Multiple bonding in Groups 13 and 14 homonuclear ethyne analogues

Synthesis and Structure of the “Dialuminyne” Na2[Ar′AlAlAr′] and Na2[(Ar′′Al)3]: AlAl Bonding in Al2Na2 and Al3Na2 Clusters

“…The calculated geometries of the organosubstituted (Me or Ph) model compounds all afforded planar trans-bent structures similar to that found experimentally with Al À Al bond lengths in the range 2.50-2.52 and Al-Al-C bond angles in the range 120-1278. [28] The longer calculated Al À Al distances support the view that some of the shortening (0.07-0.09 ) of the AlÀAl bond is indeed a result of the effect of the sodium atoms. The AlÀAl bond order, calculated by the method of Mayer, [29] for the simplest planar trans-bent model [HAlAlH] 2À is 2.51.…”

“…[26] This work has shown that the GaÀGa bond order in the model species Na 2 [PhGaGaPh] is about half that of [PhGaGaPh] 2À . Unfortunately, computational data on model compounds for 3 feature only separated anions with simple ligands such as H [27,28] or Me [28] and do not take Na À aryl interactions into consideration. The calculated geometries of the organosubstituted (Me or Ph) model compounds all afforded planar trans-bent structures similar to that found experimentally with Al À Al bond lengths in the range 2.50-2.52 and Al-Al-C bond angles in the range 120-1278.…”

“…The AlÀAl bond order, calculated by the method of Mayer, [29] for the simplest planar trans-bent model [HAlAlH] 2À is 2.51. [28] DFT calculations at the B3LYP/ 6-31g* level [30] on the model species Li 2 [HAlAlH], followed by Wiberg bond-order calculations, [31] resulted in an Al À Al bond order of 1.35. Calculations at the same level of theory on the entire molecule of 3 afforded an AlÀAl bond order of 1.13, while the same calculations on the gallium analogue 2 afforded a value of 1.39.…”

The Chemistry of Disilyne with a Genuine Si–Si Triple Bond: Synthesis, Structure, and Reactivity

“…Theoretical calculations not only on the parent H 2 Si 2 , but also on R 2 Si 2 with various substituents R have been reported so far. 13 Among them, the calculation by Nagase et al reported some very important predictions: the introduction of the electropositive silyl group on the triply-bonded Si atom, especially a triorganosilyl group, instead of hydrogen or organic groups, such as methyl, extensively reduces the energy difference between the trans-bent and linear forms with an increase in the bend angle in the trans-bent structure (the geometry of the trans-bent structure becoming much closer to linear) ( Tables 1 and 2). 21 Furthermore, the disilavinylidene structure, which is the most stable isomer for R 2 Si 2 except for the case of R ¼ H, would be relatively destabilized by the introduction of more bulky substituents on the silicon atoms.…”

“…7a, 13 Higher bond orders (2.20-2.37) were expected for the silicon species. 7a, 13 The first experimental approach to a silicon-silicon triple bond was reported by West and Sekiguchi et al in 1986. The compound 4 was synthesized as a possible precursor of dimethyldisilyne (5) by the retro-Diels-Alder reaction. When 4 was heated in the presence of anthracene at 350 C, the anthracene adduct 6 of MeSiSiMe was produced together with 1,2,3,4-tetraphenylnaphthalene (Scheme 1).…”