Observation of alkaline earth complexes M(CO) ₈ (M = Ca, Sr, or Ba) that mimic transition metals

Abstract

The alkaline earth metals calcium (Ca), strontium (Sr), and barium (Ba) typically engage in chemical bonding as classical main-group elements through their s andp valence orbitals, where is the principal quantum number. Here we report the isolation and spectroscopic characterization of eight-coordinate carbonyl complexes M(CO) (where M = Ca, Sr, or Ba) in a low-temperature neon matrix. Analysis of the electronic structure of these cubic -symmetric complexes reveals that the metal-carbon monoxide (CO) bonds arise mainly from [M(d)] → (CO) π backdonation, which explains the strong observed red shift of the C-O stretching frequencies. The corresponding radical cation complexes were also prepared in gas phase and characterized by mass-selected infrared photodissociation spectroscopy, confirming adherence to the 18-electron rule more conventionally associated with transition metal chemistry.

Electronic and geometric structure analysis of neutral and anionic metal nitric chalcogens: The case of MNX series (M=Li, Na, Be and X=O, S, Se, Te)

“…The geometric and electronic features of the main group metal‐NO species are less studied in the literature. However, recently main group metal‐ligand systems have become more and more popular because of their versatile chemical bonding patterns . Specifically, Andrews et al studied linear LiNO, linear LiON, and side‐bonded Li[NO] species under density functional theory (DFT) .…”

Face‐Centered‐Cubic Ag Nanoclusters: Origins and Consequences of the High Structural Regularity Elucidated by Density Functional Theory Calculations

“…EDA‐NOCV analyses were then undertaken to model in detail the interactions between the Ag 6 core and the AgS 3 P motifs. In this set of EDA‐NOCV analyses, the modeling of Ag 14 was separated into two parts: One AgS 3 P motif and the remaining Ag 13 S 9 P 7 .…”

Valence‐Shell Electron‐Pair Repulsion Theory Revisited: An Explanation for Core Polarization

“…Less symmetrical valence-shell geometriesw ere also evaluated. In particular, we considered trigonal-bipyramidal and triangular molecules, both with D 3h symmetry.F or the trigonal bipyramids, we analyzed AX 5 (Z) stoichiometries (with A = Si, P, and S for the 3 rd row,A= Ge, As, and Se for the 4 th row,a nd A = Sn, Sb, and Te for the 5 th row,X= H, F, and Cl,a nd the pertinent charges, as shown in Ta bleS7i nt he SupportingI nformation). Noteworthy,t he ELF maximai nt he outer core of the 3 rd row atoms have the shape of an inverted triangle( see Figure4a for PH 5 ).…”

“…Specifically, it allows molecular geometries to be predicted in terms of the repulsion between electron pairs . This theory has proven to work well for main‐group‐based systems, with only some exceptions, especially for complexes bearing a d 0 central atom . Hence, it constitutes, in conjunction with other models, such as Lewis structures and electronegativity, a basic pillar of “chemical intuition” and structural analysis in chemistry …”

“…[3] This theory hasp rovent o work well form ain-group-baseds ystems, [4] with only some exceptions,e specially for complexes bearing ad 0 central atom. [5,6] Hence,i tc onstitutes, in conjunction with other models, such as Lewis structuresa nd electronegativity,abasic pillar of "chemical intuition" and structural analysis in chemistry. [7,8] When developing the concepts behind VSEPR, the repulsion betweenelectron pairs was used to explain the organization of the valence ligandsa nd lone pairs.…”