Iron pyrrole-based PNP pincer ligand complexes as catalyst precursors

The structure of a pincer ligand consists of a backbone and two 'arms' which typically contain a P or N atom. They are tridentate ligands that coordinate to a metal center in a meridional configuration. A series of three iron complexes containing the pyrrole-based PNP pincer ligand 2,5-bis[(diisopropylphosphanyl) methyl]pyrrolide ((PNP)-P-pyr) has been synthesized. These complexes are possible precursors to new iron catalysts. {2,5-Bis[(diisopropylphosphanyl)methyl] pyrrolido-kappa(3) P, N, P'}carbonylchlorido(trimethylphosphane-kappa P) iron(II), [Fe(C18H34NP2)Cl(C3H9P)(CO)] or [Fe((PNP)-P-pyr)Cl(PMe3)(CO)], (I), has a slightly distorted octahedral geometry, with the Cl and CO ligands occupying the apical positions. {2,5-Bis[(diisopropylphosphanyl)methyl]pyrrolido-kappa(3) P, N, P'}chlorido(pyridine-kappa N)iron(II), [Fe(C18H34NP2)Cl(C5H5N)] or [Fe((PNP)-P-pyr)Cl(py)] (py is pyridine), (II), is a five-coordinate square-pyramidal complex, with the pyridine ligand in the apical position. {2,5-Bis[(diisopropylphosphanyl)methyl]pyrrolido-kappa(3) P,N,P'}dicarbonylchloridoiron(II), [Fe(C18H34NP2)Cl(CO)(2)] or [Fe((PNP)-P-pyr)Cl(CO)(2)], (III), is structurally similar to (I), but with the PMe3 ligand replaced by a second carbonyl ligand from the reaction of (II) with CO. The two carbonyl ligands are in a cis configuration, and there is positional disorder of the chloride and trans carbonyl ligands.