A Ferrocene‐Based Dicationic Iron(IV) Carbonyl Complex

Abstract

The 16-valence electron species [Cp* Fe] (Cp*=η-C Me ), formally featuring a tetravalent iron ion, quantitatively binds CO in HF solution to form the stable, diamagnetic carbonyl species [Cp* Fe(CO)] . This dication forms salts in the presence of AsF and SbF that were crystallographically characterized. The molecular structure in crystals of [Cp* Fe(CO)](AsF ) displays cyclopentadienyl rings that are clearly not parallel and an equatorially bound η -CO ligand. The formal oxidation state +IV of iron was investigated by Fe Mössbauer spectroscopy and is supported by DFT computational analysis. A detailed spectroscopic characterization of the hitherto unprecedented high-valent iron carbonyl compounds is reported.

Synthesis and Application of a Perfluorinated Ammoniumyl Radical Cation as a Very Strong Deelectronator

“…This lies between reported Fe‐(CN‐R) bond lengths of divalent [Fe II Cp(CO) 2 (CN‐Me)][BF 4 ] ( d Fe‐C =1.900(9) Å) and zero‐valent Fe(CO) n (CN‐ t Bu) m ( d Fe‐C =1.89 { n =4, m =1} 1.865(2) { n =3, m =2} 1.813(7) to 1.837(7) { n =0, m =5} Å) and is by 0.09 Å longer than in the related [Fe(CO)Cp* 2 ][AsF 6 ] 2 (cf. d Fe‐C =1.785(9) Å) . Its C≡N stretching frequency is slightly blue‐shifted to 2176 cm −1 (cf.…”

“…When repeating the reaction between [FeCp* 2 ][Al(OR F ) 2 ] and 4 under 3 atm of CO gas in o DFB, a ready color change from deep purple to red‐brown was observed allowing access to the 18 VE dicationic Fe IV complex [Fe(CO)Cp* 2 ][Al(OR F ) 4 ] 2 7 in 63 % crystalline yield. The [Fe(CO)Cp* 2 ] 2+ dication was hitherto only accessible in aHF . Compound 7 was crystallized from concentrated o DFB solution by either vapor diffusion or layering of the reaction mixture with n ‐pentane.…”

Back-bonding between an electron-poor, high-oxidation-state metal and poor π-acceptor ligand in a uranium(v)–dinitrogen complex

“…20,21 Very few isolable, structurally characterised end-on CO, N 2 , or NO actinide complexes are known, [22][23][24][25][26][27][28][29] and all terminal end-on complexes are supported by tris(cyclopentadienyl) ligand sets. [22][23][24][25][27][28][29] The back-bonding in these systems stems not from metal orbitals but cyclopentadienyl ligand orbitals, 30 reminiscent of transition metal analogues, 11 or in the case of NO formal full reduction to (NO) 1occurs, 29 so these are quite different from the classical metal-to-ligand back-bonding model. 1 Notably, all uranium complexes with end-on CO or N 2 involve electron-rich 5f 3 uranium(III).…”

“…7 Transient or matrix isolationtrapped M(IV) [M(O) 2 (CO) n ] (M = Rh, n = 1; M = Mo, W, n = 4) species have been detected spectroscopically, 8,9 and the formally +VI osmium dication [OsO 2 (CO) 4 ] 2+ has been reported, but was too unstable to be isolated and fully characterised. 10 Very recently the Fe(IV) dication [Fe(η 5 -C 5 Me 5 ) 2 (CO)] 2+ was structurally authenticated, 11 but is stabilised via C 5 Me 5 -to-CO ligand-to-ligand π-back-bonding. This bonding type is a departure from the classical model, and appears to be unique to metallocene complexes, being similarly proposed for d 0 M(IV) [M(η 5 -C 5 Me 5 ) 2 (H) 2 (CO)] (M = Zr, Hf) species detected spectroscopically at low temperature.…”

“…Back-bonding between an electron-poor, high-oxidation-state metal and poor -acceptor ligand in a uranium(V)-dinitrogen complex. Nature Chemistry,11,[806][807][808][809][810][811] Back-bonding between an electron-poor, high-oxidation-state metal and poor π-acceptor ligand in a uranium(V)-dinitrogen complex Abstract A fundamental bonding model in coordination and organometallic chemistry is the synergic, donor-acceptor interaction between a metal and a neutral π-acceptor ligand where the ligand σdonates to the metal, which π-back-bonds to the ligand. This interaction typically involves a metal with an electron-rich, mid-, low-, or even negative, oxidation state and a ligand with a π* orbital.Here, we report that treatment of a uranium-carbene complex with an organo-azide produces a uranium(V)-bis(imido)-dinitrogen complex, stabilised by a lithium counter-ion.…”