Vogt-Geisse Stefan, Wu Judy I-Chia, Schleyer Paul v R, Schaefer Henry F
Facultad de Química, Pontifícia Universidad Católica de Chile, Santiago, Chile,
J Mol Model. 2015 Aug;21(8):217. doi: 10.1007/s00894-015-2736-8. Epub 2015 Aug 1.
Natural bond orbital (NBO) analyses and dissected nucleus-independent chemical shifts (NICS π z z ) were computed to evaluate the bonding (bond type, electron occupation, hybridization) and aromatic character of the three lowest-lying Si2CH2 (1-Si, 2-Si, 3-Si) and Ge2CH2 (1-Ge, 2-Ge, 3-Ge) isomers. While their carbon C3H2 analogs favor classical alkene, allene, and alkyne type bonding, these Si and Ge derivatives are more polarizable and can favor "highly electron delocalized"? and "non-classical"? structures. The lowest energy Si 2CH2 and Ge 2CH2 isomers, 1-Si and 1-Ge, exhibit two sets of 3-center 2-electron (3c-2e) bonding; a π-3c-2e bond involving the heavy atoms (C-Si-Si and C-Ge-Ge), and a σ-3c-2e bond (Si-H-Si, Ge-H-Ge). Both 3-Si and 3-Ge exhibit π and σ-3c-2e bonding involving a planar tetracoordinated carbon (ptC) center. Despite their highly electron delocalized nature, all of the Si2CH2 and Ge2CH2 isomers considered display only modest two π electron aromatic character (NICS(0) π z z =--6.2 to -8.9 ppm, computed at the heavy atom ring center) compared to the cyclic-C 3H2 (-13.3 ppm). Graphical Abstract The three lowest Si2CH2 and Ge2CH2 isomers.
计算了自然键轨道（NBO）分析和剖析的核独立化学位移（NICS πzz），以评估三个最低能量的Si2CH2（1-Si、2-Si、3-Si）和Ge2CH2（1-Ge、2-Ge、3-Ge）异构体的键合（键型、电子占据、杂化）和芳香性。虽然它们的碳C3H2类似物倾向于经典的烯烃、丙二烯和炔烃型键合，但这些Si和Ge衍生物更具极化性，可能倾向于“高度电子离域”和“非经典”结构。能量最低的Si2CH2和Ge2CH2异构体1-Si和1-Ge表现出两组3中心2电子（3c-2e）键合；一个涉及重原子（C-Si-Si和C-Ge-Ge）的π-3c-2e键，以及一个σ-3c-2e键（Si-H-Si、Ge-H-Ge）。3-Si和3-Ge都表现出涉及平面四配位碳（ptC）中心的π和σ-3c-2e键合。尽管它们具有高度电子离域的性质，但与环状-C3H2（-13.3 ppm）相比，所有考虑的Si2CH2和Ge2CH2异构体仅显示出适度的两个π电子芳香性（在重原子环中心计算的NICS(0) πzz = -6.2至-8.9 ppm）。图形摘要：三个最低能量的Si2CH2和Ge2CH2异构体。
