Trigonal prismatic molecular geometry

Trigonal prismatic molecular geometry
Trigonal prismatic molecular geometry
Examples	W(CH3)6
Point group	D3h
Coordination number	6
μ (Polarity)	0

In chemistry, the trigonal prismatic molecular geometry describes the shape of compounds where six atoms, groups of atoms, or ligands are arranged around a central atom, defining the vertices of a triangular prism. The structure commonly occurs for d⁰, d¹ and d² transition metal complexes with covalently-bound ligands and small charge separation. In d⁰ complexes it may be ascribed to sd⁵ hybridization, but in d¹ and d² complexes the d_z² orbital is occupied by nonbonding electron (pair). Furthermore, when unoccupied, said orbital participates in bonding and causes C_3v distortion, like in W(CH₃)₆.

Examples

Portion of lattice of [Te₆](O₃SCF₃)₂. The intra- and inter-triangle Te–Te distances are 2.70 and 3.06 Å, respectively.^[1]

Hexamethyltungsten (W(CH₃)₆) was the first example of a molecular trigonal prismatic complex.^[2] The figure shows the six carbon atoms arranged at the vertices of a triangular prism with the tungsten at the centre. The hydrogen atoms are not shown.

Some other transition metals have trigonal prismatic hexamethyl complexes, including both neutral molecules such as Mo(CH₃)₆ and Re(CH₃)₆ and ions such as Ta(CH
₃)⁻
₆ and Zr(CH
₃)²⁻
₆.^[3]

The complex Mo(S−CH=CH−S)₃ is also trigonal prismatic, with each S−CH=CH−S group acting as a bidentate ligand with two sulfur atoms binding the metal atom.^[3] Here the coordination geometry of the six sulfur atoms around the molybdenum is similar to that in the extended structure of molybdenum disulfide (MoS₂).

References

^ Schulz, C.; Daniels, J.; Bredow, T.; Beck, J. (2016). "The Electrochemical Synthesis of Polycationic Clusters". Angewandte Chemie International Edition. 55 (3): 1173–1177. doi:10.1002/anie.201507644. PMID 26632775.
^ Housecroft, C. E.; Sharpe, A. G. (2004). Inorganic Chemistry (2nd ed.). Prentice Hall. p. 725. ISBN 978-0-13-039913-7.
^ ^a ^b Housecroft, C. E.; Sharpe, A. G. (2004). Inorganic Chemistry (2nd ed.). Prentice Hall. ISBN 978-0-13-039913-7.

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[1] Schulz, C.; Daniels, J.; Bredow, T.; Beck, J. (2016). "The Electrochemical Synthesis of Polycationic Clusters". Angewandte Chemie International Edition. 55 (3): 1173–1177. doi:10.1002/anie.201507644. PMID 26632775.

[2] Housecroft, C. E.; Sharpe, A. G. (2004). Inorganic Chemistry (2nd ed.). Prentice Hall. p. 725. ISBN 978-0-13-039913-7.

[HS545-3] Housecroft, C. E.; Sharpe, A. G. (2004). Inorganic Chemistry (2nd ed.). Prentice Hall. ISBN 978-0-13-039913-7.

[1]

[2]

[3]

v t e Molecular geometry
VSEPR theory Coordination number
Coordination number 2	Linear Bent
Coordination number 3	Trigonal planar Trigonal pyramidal T-shaped
Coordination number 4	Tetrahedral Seesaw Square planar
Coordination number 5	Trigonal bipyramidal Square pyramidal Pentagonal planar
Coordination number 6	Octahedral Trigonal prismatic Pentagonal pyramidal
Coordination number 7	Pentagonal bipyramidal Capped octahedral Capped trigonal prismatic
Coordination number 8	Square antiprismatic Dodecahedral Bicapped trigonal prismatic
Coordination number 9	Tricapped trigonal prismatic Capped square antiprismatic
Category

Trigonal prismatic molecular geometry

Examples	W(CH₃)₆
Point group	D_3h
Coordination number	6
μ (Polarity)	0