 The first isolated multidecker sandwich was the tris(cyclopentadienyl)dinickel triple-decker complex [Ni2Cp3]BF4, a highly air- and water-sensitive compound reported in 1972, with X-ray crystallographic confirmation in 1974.In 1973 the electrically neutral air-stable triple-decker cobaltacarborane sandwiches 1,7,2,3- and 1,7,2,4-CpCo(RHC2B3H3)Cp (where R = H, Me) were isolated and characterized by multinuclear NMR and X-ray studies (the structure of the 1,7,2,3 isomer is shown).Since then many three-, four-, five-, and six-decker sandwich complexes have been described.