New bonding modes of carbon and heavier group 14 atoms Si–Pb

Abstract

Recent theoretical studies are reviewed which show that the naked group 14 atoms E = C-Pb in the singlet (1)D state behave as bidentate Lewis acids that strongly bind two σ donor ligands L in the donor-acceptor complexes L→E←L. Tetrylones EL2 are divalent E(0) compounds which possess two lone pairs at E. The unique electronic structure of tetrylones (carbones, silylones, germylones, stannylones, plumbylones) clearly distinguishes them from tetrylenes ER2 (carbenes, silylenes, germylenes, stannylenes, plumbylenes) which have electron-sharing bonds R-E-R and only one lone pair at atom E. The different electronic structures of tetrylones and tetrylenes are revealed by charge- and energy decomposition analyses and they become obvious experimentally by a distinctively different chemical reactivity. The unusual structures and chemical behaviour of tetrylones EL2 can be understood in terms of the donor-acceptor interactions L→E←L. Tetrylones are potential donor ligands in main group compounds and transition metal complexes which are experimentally not yet known. The review also introduces theoretical studies of transition metal complexes [TM]-E which carry naked tetrele atoms E = C-Sn as ligands. The bonding analyses suggest that the group-14 atoms bind in the (3)P reference state to the transition metal in a combination of σ and π∥ electron-sharing bonds TM-E and π⊥ backdonation TM→E. The unique bonding situation of the tetrele complexes [TM]-E makes them suitable ligands in adducts with Lewis acids. Theoretical studies of [TM]-E→W(CO)5 predict that such species may becomes synthesized.

A monotopic aluminum telluride with an Al=Te double bond stabilized by N-heterocyclic carbenes

“…2) with a three-coordinate aluminum centre. The formation of 4 from 3 is a barrierless process that is usual for NHC-coordinated main group element structures32 and underlines the donor–acceptor-bonding mode33 in NHC–Al bonds. The dissociated pair of complex 4 and free L Et is only 15.0 kcal mol −1 higher in Gibbs free energy than its precursor 3 , while a comparably low energy gain of 2.9 kcal mol −1 is obtained in the overall process of forming the dimer 5 and free L Et from 3 (Supplementary Fig.…”

Advances in Phosphasilene Chemistry

“…According to DFT calculations (B3LYP/6–311 g(d) level of theory), the stability of symmetric 1,3‐diphospha‐2‐silaallenes VII (R=H, SiH 3 , CH 3 , Ph, F) largely depends on the nature of the substituents at the phosphorus atoms. The molecules display bent structures with the P‐Si‐P bond angles ranging from 168.87° (Si−P distance 2.060 Å) for R=H to 135.46° (Si−P distance 2.12 Å) for R=F), suggesting a possible contribution of a silylone structure (RP→Si←PR) into the ground state of the molecule. Compared to other possible structural isomers, including phosphasilynes R 2 PSi≡P, allenes VII represent only a local minimum structure, whereas the markedly most stable structure is the siladiphosphirene VIII (Figure ) …”

Dative and electron‐sharing bonding in transition metal compounds

“…The term may be identified with a particular type of bond by visual inspection of the shape of the deformation density Δ ρ k . The shapes of the deformation densities provide a visualization of the associated pairwise orbital interactions, which has been found very useful for the analysis of a variety of chemical bonds …”