Pyrrolylmethyl Functionalized o-Carborane Derivatives

The reactions of the 16e half-sandwich complex CpCoS2C2B10H10 (1), diazo esters, and various 1,6-diynes (3a–i; PhN(CH2C≡CH)2, 4-Me-PhN(CH2C≡CH)2, 4-OMe-PhN(CH2C≡CH)2, 4-F-PhN(CH2C≡CH)2, BzN(CH2C≡CH)2, O(CH2C≡CH)2, C(Ac)2(CH2C≡CH)2, N(CH2C≡CH)3, NH(CH2C≡CH)N(CH2C≡CH)2) were investigated, in which two novel types of B–H activated products CpCoS2B10H9(CH2CO2Et)C5H3N(R)(CH═CHCO2Et) (4a–c; R = Ph, 4-Me-Ph, 4-OMe-Ph) and the key intermediate CpCoS2B10H9(CHCO2Me) (CH2CO2Me) (9) were isolated. 9 features a reactive Co–B bond, which triggers insertion of various 1,6-diynes to further lead to different final products. Substrates 3a–c are activated by the Co–B bond to produce o-carborane derivatives 4a–c which are functionalized by a cobalt-complexed η3-pyrrolylmethyl group. The pyrrole ring is formed by in situ ring closure of 1,6-diynes. Control experiments and isolation of the intermediate CpCoS2B10H9(CHCO2Me)(CH2CO2Me)HC═CCH2N(4-Me-Ph)(CH2C≡CH) (10) support the proposed mechanism concerning the formation of 4a–c...