Titanium Insertion into CO Bonds in Anionic Ti–CO₂ Complexes

Abstract

We explore the structures of [Ti(CO) ] cluster anions using infrared photodissociation spectroscopy and quantum chemistry calculations. The existence of spectral signatures of metal carbonyl CO stretching modes shows that insertion of titanium atoms into C-O bonds represents an important reaction during the formation of these clusters. In addition to carbonyl groups, the infrared spectra show that the titanium center is coordinated to oxalato, carbonato, and oxo ligands, which form along with the metal carbonyls. The presence of a metal oxalato ligand promotes C-O bond insertion in these systems. These results highlight the affinity of titanium for C-O bond insertion processes.

Infrared Multiple Photon Dissociation Spectroscopy of Hydrated Cobalt Anions Doped with Carbon Dioxide CoCO2(H2O)n−, n=1–10, in the C−O Stretch Region

“…Cobalt carbonyl cations Co(CO) n + ( n= 1–9) were investigated in an Ar tagging experiment by the group of Duncan, finding one strong absorption for n= 1 at 2156 cm −1 . Cationic metal–CO 2 complexes M + (CO 2 ) n (M=Mg, Al, Si, V, Fe, Co, Ni, Rh, Ir) have been extensively investigated in the past decades, and also anionic species M − (CO 2 ) n (M=Ti, Mn, Fe, Co, Ni, Cu, Ag, Au, Sn, Bi) have received considerable attention, foremost by the group of Weber . Generally, the anionic CO 2 − stretching vibrations shift to the red compared to neutral CO 2 vibrations .…”

“…[105,106] In ar ecent study by Weber on [Ti(CO 2 ) n ] À ,i nw hich titanium insertsi nto aC =Ob ond, as mall band observed at 2056 cm À1 was assigned to oxalato ligands, which can be ruled out here. [51] DFT calculations predict very similar structures compared to the case of one water molecule.T he most stable isomer IIa has a( H 2 O)(OH)Co(HCO 2 ) À structure, that is, CO 2 and one H 2 Oa re activated. Isomer IIb with an inserted metal in the C=Ob ond and an activated H 2 Oi sl ess stable by only 31 kJ mol À1 .F urther isomerslie at least % 70 kJ mol À1 higher in energy.…”

“…This band might arise due to the symmetric C−O stretching mode of an HCO 2 − ligand, which lies at 1314 cm −1 in HCOO − (Ar) . In a recent study by Weber on [Ti(CO 2 ) n ] − , in which titanium inserts into a C=O bond, a small band observed at 2056 cm −1 was assigned to oxalato ligands, which can be ruled out here …”

“…Further CO 2 molecules surround this core . A very interesting study on cooperative effects which are operative during metal insertion into the C=O bond of CO 2 has been performed recently by the group of Weber with Ti − (CO 2 ) n . Insertion of neutral Ti into the C=O bond of CO 2 had been predicted by quantum chemical calculations …”

“…[29] Cationic metal-CO 2 complexes M + (CO 2 ) n (M = Mg, Al, Si, V, Fe, Co, Ni, Rh, Ir) have been exten-sively investigatedi nt he past decades, [30][31][32][33][34][35][36][37][38][39][40] and also anionic speciesM À (CO 2 ) n (M = Ti,M n, Fe, Co, Ni, Cu, Ag, Au, Sn, Bi) have received considerable attention,f oremost by the group of Weber. [41][42][43][44][45][46][47][48][49][50][51] Generally,t he anionic CO 2 À stretching vibrations shift to the red compared to neutral CO 2 vibrations. [4,52] CO 2 as al igand was also investigated as metal oxides, NbO 2 + (CO 2 ) n and Ta O 2 + (CO 2 ) n by Mackenzie and co-workers.…”