Synthesis, Structure, and Reactivity of Monomeric Two-Coordinate Copper(I) Complexes

Article abstract of DOI:10.1021/ja00357a009

The reaction of Cu(CH3CN)4BF4 with a range of imidazoles, pyrazoles, and pyridines yields two-coordinate copper(I) complexes of the form CuL2BF4.Two of those species, ligated by 1-methylpyrazole and 1,3,5-trimethylpyrazole, respectively, has been characterized by X-ray crystallography, and they both show an approximately linear N-Cu-N geometry with Cu-N bond length of 1.87 Angstroem.The bis(1-methylpyrazole) complex apparently forms dimeric units in the solid state with intermolecular distances of ca. 3.1 Angstroem.The unhindered pyrazole and pyridine complexes react with carbon monoxide in solution to form presumed three-coordinated adducts, although the binding of CO is quite weak (P_1/2 > 1 atm).The imidazole and the hindered pyrazole and pyridine complexes are all inert toward reaction with carbon monoxide.A likely explanation for this observation is that steric effects prevent the increase in coordination number for the hindered species, and increased orbital overlap between the imidazole-nitrogen and copper(I) ion stabilizes the two-coordinate form for the imidazole-ligated species.Crystal data for Cu(MePz)2BF4: triclinic, a=9.352(4) Angstroem, b=9.805(4) Angstroem, c=8.164(3) Angstroem, α=96.97(3) deg, β=109.15(3) deg, γ=62.40(3) deg, V=626.3(6) Angstroem³, space group = P<*>, Z=2.Crystal data for Cu(1,3,5-trimethylpyrazole)2BF4: triclinic, a=8.561(5) Angstroem, b=13.065(5) Angstroem, c=7.886(2) Angstroem, α=102.40(3) deg, β=106.08(4)deg, γ=91.14(4) deg, V=824.8(1.3) Angstroem³, space group = P<*>, Z=2.