What is it about?
Chemists often use the "cone angle" to describe how much space a molecule called a phosphine ligand takes up around a metal atom. Until now, these angles were mostly based on idealized models. This study introduces a new method to calculate cone angles directly from real-world crystal structures stored in a global database. By analyzing thousands of these structures, the authors show that cone angles vary much more than previously thought—depending on the shape of the ligand, how it twists, and the metal it’s bound to. This new approach gives a more accurate picture of ligand size and flexibility in real chemical environments.
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Why is it important?
This study offers the first large-scale statistical analysis of ligand cone angles based on experimental crystal structures rather than models. By examining over 4,000 compounds, the authors reveal how real-world factors—like metal identity, ligand conformation, and packing effects—influence the space a ligand occupies. This method provides chemists with a more realistic and data-driven tool for understanding and predicting steric effects in metal complexes. Such insights are crucial for designing better catalysts and tailoring molecular reactivity in organometallic chemistry.
Perspectives
I worked on this article day and night—quite literally. Back then, computers were much slower, and I had to download crystallographic data during the day and let my (actually first) laptop crunch the numbers overnight. It was a labour-intensive process, but also incredibly rewarding. I'm proud that this paper, which began with such a hands-on and personal effort, has gone on to receive so much attention in the field.
Prof. Dr. Thomas Ernst Müller
Ruhr-Universitat Bochum
Read the Original
This page is a summary of: Determination of the Tolman cone angle from crystallographic parameters and a statistical analysis using the crystallographic data base, Transition Metal Chemistry, December 1995, Springer Science + Business Media,
DOI: 10.1007/bf00136415.
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