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Hydrogen-Bond Acceptor and Donor Properties of Divalent Sulfur ( Y -S- Z and R -S-H)

1997; Wiley; Volume: 53; Issue: 4 Linguagem: Inglês

10.1107/s0108768197002644

1600-5740

Frank H. Allen, C. M. Bird, R. Scott Rowland, Paul R. Raithby,

Organometallic Compounds Synthesis and Characterization

The hydrogen-bond acceptor ability of divalent sulfur in Y —S— Z systems, Y , Z = C, N, O or S, and the donor ability of thiol S—H have been studied using crystallographic data retrieved from the Cambridge Structural Database. Of 1811 Y —S— Z substructures that co-occur with N—H or O—H donors, only 86 (4.75%) form S...H—N,O bonds within S...H < 2.9 Å. In dialkylthioethers, the frequency of S...H bond formation is 6.24%, but drops below 3% when the alkyl groups are successively replaced by C sp 2 centres. This parallels an increasing \delta-positivity of S as calculated using ab initio methods. A similar frequency trend is observed for O...H—N,O bond formation by analogous oxyethers. Mean intermolecular >S...H distances for O—H [2.67 (3) Å] and N—H [2.75 (2) Å] donors (with H positions normalized to neutron values) are ca 0.25 Å longer than in C=S...H—N,O systems, indicative of very weak hydrogen bonding to >S. Intramolecular >S...H are slightly more frequent (8.56%), with S...H slightly shorter than for the intermolecular case. In contrast, 26 (70.3%) out of 37 S—H donors that co-occur with suitable acceptors form X ...H—S bonds. The C=O...H—S system is predominant with a mean O...H distance of 2.34 (4) Å, considerably longer (weaker) than in C=O...H—O systems.