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Ligands as “Compass Needles”: How Orientations of Alkene, Alkyne, and Alkylidene Ligands Reveal π‐Bonding Features in Tetrahedral Transition Metal Complexes
Author(s) -
Gibson Ver C.
Publication year - 1994
Publication title -
angewandte chemie international edition in english
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 0570-0833
DOI - 10.1002/anie.199415651
Subject(s) - ligand (biochemistry) , tetrahedron , transition metal , crystallography , alkene , chemistry , alkyne , metal , tetrahedral molecular geometry , triad (sociology) , stereochemistry , chemical physics , computational chemistry , crystal structure , organic chemistry , psychology , biochemistry , receptor , psychoanalysis , catalysis
This article outlines the strikingly simple structural pattern to which transition metal complexes containing π‐bonding ligands conform, and suggests simple rules (and ligand classifications) by which the pattern can be understood, and by which individual structures can be rationalized or predicted. Alkenes, alkynes, and alkylidene ligands adopt distinct orientations with respect to other ligands attached to a transition metal because of competition between the various ligand types for metal‐ligand π bonds, whatever the coordination geometry. However, a particularly interesting feature of the tetrahedral geometry is that “single‐faced” π ligands can function as “sensors” of relative ligand π‐donor capacities for all other groups attached to the metal. Here, using simple “triad representations” of tetrahedral complexes, a simple qualitative analysis is presented that builds on calculations by Hoffmann et al. and which allows preferred ligand orientations and relative ligand π‐bond strengths to be deduced for a wide variety of these transition metal complexes.