A Systematic Investigation of Coinage Metal Carbonyl Complexes Stabilized by Fluorinated Alkoxy Aluminates

The reaction of Cu-I, Ag-I, and Au-I salts with carbon monoxide in the presence of weakly coordinating anions led to known and structurally unknown non-classical coinage metal carbonyl complexes [M(CO)(n)][A] (A=fluorinated alkoxy aluminates). The coinage metal carbonyl complexes [Cu(CO)(n)(CH2Cl2)(m)](+)[A](-) (n=1, 3; m=4-n), [Au-2(CO)(2)Cl](+)[A](-), [(OC)(n)M(A)] (M=Cu: n=2; Ag: n=1, 2) as well as [(OC)(3)CuClAl(ORF)(3)] and [(OC)AuClAl(ORF)(3)] were analyzed with X-ray diffraction and partially IR and Raman spectroscopy. In addition to these structures, crystallographic and spectroscopic evidence for the existence of the tetracarbonyl complex [Cu(CO)(4)](+)[Al(ORF)(4)](-) (R-F=C(CF3)(3)) is presented; its formation was analyzed with the help of theoretical investigations and Born-Fajans-Haber cycles. We discuss the limits of structure determinations by routine X-ray diffraction methods with respect to the CO bond lengths and apply the experimental CO stretching frequencies for the prediction of bond lengths within the carbonyl ligand based on a correlation with calculated data. Moreover, we provide a simple explanation for the reported, partly confusing and scattered CO stretching frequencies of [Cu-I(CO)(n)] units.