2,2'-Pyridylpyrrolide ligand redistribution following reduction

The potential redox activity of the 2,2'-pyridylpyrrolide ligand carrying two CF3 substituents (L(2)) is investigated. Synthesis and characterization of d(6) and d(7) species M(L(2))2 for M = Fe and Co are described (both are nonplanar, but not tetrahedral), as are the Lewis acidity of each. In spite of CV evidence for quasireversible reductions to form M(L(2))2(q-) where q = 1 and 2, chemical reductants instead yield divalent metal complexes KM(L(2))3, which show attractive interactions of K(+) to pyrrolide, to F, and to lattice toluene π cloud. The collected evidence on these products indicates that pyridylpyrrolide is a weak field ligand here, but CO can force spin pairing in Fe(L(2))2(CO)2. Evidence is presented that the overall reductive reaction yields 33 mol % of bulk metal, which is the fate of the reducing equivalents, and a mechanism for this ligand redistribution is proposed. Analogous ligand redistribution behavior is also seen for nickel and for trimeric monovalent copper analogues; reduction of Cu(L(2))2 simply forms Cu(L(2))2(-).