1,3-Digermabicyclo[1.1.0]butane with an Inverted Bridge Ge–Ge σ Bond

Abstract

1,3-Digermabicyclo[1.1.0]butane 2 was synthesized as yellow crystals. The molecular structure, 13C NMR and UV–vis spectra, and theoretical calculations have revealed that 2 is a typical long bond isomer, similarly to the silicon congener 1. Structural comparison between 1 and 2 is achieved.

Heavy Tetrel Clusters Based on the Bicyclobutane Framework: Bicyclo[1.1.0]butanes, [1.1.1]Propellanes, and Tricyclo[2.1.0.02,5]pentanes

“…The two title compounds, 1,3-disilabicyclo[1.1.0]butane and 1,3digermabicyclo[1.1.0]butane derivatives 29 and 34, containing rather long SiÀ Si or GeÀ Ge bridgehead bonds and two carbon atoms at the bridging positions, were prepared by Iwamoto, Kira, and co-workers by the double sila-or germa-Peterson reaction of the 1,2-dilithiodisilane or -germane derivatives and 2-adamantanone (Scheme 22). [50,53] In both 29 and 34, the bridgehead bonds are notably long measuring 2.412(1) Å (SiÀ Si in 29) and 2.5827(3) Å (GeÀ Ge in 34). [50,53] The interplanar angle is wide in both 29 [141.1(1)°] and 34 [142.26(9)°], and the bridgehead Si (in 29) and Ge (in 34) atoms feature diagnostic inverted tetrahedral configuration (in their subsequent study, [49] the same authors re-examined crystallographic measurement of 29, getting a slightly different set of metric parameters for 29 which crystallized in a different orthorhombic space group (average data for two crystallographically independent molecules in the unit cell): 2.3861( 12) Å (bridgehead SiÀ Si bond length), 140.0(2)°(interplanar angle), 339.73(14)/339.45(15)°[Σ(Si)]).…”

“…[50,53] In both 29 and 34, the bridgehead bonds are notably long measuring 2.412(1) Å (SiÀ Si in 29) and 2.5827(3) Å (GeÀ Ge in 34). [50,53] The interplanar angle is wide in both 29 [141.1(1)°] and 34 [142.26(9)°], and the bridgehead Si (in 29) and Ge (in 34) atoms feature diagnostic inverted tetrahedral configuration (in their subsequent study, [49] the same authors re-examined crystallographic measurement of 29, getting a slightly different set of metric parameters for 29 which crystallized in a different orthorhombic space group (average data for two crystallographically independent molecules in the unit cell): 2.3861( 12) Å (bridgehead SiÀ Si bond length), 140.0(2)°(interplanar angle), 339.73(14)/339.45(15)°[Σ(Si)]). Based on these structural characteristics, both 29 and 34 were assigned as the LB-isomers of 1,3disila-and 1,3-digermabicyclo[1.1.0]butane derivatives 29 and 34, respectively.…”

“…Based on these structural characteristics, both 29 and 34 were assigned as the LB-isomers of 1,3disila-and 1,3-digermabicyclo[1.1.0]butane derivatives 29 and 34, respectively. [50,53] The distinction in the structural parameters of the SB-isomer 27 [49] and the LB-isomer 29, [50] differing only in the size of their bridgehead substituents ( i Pr 3 Si vs. t BuMe 2 Si), is striking: short SiÀ Si bridgehead bond/acute interplanar angle/planar geometry around bridgehead Si atoms in 27 vs. long SiÀ Si bridgehead bond/wide interplanar angle/inverted tetrahedral geometry around bridgehead Si atoms in 29, demonstrating a decisive role of the bulkiness of bridgehead substituents on the structure of 1,3-disilabicyclo[1.1.0]butanes (preference for either SB-or LB-isomer).…”

Heavy Analogs of Organic Free Radicals: Si‐, Ge‐, Sn‐ and Pb‐Centered Radicals

“…Simple electron counting in 27 (two lone pairs from the N atoms and two odd electrons from the Sn atoms) gives rise to a total of six, implying the six π -electron four-center system The biradical nature of the transannular bonding in such cages was manifested in their diagnostically long E-E bridge separations: 2.412(1)Å (for 28), 132 2.5827(3)Å (for 29), 133 3.348(1)Å (for 30), 109,134 3.367(1)Å (for 31), 109,134 3.4226(6)Å (for 32), 135 3.363(1)Å (for 33), 136 2.869(2)Å (for 34) 137 and 3.329(1)Å (for 35) 138 . Such pyramidalization and tricoordination of both tins is indicative of the radical character of the Sn centers, which are separated by 3.398Å, well beyond the range of Sn-Sn covalent interactions, indicating the absence of transannular 2,4-bonding.…”

Lithiated 1,3-Disilabicyclo[1.1.0]butanes Synthesized via Selective Cleavage of Exocyclic Si–Si Bonds on Bridgehead Silicon Atoms

“…Most of them have been classified as the SB isomers, − and very recently silicon analogs of cyclobutane-1,3-diyl that exhibit a π-type bonding interaction between the bridgehead silicon atoms − have been reported. Nevertheless, silabicyclo[1.1.0]­butanes with the structural characteristics of the LB isomer − remain very scarce, − despite the aforementioned intriguing hemispheroidal geometry around the bridgehead silicon atoms. − In this context, the functionalization and derivatization of the molecular silicon clusters with the hemispheroidal geometry at the unsubstituted silicon vertices (siliconoids) , have been extensively examined recently. − …”