Coordination polymers of zinc with (η6-benzenecarboxylate) chromium tricarbonyl

Different coordination polymers were obtained by the reaction of (benzoic acid) chromium tricarbonyl with zinc acetate in the presence of various organic dipyridyl linkers. Depending on the nature of the linker either monomeric or polymeric compounds were obtained. Reactions of (benzoic acid) chromium tricarbonyl with zinc acetate and bidentate pyridine based ligands 4,4'-bipyridine (4,4'-bipy), 1,2-bis(4-pyridyl)ethane (bpe), 1,3-bis(4-pyridyl)propane (tmdp), and 2,2'dipyridylamine (DPA) afforded the novel coordination polymers [Zn[{η(6)-C(6)H(5)COO}Cr(CO)(3)](2)(4,4'-bipy)](n), [Zn[{η(6)-C(6)H(5)COO}Cr(CO)(3)](2)(bpe)](n), [Zn[{η(6)-C(6)H(5)COO}Cr(CO)(3)](2)(tmdp)}](n), and the monomeric complex [Zn[{η(6)-C(6)H(5)COO}Cr(CO)(3)](2)(DPA)]. The solid state structures of all compounds were determined by single crystal X-ray diffraction. By using 1,3-bis(4-pyridyl)propane as a linker a chiral infinite helical structure was formed in the solid state. Thermogravimetric analysis (TGA) studies showed that upon heating the carbonyl groups of the {η(6)-C(6)H(5)COO}Cr(CO)(3) anion were lost before the organic ligand sphere was thermally decomposed.     

Some reactions of [(η6-C6Me6)Ru(η6-[2.2]paracyclophane)]-[BF4]2 with nucleophiles

Single addition of the nucleophiles X⁻ (X = H, CN, OH) to the less sterically hindered ring in [(η⁶-C₆Me₆)Ru(η⁶-C₁₆H₁₆)][BF₄]₂ (1) proceeds smoothly to produce, as the sole product, [(exo-η⁵-C₆Me₆X)Ru(η⁶-C₁₆H₁₆)][BF₄]. Use of Na[BD₄] in place of Na[BH₄] gives the expected shift in ν(C-H_exo) in the infrared spectrum.     

Stereoselective hetero Diels–Alder reactions of chiral tricarbonyl (η6-benzaldehyde)chromium complexes

The ZnCl₂-promoted cycloaddition of a series of enantiopure ortho-substituted benzaldehyde–Cr(CO)₃ complexes and Danishefsky's diene gave the corresponding 2-aryl pyranones in good yields and complete enantiospecificity. Some of the mechanistic aspects of the cycloaddition were investigated and the reaction extended to different dienes.     

1,3-Dipolar cycloaddition reaction of nitrone η6-(arene)chromium tricarbonyl complexes with styrene and η6-(styrene)chromium tricarbonyl

The products of 1,3-dipolar cycloaddition of the nitrone-type η⁶-(arene)chromium tricarbonyl complexes (CO)₃CrC₆H₅CH=N⁺(O^?)R, where R = Me, Ph, Bu^t, with styrene and η⁶-(styrene)chromium tricarbonyl were obtained and characterized by a combination of physicochemical methods. This type of reactions proceeded with very high regio- and stereoselectivity to exclusively form cis-2,3,5-tri-substituted isoxazolidines.     

[2+4] Cycloaddition of η6-(styrene)chromium tricarbonyl and conjugated dienes

Cycloaddition of η⁶-(styrene)chromium tricarbonyl to hexa-2,4-diene or cyclopentadiene afford the Diels-Alder adducts with retention of the Cr(CO)₃ group, whereas cyclohexa-1,3-diene undergoes aromatization to give η⁶-(benzene)chromium tricarbonyl. The counter synthesis of these (arene)chromium tricarbonyl derivatives from uncoordinated adducts of the Diels-Alder reaction and chromium hexacarbonyl was carried out.     

Bis(arene)metal compounds: I. Nucleophilic substitution of bis(η6-chlorobenzo-trifluoride)chromium(0) with thiophenoxide

The ortho, meta and para complexes of bis(η⁶-chlorobenzotrifluoride)chromium(0) were made by metal-vapor synthesis. Nucleophilic substitutions by thiophenoxide of these complexes are compared to nucleophilic substitutions by thiophenoxide on the uncoordinated arenes. It was found that substitution at the chloro position is more facile on the complexes than on the free arenes. Substitution of the chloro on the meta-isomer sandwich was more facile than substitution of the chloro on the ortho-isomer sandwich, contrary to the observed reactivity pattern in the free arenes.     

Metal π complexes of benzene derivatives: Part 56. (η6-Fluoranthene)(tricarbonyl)chromium: isomerism and haptotropic equilibration

Reaction of fluoranthene with Cr(CO)₃Py₃/BF₃·OEt₂ at 25 °C affords a mixture of two isomeric complexes: traces of tricarbonyl(1-5,15-η⁶-fluoranthene)chromium (3) (coordination to benzene) and, as the major product, tricarbonyl(1-4,15,16-η⁶-fluoranthene)chromium (2) (coordination to naphthalene). The ratio 3:2 is less than 0.05 according to ¹H-NMR of crude product before crystallization. Complex 2 is thermodynamically less stable than 3: at 100 °C in decane or C₆D₆ for 8 h or at 90 °C in C₆F₆ for 100 h 2 rearranges irreversibly to 3 via an inter-ring haptotropic shift of the Cr(CO)₃ group from the naphthalene moiety to the benzene part of the fluoranthene ligand. NMR evidence for a degenerate reversible haptotropic shift within the naphthalene moiety is absent. The isomers 2 and 3 have been characterized by X-ray structural analysis.     

Analysis of vibrational spectra of naphthalene,deuterionaphthalenes, and chromium (η6-naphthalene)tricarbonyl based on density functional calculations

The vibrational frequencies and force constants for naphthalene (C₁₀H₈), 1,4,5,8- and 2,3,6,7-tetradeuterionaphthalenes (C₁₀H₄D₄), octadeuterionaphthalene (C₁₀D₈), and chromium (⁶-naphthalene)tricarbonyl were calculated by the DFT method using the PBE approximation in extended and split bases. The results calculated without the use of scaling factors are in good agreement with the IR and Raman experimental data. All vibrational frequencies for the free ligand and -complex molecules were assigned. The influence of coordination to the transition metal on the frequencies and force field of the naphthalene molecule (both for the free ring and the ring coordinated to the transition metal) was discussed.     

Enantiospecific nucleophilic substitution of the dimethylamino group in (R)-tricarbonyl[-{(1-dimethylamino)ethyl}-η6-benzene]chromium

Treatment of (R)-tricarbonyl[-{(1-dimethylamino)ethyl}-η⁶-benzene]chromium 1 with esters of chloroformic acid leads to enantiospecific substitution of the dimethylamino group for a chloro substituent. The chloro group in turn can enantiospecifically be replaced for a diphenylphosphino group. Both reactions proceed with retention.     

Studies on nucleophilic substitution reactions with η6-o-dichlorobenzene-η5-cyclopentadienyliron hexafluorophosphate

Reaction of η⁶-o-dichlorobenzene-η⁵-cyclopentadienyliron hexafluorophosphate (IPF₆) with an excess of phenol or p-thiocresol in the presence of K₂CO₃ could give disubstitution of both chloro groups of I, while a similar reaction with one equivalent of the nucleophile, and under conditions of high dilution, monosubstitution of only one of the chloro groups of I could be obtained. Similarly, di- or monosubstitution could be brought about under appropriate conditions with benzyl or methyl alcohol as the source of the nucleophile. While no reaction could take place between IPF₆ and aniline, a reaction did occur between IPF₆ and o-anisidine (o-methoxyaniline), but only the monosubstitution product was obtained, even in the presence of an excess of o-anisidine. Similar results of monosubstitution were observed with other nucleophiles containing the NH₂ group, including NH₃, NH₂NH₂, CH₃NH₂ and C₆H₅CH₂NH₂. These findings are consistent with the reported differences in yields when IPF₆ was treated with two nucleophilic groups (OH, SH and/or NH₂) located in the 1,2-positions of a benzene ring to give CpFe complexes of heterocyclic systems related to 9,10-dihydroanthracene with two hetero-atoms at the 9,10-positions [15]. Reactions were also carried out between IPF₆ and the carbanion-enolate anion derived from acetylacetone, α-benzoylacetophenone, diethyl malonate or ethyl acetoacetate. In these cases, only monosubstitution of one of the chloro groups of I was observed, leading to the formation of a CC bond. A possible explanation for the formation of only monosubstitution products in reactions with N- or C-containing nucleophiles is discussed.     

The reactions of [Fe2(η-Cp)2(CNAr)4] complexes with halogens and tin(II) halides

Summary [Fe₂(-Cp)₂(CNAr)₄] (2) (540-01, C₆H₄Me-2, C₆H₄Et-2, C₆H₃Me₂-2,4, C₆H₃Me₂-2,6, C₆H₃(Me)Et-2,6, C₆H₃Et₂-2,6 or C₆H₃ i-Pr₂-2,6) react with I₂ to give [Fe(-Cp)(CNAr)₂I], but with Br₂[Fe(-Cp) (CNAr)₃]⁺ salts are the only products; IBr gives a mixture of the two. With SnX₂ (X = F, Cl, Br or I) in refluxing n-butanol, (2) gives isolable [{Fe(-Cp)(CNAr)₂}₂SnX₂] only when the CNAr ligands have two ortho substituents, otherwise decomposition occurred. When X = F, [Fe(-Cp) (CNAr)₂SnF₃] was also obtained from this reaction. Attempts to prepare [Fe(-Cp)(CNAr)₂X] (X = Cl or Br) by reaction of (2) with HX in the presence of air gave rather unstable products which with SnX₂ formed [Fe(-C₅H₅)-(CNAr)₂SnX₃]. Similar compounds, [Fe(-Cp) (CNAr)₂ SnX₂I], were obtained from [Fe(-Cp)-(CNAr)₂I] and SnX₂ (X = Cl or Br but not I). All of these complexes are much less stable than their Fe(-Cp)(CO)₂ counterparts; all decompose in solution to [Fe(-Cp)(CNAr)₃]⁺ which then break down to unidentified species. X-ray diffraction studies show that in [Fe(-Cp)(CNC₆H₃-i-Pr₂-2,6)₂I] and [{Fe(-Cp)(CNC₆H₃Me₂-2,6)₂}₂SnBr₂] there is pseudo-octahedral coordination about Fe. In the latter there is also distorted tetrahedral coordination about Sn so that its structure is very similar to that of [{Fe(-Cp)(CO)₂}₂SnCl₂]. Spectroscopic studies show that in all complexes rotation of the aryl rings of the CNAr ligands cannot be slowed in solution, and that there is free rotation about all 540-02 bonds.     

Use of a bis-lithium amide base in asymmetric metallation of tricarbonyl(η6-1,3-dihydroisobenzothiophene)chromium(0)

Enantiomerically enriched tricarbonyl(η⁶-arene)chromium complexes derived from tricarbonyl(η⁶-1,3-dihydroisobenzothiophene)chromium(0) can be obtained in up to 95% ee by means of an enantioselective metallation reaction using the bis-lithium amide base 8.     

Synthesis of some substituted 5,6,11,12-tetrahydro-dibenzo[a,e]cyclooctene derivatives through the intermediacy of tricarbonyl(η-arene)chromium complexes

5,6,11,12-Tetrahydrodibenzo[a,e]cyclooctene derivatives with α- and β-substituents are readily accessible from [Cr(CO)₃(5,6,11,12-tetrahydrodibenzo[a,e]cyclooctene)] 2 via a two-step sequence, which involves addition of a nucleophile and oxidation of the intermediate anionic cyclohexadienyl complex. Nucleophiles used included LiCMe₂CN (A), LiCH₂CN (B), and (C). The results show that the primary carbanion LiCH₂CN and the S-stabilized carbanion give mixtures of α- and β-substituted products and in both cases α-isomers were major, whereas the opposite regioselectivity was obtained with the tertiary carbanion LiCMe₂CN.     

(η6-arene)tricarbonyl chromium complexes in organic synthesis 1,5-remote diastereoselection

1,5-Remote diastereoselection on the acyclic systems is achieved by diastereoselective Cr(CO)₃ complexation, chirality transfer in acyclic system and following stereoselective alkylation at the benzylic position.     

Indenyl and fluorenyl transition metal complexes: XIV. Synthesis and reactions of chromium tricarbonyl complexes of 5,10-dihydroindeno[2,1-α]indene

1-4,4a,10b-η⁶-5,10-dihydroindeno[2,1-α]indene chromium tricarbonyl (III) has been obtained by Rausch's method. Deprotonation of III by t-BuOK in THF solution, by potassium solution in HMPTA or by KH in THF at −65°C yields an η⁶-anion IV, which is irreversibly rearranged into η⁵-anion V at 20°C. Action of n-BuLi/t-BuOK mixture in THF at −65°C results in the formation of η⁶-dianion VI, which is irreversibly converted into η⁵-dianion VII above 0°C. Alkylation of IV with benzyl iodide yields 5-exo-benzyl(III). Reaction of V with benzyl iodide leads to the σ-benzyl derivative, which is isomerized into 5-endo-benzyl(III). The reaction of V with N-nitroso-N-methyltosylamide yields the η⁵-nitrosodicarbonyl complex of chromium (XI).     

The diastereoselectivity of the addition of tricarbonyl-(η6-2-lithiothiophene) chromium(O) complexes on aldehydes

It has been shown that the reactions of tricarbonyl(η⁶ -2-lithiothiophene)chromium(O) with various arene carboxaldehydes yields mixtures of unequal amounts of diastereoisomers, which can be separated by flash chromatography. The structures of the products have been established by ¹H NMR spectroscopy and by independent synthesis. A novel synthesis of tricarbonyl(η⁶-thiophene)-chromium(O) (1) is described.     

(η6-Arene)chromium complexes in organic synthesis: [2,3]-Wittig rearrangement of (benzyl crotyl ether)chromium complexes

The [2,3]-Wittig sigmatropic rearrangement of (benzyl (E)-crotyl ether)chromium complexes is shown to give a syn stereoselection which is different from the anti selection reported for the corresponding chromium-free compounds.     

Synthesis and reactions of dicarbonyl (η2-indene)-η5-indenyl complexes of manganese and rhenium

Photochemical reactions of M(CO)₃(⁵-C₉H₇), where M=Mn (1) or Re (2), with indene have produced ²-indene complexes M(CO)₂(²-C₉H₈)(⁵-C₉H₇), where M=Mn (3) or Re (4). Deprotonation of complex3 witht-BuOK in THF at –60 °C gives the anion [Mn(CO)₂(¹-C₉H₇)(⁵-C₉H₇)^– (5), in which there occurs a rapid interchange of the Mn(CO)₂(⁵-C₉H₇) group between positions 1 and 3 in the ¹-indenyl ligand. The reaction of complex4 with Ph₃CPF₆ in CH₂Cl₂ at 0 °C leads to the complex [Re(CO)₂(³-C₉H₇)(⁵-C₉H₇)PF₆, whereas the similar reaction of complex3 gives only decomposition products even at –20 °C.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1280–1285, July, 1993.     

Mossbauer study of reactions of Sn[Fe(CN)_6] on supports

Mossbauer spectroscopy has been applied to the investigation of reaction of Sn[Fe(CN)6] on magnesia, 7-alumina, silica and activated carbon. It was found that the thermal decomposition products of supported Sn[Fe(CN)6] are quite different from those of the unsupported one as a result of the interaction between the complex and supports. The supports could promote the oxidation in the air atmosphere and their effect led to high dispersion of the decomposition products on the surface.