Integrating the Substituent Effect into the Wade-Mingos Rules for Dicarboranes

Area of Science:

• Cluster Chemistry
• Computational Chemistry
• Materials Science

Background:

• The Wade-Mingos (W-M) rules are a cornerstone for predicting carborane structures.
• Classical frameworks often overlook the significant impact of substituents on molecular architecture.

Purpose of the Study:

• To re-evaluate the Wade-Mingos rules in carborane chemistry.
• To investigate the role of substituent effects in determining ground-state architectures of six-vertex dicarboranes.
• To develop a more accurate predictive model for carborane stability.

Main Methods:

• High-throughput computational analysis of 74,613 six-vertex dicarboranes (C2B4R6).
• Application of the Seed and Mortise-Tenon model for structural prediction.
• Development of a novel substituent-counting rule (P = nM + 1.1nH) incorporating connected-atom electronegativity (CAEN).

Main Results:

• Achieved 92.8% prediction accuracy for carborane architectures.
• Identified trigonal-bipyramidal isomers as the global ground state in 89.1% of cases, contradicting W-M predictions.
• Demonstrated that substituent effects, particularly electronegativity, control electronic balance and stability, failing W-M rules in 27 out of 28 domains.

Conclusions:

• Substituent effects are paramount in determining carborane ground-state architectures.
• The developed substituent-counting rule offers a refined, data-driven approach to predict carborane stability.
• Established a framework for substituent-guided design in cluster chemistry, highlighting limitations of classical bonding rules.