C3H4Si Species: Generation and Matrix-Spectroscopic Identification of Some Silacyclobutadiene Isomers

Heavy Analogs of Aromatic Compounds

“…By contrast, several heavily substituted and therefore kinetically stabilized cyclobutadiene derivatives have been synthesized and isolated, the latest example 63 (E = E = E = E = C, R = SiMe 3 ) being prepared by the two-electron oxidation of the corresponding cyclobutadiene dianion derivative. 163 The most recent computations by Lawson et al at RHF, B3LYP and BLYP levels employing large 311++G** and TZV basis sets convincingly demonstrated the antiaromatic nature of the parent silacyclobutadiene 63 (E = E = E = C, E = Si, R = H) deduced from the consideration of its particular geometric, energetic and magnetic properties. The early computations by Gordon performed at the HF/6-31G*//HF/3-21G level showed that the unsubstituted silacyclobutadiene 63 (E = E = E = C, E = Si, R = H) is highly antiaromatic by 53.3 kcal/mol (cyclobutadiene itself was found to be more antiaromatic than silacyclobutadiene by 14.6 kcal/mol at the same level of calculations), being nevertheless more stable than the isomeric silatetrahedrane by 33.3 kcal/mol.…”

Experimental evidence and bond characterization of a cyclopropenylgermylene

“…The bonding character of the calculated structures were investigated by means of the natural bond orbital (NBO) analysis. [12] The initial structures for optimization were chosen based on the optimized structures of SiC 3 H 4 reported by Veszprémi et al [13] and Maier et al [14] As shown in Fig. 1, five stable structures cis-2, trans-2, cis-5, trans-5, and 6 were found at the B3LYP/6-31G(d) level.…”

“…The filtrate was concentrated under reduced pressure, and the residue was chromatographed on silica gel using hexane as the eluent. The eluate was concentrated under reduced pressure to give 3b (6.72 g, 13.1 mmol, 85% 14;H,8.97;N,6.56. Found: C,73.35;H,9.00; N, 6.59%.…”

1,2,3,4-Tetra-tert-butyl-4-trimethylsilyl-4-sila-2-cyclobuten-1-yl: A Quantum Mechanical and ESR Study

“…Thus, we initiated a project directed towards the preparation of 5 and 6. [6] According to calculations (B3LYP/6-31G*) on the C 3 H 4 Si energy hypersurface, [7,8] the parent silacyclobutadiene, cyclopropenylsilylene, and silatetrahedrane are 47.8, 54.7, and 71.2 kcal mol -1 , respectively, higher in energy than the global minimum, 2-methyl-1-silacyclopropenylidene. This order of relative energies is in agreement with calculations carried out previously by Gordon et al [9] clobutenyl radical 9 can be identified as the reaction product.…”

“…Neither silatetrahedrane nor silacyclobutadiene could be isolated in a matrix at 10 K. [8] This encouraged us to look for the kinetically stabilized derivatives 5 and 6. [10] Synthesis of the Persistent Radical 9…”