Kinetics of η6→η5 isomerization of (η6-fluorenyl)(η5-cyclopentadienyl)iron

The kinetics of the reversible isomerization of the zwitterionic complex [(⁶-C₁₃H₉)Fe(⁵-C₅H₅)] (1) into dibenzoferrocene (2) was studied by electronic spectroscopy in the temperature range from 70 to 103 °C. The activation parameters of the reaction 1 2 were determined, E _a = 22.5 kcal mol^–1.     

Reaction of Mercury(II) Trifluoroacetate with Deprotonated (η6-Toluene)-, (η6-Diphenylmethane)-, and (η6-Triphenylmethane)(η5-cyclopentadienyl)iron(II) Complexes. Mercuration of Some Cationic (Arene)(cyclopentadienyl)iron(II) Complexes

Treatment with mercury(II) trifluoroacetate of deprotonated (⁶-toluene)- and (⁶-diphenyl- methane)(⁵-cyclopentadienyl)iron(II) complexes gave mono-, di-, and trisubstituted [from (⁶-toluene)(⁵-cyclopentadienyl)iron(II) cation] mercury-containing salts. The reaction of mercury(II) trifluoroacetate with deprotonated (⁶-triphenylmethane)(⁵-cyclopentadienyl)iron(II) afforded only the corresponding sym- metric mercury derivative. The same product was obtained by direct mercuration with mercury(II) trifluoroacetate of (⁶-triphenylmethane)(⁵-cyclopentadienyl)iron(II) on heating the reactants in boiling unhydrous ethanol. Reactions of the resulting mercury-containing compounds with acids, symmetrizing bases, and acylating agents were studied.     

First metal complex with the azulene dianion. Molecular structure of the (2η1:η2-Gaz)Lu(η5-Cp)(DME) complex (Gaz is 7-isopropyl-1,4-dimethylazulene)

The metallocene derivative (2¹:²-Gaz)Lu(⁵-Cp)(DME) (1) (Gaz is 7-isopropyl-1,4-dimethylazulene) was prepared by reduction of guaiazulene with the lutetium naphthalene complex (⁵-Cp)Lu(2¹:²-C₁₀H₈)(DME) in 1,2-dimethoxyethane (DME). Complex 1 crystallized from a solution as blue crystals. According to the results of X-ray diffraction analysis, molecule 1 has a skewed pseudo-sandwich structure in which the Lu atom is ⁵-coordinated by the cyclopentadienyl ring and 2¹:²-coordinated by the seven-membered ring of the guaiazulene ligand. The coordination sphere of the metal atom in complex 1 is completed with the chelating DME molecule.     

ESR study of reactivity of the complex (η2-C60)Os(CO)(PPh3)2(CNBut) toward free radicals

Addition of the ^·P(O)(OPrⁱ)₂, Me^·, Et^·, ^·Bu^t, and Cl₃C^· radicals to the (ν²-C₆₀)Os(CO)-(PPh₃)₂(CNBu^t) complex (1) was studied by ESR spectroscopy. The spectral parameters of the spin-adducts of these radicals with complex 1 were determined. The predominant direction of the attack by the ^·P(O)(OPrⁱ)₂, ^·Bu^t, and Cl₃C^· radicals are the cis-1 and cis-2 bonds of the fullerene molecule. The stability of the spin-adducts depends substantially on the nature of the added radical. The addition rate constants of the ^·P(O)(OPrⁱ)₂, ^·But, and Cl₃C^· radicals to complex 1 and the dimerization rate constants for these spin-adducts were determined. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 301–307, February, 2008.     

Stereocontrolled acylation of (η4-cycloheptatriene)iron tricarbonyl

The anion derived by deprotonating (cycloheptatriene)Fe(CO)₃ reacts with acid chlorides to give exo C-7 substitution. The acyl group is readily isomerized to C-5 on treatment with base. The C-7 acylated products can be deprotonated; the resulting anions react at oxygen with acyl chlorides and Me₃SiCl, and at carbon with MeI.     

Mercuration with Mercury(II) Trifluoroacetate of (η6-Aniline)- or (N,N-dimethylaniline)(η5-cyclopentadienyl)iron(II)

The reaction of mercury(II) trifluoroacetate with the hexafluorophosphate of the ⁶-aniline-⁵cyclopentadienyliron(II) cation under reflux in dry ethanol gives rise to N-mono- and N,N-disubstituted mercury-containing salts of this cation. The same mercury-containing salts have been synthesized by the action of mercury(II) trifluoroacetate on the deprotonation product of the (⁶-aniline)(⁵-cyclopentadienyl)iron(II) cation. Direct mercuration of the [⁶-(N,N-dimethylaniline)](⁵-cyclopentadienyl)iron(II) cation into the para position of the benzene ring of the arene ligand has been performed. The reactivity of the compounds obtained has been studied.     

A new route to iron(0) thiocarbonyl complex involving desulphurization of the Fe(η2-CS2R)+ cation with P-n-Bu3. Crystal structure of Fe(CS)(CO)2(PPh3)2

Reaction of [Fe(η²-CS₂R)(CO)₂(PPh₃)₂][X] (R = CH₃, CH₂Ph; X⁻ = PF₆⁻, I⁻) with P-n-Bu₃ or PEt₃ gives Fe(CS)(CO)₂(PPh₃)₂ (3a); (ν(CS) 1235 cm⁻¹; δ(¹³C) 324.28 ppm). The structure of 3a has been determined by X-ray diffraction. Crystal data are: a 18.821(5), b 12.113(3), c 18.149(5) Å, β 117.76(6)°, monoclinic, space group P2₁, Z = 4. The structure is a trigonal-bypyramid with equatorial CS group, trans PPh₃ ligands, a FeC(S) bond distance of 1.768(8) and a CS bond distance of 1.563(8) Å.     

Synthesis,molecular structure and spectroscopic characterization of MO(CO)2I2 (η2-dppm)(η1-dppm)

A new, high-yield method has been developed for the preparation of MO(CO)₂I₂(η²-dppm)(η¹-dppm). The title compound was prepared by the reaction of [Et₄N][Mo(CO)₄I₃] with dppm in benzene in 95% yield. It has been characterized by a single-crystal X-ray study. The crystallographic data are as follows: monoclinic, space group P2₁/n, a = 19.023(4) Å, b = 14.439(3) Å, c = 20.141(5) Å, β = 100.45(2)°, V = 5440(2) ų Z = 4. The geometry around the central metal atom could be considered as either a distortion from a capped octahedron with a carbonyl in a capping position or from a trigonal prism with the iodine capping a rectangular face. The solution behavior of Mo(CO)₂I₂(dppm)₂ was examined with ³¹P NMR, which showed it to be fluxional.     

THE CRYSTALLIZATION BEHAVIOR OF [cis-α-Co(trien)(OX)lCl 2H2O (I), [cis-α-Co(trien)(NO2)2]BF4 (II), [cis-α-Co(trien)(NO2)2]-(cis-α-Co(trien)(OX)]Cl l/2SiF6 (III)

Abstract

Three new compounds were synthesized and their crystal structures determined. For compound (I). [cis-α-Co(trien)(OX)]Cl 2H₂O, CoClO₆N₄C₈H₂₂, triclinic, space group P-l (No. 2) a = 6.980(5), b = 8.801(4), c = 12.554(8) Å, α = 89.07(5)°, ? = 75.74(4)°, γ = 81.44(5)°, V = 738.9(8) ų, cell dimensions were obtained from 24 reflections giving FW = 364.4, Z = 2, F[000) = 380.06, Dcalc=1.634mg m-³, μ = 1.36mm-¹. A total of 1907 data were collected over the range of 4° ≤ 2θ ≤ 45°; of these, 1647 (independent and I≥3σ(I)) were used in the structure analysis. Data were corrected for absorption; transmission coefficients ranged from 0.51754 to 0.73648. The final RF and Rw residuals were 0.033 and 0.042.

For compound (II), [cis-α-Co(trien)(NO₂)₂]BF₄, CoN₆C₆O₄BF₄H₁₈, orthorhombic space group Pbca (No. 61) α= 12.260(10), b=12.880(14), c= 17.940(14)A F=2833(4)A³, cell dimensions were obtained from 24 reflections with 2θ in the range of 4.00–45.00 degrees, FW = 383.98, Z = 8, F(000) = 1571.52, Dcalc= 1.801 mgirT³, μ=1.28mm^_1, λ = 0.70930 Å. A total of 1637 data were collected over the range of 4° ≤ 2θ ≤ 45°; of these, 883 (independent and I≥ 2.5σ(I)) were used in the structure analysis. The final RF and Rw residuals were 0.122 and 0.132.

For compound (III), [cis-α-Co(trien)(OX)][cis-α-Co(trien)(NO₂)₂]Cl-l/2SiF₆, Co₂ClSi-l/2N₁₀C₁₄F₃O₁₂H₃₆, orthorhombic, space group Pbca (No. 61) a = 12.804(10), b= 16.543(10), c = 27.419(23) A, V= 5808(7) ų, cell dimensions were obtained from 25 reflections, FW = 760.85, Z = 8, F(000) = 3136.06, Dcalc= 1.740mg m^?3, 4mU= 1.34 mm-¹, λ = 0.70930 Å. A total of 2657 data were collected over the range of 4° ≤ 2θ ≤ 40°; of these, 1902 (independent and I≥ 2.5σ(I)) were used in the structure analysis. The final RF and Rw residuals were 0.058 and 0.062.     

The mechanism of fluxionality of (1,2,7-η3-2-Me-benzyl)(η5-C5H5)Mo(CO)2

It is shown that (1,2,7-η³-2-Me-benzyl)(η⁵-C₅H₅)Mo(CO)₂ exits in solution as one isomer which is fluxional, probably via (7-η¹-2-Me-benzyl)((η⁵-C₅H₅)Mo(CO)₂, with ΔG^≠₃₇₀ = 23.6 ± 1.0 kcal mol⁻¹. In contrast, (1,2,7-η³-3-Me-benzyl)(η⁵-C₅H₅)Mo(CO)₂ exits as two isomers at −20°C, which undergo interconversion at room temperature with ΔG^≠ 15.7 kcal mol⁻¹. This dynamic process is an allyl rotation. It is probable that there is also a low energy [1,5]-sigmatropic shift.     

Study of the origin of enantioselectivity in cyclopropanation reactions using the chiral iron carbene complex [(η5-C5H5)(CO)2FeCH[(η6-o-MeOC6H4)Cr(CO)3]]+

During our low temperature NMR studies we observed two rotational isomers of the carbene complex [(η⁵-C₅H₅)(CO)₂FeCH[(η⁶-o-MeOC₆H₄)Cr(CO)₃]]+ (3) with the O–Me group either anti or anti to the Fp moiety. While the Cr(CO)₃ group very effectively shields one face of the carbene complex from attack by the olefin, the presence of anti and anti isomers allows for the formation of both R and S configuration on C-1 of the cyclopropane through a backside or a frontside ring closure mechanism. The reaction of olefin with anti R-3 can result in R-configuration of the cyclopropane carbon C-1 through a frontside closure mechanism, or in S-configuration if backside closure takes place. In a similar manner, anti R-3 may produce S-configuration through frontside closure or R-configuration through backside closure. We previously have shown by crystallography that reaction the R-isomer of 3 with 2-methyl-propene induces predominantly a R-configuration at C-1 of the resulting cyclopropane (RR-(−)-2,2 dimethyl-1-o-methoxyphenyl(tricarbonyl chromium)cyclopropane, whereas the S-carbene results in the corresponding SS isomer. These findings are consistent with cyclopropane formation from the syn isomer through a frontside closure mechanism or from anti isomer through a backside closure mechanism. In the case of [(η⁵-C₅H₅)(CO)₂FeCH[(η⁶-o-MeC₆H₄)Cr(CO)₃]]+ (4), only anti isomer is observed and optical rotation data indicate that the methylcarbene exhibits the same asymmetric induction (i.e., R-carbene yields R-cyclopropane C-1 and S-carbene yields S-cyclopropane C-1) as the methoxy analogue, and the assumption of the anti isomer being the reactive one then implies that the reaction proceeds through a backside closure mechanism rather a frontside mechanism. It is very likely that this preference is also valid for the methoxy substituted complex 4. Our results on 4 indicate that the enantioselectivity of the cyclopropanation reaction is not determined by the relative abundance of the isomers. As the syn isomer is the more abundant one, the anti isomer has to be the more reactive one compared to the syn isomer. Interchange of syn and anti isomers occurs fast compared to the rate of reaction of the carbene with olefin. The fast rate of interchange of syn and anti isomers relative to the rate of reaction with olefin precludes the direct observation of any differential reactivity form a change in the syn to anti ratio in the NMR spectrum. However, the in general lower ee values observed for 3 compared with 4 are consistent with the fact that the reactive isomer is less abundant in this case. Our data thus show that enantioselectivity of cyclopropanation with “chiral at carbene” complexes is controlled by the higher reactivity of the anti isomer and occurs through a backside ring closure mechanism.     

Migration of hydrogen from metal to alkene promoted by dioxygen addition. Oxygen atom transfer from a cis-(alkyl)(η2-dioxygen) complex of rhodium to organic and inorganic substrates

The novel cis-(σ-alkyl)(η²-O₂) complexes of rhodium [(THF)(EtOH)Naμ-EtOH₂μ-(CO₂R)CH₂CH(CO₂R)Rh(η²-O₂)(triphos)₂Na(EtOH)(THF)][BPh₄]₂·2EtOH (R = Me,3; Et,4) have been synthesized by reaction of dioxygen with the hydrides (triphos)(RhH(η²-alkene) followed by NaBPh₄ addition (alkene = dimethyl fumarate,1; diethyl fumarate,2) (triphos = MeC(CH₂PPh₂)₃). The structure of4 has been determined by X-ray diffraction. Oxygen atom transfer reactions from the η²-O₂ complexes to various inorganic and organic substrates have been studied.     

Synthesis of (η-arene)(η-cyclopentadienyl) iron (II) complexes with heteroatom and carbonyl substituents. Part I: Oxygen and carbonyl substituents

A series of reactions have been used to introduce oxygen substituents into (η-arene)(η-cyclopentadienyl) iron (II) complexes. Photochemical ligand exchange led to the formation of the first recorded trioxygenated complex as well as mono- and di-oxygenated species. Using microwave techniques, reaction times for S_NAr displacement reactions of halobenzene complexes by phenols were reduced from several hours to a few minutes. Phenols protected by either t-butylation or trimethylsilylation were found to give modest yields of the corresponding phenol complexes, using conventional thermal ligand exchange reactions. Without such protection, yields were extremely low. The above method led to the synthesis of the first example of a dihydroxybenzene complex. Some miscellaneous syntheses are also reported.The Nef reaction has been adapted to convert (η⁶-α-nitroalkylarene)(η⁵-Cp) iron (II) salts to corresponding aldehyde and ketone complexes. The α-nitroalkyl arene complexes were synthesised in good yields from (η⁶-halobenzene)(η⁵-Cp) iron (II) complexes using NaOtBu in DMSO. H/D exchange reactions with ²[H]₆-DMSO in the presence of K₂CO₃ showed partial D incorporation in the methyl group for the unreacted α-nitroethylbenzene complex and complete exchange for the carbanion generated by deprotonation. Conversion of the α-nitroalkylarene complexes to the corresponding aldehyde and ketone complexes was accomplished in moderate yields using three methods:

(A)

H₂O₂ and NaOtBu in DMSO followed by reaction with CF₃CO₂H.

(B)

SnCl₂/aq. HCl.

(C)

K₂CO₃ in DMF using microwave-mediated reactions.

In addition, two one-pot syntheses are reported using methods B and C.     

Transition metal catalyzed Fe–C coupling reactions in synthesis of dicarbonyl(2-thienylethynyl)(η5-cyclopentadienyl)iron complex: Spectroscopic,structure and electrochemical study

Transition Metal Chemistry - The new σ-alkynyl iron(II) complex Cp(CO)2Fe-C≡C-(2-C4H3S) was synthesized with application of several known approaches based on the transition metal...     

Synthesis, characterization, and reactivity of a novel μ-η2:η2-diselenidodicopper(II) complex

The first μ-η(2):η(2)-diselenidodicopper(II) complex has been obtained in the reaction of a copper(I) complex with N,N',N″-tribenzyl-cis,cis-1,3,5-triaminocyclohexane and elemental selenium. The structure and reactivity of the complex is described.     

Inter-ring η6⇌η5 haptotropic rearrangements of 18ē and 19ē (η5-pentamethylcyclopentadienyl)(η6-9-methylfluorenyl)iron complexes

New cationic complexes [(⁶-C₁₃H₁₀)Fe(⁵-Cp^*)]PF₆ and [(⁶-9-CH₃-C₁₃H₉)Fe(⁵-Cp^*)]PF₆ were obtained by the reaction of Cp^*Fe(CO)₂Br with fluorene and 9-methylfluorene, respectively. Deprotonation of these complexes byt-BuOK in THF affords zwitter-ionic compounds (⁶-C₁₃H₉)Fe(⁵-Cp^*) and (⁶-9-CH₃-C₁₃H₈)Fe(⁵-Cp^*) (A). WhenA is heated in nonane at 150 °C it undergoes ⁶⁵ inter-ring rearrangement with the formation of hexamethyldibenzoferrocene (B). The electrochemical behavior ofA andB was studied by cyclic voltammetry. One-electron reduction ofA andB to the corresponding radical anions induces inter-ring haptotropic rearrangementA ^.–B ^.–. The equilibrium in the 19 state is shifted to the ⁶-isomeric radical anionA ^.–, while in the 18 precursors, it shifts to the ⁵-isomerB.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 319–324, February, 1994.The authors are grateful to D. V. Zagorevskii (A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences) for recording and interpreting the mass spectra, and to A. A. Borisenko (Moscow State University) for recording the NMR spectra.This work was financially supported by the Russian Foundation for Basic Research (Grant 93-03-5209).     

Crystal structure and catalytic properties of a vanadium complex cis-[VO2(Him-py)(im-py)]2·3H2O

Abstract

The coordination behavior of Him-py (2-(1H-imidazol-2-yl)pyridine) toward vanadium has been explored. The six-coordinate complex, cis-[VO₂(Him-py)(im-py)]₂·3H₂O (1), was synthesized by the coordination reaction of NH₄VO₃ and Him-py in the aqueous methanol solution, which was characterized by single-crystal X-ray technology. It belongs to the monoclinic space group P2₁/n with a?=?8.0756(6), b?=?19.3531(15), c?=?11.4433(8), β?=?106.905(2), V?=?1711.2(2), and Z?=?2. The crystal structure shows that the six-coordinate vanadium is bonded to two cis-oxido ligands and two bidentate ligands, Him-py and im-py. Interestingly, when crystals of 1 were immersed in H₂O₂, a peroxovanadium compound, (H₂im-py)[OV(O₂)₂(Him-py)] (2), was obtained, which crystallizes in the orthorhombic space group Fdd2 with a?=?22.600(2), b?=?22.7259(13), c?=?18.0146(11), V?=?9252.4(12), and Z?=?16, and consists of a seven-coordinate peroxovanadate(V) ion, one Him-py and one H₂im-py ligand. Moreover, we also studied the catalytic activity of 1 in the oxidative bromination of phenol/aniline-like compounds towards mimicking bromoperoxidase reactivity.