Fourier transform infrared studies of atomic titanium, vanadium, chromium, iron, cobalt, nickel and copper reactions with carbon dioxide in low-temperature matrices

Titanium, vanadium, chromium, iron, cobalt, nickel, and copper metal atoms were cocondensed with CO/sub 2/ in neat matrices at 15 K. Even though a large proportion of atoms do not react, new complexes with CO/sub 2/ are characterized by using FTIR techniques and their infrared absorption bands are assigned. It is clearly shown that CO/sub 2/ is highly bent in these complexes. The behavior of oxophile metals is different from that of other metals which spontaneously form 1:1 complexes with CO/sub 2/. For Ti, V, and Cr, the authors observe first an insertion of metallic atom into a CO bond, leading to the formation of the intermediate (O)M(CO) molecule, followed by the CO/sub 2/ fixation on this complex, to form (O)M(CO)(CO/sub 2/). The other identified products in the matrices are CO, M(O), M(CO)/sub n/, and possibly a few carbonates. Most complexes are thermally unstable and decompose above 60 K. Only Fe and Ni compounds give rise upon annealing above 80 K to CO/sub 2/ reduction to CO along with the simultaneous formation of metal carbonyl complexes. Isotopic experiments with /sup 13/CO/sub 2/ and C/sup 18/O/sub 2/ allow them to conclude that the geometry of complexes is both metal and matrixmore » dependent: in neat CO/sub 2/ matrices, Fe and CO lead to a C coordination, the others being fixed in a side-on and end-on manner.« less