The reaction of N,C,N-chelated stibinidene ArSb (1) (Ar = C6H3-2,6-(CH=NtBu)2) with selected N-alkyl/aryl-maleimides RN(C(O)CH)2 (R = Me, tBu, Ph) gave the addition products with bridged bicyclic [2.2.1] structure containing antimony atom at bridgehead position, fused with 6-membered benzene and 5-membered N-alkyl/aryl-pyrrolidine ring. These compounds were completely characterized. More importantly, additional studies showed that these reactions are reversible in solution, thereby representing an unprecedented reversible activation of a C=C bond by the antimony(I) compound 1.