Manganese Thiophene Tricarbonyl Complexes:  Nucleophilic Addition to Sulfur and Synthesis of Thiophenium Salts

New thiophene manganese derivatives, [(2-R<sup>1</sup>-C<sub>4</sub>H<sub>3</sub>S)Mn(CO)<sub>3</sub>]<sup>+</sup> <b>1</b>(sil) (R<sup>1</sup> = Si(OCH<sub>2</sub>CH<sub>2</sub>)<sub>3</sub>N) and <b>1</b>(Mn) (R<sup>1</sup> = (C<sub>6</sub>H<sub>6</sub>)Mn(CO)<sub>3</sub>), have been synthesized and their reaction with nucleophiles studied. Except for the Grignard reagent, nucleophiles (Nu<sup>-</sup> = H<sup>-</sup>, <sup>-</sup>CN, <sup>-</sup>P(O)(OR)<sub>2</sub> (R = Me, Ph)) usually attack the C5 position. Grignard reagents attack the sulfur atom to yield manganese <i>S</i>-R-thiophene carbonyls <b>3</b>. To compare the reactivities of <b>1</b>(sil) and <b>1</b>(Mn) with that of (thiophene)Mn(CO)<sub>3</sub><sup>+</sup> with respect to Grignard reagent addition, the known compounds [(thiophene)Mn(CO)<sub>3</sub>]<sup>+</sup> (thiophene = thiophene, 2-methylthiophene, 2,5-dimethylthiophene) have been synthesized and their reaction with Grignard reagents studied. In all cases, <i>S</i>-R-thiophene manganese carbonyls <b>3</b> were obtained as a sole product. Refluxing <b>3</b> (R = Ph, <i>p</i>-tolyl, 2-thienyl) with Me<sub>3</sub>NO in benzene yielded diaryl sulfide. Treatment of <b>3</b> with NOBF<sub>4</sub> in CH<sub>2</sub>Cl<sub>2</sub> led to S-R-thiophenium−manganese dicarbonyl nitrosyl cations <b>4</b>. Photolysis of <b>4</b> in acetone gave rise to <i>S</i>-R-thiophenium <b>5</b> in high yields. The molecular structures of [{2-<i>exo</i>-P(O)(OMe)<sub>2</sub>-η<sup>4</sup>-C<sub>4</sub>H<sub>3</sub>S}Mn(CO)<sub>3</sub>] (<b>2</b>(sil,P(O)(OMe)<b><sub>2</sub></b>)), [<i>S</i>-Ph-η<sup>4</sup>-2-{(η<sup>5</sup>-C<sub>6</sub>H<sub>6</sub>)Mn(CO)<sub>3</sub>}SC<sub>4</sub>H<sub>3</sub>]Mn(CO)<sub>3</sub> (<b>3</b>(Mn,Ph)), and [<i>p</i>-CH<sub>3</sub>C<sub>6</sub>H<sub>5</sub>-S-2-CH<sub>3</sub>C<sub>4</sub>H<sub>3</sub>] (<b>5</b>(Me,<i>p</i>-tolyl)) have been determined by X-ray studies.