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Solution, Solid‐State, and Computational Analysis of Agostic Interactions in a Coherent Set of Low‐Coordinate Rhodium(III) and Iridium(III) Complexes
Author(s) -
Knighton Richard C.,
EmersonKing Jack,
Rourke Jonathan P.,
Ohlin C. André,
Chaplin Adrian B.
Publication year - 2018
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.201705990
Subject(s) - agostic interaction , chemistry , crystallography , iridium , rhodium , mesitylene , molecule , crystal structure , natural bond orbital , stereochemistry , organic chemistry , catalysis , metal
A homologous family of low‐coordinate complexes of the formulation trans ‐[M(2,2′‐biphenyl)(PR 3 ) 2 ][BAr F 4 ] (M=Rh, Ir; R=Ph, Cy, i Pr, i Bu) has been prepared and extensively structurally characterised. Enabled through a comprehensive set of solution phase (VT 1 H and 31 P NMR spectroscopy) and solid‐state (single crystal X‐ray diffraction) data, and analysis in silico (DFT‐based NBO and QTAIM analysis), the structural features of the constituent agostic interactions have been systematically interrogated. The combined data substantiates the adoption of stronger agostic interactions for the Ir III compared to Rh III complexes and, with respect to the phosphine ligands, in the order P i Bu 3 >PCy 3 >P i Pr 3 >PPh 3 . In addition to these structure–property relationships, the effect of crystal packing on the agostic interactions was investigated in the tricyclohexylphosphine complexes. Compression of the associated cations, through inclusion of a more bulky solvent molecule (1,2‐difluorobenzene vs. CH 2 Cl 2 ) in the lattice or collection of data at very low temperature (25 vs. 150 K), lead to small but statistically significant shortening of the M −H− C distances.