Electron transfer activity of nickelacyclic complex analogues of nickelocene: Synthesis of (eta(5)-R-cyclopentadienyl){eta(4)-[1-(eta(5)-R-cyclo pentadienyl)]-2,3,4,5-tetraphenyl-1-nickela-2-cyclopentenyl}nickel complexes (R=H,CH3) and crystal structures of the redox couples [(eta(5)-methylcyclopentadienyl){eta(4)-[1-(eta(5)-methylcyclopentadieny l)]-2,3,4,5-tetraphenyl-1-nickela-2-cyclopentenyl}nickel]((0/+)) and [(eta 5-methylcyclopentadienyl){eta(5)-[1(eta(5)-methylcyclopentadienyl)-1-nic kelafluorenyl}nickel]((0/+))