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

Abstract

In this account, our recent results on the chemistry of a stable silicon-silicon triply-bonded compound, disilyne, including recent advances in the chemistry of stable alkyne analogues of heavier group 14 elements, are described. Our original extremely bulky trialkylsilyl substituent, Dis 2 i PrSi [Dis = CH(SiMe 3 ) 2 ], has enabled the isolation of disilyne as a stable compound, which has been completely characterized by various spectroscopic techniques, as well as X-ray crystallography. Some reactivity of our isolable disilyne will be discussed.

Unsymmetrically Substituted Disilyne Dsi2iPrSi—Si≡Si—SiNpDsi2 (Np = CH2tBu): Synthesis and Characterization

“…15 The disilyne 2 also exhibits a trans-bent structure with bending angles of 138.78(5)°for the Dsi 2 i PrSi side and 137.89(5)°for the Dsi 2 NpSi side. The SitSi bond length of 2 (2.0569(12) Å) is remarkably shorter than typical SidSi bond lengths (2.143-2.228 Å), 18 demonstrating its triple-bond character, and is also shorter than those of 1a (2.0622(9) Å) 10 and BbtsSitSisBbt (2.108(5) Å). 13 In the 29 Si NMR spectrum of 2 in C 6 D 6 , eight signals are observed at -3.5, -0.5, -0.3, 0.0, 0.1, 22.1, 62.6, and 106.3 ppm, the former six signals being due to the silicon atoms of the substituents.…”

“…15 The silicon-silicon triple bonds of all reported disilynes are trans-bent, not linear, which results in two nondegenerate occupied π-MOs (π in as the HOMO -1 and π out as the HOMO) and two unoccupied antibonding π*-MOs (π* in as the LUMO and π* out as the LUMO + 1). 10 The molecular structure of disilyne 2 as determined by X-ray crystallographic analysis is shown in Figure 1. 15 The disilyne 2 also exhibits a trans-bent structure with bending angles of 138.78(5)°for the Dsi 2 i PrSi side and 137.89(5)°for the Dsi 2 NpSi side.…”

“…These 29 Si NMR resonances of the triply bonded silicon atoms in 2 are remarkably shifted to higher and lower fields compared with those of the corresponding symmetrically substituted disilynes (e.g., Dsi 2 i PrSi-substituted disilyne 1a: 89.9 ppm, Dsi 2 NpSisubstituted disilyne 1b: 77.1 ppm). 10,15 The structural parameters determined by X-ray crystallography are not fully explained by the different 29 Si chemical shifts of the 19 To provide an estimate of the relationship between the 29 Si chemical shifts of triply bonded silicon atoms and the RsSitSi bond angles, calculations were performed on the model compound Me 3 SisSi 1 tSi 2 sSiMe 3 (2′). In these calculations, the bond angle of SisSi 2 tSi 1 was fixed at 135°and θ (SisSi 1 tSi 2 ) was the variable parameter, θ (θ ) 90°to 180°).…”

Synthesis, Characterization and Real Molecule DFT Calculations for Neutral Organogallium(I) Aryl Dimers and Monomers: Weakness of GalliumGallium Bonds in Digallenes and Digallynes

“…In essence the structure of the di-A C H T U N G T R E N N U N G stannene demonstrated that the familiar valence-bond model used for multiple bonding in alkenes and alkynes was insufficient to deal with the structural changes observed in their heavier-element analogues. Numerous examples of heavier group 14 element alkene analogues, [3] most notably the landmark disilenes, [4,5] and more recently a complete series of alkyne congeners [6][7][8][9][10] has been synthesized and characterized. Currently it is broadly accepted (although controversies continue to arise) that the structural differences seen in the heavier element derivatives are a manifestation weakened bonding and an increasing preference for lone pair character over p-bonding as the group is descended.…”

Reactivity of the Disilyne RSi≡SiR (R = SiiPr[CH(SiMe3)2]2) toward Nitriles: Unexpected Formation of Triaza-1,4-disilabicyclo[2.2.2]octa-2,5,7-triene Derivatives

“…Very recently, Tokitoh et al also reported a diaryldisilyne by using Bbt substituents (Bbt ) 2,6-bis[bis(trimethylsilyl)methyl]-4-[tris(trimethylsilyl)methyl]phenyl). 7 Since our report on disilyne 1 in 2004, 5 we have also investigated the reactivity of 1 toward alkenes, 8 alkynes, 8 t BuLi, 9 alkali metals, 9,10 and silyl cyanide, 11 to understand the nature of the π bonds of the triple bond. 12 Among them, we found that the reaction of 1 with trimethylsilyl cyanide unexpectedly produced two types of products: the 1:2 adduct with bis(silaketenimine) character and the 1,4-diaza-2,3-disilabenzene analogue, in which two isomers of trimethylsilyl cyanide, the isocyanide and cyanide forms, compete to react with 1.…”