Related Experiment Video
Updated: May 20, 2026
07:50
Efficient Synthesis of All-Carbon Quaternary Centers via the Conjugate Addition of Functionalized Monoorganozinc Bromides
Published on: May 26, 2019
Plane and simple: planar tetracoordinate carbon centers in small molecules
Chad Crigger1, Bernard K Wittmaack, Marina Tawfik
1Department of Chemistry, Gottwald Center for the Sciences, University of Richmond, 28 Westhampton Way, Richmond, VA 23173, USA.
Physical Chemistry Chemical Physics : PCCP
|July 10, 2012
Summary
Researchers discovered new neutral 18-electron molecules featuring planar tetracoordinate carbon (ptC) centers. These molecules, including C(BeH)3BH2, exhibit stable planar structures, challenging traditional tetrahedral assumptions for main group elements.
Area of Science:
- Computational Chemistry
- Main Group Chemistry
- Molecular Structure
Background:
- Traditional chemical structures often assume tetrahedral arrangements around carbon centers.
- The existence and stability of planar tetracoordinate carbon (ptC) in neutral main group molecules remain an active area of research.
Purpose of the Study:
- To introduce and computationally investigate a class of neutral 18-valence electron molecules with ptC centers.
- To explore the geometric preferences of these molecules, specifically the tendency to adopt planar configurations.
Main Methods:
- Density Functional Theory (DFT) calculations using B3PW91 functional.
- High-level ab initio methods including MP2(full) and CCSD.
- Analysis of potential energy surfaces to determine stable molecular geometries.
Main Results:
- The neutral singlet molecule C(BeH)3BH2 and related isoelectronic species were found to prefer planar tetracoordinate structures over tetrahedral ones.
- For C(BeH)3BH2 and C(CH3)(BH2)Li2, tetrahedral conformations were not minima on the potential energy surface.
- The magnesium analogue, C(MgH)3BH2, also exhibits a planar global minimum, indicating broader applicability of this phenomenon.
Conclusions:
- Neutral 18-electron molecules with main group elements can stabilize planar tetracoordinate carbon centers.
- These findings open new avenues for experimental synthesis and theoretical studies of ptC systems.
- The planar geometry is stable and may be observed in larger clusters of ptC molecules.
More Related Videos
Related Concept Videos
01:07Radicals: Electronic Structure and Geometry
This lesson delves into the geometry of a radical, which is influenced by the electronic structure of the molecule. The principle is similar to that of a lone pair, where the unpaired electron influences the geometry at the radical center.
Accordingly, the structure of a trivalent radical lies between the geometries of carbocations and carbanions. An sp2-hybridized carbocation is trigonal planar, while an sp3-hybridized carbanion is trigonal pyramidal. Here, the difference in geometry is...
Accordingly, the structure of a trivalent radical lies between the geometries of carbocations and carbanions. An sp2-hybridized carbocation is trigonal planar, while an sp3-hybridized carbanion is trigonal pyramidal. Here, the difference in geometry is...
02:25Molecules with Multiple Chiral Centers
Molecules that possess multiple chiral centers can afford a large number of stereoisomers. For instance, while some molecules like 2-butanol have one chiral center, defined as a tetrahedral carbon atom with four different substituents attached, several molecules like butane-2,3-diol have multiple chiral centers. A simple formula to predict the number of stereoisomers possible for a molecule with n chiral centers is 2n. However, there can be a lower number where some of the stereoisomers are...
02:30Chirality at Nitrogen, Phosphorus, and Sulfur
Chirality is most prevalent in carbon-based tetrahedral compounds, but this important facet of molecular symmetry extends to sp3-hybridized nitrogen, phosphorus and sulfur centers, including trivalent molecules with lone pairs. Here, the lone pair behaves as a functional group in addition to the other three substituents to form an analogous tetrahedral center that can be chiral.
A consequence of chirality is the need for enantiomeric resolution. While this is theoretically possible for all...
A consequence of chirality is the need for enantiomeric resolution. While this is theoretically possible for all...
02:06Newman Projections
Different notations are used to represent the three-dimensional structure of molecules on two-dimensional surfaces. One of the most commonly used representations is the dash-wedge formula. The dashed wedges, solid wedges, and the plane lines indicate the groups situated behind the plane, coming out of the plane, and in the plane, respectively.
The organic molecules rotate across the single bonds leading to numerous temporary three-dimensional structures of varying energy known as conformers.
The organic molecules rotate across the single bonds leading to numerous temporary three-dimensional structures of varying energy known as conformers.
02:52VSEPR Theory and the Basic Shapes
Overview of VSEPR Theory
02:37VSEPR Theory
Valence shell electron-pair repulsion theory (VSEPR theory) enables us to predict the molecular structure around a central atom from an examination of the number of bonds and lone electron pairs in its Lewis structure. The VSEPR model assumes that electron pairs in the valence shell of a central atom will adopt an arrangement that minimizes repulsions between these electron pairs by maximizing the distance between them. The electrons in the valence shell of a central atom form either bonding...