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Small “Yaw” Angles, Large “Bite” Angles and an Electron‐Rich Metal: Revealing a Stereoelectronic Synergy To Enhance Hydride‐Transfer Activity
Author(s) -
Semwal Shrivats,
Mukkatt Indulekha,
Thenarukandiyil Ranjeesh,
Choudhury Joyanta
Publication year - 2017
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201702173
Subject(s) - hydride , chemistry , ring (chemistry) , bite angle , catalysis , ligand (biochemistry) , metal , electronic effect , computational chemistry , electron transfer , photochemistry , stereochemistry , organic chemistry , biochemistry , receptor , denticity
Cyclometalated complexes are an important class of (pre)catalysts in many reactions including hydride transfer. The ring size of such complexes could therefore be a relevant aspect to consider while modulating their catalytic activity. However, any correlation between the cyclometalating ring size and the catalytic activity should be drawn by careful assessment of the pertinent geometrical parameters, and overall electronic effects thereof. In this study, we investigated the vital role of key stereoelectronic functions of two classes of iridacyclic complexes—five‐membered and six‐membered cycles—in manupulating the catalytic efficiency in a model hydride‐transfer reaction. Our investigation revealed that there exists an interesting multidimensional synergy among all the relevant stereoelectronic factors—yaw angle, bite angle, and the electronic properties of both the ligand and the metal center—that governs the hydride donor ability (hydricity) of the complexes during catalysis. Thus the six‐membered chelate complexes with small yaw and large bite angles, strong donor ligand, and electron‐rich metal were found to be better catalysts than their five‐membered analogues. A frontier molecular orbital analysis supported the significant role of the above stereoelectronic synergistic effect associated with the chelate ring to control the hydride donor ability of the complexes.