M←NCCH₃, M-η²-(NC)–CH₃, and CN–M–CH₃ Prepared by Reactions of Ce, Sm, Eu, and Lu Atoms with Acetonitrile: Matrix Infrared Spectra and Theoretical Calculations

Abstract

The reactions of laser-ablated Ce, Sm, Eu, and Lu atoms with acetonitrile were studied by matrix infrared spectra in a neon matrix, and M← NCCH 3 , M-η 2 -(NC)−CH 3 , and CN−M−CH 3 were identified with isotopic substitution and quantum chemical calculations. The major product is the insertion complex (CN−M−CH 3 ), while the end-on and side-on complexes (M←NCCH 3 and M-η 2 -(NC)−CH 3 ) are also trapped in the matrix. The CCN antisymmetric stretching mode for Ce-η 2 -(NC)−CH 3 was observed at 1536.9 cm −1 , which is much lower than the same modes observed for other lanthanides. NBO analysis reveals that Ce exhibits a remarkable 4f-orbital contribution in bonding to N and to C, reconfirming an active 4f-orbital contribution of cerium in bonding in the side-on complex, while the 4f contributions of Sm and Eu to the M−N and M−C bonds are much lower and the 4f orbital of Lu is not involved in bonding.

Beryllium Dimer Reactions with Acetonitrile: Formation of Strong Be−Be Bonds

“…The bands at 1082.3, 1020.8 and 1068.7 cm −1 for 12 C, D and 13 C isotopes are in good agreement with the calculated results of N−Be stretching mode at 1106.0 ( 12 C), 1043.4 (D) and 1091.5 cm −1 ( 13 C), respectively. The absorption observed at 831.4 cm −1 with a 13 C isotopic substitution at 811.6 cm −1 lays in the region expected for a C−C stretching vibration, [ 37 ] and the large 12 C/ 13 C ratio of 1.0244 was obtained to verify our assignment. The corresponding D isotopic absorption was covered by the precursor bands.…”

“…The optimized structures of diberyllium and mono beryllium end-on and insertion complexes are shown in Figure 3 , with the end-on products in C s symmetry and the insertion complexes possessing C 3v symmetry. The point groups of beryllium products happen to be reverse with the C 3v point groups of N-coordination transition-metal complexes and C s structures of transition-metal insertion complexes (except for Mn products) [ 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 ]. According to the NBO analysis in Table S8 , the electropositive beryllium forms sp hybrid orbitals, which make σ bonds with sp hybrid orbitals on the C atoms in the insertion complexes.…”

“…Acetonitrile is known as an effective electron donor based on the previous research of reactions with metal atoms [ 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 ], and it could be a good candidate for stabilizing the Be 2 dimer. In this paper, we investigated the reactions of beryllium atoms with acetonitrile by means of matrix-isolation infrared spectroscopy and theoretical calculations, in order to further supplement the reactions of alkali metal with acetonitrile, and search for stable diberyllium complexes that might be formed.…”

Probing the Chemical Bond between Lanthanides and Carbon: CeC, PrC, NdC, LuC, and TmC2

“…In a study of La-based endohedral metallofullerenes (EMFs), the La 4f-orbitals are found to play a critical role in the chemical reactivity and structure of the EMFs, with the La 4f-orbitals becoming more important as the size of the carbon cage is reduced . Reactions between Ce and acetonitrile studied by matrix infrared spectroscopy in neon matrices and density functional theory calculations reveal that the 4f-orbitals of Ce become active and participate in the bonding between Ce and C and N in Ce-η 2 -(NC)–CH 3 π-complexes . In addition to the brief overview of the literature above, there is a plethora of other recent examples where 4f-orbitals have been found to play an important role in lanthanide-containing compounds. − It is of current interest to add to this developing field by probing small Ln containing molecules, like the diatomic lanthanide carbides, to further investigate the contributions of the 4f orbitals to the chemical bond.…”