ASNA-ETA-CYCLOPENTADIENYLIMIDE DERIVATIVES OF NIOBIUM

Treatment of the ansa-bridged eta-cyclopentadienylimide compound [Nb{e ta(5),kappa N-C5H4(CH2)(3)N}Cl-2] 1 with MgMeBr gave the binuclear ans a-bridged eta-cyclopentadienylimide derivative [MeNb{mu-C5H4(CH2)(3)N} -{mu-NCH(CH2)(2)C5H4}NbMe2] 2. The crystal structure of 2 has been det ermined. Detailed H-1 and C-13 NMR studies showed that 2 undergoes an interesting fluxional process involving interchange of two methyl grou ps under an ansa arch. Reaction of 1 with Na(C5H5) gave [Nb{eta(5),kap pa N-C5H4(CH2)(3)N}(eta(5)-C5H5)(eta(1)-C5H5)] 3, which is also fluxio nal and undergoes diverse dynamic processes including exchange between eta(1)- and eta(5)-cyclopentadienyl rings. The compounds [Nb{eta(5),k appa N-C5H4(CH2)(3)N}(CH2Ph)(2)] and [Nb{eta(5),kappa N-C5H4(CH2)(3)N} {CH2C(Me)CH2}(2)] have also been prepared.