Triphenylphosphine, reaction with elemental sulfur

The red [SSNO] anion (37) is produced by the reaction of an ionic nitrite with elemental sulfur or a polysulfide in acetone, DMF or DMSO.115 The [SSNO] anion has a planar cis structure with a short S-S distance (1.99 A), and S-N and N-O distances of 1.67 and 1.22 A, respectively. The treatment of [SSNO]- with triphenylphosphine produces the thionitrite anion [SNO]- (38) with a bond angle of ca. 120° at nitrogen and S-N and N-O bond lengths of 1.69 and 1.21 A, respectively. 

Although the stabihty of stannanethione 141, which was generated in the sulfur-ization of the corresponding stannylene Tbt(Tip)Sn (142) with elemental sulfur, was evidenced by the characteristic absorption maxima (k ax = 465 nm) in its electronic spectra, concentration of the reaction mixtnre resulted in the dimerization of 141 giving 1,3,2,4-dithiadistannetane derivative 143 (Scheme 51) ° . Stannanethione 141 can also be formed in the desulfurization of the corresponding tetrathiastannolane 144 with triphenylphosphine, but the formation of 141 has been confirmed only by trapping experiments vide infra) ° and the Sn NMR chemical shift for the central tin atom of 141... 

Bartlett PD, Cox EF, Davis RE (1961) Reactions of elemental sulfur. IV. Catalytic effects in the reaction of sulfur with triphenylphosphine. J Am Chem Soc 83 103-109... 

The reaction is believed to involve homolysis of the S—S bond to give a biradical which is intermediate to isomerization and product formation. Thermal decomposition of (4a) gives elemental sulfur and thioketone (16) <94AG(E)777>. Treatment of (4a) with triphenylphosphine also leads to (16) plus triphenylphosphine thiooxide. Oxidation of the dithiirane with MCPBA gives the sulfine (15). Heating of a dilute solution of (4a) in 1,2-dichloroethane gives the bicyclic 1,3,4-oxadithiolane (19) along with (16) and (18). 

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