Syntheses and crystal structures of "unligated" copper(I) and copper(II) trifluoroacetates

Two extremely unstable copper trifluoroacetates with no exogenous ligands, namely, Cu(O2CCF3) (1) and Cu(O2CCF3)(2) (2), are prepared for the first ti me and obtained in crystalline form by deposition from the vapor phase. The ir structures are determined by X-ray crystallography. The crystallographic parameters are as follows: for 1, monoclinic space group P2(1)/c, with a = 9.7937(6) Angstrom, b = 15.322(1) Angstrom, c = 12.002(1) Angstrom, beta = 106.493(9)degrees, and Z = 4; for 2, orthorhombic space group Peen, with a = 16.911(1) Angstrom, b = 10.5063(9) Angstrom, c = 9.0357(6) Angstrom, and Z = 4. Both structures are unique among other Cu-I and Cu-II carboxylates, as well as among metal carboxylates in general. Compound 1 consists of a p lanar rhombus of four copper atoms with sides of 2.719(1)-2.833(1) Angstrom and trifluoroacetate ligands bridging the pairs of adjacent metal atoms al ternately above and below the plane. The tetrameric units are further aggre gated in a polymeric zigzag ribbon [Cu-4(O2CCF3)(4)](infinity) by virtue of intermolecular Cu . . .O contacts. The structure of 2 is built on cis bis- bridged dimers in which every metal atom is also connected with two copper atoms of the neighboring units. The stacking planes in this extended chain are almost perpendicular to one another. The Cu . . . Cu distance inside th e dimer is 3.086(2) Angstrom, indicating a nonbonding interaction.