Influence of the electronic effects of phosphine ligands upon the properties of cyclopalladated complexes containing a σ(Pd—Csp2, ferrocene)bond X-Ray crystal structures of [Pd{(η5-C5H5)Fe[(η5-C5H3)C(Me)ξN(C6H4-4-Me)]}Cl(PPh3)] and [Pd{(η5-C5H5)Fe[(η5-C5H3)CH2NMe2]}Cl(PPh3)]

Abstract

The synthesis, characterization and study of the properties of the cyclopalladated compounds [Pd{(η⁵-C₅H₅)Fe[(η⁵-C₅H₃)C(Me)N(C₆H₄-4-Me)]}Cl(L)] and [Pd{(η⁵-C₅H₅)Fe[(η⁵-C₅H₃)CH₂NMe₂]}Cl(L)] (L=PPh₃, PPh₂Et, PPhEt₂ or PEt₃) are reported. The comparison of the electrochemical and electronic properties of these compounds has allowed us to elucidate the influence of the phosphine and chelate ligands upon the environment of the Fe^II. As a first approach to clarify the factors affecting the properties of these complexes, molecular orbital (MO) calculations using the PM3(tm) semiempirical method were also undertaken. [Pd{(η⁵-C₅H₅)Fe[(η⁵-C₅H₃)C(Me)N(C₆H₄-4-Me)]}Cl(PPh₃)] (3a) and [Pd{(η⁵-C₅H₅)Fe[(η⁵-C₅H₃)CH₂NMe₂]} Cl(PPh₃)] (3b) have also been characterized structurally. Complex 3a is triclinic, space group P, with a=12.795(2), b=11.534(2) and c=11.267(2) Å and α=106.660(10)°, β=98.660(10)° and γ=94.500(10)°; compound 3b is monoclinic, space group P2₁/a, with a=13.650(3), b=19.678(4) and c=10.169(2) Å and α=γ=90.0° and β=94.69(2)°. In both cases the molecules contain a [5,5] bicyclic system formed by a five-membered palladacycle and the C₅H₃ ring of the ferrocenyl moiety.