HETEROBIMETALLIC CARBENE AND ALLENYLIDENE COMPLEXES SYNTHESES AND CRYSTAL-STRUCTURES OF IRON(II)CHROMIUM(0) CYCLOHEPTATRIENYLIDENE AND (CYCLOHEPTATRIENYLIDENE)ETHENYLIDENE COMPLEXES

The heterobimetallic iron(II) chromium(0) complexes [(OC)(2)CpFe(mu-et a(1):eta(7)-C7H6)Cr(CO)(3)](+) and [(OC)(2)CpFe(mu-eta(1): eta(7)-C2C7 H6)Cr(CO)(3)](+) containing the bridging carbene ligand cycloheptatrie nylidene C7H6 and the cumulogous allenylidene ligand (cycloheptatrieny lidene)ethenylidene C2C7H6 have been prepared and their properties stu died. The former has been prepared by hydride abstraction from the het erobimetallic mu-eta(1):eta(6)-cyclohepta-1,3,5-trien-2-yl complex obt ained by lithiation of 2-trimethylstannyl-cyclohepta-1,3,5-triene foll owed by reaction with [FeCp(CO)(2)Br] and [Cr(CO)(3)(NCEt)(3)]. Treatm ent of 7-ethynyl-cyclohepta-1,3,5-triene with LiBun and consecutive re action with [FeCp(CO)(2)Br] and [Cr(CO)(3)(NCEt)(3)] led to the format ion of -[(OC)(2)CpFe(mu-eta(1):eta(6)-C=C-C7H7)Cr(CO)(3)] which was tr eated with [Ph3C][BF4] to give C)(2)CpFe(mu-eta(1):eta(7)-C2C7H6)Cr(CO )(3)][BF4]. The crystal structures of [(OC)(2)CpFe(mu-eta(1):eta(6)-C7 H7)Cr(CO)(3)], (OC)(2)CpFe(mu-eta(1):eta(7)-C7H6)Cr(CO)(3)][PF6]. 0.25 CH(2)Cl(2) and [(OC)(2)CpFe(mu-eta(1): eta(7)-C2C7H6)Cr(CO)(3)](+)[BF4 ]. CH2Cl2 have been determined.