title: Infrared spectra of M-η2-C2H2, HM-C≡CH, and HM-C≡CH- prepared in reactions of laser-ablated group 3 metal atoms with acetylene.
abstract: The major HM-C≡CH and M-η(2)-C(2)H(2) products are observed in the matrix infrared spectra from reactions of laser-ablated group 3 metal atoms with acetylene, while the vinylidene product is not detected. These results reveal that coordination of group 3 metal atoms to the acetylene π-bond and H-migration from C to M readily occur during codeposition and photolysis afterward. The product absorption assigned to the La-vinylidene complex in a previous study is reassigned to one of the absorptions of La-η(2)-C(2)H(2)···C(2)H(2). Two strong Sc-H stretching absorptions are assigned to the free HSc-CCH(-) anion, in accord with a previous study, but a lower frequency counterpart is reassigned to HSc-CCH(-) coordinated to acetylene based on the increasing relative intensity of the low-frequency component at higher acetylene concentration. The group 3 metals evidently form weaker π-complexes than the group 4 metals. The addition of an electron to HM-CCH elongates the M-H and M-C bonds in the anionic species due to the lower ionic contributions to the bonding.
authors.affiliation: Department of Chemistry, University of Incheon, Yeonsu-gu, Incheon 406-772, South Korea. hgc@incheon.ac.kr
authors.forename: Han-Gook
authors.initials: HG
authors.lastname: Cho
authors.forename: Lester
authors.initials: L
authors.lastname: Andrews