Sulfur dioxide molecules binding

An X-ray structure determination Cmcm i i= 0.061 of pale yellow crystals of compound B obtained from the sulfur dioxide reaction, shows a neutral complex of symmetry mm2 to be present in the solid. The anionic part of the molecule consists of two anellated l,2-dihydro-5-oxo-l,2,4-triphosphol-3-olate rings which share the central P-P group (P-P 215.3 P-C 189.1 P-C 178.4 C-O 123.9pm C-P-P 98.4° C-P-C 91.2° C P C 98.7°). The lithium cations are coordinated square pyramidally (Li-0 193.5 to 209.1 pm), each binding a 1,2-dimethoxyethane and a tetrahydrofiiran ligand in addition [30]. 

The words sulfur dioxide, sulfur anhydride or sulfurous gas can all be used equally, or even sul-furous acid, though the corresponding molecule cannot be isolated. The expression sulfur , however, is fundamentally incorrect. Additions made to wine are always expressed in the anhydrous form, in mg/1 or in g/hl, regardless of the form effectively employed—sulfur dioxide gas or liquid solution, potassium bisulfite (KHSO3) or potassium metabisulfite (K2S2O5). The effect of the addition to wine is the same, regardless of the form used. The equilibrium established between the various forms is identical. It depends on the pH and the presence of molecules that bind with the sulfur dioxide. 

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