Nucleophilic addition to organotransition metal cations containing unsaturated hydrocarbon ligands

Abstract:Hydride and cyanide addition to a series of di-and polycyclopentadienyliron arene complex cations with etheric bridges is described. Reaction of the di-iron complexes with sodium borohydride resulted in the formation of a number of adducts. p-Methyl-and o,o-dimethylphenoxybenzene cyclopentadienyliron complexes were used as models in this study to allow for the characterization of the analagous di-iron complexes. The use of HH COSY and CH COSY NMR techniques enabled us to identify the isomeric nature of these adducts. The hydride addition results indicated that the etheric substituent had the predominant effect over the methyl group, leading to a higher addition ratio to the meta-, followed by the ortho-, then the para-positions. It was also clear that in the di-iron system, the hydride addition to each complexed arene ring took place independently. The addition of the cyanide anion to di-and poly-iron arene systems was more selective than that of the hydride anion. Reaction of sodium cyanide with p-methyl-or o-methyl-substituted arene complexes led to the formation of one adduct, with the cyanide being added to the meta position to the etheric bridges. However, cyanide addition to the di-iron complex, with a methyl substituent attached at the meta position of each complexed arene, led to the formation of a mixture of adducts. Cyanide addition to the poly-iron system withp-substituted arenes proved to be very selective, allowing for the formation of one adduct.Oxidative demetallation with 2,3-dichloro-5,6-dicyano-1.4-benzoquinone (DDQ) produced the uncomplexed polyaromatic ethers with cyano groups in a very good yield. des Cthers polyaromatiques non complexCs portant des groupes cyano.

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Nucleophilic addition to di- and poly-iron arene complex cations

Abd‐El‐Aziz¹,

Armstrong²,

Bernardin³

et al. 1996

“…Nucleophilic attack on metal-complexed polyenyls generally occurs at one of the termini of the delocalized system (19) For personal use only.…”

Section: Discussionmentioning

confidence: 99%

The reactions of nitrosoarenes with cationic cyclohexadienyl complexes of iron tricarbonyl: an ESR study

Li¹,

Perrier²,

Eaton³

et al. 1989

. Can. J. Chem. 67, 1868Chem. 67, (1989. The reactions of nitrosoarenes with the (cy~lohexadienyl)Fe(CO)~ cation have been investigated by using electron spin resonance spectroscopy. The radicals produced are nitroxides of the type (0Q3Fe(C6H7)(Ar)N-O. but, in some cases, disproportionation and loss of the metal carbonyl fragment leads to the corresponding C6H5(k)N-o* radical. With bulky nitrosoarenes, such as C&ieSNO, isomers are observed in which the aryl ring rotation is slow on the ESR time scale. The analogous reactions with the cyclohexadienyl cation derived from the B ring of (ergosteryl a~etate)Fe(CO)~ lead to initial attack not at one of the termini of the delocalized system but rather at the central carbon, i.e., at C-7. Subsequent hydrogen migration leads to the (5,7-diene)Fe(C0)3 complex bearing the arylnitroxide at the 7-position. The mechanisms of these reactions are discussed.Key words: nitrosoarenes, iron cations, ESR.LIJUAN LI, RICHARD E. PERRIER, DONALD R. EATON et MICHAEL J. MCGLINCHEY. Can. J. Chem. 67, 1868 (1989. Utilisant la spectroscopie RPE, on a &tudiC les reactions des nitrosoarenes avec le cation (cy~lohexadiCnyl)Fe(CO)~. Les radicaux qui sont produits sont des nitroxydes du type (OC)3Fe(C6H7)(Ar)N-0.; toutefois, dans quelques cas, il se produit une disproportionation et la perte du fragment mCtallocarbonyle conduit h la formation du radical C6HS(Ar)N--O* correspondant. Avec des nitrosoarenes encombrts, comrne le C6Me5N0, on observe la formation d'isomeres dans lesquels la rotation du noyau aryle est lente pour l'tchelle de temps de la RPE. Les reactions analogues effectuees sur le cation cyclohexadiCnyle derive du cycle B de l'(ac6tate d'erg~stCryle)Fe(CO)~ conduisent a une premiere attaque qui s'effectue sur le carbone central, C-7, et non sur les extrCmitCs du systtme dClocalisC. Une migration subsequente d'hydrogkne conduit au complexe (5,7-ditr1e-Fe(CO)~ portant le nitroxyde d'aryle en position 7. On discute des mCcanismes de ces reactions.Mots cle's : nitrosoarknes, cations du fer, RPE.[Traduit par la revue]

“…Attention has recently concentrated upon cyclohexadienyl (Ch) ligands as possible reaction intermediates for bifunctionalized arenes (1)(2)(3)(4)(5), for synthetically applicable cyclohexadienes (6), or for highly substituted arenes (7). However, progress has been impeded by the lack of facile, high yield routes to cyclohexadienyl intermediates via inexpensive and readily available substrates.. For example, traditional alkylating reagents such as organolithiums, Grignards, and organocuprates often react to yield undesirable products (5).…”

Section: Introductionmentioning

confidence: 99%

Synthesis, characterization, and dynamic behaviour of pseudoferrocene complexes

Clerk¹,

Zaworotko²,

Borecka³

et al. 1990

Carbanion sources (organolithium and Grignard reagents) react with [(me~it~lene)~Fe]~' and [(mesitylene)(Ch)FeIf cations (Ch = cyclohexadienyl) to afford neutral Ch2Fe and ChCh'Fe ("pseudoferrocene") complexes, respectively. Addition of R-(R-= methyl, phenyl, benzyl, and t-butyl) occurs stereospecifically via exo addition at an unsubstituted carbon atom of the arene ring. The synthesis and characterization of these complexes is detailed and the structure of bi~(q~-exo-6-~hen~1-1,3,5-trimethylcyclohexadieryl)iron(II), 36, has been determined by single crystal X-ray diffraction analysis. 36 crystallizes in the triclinic space group P1, with a = 11.947(2), 6 = 12.784(1), c = 8.865(2), a = 108.59(1)", P = 108.19 (1)