Local structure of [Cu I (CO)2 ] 1 adducts hosted inside ZSM-5 zeolite probed by EXAFS, XANES and IR spectroscopies

EXAFS spectroscopy, analysed in the frame of the multiple scattering theory, has been able to determine the local structure of [Cu(CO)2 ] 1 complexes hosted inside ZSM-5 channels upon contacting the activated zeolite with CO from the gas phase at room temperature. We found that the number of coordinated CO molecules (1.8 0.3) is in good agreement with the [Cu(CO)2 ] 1 stoichiometry suggested by IR. The Cu-C distance obtained for the [Cu(CO)2] 1 complex is 1.880.02 A ? , with a C-O distance (1.12 0.03 A ? ). This work complements a previous one [C. Lamberti, G. Turnes Palomino, S. Bordiga, G. Berlier, F. D'Acapito and A. Zecchina,Angew. Chem. Int. Ed., 2000, 39, 2138], performed at liquid nitrogen temperature, where the structure of [Cu(CO)3] 1 complexes was identified by combined EXAFS/XANES/IR spectroscopies. An increase of the Cu-C distance of 0.05 A ? by moving from [Cu(CO)2] 1 to [Cu(CO)3] 1 complexes has been observed, which is the local rearrangement needed to accommodate a third CO ligand in the first coordination shell of copper. EXAFS determined that the Cu-C-O bond angle is linear within the error bars (170101), while IR and XANES indicate that intrazeolitic [Cu(CO)2]complexes haveC2vsymmetry. The experimentally obtained moieties are in good agreement with the values obtained with advanced quantum mechanical methods.