Synthesis of [Cu(dcmpz)]n and its reactions with carbon monoxide and cyclohexyl isocyanide. Crystal structures of [Cu2(dcmpz)2(py)2(CO)] and [Cu(dcmpz)(RNC)]2 (Hdcmpz = 3,5-dicarbomethoxypyrazole, R = cyclohexyl)

The reaction of [Cu(CH3CN)4](BF4) with 3,5-dicarbomethoxypyrazole (Hdcmpz) in the presence of triethylamine yields the new copper(I) complex [Cu(dcmpz)]n (1) quantitatively. This method of synthesis appears to be a particularly useful general synthetic route leading to copper(I) pyrazolates. Reaction of 1 with stoichiometric amounts of cyclohexyl isocyanide (RNC) in diethyl ether affords the dimeric complex [Cu(dcmpz)(RNC)]2 (2). Carbonylation of 1 in pyridine leads to the isolation of the dinuclear copper(I) derivative [Cu2(dcmpz)2(py)2(CO)] (3), which represents an unprecedented dinuclear copper(I) complex containing only one terminal carbonyl ligand per two copper atoms. For both complexes 2 and 3 an X-ray crystal structure analysis has been performed. Crystals of 2 are triclinic, space group P1 (No. 2), with a = 11.243 (3) Å, b = 11.188 (2) Å, c = 12.946 (3) Å, α = 90.75 (1)°, β = 100.17 (2)°, γ = 89.10 (2)°, and Z = 2. Final R = 0.030 for 4255 reflections having I > 3σ(I). Crystals of 3 are triclinic, space group P1 (No. 2), with a = 8.423 (6) Å, b = 9.462 (5) Å, r = 20.311 (8) Å, α = 77.42 (3)°, β = 88.97 (3)°, γ = 64.83 (3)°, and Z = 2. Final R = 0.043 for 2190 reflections having I > 3σ(I).