Reactivity of iron complexes containing monodentate aminophosphine ligands – Formation of four-membered carboxamido-phospha-metallacycles

Abstract

Treatment of [FeCp(CO)2Cl] with 1 equiv of the amidophosphine ligands Li[R2PNR′] (R = Ph, iPr, R′ = iPr, tBu, Cy) afforded complexes of the type [FeCp(CO)(κ2(C,P)-(CO)–NiPr-PPh2)] (1a), [FeCp(CO)(κ2(C,P)-(CO)-NtBu-PPh2)] (1b), and [FeCp(CO)(κ2(C,P)-(CO)-NCy-PiPr2)] (1c) in 40–50% yields. Complex 1a was also formed when [FeCp(CO)2(PPh2NHiPr)]+ (2) was reacted with 1 equiv of KOtBu. These complexes feature a four-membered carboxamido-phospha-ferracycle as a result of an intramolecular nucleophilic attack of the amidophosphine ligand on coordinated CO. Upon treatment of 1a with the electrophile [Me3O]BF4 the aminocarbene complex [FeCp(CO)(κ2(C,P)C(OMe)-NiPr-PPh2)]+ (3) was obtained bearing an aza-phospha-carbene moiety. Upon treatment of cis,trans,cis-[Fe(CO)2(Ph2PNHiPr)2(Br)2] (4a) and cis,trans,cis-[Fe(CO)2(Ph2PNHtBu)2(Br)2] (4b) with KOtBu the carboxamido-phospha-ferracycles trans-[Fe(CO)2(κ2(C,P)-(CO)-NiPr-PPh2)(Ph2PNHiPr)Br] (5a) and trans-[Fe(CO)2(κ2(C,P)-(CO)-NtBu-PPh2)(Ph2PNHtBu)Br] (5b) were formed in moderate yield. Finally, representative structures were determined by X-ray crystallography.

Coordinatively Labile 18‐Electron Arene Ruthenium Iminophosphonamide Complexes

“…The peculiarity of the monocarbonyl intermediate C is the high nucleophilicity of the nitrogen atoms, which is related to the presence of more electron‐donating alkyl substituents. Although facile CO insertion into M−N bonds is a known phenomenon for certain metal aminopyridinates, triazenides, amidinates, and aminophosphines, to the best of our knowledge, this reaction has not been previously reported for arene ruthenium complexes. The process that most resembles the formation of 3 c involves a carbene insertion into a Ru−N bond in the arene ruthenium amidinate complex [(C 6 Me 6 )Ru{( i PrN) 2 CMe}](PF 6 ), followed by CO coordination to give [(C 6 Me 6 )Ru(CO){( i PrN)CMe(N i Pr)CHSiMe 3 }](PF 6 ) ( 5 ) .…”

Dibromine Promoted Transmetalation of an Organomercurial by Fe(CO)5: Synthesis, Properties, and Cytotoxicity of Bis(2-C6H4-2′-py-κC,N)dicarbonyliron(II)

“…No further characterization could be achieved because of its low solubility in CH 2 Cl 2 , CHCl 3 , acetone, methanol, ethanol, DMF, and CH 3 CN. In another series of experiments, we started with [FeBr 2 (CO) 4 ], as it is known that the CO and Br – can be substituted by N, P, and S donor ligands. − The reaction between sublimed [FeBr 2 (CO) 4 ] and phpyH in acetonitrile at room temperature produced a yellow solid which could not be characterized because of its insolubility. These two examples demonstrated the difficulties in the synthesis via C–H bond activation.…”

Production of Formamides from CO and Amines Induced by Porphyrin Rhodium(II) Metalloradical

“…The synthetic utilization of carbon monoxide (CO) in the construction of carbonyl containing organic materials is of great significance in sustainable chemistry. − The mechanism that predominates over a myriad of CO activation strategies starts from the linear coordination of CO to the metal center, from which the strong CO bond is activated by the π-back bonding (Figure a). The final products are almost universally formed via nucleophilic attack on the weakened CO bond, − which reduces the scope of substrates eligible for the carbonylation and restricts the design of new CO conversion pathways. Alternative CO activation strategies aiming at breaking this limitation can be envisioned by transforming CO to more reactive intermediates, such as carbonyl cations, anions, or radicals (Figure b), , which can further activate other substrates with low activation energy barriers.…”