Crystallographic Characterization of a Palladium(II) Metallamacrocycle Supported by an Amino-Functionalized Ferrocene and Its Use as an Efficient Suzuki-Coupling Catalyst

Complexation of the bidentate ferrocenylamine [η-C5H4(CH2)2N(CH3)2]2Fe (1) with PdCl2(MeCN)2 in MeOH at room temperature gives air-stable Pd2Cl4{Fe[η-C5H4(CH2)2N(CH3)2]}2
(2; yield 71%) of limited solubility in common organic solvents. X-ray single-crystal diffraction
analyses showed that 2 has self-assembled into a metallamacrocyclic structure comprising
two trans palladium(II) atoms intercalated with two eclipsed bis[(2-(dimethylamino)ethyl)cyclopentadienyl]ferrocene groups, thus forming a {Pd2Fe2} heterometallic molecular
“rectangle”. Chloride abstraction with NH4PF6 leads to decomplexation, giving {[η-C5H4(CH2)2N(CH3)2H]2Fe}{PF6}2 (3), which is the protonated form of 1. Complex 2 effectively
catalyzes Suzuki cross-coupling reactions of aryl bromides with aryl boronic acids in MeOH
at room temperature and 60 °C, giving generally high yields even under low catalytic loads.
The reaction conditions are reported together with comparison with other common catalysts.