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Electronic and Steric Manipulation of the Preagostic Interaction in Isoquinoline Complexes of Rh I
Author(s) -
Nielson Alastair J.,
Harrison John A.,
Sajjad M. Arif,
Schwerdtfeger Peter
Publication year - 2017
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201700086
Subject(s) - chemistry , agostic interaction , rhodium , isoquinoline , ligand (biochemistry) , steric effects , crystallography , electronic effect , stereochemistry , catalysis , metal , organic chemistry , biochemistry , receptor
Structures and properties were obtained by density functional calculations for the complexes [RhCl(CO) 2 (L)] (L = isoquinoline ligands) containing close Rh ···· H separations. Electrostatic repulsion keeps the atoms apart and Rh ···· C separations are prevented from developing much further by ligand inflexibility. Natural bond orbital analysis shows small components of C–Hσ to Rh (agostic) donation and Rh to C–Hσ* backdonation. Both σ‐ and π‐electron‐withdrawing substituents produce an increase in the Rh ···· H separation, while ligand inflexibility prevents σ‐ and π‐electron‐donating substituents from decreasing the Rh ···· C separation. Substitution at C 2 by Me closes up the Rh ···· H separation and CHMe 2 and CMe 3 groups cause a structural change which minimises the interaction. Substitution at C 2 by a Ph group gives the shortest Rh ···· H separation (2.187 Å) and largest Rh to C–Hσ* backdonation. Electron donation at C 7 or at C 7 and C 9 increases the Rh ···· H separation, as the ligand flexes substantially to accommodate a decrease in the Rh ···· C separation. On the basis of the minimal C–Hσ to Rh (agostic) donation involved, the complexes are best described as preagostic.