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.
Highlights
This review summarizes recent theoretical work which deals with molecules where novel types of chemical bonds of group 14 atoms C–Pb in main group compounds and transition metal complexes were found
This was recognized in a comment article by Bertrand entitled ‘‘Rethinking carbon’’ where the author expressed his belief that the new concept may lead to ‘‘new chemistry and applications for carbon, the basic element for all known life.’’33 Very recently, another set of carbones has been investigated with quantum chemical methods which show that there are new examples of the class of compounds that may become synthesized, but that molecules which have been isolated in the past were not recognized as carbones
The results strongly suggest that the Scheme 3 Overview of the calculated two-coordinated compounds 11E–15E which were studied by Takagi et al.[50]
Summary
This review summarizes recent theoretical work which deals with molecules where novel types of chemical bonds of group 14 atoms C–Pb in main group compounds and transition metal complexes were found. The electronic reference state of carbon in CL2 is the excited 1D singlet state with the electron configuration 1s22s22px02py02pz[2] which is 29.1 kcal molÀ1 higher in energy than the 3P ground state (Fig. 1).[10] The donation from the lone-pair electrons of the ligands takes place from the in-phase (+,+) combination of the donor orbitals into the vacant 2px orbital (s symmetry) and Gernot Frenking studied chemistry at the universities. It was concluded that carbodiphosphoranes C(PR3)[2] are double electron pair donors having s- and p-carbon lone-pair orbitals.[18] The latter finding was elaborated in the 2006 theoretical study where the twofold donor strength of carbodiphosphoranes C(PR3)[2] with different substituents R with respect to H+ and the Lewis acids BH3, BCl3 and AlCl3 was estimated and analyzed using ab initio and DFT methods.[16] The calculations showed that carbodiphosphoranes have a very large first proton affinity (PA) which classifies them as very strong bases.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
