Mixed Copper/Iron Clusters. The Preparation and Stuctures of 2Fe(CO)4 and 2Cu6Fe4(CO)16

Article abstract of DOI:10.1021/ja00312a019

Depending on the nature of the ligands and the reaction conditions, phosphine substituted copper(I) halides (L_nCuX) can react with Fe(CO)4(2-) to form either trinuclear Cu2Fe derivatives or the novel 10-atom Cu6Fe4(CO)16(2-) cluster anion. <(C6H5)3P>2CuCl and Fe(CO)4(2-) react to form <<(C6H5)3P>2Cu>2Fe(CO)4, the stucture of which was determined by X-ray methods.Crystals were monoclinic, space group P2₁/c with z = 4 in a unit cell with dimensions a = 10.723(3) Angstroem, b = 39.960(14) Angstoem, c = 15.283(6) Angstroem, and β = 99.31(3) deg.The structure was solved by direct methods and refined by full-matrix least squares to R = 0.105, R_w = 0.094 for 2141 observed reflections.The structure consists of two <(C6H5)3P>2Cu groups bridging opposite edges of a flattened Fe(CO)4 tetrahedron resulting in a nearly linear Cu-Fe-Cu angle.All four carbonyl groups show a semibridging interaction with the copper atoms.The reaction of (diphos)CuCl (diphos = 1,2-bis(diphenylphosphino)ethane) and Fe(CO)4(2-) results in the formation of the ionic complex <(diphos)2Cu>2Cu6Fe4(CO)16; its structure was also determined by X-ray methods.The complex crystallizes in the trigonal space group P3 with a = 28.495(7) Angstroem, c = 12.471(2) Angstroem, and z = 3.The metal atoms were located by direct methods and the remaining non-hydrogen atoms were located from a series of difference Fourier syntheses.Refinement of carbon atoms with isotropic and other non-hydrogen atoms with anisotropic temperature factors led to values of R = 0.055 and R_w = 0.047 for 5722 observed reflections.In the cation 4 phosphorus atoms are bound to the copper in a distorted tetrahedral arrangement.The anion consists of an octahedron of copper atoms capped on four faces by Fe(CO)4 groups forming a ν₂-tetrahedron.Three carbonyl groups on each iron show some semibridging interaction with the copper atoms.