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

New thiophene manganese derivatives, [(2-R1-C4H3S)Mn(CO)3]+ 1(sil) (R1 = Si(OCH2CH2)3N) and 1(Mn) (R1 = (C6H6)Mn(CO)3), have been synthesized and their reaction with nucleophiles studied. Except for the Grignard reagent, nucleophiles (Nu- = H-, -CN, -P(O)(OR)2 (R = Me, Ph)) usually attack the C5 position. Grignard reagents attack the sulfur atom to yield manganese S-R-thiophene carbonyls 3. To compare the reactivities of 1(sil) and 1(Mn) with that of (thiophene)Mn(CO)3+ with respect to Grignard reagent addition, the known compounds [(thiophene)Mn(CO)3]+ (thiophene = thiophene, 2-methylthiophene, 2,5-dimethylthiophene) have been synthesized and their reaction with Grignard reagents studied. In all cases, S-R-thiophene manganese carbonyls 3 were obtained as a sole product. Refluxing 3 (R = Ph, p-tolyl, 2-thienyl) with Me3NO in benzene yielded diaryl sulfide. Treatment of 3 with NOBF4 in CH2Cl2 led to S-R-thiophenium−manganese dicarbonyl nitrosyl cations 4. Photolysis of 4 in acetone gave rise to S-R-thiophenium 5 in high yields. The molecular structures of [{2-exo-P(O)(OMe)24-C4H3S}Mn(CO)3] (2(sil,P(O)(OMe)2)), [S-Ph-η4-2-{(η5-C6H6)Mn(CO)3}SC4H3]Mn(CO)3 (3(Mn,Ph)), and [p-CH3C6H5-S-2-CH3C4H3] (5(Me,p-tolyl)) have been determined by X-ray studies.