Attila Kovács and Zoltán Varga

Halogen acceptors in hydrogen bonding

Coordination Chemistry Reviews, 250 (2006) 710-727


In the present review we performed a comparative assessment of hydrogen bonding (HB) interactions with halogen (X) acceptors. Based on the available data in the literature we selected various inter- and intramolecular systems, for which (possibly) all the four halogen derivatives have been studied either by experimental or theoretical methods. Four main acceptor types have been considered in our assessment, viz., free X- anions, halogens involved in M–X (M = transition metal), H–X and C–X bonds. The hydrogen donors in the HB systems (DH) included the simple H2O, NH3, HX, H2 molecules, various alcohols, amines as well as aliphatic and aromatic CH groups. Among the molecular properties we focussed on the HB energy and structural characteristics (at the first place on the HX distance), which are particularly informative on the HB propensities of the halogens. Where available, the shift of the DH stretching frequency (nDH) upon the HB interaction was also discussed.



1. Introduction

2. Methods important in HB research

2.1. Experimental methods for gas-phase studies

2.2. X-ray and neutron diffraction

2.3. Quantum chemical computations

3. Intermolecular HB interactions

3.1. Anionic (X-) acceptors

3.1.1. Hydrogen bihalides [X–H–X]-

3.1.2. Small halide complexes

3.1.3. Halide complexes observed in the condensed phase

3.2. M–X acceptors

3.3. H–X acceptors

3.3. C–X acceptors

4. Intramolecular HB interactions

4.1. 2-Halophenols

4.2. 2-Haloethanols

5. Conclusions