Theoretical evidence of d‐orbital aromaticity in anionic metal X (X = Sc, Y, La) clusters

Abstract

The equilibrium geometries, total electronic energies, and vibrational frequencies for singlet, triplet, and quinted states of three all-metal X 3 -(X ϭ Sc, Y, and La) anions and nine relevant neutral singlet MX 3 (M ϭ Li, Na, K, X ϭ Sc, Y, La) clusters are investigated with four density functional theory (DFT) and correlated ab initio methods B3LYP, B3PW91, MP2, and CCSD(T). To our knowledge, the theoretical study on these clusters composed of the transition metal Sc, Y, La is first reported here. The calculated results show that for the X 3 clusters the singlet states with trigonal D 3h structures are the lowest energetically, while the neutral singlet MX 3 clusters each have two stable isomers: one trigonal pyramidal C 3v and one bidentate C 2v structures with the pyramidal C 3v isomer being ground state. In addition, we calculate the resonance energies (RE) and nucleusindependent chemical shift (NICS) for the singlet trigonal X 3 rings and show that these singlet trigonal X 3 rings exhibit higher degree of aromaticity. The detailed molecular orbital (MO) analyses reveal that the singlet trigonal X 3 anions have one delocalized -type and one delocalized -type MOs, which follow the 4n ϩ 2 electron counting rule, respectively and play an important role in rendering these species two-fold aromaticity. Here, an explicit theoretical evidence is given to prove that the contribution to the two-fold aromaticity of the singlet trigonal X 3 -(X ϭ Sc, Y, and La) rings originates primarily from the d-orbital bonding interactions of these component transition metal X atoms.

Calculations of magnetically induced current densities: theory and applications

“…The molecular structure of Ag 4 Na − cluster was suggested to be the same as for Cu 4 Na − , whereas the energetically lowest structure for Au 4 Na − was found to be planar . Current density calculations for and showed that is practically nonaromatic, whereas NICS calculations suggested that it is either σ + π or σ + δ aromatic . is weakly aromatic sustaining a diatropic ring current of 8.2 nA/T at the complete active space self‐consistent field (CASSCF) level of theory .…”

“…287 Current density calculations for Sc practically nonaromatic, 293 whereas NICS calculations suggested that it is either σ + π or σ + δ aromatic. 294,295 Cu + 3 is weakly aromatic sustaining a diatropic ring current of 8.2 nA/T at the complete active space self-consistent field (CASSCF) level of theory. 293 Metal aromaticity in a much broader sense has recently been reviewed.…”

Why is Benzene Unique? Screening Magnetic Properties of C6H6Isomers

“…To verify whether or not magnetic and SEE criteria of aromaticity are connected, many researchers have studied empirical correlations between these criteria. Some studies suggest these criteria are parallel,, some hint to the lack of a correlation,,,,,, and some studies reveal that energetically stable, even a structure corresponding to a global minimum, may sustain paramagnetic ring currents that are considered as a sign of antiaromaticity on the basis of magnetic criterion of aromaticity ,,. Our previous studies in particular suggest that magnetic indices of aromaticity fail in case of all‐metal and metalorganic molecules containing transition metals , where molecules sustain very strong ring currents because of their relatively small HOMO‐LUMO energy gaps ,.…”

Multi‐decker sandwich complexes using Be32− and Mg32− dianions

“…An expected area of extension is to study the possibility of such complexes using other aromatic rings and/or metal ions. Aromaticity (both σ‐ and π‐types) in all metal cluster anions 3–10 like Al 4 2− , Al 4 4− ; M 3 − : M = Al, Ga, Sc, Y, La; M 4 2− : M = Ge, In, Tl, Sb, Bi; Hg 4 6− ; M 5 − : M = Sb, Bi; M 5 6− : M = Ge, Sn, Pb, and their binary complexes and salts 6, 11, e.g., MX 3 : M = Li, Na, K; X = Sc, Y, La; XCl 3 : X = H, Li, Na, K, Cu, etc. has been studied extensively in recent years.…”