Cyclodimerization of 1-(Dimethoxyniethyl)-5,6-dimethylidene-7-oxa-bicyclo[2.2.1]hept-2-ene Induced by Nonacarbonyldiiron. Crystal Structure of (1RS, 2SR, 3RS, 4RS, 4aRS, 9aSR)- Tricarbonyl[C, 2,3, C-η-(1,4-epoxy-1,5-bis(dimethoxymethyl)-2,3-dimethylidene-1,2,3,4,4a,9,9a,10-octahydroanthracene)]iron

The transition-metal-carbonyl-induced cyclodimerization of 5,6-dimethylidene-7-oxabicyclo[2.2.1]hept-2-ene is strongly affected by substitution at C(1) While 5,6-dimethylidene-7-oxabicyclo[2.2.1]hept–2-ene-l-methanol ( 7 ) refused to undergo [4 + 2]-cyclodimerization in the presence of [Fe₂(CO)⁹] in MeOH, 1-(dimethoxymethyl)-5,6-di-methylidene-7-oxabicyclo[2.2.1]hept-2-ene ( 8 ) led to the formation of a 1.7:1 mixture of ‘trans’ ( 19, 21, 22 ) vs. ‘cis’ ( 20, 23, 24 ) products of cyclodimerization together with tricarbonyl[C, 5,6, C-η-(l-(dimethoxymethyl)-5,6-di-methylidenecyclohexa-1,3-diene)]iron ( 25 ) and tricarbonyl[C,3,4, C-η-(methyl 5-(dimethoxymethyl)-3,4-di-methylidenecyclohexa-1,5-diene-l-carboxylate)]iron ( 26 ). The structures of products 19 and of its exo ( 21 ) and endo ( 22 ) [Fe(CO)₃(1,3-diene)]complexes) and 20 (and of its exo ( 23 ) and endo (24) (Fe(CO)₃(1,3-diene)complexes) were confirmed by X-ray diffraction studies of crystalline (1RS, 2SR, 3RS, 4RS, 4aRS, 9aSR)-tricarbonyl[C, 2,3, C-η-(1,4-epoxy-1,5-bis(dimethoxymethyl])-2,3-dimethylidene-1,2,3,4,4a,9,9a,10-octahydroanthracene)iron ( 21 ). In the latter, the Fe(CO)₃(1,3-diene) moiety deviates significantly from the usual local C_s symmetry. Complex 21 corresponds to a ‘frozen equilibrium’ of rotamers with η-alkyl, η³-allyl bonding mode due to the acetal unit at the bridgehead centre C(1).     

The kinetics and mechanism of diene exchange in (η4-enone) Fe(CO)2L complexes (L = phosphine,phosphite)

Kinetic data for the exchange of 1,3-cyclohexadiene with (η⁴-benzylideneacetone)Fe(CO)₂L complexes (L = CO, PPh_3-xMe_x (x = 0-2) or P(OPh)₃) to give (η⁴-1,3-cyclohexadiene)Fe(CO)₂L derivatives indicate a mechanism involving stepwise competing D and I_d opening of the ketonic M-CO π-bond. Rates increase in the order CO ? PPh₃ ≈ P(OPh)₃ > PPh₂Me ? PPhMe₂, and both steric and electronic factors appear to be important. (η⁴-1,3-cyclohexadiene)Fe(CO)₂L complexes of potential use in enantioselective synthesis (L=(+)-Ph₂P(menthyl) or (+)-Ph₂PCH₂CH(Me)Et) may be prepared via their (η⁴-benzylideneacetone)Fe(CO)₂L complexes.     

Synthesis and characterization of complexes η5,η5-(CO)3Mn(C5H4-C5H4)(CO)2Fe-η1,η5-C5H4Mn(CO)3 and μ-(C≡C)[C5H4(CO)2Fe-η1,η5-C5H4Mn(CO)3]2

The complex η⁵,η⁵-(CO)₃Mn(C₅H₄-C₅H₄)(CO)₂Fe-η¹,η⁵-C₅H₄Mn(CO)₃ was synthesized by the reaction of η⁵-Cp(CO)₂Fe-η¹,η⁵-C₅H₄Mn(CO)₃ with BuⁿLi (THF, ?78 °C) and then with anhydrous CuCl₂. The complex μ-(C≡C)[C₅H₄(CO)₂Fe-η¹,η⁵-C₅H₄Mn(CO)₃]₂ was prepared by the reaction of η⁵-IC₅H₄(CO)₂Fe-η¹,η⁵-C₅H₄Mn(CO)₃ with Me₃SnC≡CSnMe₃ (2:1) in the presence of Pd(MeCN)₂Cl₂.     

Komplexchemie reaktiver organischer verbindungen : XXXIX. Synthese eines 1,3-dien-komplexes durch metallzentrierte ethylen-isomerisierung unter CC-kupplung

Metal-centered ethylene isomerization occurs under relatively mild conditions when the η¹-acyl/η³-allyl type diphenylketeneiron complex [(C₆H₅)₂CCO]Fe(CO)₃ is treated with ethylene. The resulting, structurally characterized 1,3-diene complex formally results from replacement of an ethylidene building block (ex ethylene) for the carbonyl moiety of the heterocumulene ligand.     

Synthese und Struktur von η1‐Phosphaallyl‐, η1‐Arsaallylund η1‐Stibaallyleisen‐Komplexen [(η5‐C5Me5)(CO)2Fe–E(SiMe3)C(OSiMe3)=CPh2] (E = P,As, Sb)

Syntheses and Structures of η¹‐Phosphaallyl, η¹‐Arsaallyl, and η¹‐Stibaallyl Iron Complexes [(η⁵‐C₅Me₅)(CO)₂Fe–E(SiMe₃)C(OSiMe₃)=CPh₂] (E = P, As, Sb) The reaction of equimolar amounts of [(η⁵‐C₅Me₅)(CO)₂Fe–E(SiMe₃)₂] ( 1 a : E = P; 1 b : As; 1 c : Sb) and diphenylketene afforded the η¹‐phosphaallyl‐, η¹‐arsaallyl‐, and η¹‐stibaallyl complexes [(η⁵‐C₅Me₅)(CO)₂Fe–E(SiMe₃)C(OSiMe₃)=CPh₂] ( 2 a : E = P; 2 b : As; 2 c : Sb). The molecular structures of 2 b and 2 c were elucidated by single crystal X‐ray analyses.     

Synthesis and structures of the η5-C5H5Cl(CO)2W-η1,η5-(PPh2)C5H4(CO)2Fe-η1,η5-C5H4Mn(CO)3 and MeSi[C5H4(CO)2Fe-η1,η5-C5H4Mn(CO)2PPh3]3 complexes

The metallation of the η⁵-C₅H₅(CO)₂Fe-η¹,η⁵-C₅H₄Mn(CO)₃ complex with BuⁿLi (THF, ?78 °C) followed by the treatment of the lithium derivative with Ph₂PCl afforded the η⁵-Ph₂PC₅H₄(CO)₂Fe-η¹,η⁵-C₅H₄Mn(CO)₃ complex. The reaction of the latter with η⁵-C₅H₅(CO)₃WCl in the presence of Me₃NO produced the trinuclear complex η⁵-C₅H₅Cl(CO)₂W-η¹,η⁵-(Ph₂P)C₅H₄(CO)₂Fe-η¹,η⁵-C₅H₄Mn(CO)₃. The structure of the latter complex was established by IR, UV, and 1H and ³¹P NMR spectroscopy and X-ray diffraction. The reaction of MeSiCl₃ with three equivalents of LiC₅H₄(CO)₂Fe-η¹,η⁵-C₅H₄Mn(CO)₂PPh₃ gave the hexanuclear complex MeSi[C₅H₄(CO)₂Fe-η¹,η⁵-C₅H₄Mn(CO)₂PPh₃]₃.     

Synthesis and 1H-, 13C-, and 57Fe-NMR spectra of mono- and bis[tricarbonyl(η4-diene)iron], and (η3-allyl)tetracarbonyliron trifluoroborate complexes

A variety of mono- and bis[Fe(CO)₃(η⁴-diene)] complex with alky, CH₂OH, CHO, COCH₃, COOR, and CN substituents on the 1,3-diene system have been synthesized. Dienes with a (Z)-configuration terminal Me group show steric inhibition of metal complexation resulting in lower yields and formation of tetracarbonyl(η²-diene) and tricarbonyl(η⁴-heterodiene) complexes as additional products. Regioselective attack by C-nucleophiles at the carbonyl C-atoms of the functional group with or without concomitant 1,3 mogration of the Fe(CO)₃ group was used to synthesize polyenes and isoprenoid building blocks as mono- or dinucliar Fe(CO)₃ complexes. Wittig-Horner-type reactions of Fe(co)₃-complexed synthons result in sterospecific formation of (E)-configurated olefins. The ¹H-, ¹³C- and ⁵⁷Fe-NMR spectra of olefinic and allylic organoiron complexes are reported, H,H,C,H, and C,C coupling constants have been evaluated and are analyzed in terms of the geometry of the coordinated diene. The results are corroborated by the crystal structure of tricarbonyl[3–6-η-((E)-6-methyl-3,5-heptadiene-2-one)]iron( 34 ) which shows an unusual distortion of the (CH₃)₂C = group, The ⁵⁷Fe-NMR chemical shifts extend over the ranges of 0–600 ppm for [Fe(CO)₃(η⁴-diene)] complexes, 780–1710 ppm for [Fe(CO)₄(η³-allyl)] [BF₄] and [FeX(CO)₃(η⁴-allyl)] complexes, and 1270–1690 ppm for [Fe(CO)₃(η⁴-enone)] complexes, relative to Fe(CO)₅.     

CC bond formation using allylic organozirconium compounds. Nucleophilic additions on to isolated and in situ generated η-pentadienyl-Fe(CO)3/Fe(CO)2PPh3(+1) cations

Two nucleophilic allylic organozirconium compounds 9-10 (R⁵: Me and tBu) have been reacted with acyclic isolated η⁵-pentadienyl-Fe(CO)₃/Fe(CO)₂PPh₃(+1) cations or with these intermediates generated in situ (Uemura-like conditions). Depending on reaction conditions, iron-complexed η⁴-dienyl-Fe(CO)₃/Fe(CO)₂PPh₃ and σ,η³-π-allyl-Fe(CO)₃/Fe(CO)₂PPh₃ condensation products have been selectively isolated and fully characterized.     

Darstellung und Charakterisierung von kationischen η2-1-Buten- und Acetonitrilkomplexen

Preparation and Characterization of Cationic η²-1-Butene and Acetonitrile Complexes The reaction of the species η⁵-C₅H₅M(CO)_n-σ-C₄H₇ (M = Fe, Mo, W; n = 2, 3) with (C₆H₅)₃CBF₄ yielded – instead of the expected cationic butadiene complexes of the type [η⁵-CpM(CO)_n?1-η⁴-C₄H₆][BF₄], which would have been formed in case of hydride cleavage – compounds of the type [η⁵-CpM(CO)_n η²-C₄H₈][BF₄], which were formed by protonation of the σ-C₄H₇ ligands. The reaction proceeded quantitatively. The BF₄^? anion can be substituted by other anions, such as ClO₄^?, B(C₆H₅)₄^?, PF₄^?, and [Cr(SCN)₄(NH₃)₂]^? in the complexes obtained. The mechanism of the reaction leading to the η²-bonded 1-butene complexes was determined by isotope experiments. In trying to recrystallize the butene complexes from acetonitrile the cationic complexes [η⁵-C₅H₅ Fe(CO)₂CH₃CN]BF₄ and [η⁵-C₅H₅ M(CO)₃CH₃CN]BF₄ were observed; the X-ray structure analysis of the former is reported.     

Reactions of coordinated molecules: XLIX. Carboncarbond bond formation between the donor atoms of adjacent acyl and alkenyl ligands

When the ferraenolate anion, (η-C₅H₅)(CO)₂FeC(O)CH₂⁻, is treated sequentially with methyllithium/TMEDA and benzoyl chloride, the known η³-allyl complex, (η-C₅H₅)(OC)Fe{η³-CH₂C[OC(O)Ph]C[OC(O)Ph](CH₃}, is isolated in 36% yield. When the neutral alkenyl complexes, (η-C₅H₅)(CO)₂Fe[C(Me)CH₂] and (η-C₅H₅)(OC)₂Fe{C(OMe)CH₂], were treated sequentially with methyllithium and benzoyl chloride, the η³-allyl complexes, (η-C₅H₅)(OC)Fe{η³-CH₂C(Me)C[OC(O)Ph](Me) and (η-C₅H₅)(OC)Fe{η³-CH₂C(OMe)C[OC(O)Ph](Me) are isolated in 8 and 11% yield, respectively. These η³-allyl ligands are presumably formed via CC coupling of the donor atoms of the formal acyl and alkenyl ligands in the intermediate complexes.     

Reactions of coordinated propargyl and allene ligands in cyclopentadienyliron dicarbonyl complexes

Reactions of η⁵-C₅H₅Fe(CO)₂CH₂CCR (R  CH₃, C₆H₅, and CH₂Fe(CO)₂(η⁵-C₅H₅)) with HBF₄ in acetic anhydride yield [η⁵-C₅H₅Fe(CO)₂(η²CH₂CCHR)]⁺BF^?₄. The resultant cationic iron-η²-allene complexes react with a wide range of nucleophiles (Nu) to give the following types of behavior: (a) addition of Nu to carbon-1 of the η²-allene fragment (with NaBH₄, (C₂H₅)₂NH, and P(C₆H₅)₃, inter alia), (b) addition of Nu to carbon-2 of the η²-allene fragment (with NaOCH₃), (c) addition of Nu to the carbonyl carbon (with NaOC₂H₅), (d) deprotonation of the iron-η²-allene cation to the parent propargylic complex (with N(C₂H₅)₃), and (e) nonselective reactions to yield a mixture of products (with CH₃Li). Of these, the most common is behavior (a); together with the protonation of η⁵-C₅H₅Fe(CO)₂CH₂CCR it stimulates the two-step (3 + 2) cycloaddition reactions between electrophilic molecules and these iron-propargyl complexes.     

Verknüpfung von 1,3-dienen mit acrylsäuremethylester durch photochemische umsetzung mit pentacarbonyleisen

Pentacarbonyliron and methyl acrylate/1,3-diene (2,3-dimethylbutadiene, isoprene, butadiene) mixtures react photochemically via diene—Fe(CO)₃ and methyl acrylate—Fe(CO)₄ to give products in which a methyl acrylate—diene adduct is 1,4,5,6-η-coordinated to the Fe(CO)₃ moiety. (η²-diene)(η²-methyl acrylate)Fe(CO)₃ is proposed to be an intermediate.     

The hapticity of cyclooctatetraene in its first row mononuclear transition metal carbonyl complexes: Several examples of octahapto coordination

The two cyclooctatetraene metal carbonyls that have been synthesized are the tetrahapto derivative (η⁴-C₈H₈)Fe(CO)₃ and the hexahapto derivative (η⁶-C₈H₈)Cr(CO)₃ using the reactions of cyclooctatetraene with Fe(CO)₅ and with fac-(CH₃CN)₃Cr(CO)₃, respectively. Related C₈H₈M(CO)_n (M = Ti, V, Cr, Mn, Fe, Co, Ni; n = 4, 3, 2, 1) species have now been investigated by density functional theory in order to explore the scope of cyclooctatetraene metal carbonyl chemistry. In this connection, the existence of octahapto (η⁸-C₈H₈)M(CO)_n species is predicted as long as the central metal M does not exceed the 18-electron configuration by receiving eight electrons from the η⁸-C₈H₈ ring. Thus the lowest energy structures (η⁸-C₈H₈)Ti(CO)_n (n = 3, 2, 1), (η⁸-C₈H₈)M(CO)_n (M = V, Cr; n = 2, 1), and (η⁸-C₈H₈)Mn(CO) all have octahapto η⁸-C₈H₈ rings. An exception is (η⁶-C₈H₈)Fe(CO), with a hexahapto η⁶-C₈H₈ ring and thus only a 16-electron configuration for the iron atom. Hexahapto (η⁶-C₈H₈)M(CO)_n structures are predicted for the known (η⁶-C₈H₈)Cr(CO)₃ as well as the unknown (η⁶-C₈H₈)Ti(CO)₄, (η⁶-C₈H₈)V(CO)₃, (η⁶-C₈H₈)Mn(CO)₂, and (η⁶-C₈H₈)Fe(CO)₂ with 18, 18, 17, 17, and 18 electron configurations, respectively, for the central metal atoms. There are two types of tetrahapto C₈H₈M(CO)_n complexes. In the 1,2,3,4-tetrahapto (η⁴-C₈H₈)M(CO)_n complexes two adjacent CC double bonds, forming a 1,3-diene unit similar to butadiene, are bonded to the metal atom. In the 1,2,5,6-tetrahapto (η^2,2-C₈H₈)M(CO)₃ derivatives two non-adjacent CC double bonds of the C₈H₈ ring are bonded to the metal atom. The known (η⁴-C₈H₈)Fe(CO)₃ is a 1,2,3,4-tetrahapto complex. The unknown isomeric 1,2,5,6-tetrahapto complex (η^2,2-C₈H₈)Fe(CO)₃ is predicted to lie ∼15 kcal/mol above (η⁴-C₈H₈)Fe(CO)₃. The related 1,2,5,6-tetrahapto complexes (η^2,2-C₈H₈)Cr(CO)₄, (η^2,2-C₈H₈)Mn(CO)₄, [(η^2,2-C₈H₈)Mn(CO)₃]⁻, (η^2,2-C₈H₈)Co(CO)₂, and (η^2,2-C₈H₈)Ni(CO)₂ are all predicted to be low-energy structures.     

Regiospecific carboncarbon bond formation by oxidative coupling of η1-allyl or η1-propargyl ligands of organoiron complexes

Novel and regiospecific coupling reactions of η⁵-C₅H₅(CO)₂Fe(η¹-allyl) and (η⁵-C₅H₅(CO)₂Fe(η¹-propargyl) complexes due to oxidation by silver hexafluorophosphate are reported. The mono- and bi-nuclear products contain (substituted) hexadiene and hexatetraene ligands while variable amounts of protonation products are also formed.     

Alkylsulfito,bisulfito and sulfito complexes of η5-cyclopentadienyldicarbonyliron(II)

Alkylsulfito complexes η⁵-C₅H₅Fe(CO)₂S(O)₂OR (R = CH₃, C₂H₅, n-C₃H₇, i-C₃H₇) have been prepared by reaction of [η⁵-C₅H₅Fe(CO)₂H₂O]BF₄ with Na[S(O)₂OR] (R = CH₃, C₂H₅) and the respective alcohol as solvent. These products may be interconverted by the use of the appropriate alcohol at reflux; such exchange occurs also at 25°C in the presence of HBF₄. Reaction of η⁵-C₅H₅Fe(CO)₂S(O)₂OCH₃ with (+)₅₈₉-2-C₈H₁₇OH and HBF₄ followed by treatment of the optically active product (+)₅₈₉-η⁵-C₅H₅Fe(CO)₂S(O)₂OC₈H₁₇ with CH₃OH and HBF₄ regenerates (+)₅₈₉-2-C₈H₁₇OH with unchanged specific rotation. Hydrolysis of η⁵-C₅H₅Fe(CO)₂S(O)₂OR affords η⁵-C₅H₅Fe(CO)₂S(O)₂OH, which is a strong acid.     

The photochemistry of (η-2-R-C3H4)Fe(CO)(NO)(X) (R = H or Cl; X = CO or PPh3) in room temperature solution or frozen gas matrixes

A photochemical study of allyl iron complexes of the type, (η³-2-R-C₃H₄)Fe(CO)(NO)(X) (R = H or Cl; X = CO or PPh₃) is presented. These compounds were studied in solid matrixes at 20 K, and at room temperature, by a combination of laser flash at 355 nm and steady-state photolysis. The predominant photochemical process for these compounds is loss of a CO ligand. In addition, exhaustive irradiation of (η³-2-R-C₃H₄)Fe(CO)(NO)(PPh₃) with λ_exc > 300 nm provided evidence for a haptotropic shift of the allyl group from η³ to η¹ coordination.     

Some reactions of Ni-Mo and Ni-W propargylic cations with nucleophiles

Preliminary reactions of the metal stabilized carbocationic species [(η-C₅H₅)Ni(μ-η²(Ni),η³(Mo)-HC₂CMe₂)Mo(CO)₂(η-C₅H₄Me)]⁺ BF₄⁻ (Ni-Mo) with nucleophiles are reported. The Ni-Mo cationic propargylic complex undergoes nucleophilic attack by sodium methoxide to regenerate the neutral μ-alkyne complex [(η-C₅H₅)Ni{μ-η²,η²-HC₂CMe₂(OMe)}Mo(CO)₂(η-C₅H₄Me)] (Ni-Mo), from which the stabilized carbocation was originally derived by protonation. The new complexes [(η-C₅H₅)Ni{μ-η²,η²-HC₂CMe₂(C₅H₅)}Mo(CO)₂(η-C₅H₄Me)] (Ni-Mo), which exist as an inseparable mixture of 1(c)-1,3- and 2(c)-1,3-cyclopentadienyl isomers, were also obtained. When the Ni-Mo cations were treated with potassium t-butoxide, the alkyne isomers with pendant 1(c)-1,3- and 2(c)-1,3-cyclopentadienyl groups are also formed. The μ-hydroxyalkyne complex [(η-C₅H₅)Ni{μ-η²,η²-HC₂CMe₂(OH)}-Mo(CO)(η-C₅H₄Me)] (Ni-Mo) was also isolated concurrently, and presumably arises from nucleophilic attack of fortuitously present hydroxide ions in the BuO⁻ reagent on the Ni-Mo cation. When NaBH₄ was added to the Ni-Mo propargylic, nucleophilic attack by hydride resulted and the μ-ⁱPrC₂H heterobimetallic complex [(η-C₅H₅)Ni{μ-η²,η²-HC₂Prⁱ}Mo(CO)₂(η-C₅H₄Me)] (Ni-Mo) was recovered in good yield. Small quantities of other side-products were isolated and characterized spectroscopically. Some tantalizing differences in reactivity were observed when the corresponding Ni-W stabilized carbocation was reacted with methoxide ions. When the not fully characterized solid formed by protonating [(η-C₅H₅)Ni(μ-η²,η²-{HC₂CMe₂)(OMe)}W(CO)₂(η-C₅H₄Me)] (Ni-W) was treated with methoxide ions, regioisomers (1(c)-1,3- and 2(c)-1,3-cyclopentadienyl species) of composition [(η-C₅H₅)Ni{μ-η²,η²-HC₂CMe₂(C₅H₅)}W(CO)₂(η-C₅H₄Me)] (Ni-W) were formed. Direct reaction of the pure cation [(η-C₅H₅Niμ-η²,η³-HC₂CMe₂)W(CO)₂(η-C₅H₄Me)]⁺ (Ni-W) with methoxide also generated the same 1(c)-1,3- and 2(c)-1,3-cyclopentadiene-substituted alkyne complexes. Unlike the case with the Ni-Mo complexes, the initial μ-HC₂CMe₂(OMe) species was not regenerated.     

Phosphine-centred resolution of (η4-diene)Fe(CO)3 complexes: (η4-tropone)Fe(CO)2L and (η4-isoprene)Fe(CO)2L [L = (+)-(neomenthyl)PPh2]

(η⁴-Tropone)Fe(CO)₃ and (η⁴-isoprene)Fe(CO)₃ form separable diastereoisomers on substitution of CO by (+)-(neomenthyl)PPh₂. In the tropone complex, diastereoisomer interconversion occurs by a 1,3-metal shift. The absolute configuration of the isoprene complex has been determined crystallographically.     

Photochemical reactions of 1-ferrocenyl-4-phenyl-1,3-butadiyne with Fe(CO)5 and CO

Photolysis of a hexane solution containing ironpentacarbonyl, 1-ferrocenyl-4-phenyl-1,3-butadiyne at low temperature yields six new products: [Fe(CO)₂{η²:η²-PhCCCC(Fc)C(CCPh)C(Fc)Fe(CO)₃}-μ-CO] (1), [Fe₂(CO)₆{μ-η¹:η¹:η²:η²-PhCCCC(Fc)-C(O)-C(Fc)CCCPh}] (2), [Fe₂(CO)₆{μ-η¹:η¹:η²:η²-FcCC(CC Ph)-C(O)-C(Fc)CCCPh}] (3), [Fe₂(CO)₆{μ-η¹:η¹:η²:η²-FcCCCC(Fc)-C(O)-C(Fc)CCCPh}] (4), [Fe(CO)₃{μ-η²: η²-[FcCC(CCPh)C(CCPh)C(Fc)}CO] (5) and [Fe(CO)₃{μ-η²: η²-[FcCC(CCPh)C(CCPh)C(Fc)}CO] (6) formed by coupling of acetylenic moieties with CO insertion on metal carbonyl support. In presence of CO, formation of another new product 2,5-bis(ferrocenyl)-3,6-bis(tetracarbonylphenylmaleoyliron)quinone (7) was observed which on further reaction with ferrocenylacetyene gave the quinone, 2,5-bis(ferrocenyl)-3,6-bis(ethynylphenyl)quinone (8). Structures of 1-5 and 8 were established crystallographically.     

Darstellung und Eigenschaften neuer kationischer Dienyl-isonitril-dicarbonyl-Komplexe des Eisens und Rutheniums

Preparation and Properties of New Cationic Dienyl-isonitrile-dicarbonyl Complexes of Iron and Ruthenium The hydride abstraction from the η⁴-diene isonitrile metal dicarbonyls M(η⁴-dien)(CNR)(CO)₂ (M = Fe, Ru; dien = C₆H₈ cyclohexadiene-1.3; C₇H₁₀ cycloheptadiene-1.3; R = Me, Et) with [Ph₃C]BF₄ lead to the η⁵-dienyl isonitrile dicarbonyl metal cations [M(η⁵-dienyl)(CNR)(CO)₂]⁺ [dienyl = cyclohexa-2.4-dien-1-yl (C₆H₇), cyclohepta-2.4-dien-1-yl (C₇H₉)]. [Fe(η⁵? C₈H₉)(CNMe)(CO)₂]⁺ (C₈H₉ = bicyclo[5.1.0]octa-3.5-dien-2-yl) is formed by protonation of Fe(η⁴? C₈H₈)(CNMe)(CO)₂ (C₈H₈ = COT) under valency isomerization. The two cations [Fe(η⁵? C₇H₉)(CNMe)(CO)₂]⁺ and [Fe(η⁵? C₈H₉)(CNMe)(CO)₂]⁺ can be deprotonated with NEt₃ to the neutral cycloheptatriene respectively COT complexes Fe(η⁴? C₇H₈)(CNMe)(CO)₂ and Fe(η⁴? C₈H₈)(CNMe)(CO)₂. The temperature dependent ¹³C-NMR spectra of [Fe(η⁵? C₇H₉)(CNMe)(CO)₂]⁺ and [Ru(η⁵? C₆H₇)(CNMe)(CO)₂]⁺ show the fluctional behaviour of these cations in solution. At low temperatures one CO group occupies the apical position of a square pyramid whereas the isonitrile ligand, the other CO group and the dienyl part are in the basal positions. The ΔG values of the CP exchange points out a higher activation energy as in the corresponding η⁴-diene metal complexes.