Silicon Compounds with Inverted Geometry around Silicon Atoms

Abstract

In the last decade, several stable silicon compounds with nonclassical inverted geometry around silicon atoms have been synthesized. Their unusual structures, bonding, and reactivity have been investigated extensively by X-ray analysis, spectroscopy, and theoretical calculations. In this highlight review, recent progress on chemistry of silicon compounds with inverted geometry around silicon atoms is summarized.

Site-selective functionalization of Si6R6siliconoids

“…Partially substituted neutral silicon clusters (siliconoids) [1][2][3][4] are eeting intermediates during the production of silicon from molecular precursors and can typically only be detected in the gas phase. [5][6][7][8][9] The synthesis of stable derivatives has attracted considerable interest as the unsubstituted vertices of siliconoids are reminiscent of the free valences at bulk and nano surfaces of silicon, the so-called "dangling bonds".…”

A highly unsaturated six-vertex amido-substituted silicon cluster

“…In the isolated silicon analogues of benzene as well as in the computationally investigated Si 6 H 6 isomers, silicon atoms with no substituent occur that are only connected to other silicon atoms. These so-called unsubstituted or “naked” silicon atoms display inverted tetrahedral 7 or hemispheroidal configurations. 8 Therefore, the topology of these clusters resembles surface structures of bulk silicon or silicon nanoparticles.…”

A Puckered Singlet Cyclopentane‐1,3‐diyl: Detection of the Third Isomer in Homolysis

“…For the carbon–carbon homolysis in bicyclo[1.1.0]butane SB1 (E=C), two structural isomers have been so far reported on the potential energy surface, namely, the σ‐bonded isomer SB1 and planar diradical structure pl‐ DR1 (Scheme a) . In addition to these two isomers, a third one, the so‐called long‐bond isomer LB2 (E=Si), has been found for the bicyclic molecule containing the heavier group 14 elements …”

“…[3] In addition to these two isomers, at hird one, the so-called longbond isomer LB2 (E = Si), has been found for the bicyclic molecule containing the heaviergroup 14 elements. [4][5][6][7][8][9][10][11][12] In 2003, Ollivucci and co-workers computationally investigated the photochemical denitrogenation of diazabicyclo[2.2.1]hept-2-ene (DBH) AZ at the CASPT2//CASSCF/6-31G(d) level of theoryt oc larify the curious inversion selectivity [13,14,15] in the ring-closed product bicyclo[2.1.0]pentane (SB3)( Scheme 1b). [15] Ab initio computations suggestt hat the stereoselectivity of strained product SB3 is rationalized by the presence of the short-lived diradical intermediates DR3 and DZ3.T he puckered structure of the singlet diradical puc-DR3 was found as an equilibrated structure together with bicyclo[2.1.0]pentane SB3, the planar singlet diradical pl-DR3,a nd 1,4-diazenyl diradicals DZ3.T he homolytic substitution (S H 2) process throught he equatorial diazenyl diradical eq-DZ3 offers ap lausible pathway for the formation of inv-SB3.…”