Crystal structures and vibrational and solid-state (CPMAS) NMR spectroscopic studies in the tris(triphenylphosphine)-copper(I) and -silver(I) formatesystems

The complexes [Cu(PPh3)(3)O2CH]. HCO2H (1), [Cu(PPh3)(3)O2CH]. 0.5EtOH (2), [Ag(PPh3)(3)O2CH]. HCO2H (3) and [Ag(PPh3)(3)O2CH] (4) have been prepared and studied by infrared and solid-state C-13 and P-31 cross-polarization ma gic-angle-spinning (CPMAS) NMR spectroscopy. Crystal structures of 1, 2 and 3 show increasing degrees of disorder, but all are shown to contain [M(PPh 3)(3)O2CH] molecular units containing a four-coordinate metal centre with t he three crystallographically independent PPh3 ligands occupying three of t he coordination sites and the formate anion coordinated through one oxygen atom to the fourth site. The formic acid molecule in [Cu(PPh3)(3)O2CH]. HCO 2H is hydrogen-bonded to the formate ion (O ... O = 2.529(5) Angstrom) to f orm an assembly that is best described as a biformate anion [H(HCO2)(2)](-) . Unlike the corresponding silver(I) complex, [Cu(PPh3)(3)O2CH] is not stab le in its unsolvated form; the loss of the solvent of crystallization resul ts in conversion of the complex to [Cu(PPh3)(2)O2CH] and PPh3. Bands in the IR spectra due to the formate and formic acid groups are assigned, and the se are consistent with the silver complexes having structures analogous to those of the corresponding copper complexes. The C-13 CPMAS NMR spectra cle arly resolve resonances from the formate and formic acid carbon atoms, whil e the P-31 CPMAS NMR spectra exhibit complex, partially resolved multiplets arising from inequivalence of the phosphine ligands and the presence of (1 )J(M,P-31) and (2)J(P-31,P-31) scalar (or spin-spin) coupling. These spectr a were interpreted with the aid of the 2D P-31 CPCOSY technique.