Gas-phase ligand substitution reactions with the 17-electron transition-metal complexes (OC)4Fe.-, (OC)5Cr.-, and (OC)4MnH.-

Article abstract of DOI:10.1021/om00098a020

Three transition-metal complex negative ions, (OC)₄Fe^.-, (OC)₅Cr^.-, and (OC)₄MnH^.-, were generated and studied in ligand substitution reactions with a variety of neutral ligand substrates. Only (OC)₄Fe^.- reacted with PF₃ and gave sequentially the product ions (OC)_4-xFe(PF₃)_x^.- where x = 1-3. The three metal complex negative ions formed ligand substitution product anions with NO; the reaction with (OC)₄MnH^.- also produced some of the corresponding adduct anion. With SO₂, (OC)₄Fe^.- gave only ligand substitution, (OC)₅Cr^.- formed a mixture of the adduct and the product of ligand substitution, and (OC)₄MnH^.- produced only the adduct. Both the NO and SO₂ reactions were believed to occur by the associative mechanism with the SO₂ reactions proceeding via Lewis acid-base complexes. Only (NC)₂C=C(CN)₂ (TCNE) of the seven olefins examined reacted with the metal complex negative ions forming the product of electron transfer (TCNE^.-) as well as the product ions of ligand substitution. The reactions of all three metal complex negative ions with (CF₃)₂C=O and of (OC)₅Cr^.- with biacetyl were considered to involve initial electron transfer within the orbiting collision complex. The reaction of (OC)₄MnH^.- with O₂ produced various oxidation products, the most noteworthy being HCO₂^- as a major product anion. This latter result is considered to be evidence for the migratory insertion reaction, OC-Mn-H ? Mn-CHO, in the adduct formed from (OC)₄MnH^.- with O₂.