(Tri-tert-butyl-eta(5)-cyclopentadienyl)(1,2,4-tri-tert-butyl-eta(3)-cyclopentenyl)nickel (1) is accessible by the metal vapor route. The molecule adopts a slipped sandwich structure in the solid state with the nickel atom eta(5)-eta(3)-coordinated to the five-membered rings. Its C-13-NMR data are reported together with data on (tert-butyl-eta(5)-cyclopentadienyl)(tert-butyl-eta(3)-cyclopentenyl)nickel 2 and (di-tert-butyl-eta(5)-cyclopentadienyl)(di-tert-butyl-eta(3)- cyclopentenyl)nickel 3.