordination sphere. Bis(triphenylphosphine)copper() compounds with monovalent anions, Cu(PPh 3 ) 2 X, have been shown by single crystal structure determinations to crystallize from polar organic solvents as discrete monomeric [Cu(PPh 3 ) 2 X] or dimeric [{Cu(PPh 3 ) 2 X} 2 ] molecules with X acting as monodentate, bidentate or bridging ligands and the copper site(s) three-or four-co-ordinate, depending on the donor and steric properties of the anion. 1-9 For the weakly co-ordinating anions PF 6 Ϫ , BF 4 Ϫ and ClO 4 Ϫ , however, recrystallization from acetonitrile results instead in the formation of mixed ligand ionic compounds [Cu(PPh 3 ) 2 -(MeCN) 2 ]X in which the anion is displaced from the copper co-ordination sphere by a pair of solvent molecules. 10-13 Single crystal structure determinations for the ClO 4 10 and BF 4 12 compounds show the overall structure of the P 2 CuN 2 copper coordination sphere to be similar and considerably distorted from tetrahedral symmetry. However, line spacing distortions in the solid state 31 P CP MAS NMR spectra of the perchlorate compound 10 arising from perturbation of the spectra by copper quadrupolar interactions 14-18 were found to be unusually small and consistent with a relatively balanced charge distribution about the copper site. In order to improve the quality of the NMR data for these compounds, and because the cation has been shown to be an active catalyst in cyclopropanation reactions, 12 we recorded one-and two-dimensional (COSY) solid state 31 P CP MAS NMR parameters at 9.40 T for all three compounds, together with a determination of the structure of the PF 6 compound, completing the availability of structural data for the series. As part of this work we also redetermined the structure of the ClO 4 compound as the initial structure determination was completed on a crystal of marginal quality. The results of this work form the basis of the present report. † E-Mail: [email protected] Experimental Synthesis The compounds [Cu(PPh 3 ) 2 (MeCN) 2 ]X, for X = PF 6 , BF 4 , ClO 4 , were prepared according to established procedures. 10-13 Dissolution of [Cu(MeCN) 4 ]X (2 mmol) and PPh 3 (4 mmol) in warm acetonitrile (20 ml) followed by slow cooling and partial evaporation of the solvent gave well formed air stable crystals of the desired complex. Melting points: X = PF 6 , 168-172; BF 4 , 171-176; ClO 4 , 182-186 ЊC (decomp.). Crystallography Unique diffractometer data sets were measured at ca. 293 K (2θ-θ scan mode, monochromatic Mo-Kα radiation, λ = 0.710 73 Å) for [Cu(PPh 3 ) 2 (MeCN) 2 ]X, X = PF 6 or ClO 4 . N Independent reflections were obtained, N o with I > 3σ(I) being considered 'observed' and used in the full matrix least squares refinements after absorption correction. Anisotropic thermal parameters were refined for the non-hydrogen atoms; (x, y, z, U iso ) H were included, constrained at estimated values. Conventional residuals at convergence, R, RЈ on |F| are recorded, statistical reflection weights derivative of σ 2 (I) = σ 2 (I diff ) ϩ 0.0004σ 4 (I diff ) being used. Neutral atom complex scattering factors were used, computation with the XTAL 3.2 program system implemented by S. R. Hall. 19 The phenyl rings of the PPh 3 ligands are labelled nm where n is the ligand number 1 or 2 and m is the ring number 1, 2 or 3. Phenyl carbons are labelled C(nml), l = 1-6 where 1 is the ipso-and 2 the ortho-carbon that points towards the P atom. Crystal/refinement data. [Cu(PPh 3 ) 2 (MeCN) 2 ]PF 6 ≡ C 40 H 36 -CuF 6 N 2 P 3 , M = 814.9, monoclinic, space group P2 1 /n, (C 5 2h , no. 14, variant), a = 15.616(3), b = 27.38(1), c = 9.194(7) Å, β
