Heterobimetallic Silver-Iron Complexes Involving Fe(CO) Ligands.

Iron(0) pentacarbonyl is an organometallic compound with a long history. It undergoes carbonyl displacement chemistry with various donors (L), leading to molecules of the type Fe(CO)(L). The work reported here illustrates that Fe(CO) can also act as a ligand. The reaction between Fe(CO) with the silver salts AgSbF and Ag[B{3,5-(CF)CH}] under appropriate conditions resulted in the formation of [(μ-HO)AgFe(CO)][SbF] and [B{3,5-(CF)CH}]AgFe(CO), respectively, featuring heterobimetallic {Ag-Fe(CO)} fragments. The treatment of [B{3,5-(CF)CH}]AgFe(CO) with 4,4'-dimethyl-2,2'-bipyridine (MeBipy) and Fe(CO) afforded a heterobimetallic [(MeBipy)AgFe(CO)][B{3,5-(CF)CH}] species with a Ag-Fe(CO) bond and a heterotrimetallic [{Fe(CO)}(μ-Ag)][B{3,5-(CF)CH}] with a (CO)Fe-Ag-Fe(CO) core, respectively, illustrating that it is possible to manipulate the coordination sphere at silver while keeping the Ag-Fe bond intact. The chemistry of [B{3,5-(CF)CH}]AgFe(CO) with EtO and PMes (Mes = 2,4,6-trimethylphenyl) has also been investigated, which led to [(EtO)Ag][B{3,5-(CF)CH}] and [(MesP)Ag][B{3,5-(CF)CH}] with the displacement of the Fe(CO) ligand. X-ray structural and spectroscopic data of new molecules as well as results of computational analyses are presented. The Fe-Ag bond distances of these metal-only Lewis pairs range from 2.5833(4) to 2.6219(5) Å. These Ag-Fe bonds are of primarily an ionic/electrostatic nature with a modest amount of charge transfer between Ag and Fe(CO). The ν̅(CO) bands of the molecules with Ag-Fe(CO) bonds show a notable blue shift relative to those observed for free Fe(CO), indicating a significant reduction in Fe→CO back-bonding upon its coordination to silver(I).