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Chemical Bonding in Homoleptic Carbonyl Cations [M{Fe(CO) 5 } 2 ] + (M=Cu, Ag, Au)
Author(s) -
Pan Sudip,
Gorantla Sai Manoj N. V. T.,
Parasar Devaborniny,
Dias H. V. Rasika,
Frenking Gernot
Publication year - 2021
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.202004041
Subject(s) - homoleptic , copper , chemistry , crystallography , dissociation (chemistry) , moiety , ion , ligand (biochemistry) , transition metal , metal , inorganic chemistry , stereochemistry , catalysis , organic chemistry , biochemistry , receptor
Syntheses of the copper and gold complexes [Cu{Fe(CO) 5 } 2 ][SbF 6 ] and [Au{Fe(CO) 5 } 2 ][HOB{3,5‐(CF 3 ) 2 C 6 H 3 } 3 ] containing the homoleptic carbonyl cations [M{Fe(CO) 5 } 2 ] + (M=Cu, Au) are reported. Structural data of the rare, trimetallic Cu 2 Fe, Ag 2 Fe and Au 2 Fe complexes [Cu{Fe(CO) 5 } 2 ][SbF 6 ], [Ag{Fe(CO) 5 } 2 ][SbF 6 ] and [Au{Fe(CO) 5 } 2 ][HOB{3,5‐(CF 3 ) 2 C 6 H 3 } 3 ] are also given. The silver and gold cations [M{Fe(CO) 5 } 2 ] + (M=Ag, Au) possess a nearly linear Fe‐M‐Fe’ moiety but the Fe‐Cu‐Fe’ in [Cu{Fe(CO) 5 } 2 ][SbF 6 ] exhibits a significant bending angle of 147° due to the strong interaction with the [SbF 6 ] − anion. The Fe(CO) 5 ligands adopt a distorted square‐pyramidal geometry in the cations [M{Fe(CO) 5 } 2 ] + , with the basal CO groups inclined towards M. The geometry optimization with DFT methods of the cations [M{Fe(CO) 5 } 2 ] + (M=Cu, Ag, Au) gives equilibrium structures with linear Fe‐M‐Fe’ fragments and D 2 symmetry for the copper and silver cations and D 4 d symmetry for the gold cation. There is nearly free rotation of the Fe(CO) 5 ligands around the Fe‐M‐Fe’ axis. The calculated bond dissociation energies for the loss of both Fe(CO) 5 ligands from the cations [M{Fe(CO) 5 } 2 ] + show the order M=Au ( D e =137.2 kcal mol −1 )>Cu ( D e =109.0 kcal mol −1 )>Ag ( D e =92.4 kcal mol −1 ). The QTAIM analysis shows bond paths and bond critical points for the M−Fe linkage but not between M and the CO ligands. The EDA‐NOCV calculations suggest that the [Fe(CO) 5 ]→M + ←[Fe(CO) 5 ] donation is significantly stronger than the [Fe(CO) 5 ]←M + →[Fe(CO) 5 ] backdonation. Inspection of the pairwise orbital interactions identifies four contributions for the charge donation of the Fe(CO) 5 ligands into the vacant ( n )s and ( n )p AOs of M + and five components for the backdonation from the occupied (n‐1)d AOs of M + into vacant ligand orbitals.