Electronic structure of the sulfonyl and phosphonyl groups: a computational and crystallographic study.
A computational and X-ray crystallographic investigation of the electronic and geometric structures of a range of sulfonyl (-SO(2)-) and phosphonyl (-PO(2)--) containing species was undertaken to investigate the nature of valency and bonding in these functional groups. The traditional representation of sulfonyl and phosphonyl species is with octet-violating Lewis structures, which require d-orbital participation at the central atom. However, computational studies cast serious doubt upon this bonding model. In this work, we have employed NBO/NRT analysis to investigate hybridization, atomic formal charges, donor-acceptor interactions, and resonance structure contributions. Our results predict that within sulfonyl and phosphonyl systems, bonding interactions are highly polarized, of the form X+-Y- (X = P, S), and possess additional contributions from reciprocal n --> sigma* interactions where substituents off sulfur or phosphorus simultaneously act as donors and acceptors. Experimental evidence for the proposed bonding arrangement is provided for the sulfonyl functional group through a series of low-temperature X-ray structure correlations for sulfate monoesters, sulfamates, and methanesulfonates. Examination of changes to bond lengths and geometries upon substituent variation support the computational results. Together, our studies lend support for a bonding network in sulfonyl and phosphonyl groups composed of polar interactions augmented with reciprocal hyperconjugative bonding, which does not necessitate significant d-orbital participation nor formal octet violation at the central sulfur or phosphorus.
Denehy
Emma
E
School of Chemistry and Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Parkville, Victoria, Australia 3010.
White
Jonathan M
JM
Williams
Spencer J
SJ
D018360:Crystallography, X-Ray / Q000379:methods; D004563:Electrochemistry / Q000379:methods; D004581:Electronics; D006860:Hydrogen Bonding; D008956:Models, Chemical; D008958:Models, Molecular; D008968:Molecular Conformation; D015394:Molecular Structure; D016011:Normal Distribution; D010100:Oxygen / Q000737:chemistry; D010710:Phosphates / Q000737:chemistry*; D010758:Phosphorus / Q000737:chemistry; D012984:Software; D013329:Structure-Activity Relationship; D013455:Sulfur / Q000737:chemistry*; D013461:Sulfur Oxides / Q000737:chemistry; D013463:Sulfuric Acid Esters / Q000737:chemistry
D010710:Phosphates; D013461:Sulfur Oxides; D013463:Sulfuric Acid Esters; D010758:Phosphorus; D013455:Sulfur; C011118:sulfur trioxide; C033522:methyl sulfate; D010100:Oxygen