Mono- and bis(cyclopalladation) of the bis(ferrocenylimine) [(η5-C5H5)Fe{(η5-C5H4)-CH=N-(C6H3-2-CH3)-}]2

Article abstract of DOI:10.1016/S0022-328X(96)06404-2

The reaction of the novel bis(ferrocenylimine) [(η⁵-C5H5)Fe{(η⁵-C 5H4)-CH=N-(C6H3-2-CH3)-}] 2 (1) with Na2[PdCl4] and NaCH3COO - 3H2O in methanol in a 1:2:2 or a 1:1:1 molar ratio produces the polynuclear di-μ-chloro-bridged cyclopalladated compounds [Pd2{η⁵-C 5H5)Fe[(η⁵-C5H3)-CH=N-(C6H3-2-CH3)-]} 2(μ-Cl)2]2 (2a) or [Pd{(η⁵-C 5H5)Fe[(η⁵-C5H3)-CH=N-C6H3-2-(CH3)-4-{(C 6H3-2′-CH3)-N=CH-(η⁵-C5H4)}]Fe(η⁵-C 5H5)}(μ-Cl)] 2 (2b) respectively, which arise from the activation of two (for 2a) or one (for 2b) σ(Csp²,ferrocene-H) bonds. Addition of triphenylphosphine to benzene suspensions of compounds 2 produces the cleavage of the 'Pd(μ,-Cl)2Pd' units and the formation of [Pd2{η⁵-C 5H5)Fe[(η⁵-C5H3)-CH=N-(C6H3-2-CH3)-]} 2Cl2(PPh3)2] (3a), or [Pd{(η⁵-C 5H5)Fe[(η⁵-C5H3)-CH=N-C6H3-2-(CH3)-4-{C 6H3-(2′-CH3)-N=CH-(η⁵-C5H4)}]Fe(η⁵-C 5H5)}Cl(PPh 3)] (3b). Proton and ³¹P NMR studies on compounds 3 confirm the existence of two (in 3a) or one (in 3b) five-membered palladocycles fused with the ferrocenyl units, and a trans arrangement of the PPh3 ligand and the imine nitrogen. Electrochemical studies of these compounds are also reported.