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Do Gold(III) Complexes Form Hydrogen Bonds? An Exploration of Au III Dicarboranyl Chemistry
Author(s) -
Chambrier Isabelle,
Hughes David L.,
Jeans Rebekah J.,
Welch Alan J.,
Budzelaar Peter H. M.,
Bochmann Manfred
Publication year - 2020
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.201904790
Subject(s) - chemistry , protonolysis , pyridinium , pyridine , reactivity (psychology) , trans effect , ligand (biochemistry) , hydrogen bond , oxidative addition , trifluoroacetic acid , stereochemistry , medicinal chemistry , crystallography , triflic acid , agostic interaction , platinum , metal , crystal structure , molecule , catalysis , organic chemistry , medicine , biochemistry , alternative medicine , receptor , pathology
The reaction of 1,1′‐Li 2 [(2,2′‐C 2 B 10 H 10 ) 2 ] with the cyclometallated gold(III) complex (C^N)AuCl 2 afforded the first examples of gold(III) dicarboranyl complexes. The reactivity of these complexes is subject to the trans ‐influence exerted by the dicarboranyl ligand, which is substantially weaker than that of non‐carboranyl anionic C‐ligands. In line with this, displacement of coordinated pyridine by chloride is only possible under forcing conditions. While treatment of (C^N)Au{(2,2′‐C 2 B 10 H 10 ) 2 } ( 2 ) with triflic acid leads to Au−C rather than Au−N bond protonolysis, aqueous HBr cleaves the Au−N bond to give the pyridinium bromo complex 7 . The trans ‐influence of a series of ligands including dicarboranyl and bis(dicarboranyl) was assessed by means of DFT calculations. The analysis demonstrated that it was not sufficient to rely exclusively on geometric descriptors (calculated or experimental) when attempting to rank ligands for their trans influence. Complex (C^N)Au(C 2 B 10 H 11 ) 2 containing two non‐chelating dicarboranyl ligands was prepared similar to 2 . Its reaction with trifluoroacetic acid also leads to Au−N cleavage to give trans ‐(Hpy^C)Au(OAc F )(C 2 B 10 H 11 ) 2 ( 8 ). In crystals of 8 the pyridinium N−H bond points towards the metal centre, while in 7 it is bent away. The possible contribution of gold(III)⋅⋅⋅H−N hydrogen bonding in these complexes was investigated by DFT calculations. The results show that, unlike the situation for platinum(II), there is no evidence for an energetically significant contribution by hydrogen bonding in the case of gold(III).