The reactions of [CptRhCl(m-Cl)]2 (1) (Cpt = tBu2C5H3) with Li2E2C2B10H10 (E = S, Se) lead to the green 16-electron dichalcogenolate complexes CptRh(E2C2B10H10) [E = S(2a), Se(2b)]. The 16-electron complexes 2a and 2b can take up two-electron donor ligands such as tert-butyl isoni-trile and carbon monoxide to give the 18-electron dichalco-genolate derivatives Cpt(L)(E2C2B10H10) [L = tBuNC, E = S(3a), Se(3b); L = CO, E = S(4a), Se(4b)]. The molecular structures of complexes 2a and 3a were determined by X-ray crystal structure analysis. The molecular structure of 16- electron complex 2a shows the pseudoaromatic system in IrSe2C2 five numbered ring.