Heterobimetallic Silver–Iron Complexes Involving Fe(CO)₅Ligands

Abstract

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).

Stable salts of the hexacarbonyl chromium(I) cation and its pentacarbonyl-nitrosyl chromium(I) analogue

“…Whilst Ag + ( E ° = +0.65 V vs. Fc/Fc + in CH 2 Cl 2 ) 37 deelectronates [Co 2 (CO) 8 ] in CO atmosphere generating [Co(CO) 5 ] + at room temperature (r.t.) in ortho-difluorobenzene ( o DFB) 38 , its redox potential is too low to oxidize Fe(CO) 5 . This leads to the formation of the peculiar metal-only Lewis pair [Ag{Fe(CO) 5 } 2 ] + 39,40 . [NO] + might be a strong enough oxidant (cf.…”

Group 6 Hexacarbonyls as Ligands for the Silver Cation: Syntheses, Characterization, and Analysis of the Bonding Compared with the Isoelectronic Group 5 Hexacarbonylates

“…As ubsequentc rystallization from TFB layered with n-pentane gave an 86 %y ield of ac rystalline material, whichw as shown by powder X-ray diffractiona nalysis to be the phase-pure product ( Figure S2 in the SupportingI nformation). It seems likely that the synthesis also works when TFB is used as as ol-vent altogether.T he same method can also be appliedt o Mo(CO) 6 and yields colorless crystals of [Ag{Mo(CO) 6…”

“…Mo(CO) 6 :2 05.9(4) pm, [18] W(CO) 6 :2 04.9(5) pm [19] ), the experimental MÀCO bonds are shorter for W( Ta ble 1) unlike in the calculations.H owever, owing to thel arge standard deviations for the Ws tructure as well as the 150 Kd ata for the Mo system,t hese data should be interpreted with caution. For comparison, Ta ble 1i ncludes the spectroscopic and structural data of [Ag{Fe(CO) 5 [7] The Ramans pectra of [Ag{Mo(CO) 6…”

“…[Ag{Mo(CO) 6 [a] [Ag{W(CO) 6 [a] [Ag{Cr(CO) 6 } 2 ] + calcd [a] Assignment[ Ag{Fe(CO) 5 } 2 ] + -[Al(OR F ) 4 ] À [7] ñ (CO) IR [cm À1 ] - that the charged ensitiesr esiding on the AgÀCb cpsa re consistently higherthan those on the existing AgÀMbcps. EDA-NOCV analysis:W ea nalyzed the bondings ituation in [Ag{M(CO) 6 } 2 ] + (M = Cr,M o, W) with the EDA-NOCV method [23] focusingo nt he orbital interactions between Ag + and the {M(CO) 6 } 2 ligands.…”

“…The [Ag{Fe(CO) 5 } 2 ] + cation was the first, reported by us in 2014 and re-investigated by the Dias group in 2017. [6,7] Interestingly, unlike its neutral or anionic relatives, it featured an, at that time, unprecedented coordinationo faneutral carbonyl complex to as ilver cation ( Figure 1). We note that Ag + complexes with octahedral transitionm etal carbonyl units [M(CO) 6 ] x (x = À1, M = V, Nb, Ta ; x = 0, M = Cr,Mo, W) are hitherto rather scarce and only in 2020 the first examples [8,9] fora ny [Ag a {M(CO) 6 } b ] c units were published with M = Nb and Ta and the series of ions included with Figure 1.…”