Mechanistic aspects of the photochemistry of [CpM(η6-arene)]+ complexes of Fe, Ru and Os

Abstract

Abstract

A Photolabile Fe Catalyst for Light-Triggered Alkyd Paint Curing

“…Photo-induced loss of arene from [(Cp)Fe(arene)] + complexes has been proposed to take place from the triplet exited state, formed by intersystem crossing from the initially formed singlet excited state. [27] Irradiation of 1 in a frozen THF glass under anaerobic conditions in the cavity of an EPR spectrometer resulted in an EPR signal characteristic for an S = 2 (high spin) Fe II species (Figure S18), most likely a [(Cp)Fe(L)] + species (L = solvent), in line with earlier reports of an S = 2 spin state for (coordinatively unsaturated) mono-CpFe II complexes. [28] Freshly dried paint samples (after 1 day of curing) reveal similar (but not identical) S = 2 signals, together with smaller amounts of S = 5/2 signals characteristic for high spin Fe III ions present in Fe2O3 nanoparticles.…”

(Tetramethylcyclobutadiene)cobalt Complexes − Syntheses of Tris(ligand) Derivatives and Structures of [(C4Me4)Co(CO)3]BF4 and [(C4Me4)Co(NCMe)3]PF6

“…It undergoes slow oxidation by CH 2 Cl 2 that is seen as a fast deterioration in the NMR spectra performed in the same solvent. 6 ]acetone/[D 3 ]acetonitrile mixtures (with comparable quantities of free and coordinated acetonitrile), taken at 500 MHz, showed line-broadening at ambient temperature, decoalescence at Ϫ10°C, and below two signals corresponding to a low-temperature exchange regime; at Ϫ84°C, these two signals were sharp with chemical shifts of δ ϭ 2.50 ppm for coordinated acetonitrile and of δ ϭ 2.12 ppm for free acetonitrile.…”

“…Scheme 2. Thermal ligand substitution reactions of [Cb* Co(NCMe) 3 ]PF 6 (8) There are some obvious limitations to this method. The ligand to be introduced should either bind strongly to the metal atom or should be less volatile than acetonitrile.…”

“…[1,2] Early examples of metallo-electrophiles are the 1,5-cyclooctadiene complex [(COD)Rh(THF) x ] ϩ [3] and the cation [Cp*Rh(OCMe 2 ) 3 ] 2ϩ . [4] These species are usually generated from corresponding chlorides by dehalogenation with Ag ϩ or Tl ϩ salts with nonbasic anions such as BF 4 Ϫ , PF 6 Ϫ , or CF 3 SO 3 Ϫ . Weakly coordinating solvents such as nitromethane, dichloromethane, THF, acetone, or acetonitrile are used in the generation of the metallo-electrophiles to provide a maximum reactivity and a minimal stabilization.…”

“…On the other hand, the acetonitrile ligand provides sufficient stabilization to the electrophilic metal center to allow the isolation of less reactive, but welldefined compounds. The species [CpFe(NCMe) 3 ] ϩ , [5,6] [Cp*Fe(NCMe) 3 ] ϩ , [7] [CpRu(NCMe) 3 ] ϩ , [6,8] [Cp*Ru-(NCMe) 3 ] ϩ , [9] and [CpOs(NCMe) 3 ] ϩ [10] are pertinent examples, and the more recently discovered species [Cb* Co(solv) x ] ϩ (Cb* ϭ C 4 Me 4 , solv ϭ inter alia MeCN) [11] is related to these by virtue of the isolobal analogy.…”