This paper describes a tandem strategy to synthesize a series of new Fischer carbene complexes [(CO)₄MC[N–(CH₂)₄–]CHC(NRR′)(SR′); M = Cr, W; R = Ar, R′ = Me, –(CH₂)₂–] with a thioimide or thiazoline fragment, in which the sulfur or nitrogen atom is coordinated to a metal center, depending on the nature of alkylating groups included as R′. We have trapped by protonation the proposed intermediate as the thioamide 12 [(CO)₅WC[N–(CH₂)₄–]CH₂C(S)NHPh], which reveals the pathway of this reaction