1 research outputs found
End-On and Side-On ĻāAcid Ligand Adducts of Gold(I): Carbonyl, Cyanide, Isocyanide, and Cyclooctyne Gold(I) Complexes Supported by NāHeterocyclic Carbenes and Phosphines
N-Heterocyclic carbene ligand SIDipp (SIDipp = 1,3-bisĀ(2,6-diisopropylphenyl)Āimidazolin-2-ylidene)
and trimesitylphosphine ligand have been used in the synthesis of
goldĀ(I) cyanide, <i>t</i>-butylisocyanide, and cyclooctyne
complexes (SIDipp)ĀAuĀ(CN) (<b>3</b>), (Mes<sub>3</sub>P)ĀAuĀ(CN)
(<b>4</b>), [(Mes<sub>3</sub>P)<sub>2</sub>Au]Ā[AuĀ(CN)<sub>2</sub>] (<b>5</b>), [(SIDipp)ĀAuĀ(CN<sup><i>t</i></sup>Bu)]Ā[SbF<sub>6</sub>] (<b>[6]Ā[SbF</b><sub><b>6</b></sub><b>]</b>), [(SIDipp)ĀAuĀ(cyclooctyne)]Ā[SbF<sub>6</sub>] (<b>[8]Ā[SbF</b><sub><b>6</b></sub><b>]</b>), and [(Mes<sub>3</sub>P)ĀAuĀ(cyclooctyne)]Ā[SbF<sub>6</sub>] (<b>[9]Ā[SbF</b><sub><b>6</b></sub><b>]</b>). A detailed computational study has been carried out on these and
the related goldĀ(I) carbonyl adducts [(SIDipp)ĀAuĀ(CO)]Ā[SbF<sub>6</sub>] (<b>[1]Ā[SbF</b><sub><b>6</b></sub><b>]</b>),
[(Mes<sub>3</sub>P)ĀAuĀ(CO)]Ā[SbF<sub>6</sub>] (<b>[2]Ā[SbF</b><sub><b>6</b></sub><b>]</b>), and [(Mes<sub>3</sub>P)ĀAuĀ(CN<sup><i>t</i></sup>Bu)]<sup>+</sup> (<b>[7]</b><sup><b>+</b></sup>). X-ray crystal structures of <b>3</b>, <b>5</b>, <b>[6]Ā[SbF</b><sub><b>6</b></sub><b>]</b>, <b>[8]Ā[SbF</b><sub><b>6</b></sub><b>]</b>, and <b>[9]Ā[SbF</b><sub><b>6</b></sub><b>]</b> revealed that
they feature linear gold sites. Experimental and computational data
show that the changes in Ļ-acid ligand on (SIDipp)ĀAu<sup>+</sup> from CO, CN<sup>ā</sup>, CN<sup><i>t</i></sup>Bu,
cyclooctyne as in <b>[1]</b><sup>+</sup>, <b>3</b>, <b>[6]</b><sup>+</sup>, and <b>[8]</b><sup>+</sup> did not
lead to large changes in the AuāC<sub>carbene</sub> bond distances.
A similar phenomenon was also observed in AuāP distance in
complexes <b>[2]</b><sup>+</sup>, <b>4</b>, <b>[7]</b><sup>+</sup>, and <b>[9]</b><sup>+</sup> bearing trimesitylphosphine.
Computational data show that the AuāL bonds of ānakedā
[AuāL]<sup>+</sup> or SIDipp and Mes<sub>3</sub>P supported
[AuāL]<sup>+</sup> (L = CO, CN<sup>ā</sup>, CN<sup><i>t</i></sup>Bu to cyclooctyne) have higher electrostatic character
than covalent character. The AuāL Ļ-donation and AuāL
Ļ-back-donation contribute to the orbital term with the former
being the dominant component, but the latter is not negligible. In
the AuāCO adducts <b>[1]</b><sup>+</sup>and <b>[2]</b><sup>+</sup>, the cationic gold center causes the polarization of
the CāO Ļ and Ļ orbitals toward the carbon end
making the coefficients at the two atoms more equal which is mainly
responsible for the large blue shift in the CO stretching frequency.
The SIDipp and Mes<sub>3</sub>P supported goldĀ(I) complexes of cyanide
and isocyanide also exhibit a significant blue shift in Ļ
Ģ
<sub>CN</sub> compared to that of the free ligands. Calculated results
for AuĀ(CO)Cl and AuĀ(CF<sub>3</sub>)ĀCO suggest that the experimentally
observed blue shift in Ī½Ģ
<sub>CO</sub> of these compounds
may at least partly be caused by intermolecular forces