Reactions of (η6-diphenylacetylene) chromiumtricarbonyl complexes with polynuclear carbonyls I. Synthesis of Cr(CO)3(η6-diphenylacetylene) complex and its reaction with Co2(CO)8. Crystal and molecular structure of Cr(CO)3(η6:η2-diphenylacetylene)Co2(CO)6

The reaction of Cr(CO)₃(NH₃)₃ with diphenylacetylene affords as a main product the complex with Cr(CO)₃ moiety bound to a phenyl ring of diphenylacetylene; Cr(CO)₃(η⁶-PhC₂Ph) (I). Complex I readily reacts with Co₂(CO)₈ yielding the mixed metal complex Cr(CO)₃(η⁶:η²-PhC₂Ph)Co₂(CO)₆ (II). The reaction proceeds with retention of the Cr(CO)₃ (η⁶-arene) structural unit, the Co₂(CO)₆ fragment being bound to the triple bond of diphenylacetylene in μ₂,η²-mode. The structure of II was determined by single crystal X-ray analysis. The complex crystallizes in space group P2₁/c with unit cell parameters a 8.666(3) Å, b 18.046(3) Å, c 15.155(6) Å. β 97.57(3)°, V 2349(2) ų, Z = 4, D_x = 1.70 g/cm³. The structure was solved by direct methods and refined by full-matrix least-squares technique to R and R_w values of 0.032 and 0.034, respectively, for 3655 observed reflections. The data obtained show that two structural units in II, Cr(CO)₃(η⁶-Ph-) and Co₂(CO)₆(μ₂,η²-CC), are distorted due to steric repulsion between these metal carbonyl moieties. The Cr(CO)₃ fragment is shifted from the centre of the phenyl ring and slightly tilted with respect to the phenyl ring plane. The Co₂C₂ tetrahedron in the Co₂(CO)₆(μ₂,η²-CC) moiety is distorted in such a way that two of the four Co_iC_j bonds are elongated.     

Palladium-catalyzed asymmetric allylic substitution using novel phosphino-ester (PHEST) ligands with 1,1′-binaphthyl skeleton

The asymmetric allylic alkylation of rac-1,3-diphenyl-2-propenyl acetate 1 with dimethyl malonate 2a proceeded smoothly in the presence of lithium acetate, BSA (N,O-bis(trimethylsilyl)acetamide), [Pd(η³-C₃H₅)Cl]₂, and the chiral ligand (R)-i-Pr₂N-PHEST (R)-5a to give the allylic alkylation product (R)-3a in 89% yield with 99% ee. Furthermore, the asymmetric allylic amination of 1 with potassium phthalimide 2c has been carried out using the same ligand to give the allylic amination product (S)-3c in 10% yield with 66% ee.     

Electrochemical reductive acylation of (η6-arene)Cr(CO)3 complexes and (benzophenone)[Cr(CO)3]2

The electrochemical reductive acylation of (benzophenone)Cr(CO)₃ and (benzophenone) [Cr(CO)₃]₂ has been performed in DMF, by electrochemical reduction of complexed ketones in the presence of acetic and benzoic anhydride in excess. Three complexed benzhydryl esters ArCH(OCOR)PhCr(CO)₃, (Ar = Ph, R = Me: Ar = PhCr(CO)₃, R = Me; Ar = PhCr(CO)₃, R = Ph) were obtained in 46–57.5% yields after purification. Electrochemical reduction of (diphenylmethane)Cr(CO)₃ in the presence of acetic anhydride in excess leads to m-benzyl acetophenone.     

Synthesis and crystal structure of [(η3-C3H5)(CO)2Mo(μ-S2CPCy3)-Mo(η3-CH2CMeCH2)(CO)2]

A novel dimolybdenum complex [(³-C₃H₅)(CO)₂Mo(-S₂CPCy₃)Mo(³-CH₂CMeCH₂)(CO)₂], obtained by reacting the [(CO)₂(³-C₃H₅)Mo(-S₂CPCy₃)Mo(CO)₃]^– anion with an excess of ClCH₂CMe=CH₂, has been characterized by i.r., ³¹P{¹H}, ¹H- and ¹³C-n.m.r. spectroscopy and by elemental analysis. The crystal structure of the complex, determined by X-ray diffraction, shows a definite preference for the central carbon of the S₂CPCy₃ bridge to bind to the Mo(2) atom coordinated by ³-2-methylallyl, rather than the Mo(1) atom attached to unsubstituted ³-allyl ligand.     

Regiospecific substitution of carbonyl by phosphine ligands in hydrocarbyl-substituted carbonyl clusters. Synthesis and spectroscopic characterization of Fe3(CO)8(PPh3)(μ3-η2- ⊥ -EtC2Et) and (η5-C5H5)NiFe2(CO)5(PPh3)(η3-η2- ⊥-C2But)

The complexes Fe₃(CO)₈(PPh₃)(μ₃-η²- ⊥ -EtC₂Et) and (η⁵-C₅H₅)NiFe₂(CO)₅(PPh₃)(η₃-η²- ⊥-C₂Bu^t) have been obtained by treating Fe₃(CO)₉(C₂Et₂) or (Cp)NiFe₂(CO)₆(C₂Bu^t) with PPh₃ under mild conditions; the substituted clustes have been characterized spectroscopically. Structures are proposed in which the phosphine is on the unique metalatom σ-bonded to the alkyne or acetylide moiety. Replacement of CO by PPh₃ ligands rather than by addition, is observed for the formally unsaturated Fe₃(CO)₉(C₂Et₂). Reorientation of the acetylide was expected for (Cp)NiFe₂(CO)₆(C₂Bu^t) upon substitution, but was not observed.     

Synthesis of Platinum-Triruthenium Clusters Using the Zero-Valent Platinum Reagent Pt(nb)3: X-Ray Crystal Structures of Ru3Pt(CO)11(P-iPr3)2, Ru3Pt(μ-H)(μ3-η3-MeCCHCMe)(CO)9(P-iPr3), Ru3Pt(μ3-η2-PhCCPh)(CO)10(P-iPr3), Ru3Pt(μ-H)(μ4-N)(CO)10(P-iPr3) and Ru3Pt(μ-H)(μ4-η2-NO)(CO)10(P-iPr3)

The complexes Pt(nb)_3-n(P-iPr₃)_n (n=1, 2, nb=bicyclo[2.2.1]hept-2-ene), prepared in situ from Pt(nb)₃, are useful reagents for addition of Pt(P-iPr₃)_n fragments to saturated triruthenium clusters. The complexes Ru₃Pt(CO)₁₁(P-iPr₃)₂ (1), Ru₃Pt(-H)(₃-³-MeCCHCMe)(CO)₉(P-iPr₃) (2), Ru₃Pt(₃-²-PhCCPh)(CO)₁₀(P-iPr₃) (3), Ru₃Pt(-H)(₄-N)(CO)₁₀(P-iPr₃) (4) and Ru₃Pt(-H)(₄-²-NO)(CO)₁₀(P-iPr₃) (5) have been prepared in this fashion. All complexes have been characterized spectroscopically and by single crystal X-ray determinations. Clusters 1–3 all have 60 cluster valence electrons (CVE) but exhibit differing metal skeletal geometries. Cluster 1 exhibits a planar-rhomboidal metal skeleton with 5 metal–metal bonds and with minor disorder in the metal atoms. Cluster 2 has a distorted tetrahedral metal arrangement, while cluster 3 has a butterfly framework (butterfly angle=118.93(2)°). Clusters 4 and 5 posseses 62 CVE and spiked triangular metal frameworks. Cluster 4 contains a ₄-nitrido ligand, while cluster 5 has a highly unusual ₄-²-nitrosyl ligand with a very long nitrosyl N–O distance of 1.366(5) Å.     

Probing the metal-to-ligand charge transfer first excited state in (η6-naphthalene)Cr(CO)3 and (η6-phenanthrene)Cr(CO)3 by resonance Raman spectroscopy and density functional theory calculations

The nature of the lowest energy optical transition for the complexes (η(6)-naphthalene)Cr(CO)(3) and (η(6)-phenanthrene)Cr(CO)(3) in the solid state has been investigated by Raman spectroscopy using a range of different excitation wavelengths progressively approaching the resonant condition. Examination of the resonantly enhanced Raman modes confirms that the first absorption is attributed predominantly to a metal-to-arene charge transfer transition for both complexes. A notable difference in the photochemistry of the two complexes was observed. In the case of the phenanthrene complex, population of the lowest energy excited state leads to a photochemical process which resulted in the loss of the arene ligand and formation of Cr(CO)(6).     

Palladium-catalyzed allylic nucleophilic substitution reactions of (E)-γ-acetoxy-α,β-unsaturated p-tolylsulfoxides

Regio- and diastereoselective nucleophilic allylic substitutions of optically pure (E)-γ-acetoxy-α,β-unsaturated p-tolylsulfoxides 2 and 3 with sodium dimethyl malonate have been carried out. The reactivity of these substrates is controlled by both the chiral sulfinyl group and the size of the alkyl group attached at the γ-terminus of the allylic system. This process constitutes an example of palladium-mediated resolution of a 1:1 mixture of acetates 2 and 3.     

Comparison of the Bonding of Benzene and C60 to a Metal Cluster: Ru3(CO)9(μ3-η2,η 2,η2-C6H6) and Ru3(CO)9(μ3-η2,η2,η2-C60)

The electron distributions and bonding in Ru₃(CO)₉( ³- ², ², ²-C₆H₆) and Ru₃(CO)₉( ³- ², ², ²-C₆₀) are examined via electronic structure calculations in order to compare the nature of ligation of benzene and buckminsterfullerene to the common Ru₃(CO)₉ inorganic cluster. A fragment orbital approach, which is aided by the relatively high symmetry that these molecules possess, reveals important features of the electronic structures of these two systems. Reported crystal structures show that both benzene and C₆₀ are geometrically distorted when bound to the metal cluster fragment, and our ab initio calculations indicate that the energies of these distortions are similar. The experimental Ru–C_fullerene bond lengths are shorter than the corresponding Ru–C_benzene distances and the Ru–Ru bond lengths are longer in the fullerene-bound cluster than for the benzene-ligated cluster. Also, the carbonyl stretching frequencies are slightly higher for Ru₃(CO)₉( ³- ², ², ²-C₆₀) than for Ru₃(CO)₉( ³- ², ², ²-C₆H₆). As a whole, these observations suggest that electron density is being pulled away from the metal centers and CO ligands to form stronger Ru–C_fullerene than Ru–C_benzene bonds. Fenske-Hall molecular orbital calculations show that an important interaction is donation of electron density in the metal–metal bonds to empty orbitals of C₆₀ and C₆H₆. Bonds to the metal cluster that result from this interaction are the second highest occupied orbitals of both systems. A larger amount of density is donated to C₆₀ than to C₆H₆, thus accounting for the longer metal–metal bonds in the fullerene-bound cluster. The principal metal–arene bonding modes are the same in both systems, but the more band-like electronic structure of the fullerene (i.e., the greater number density of donor and acceptor orbitals in a given energy region) as compared to C₆H₆ permits a greater degree of electron flow and stronger bonding between the Ru₃(CO)₉ and C₆₀ fragments. Of significance to the reduction chemistry of M₃(CO)₉( ³- ², ², ²-C₆₀) molecules, the HOMO is largely localized on the metal–carbonyl fragment and the LUMO is largely localized on the C₆₀ portion of the molecule. The localized C₆₀ character of the LUMO is consistent with the similarity of the first two reductions of this class of molecules to the first two reductions of free C₆₀. The set of orbitals above the LUMO shows partial delocalization (in an antibonding sense) to the metal fragment, thus accounting for the relative ease of the third reduction of this class of molecules compared to the third reduction of free C₆₀.     

Co3(CO)7(μ3-S)(μ,η2-SCNR2)的合成和晶体结构

Co2(CO)8与4个二硫代双(烷基硫代甲酰胺)类前配体[R2NC(S)S]2反应,得4个含烷基硫代甲酰胺基的三核钴羰基硫簇合物.通过元素分析、IR、1H NMR和MS等方法表征了它们的结构,用X射线衍射法测定了其中一个簇合物Co3(CO)7(μ3-S)[μ,η2-SCN(i-Pr)2](Ⅲ)的晶体结构.晶体属单斜晶系,P21/n空间群,晶胞参数a=1.145 2(2)nm,b=1.502 8(3)nm,c=1.2144(2)nm,a=90°,β=92.15(3)°,γ=90°,V=2.088 5(7)nm3,Z=4,F(000)=1 096,Dc=1.747 mg·m-3,GOF(F2)=0.835,μ=2.588 nm-1.最终因子R[I＞2σ(I)]=0.040 7,Rw=0.062 4.     

Reactions of Unsaturated Quinoline Triosmium Clusters [Os3(CO)9(μ3-η2-C9H5(4-R)N)(μ-H)] (R=Me or H) with Tetramethylthiourea: X-ray Structures of [Os3(CO)8(μ-η2-C9H5(4-Me)N)(η2-SC(NMe2NCH2Me)(μ-H)2] and [Os3(CO)9(μ-η2-C9H6N)(η1-SC(NMe2)2)(μ-H)]

Treatment of the electronically unsaturated 4-methylquinoline triosmium cluster $[\hbox{Os}_{3}\hbox{(CO)}_{9}(\upmu_3\hbox{-}\upeta^{2}\hbox{-}\hbox{C}_{9}\hbox{H}_{5} \hbox{(4-Me)N})(\upmu\hbox{-H})]$ (1) with tetramethylthiourea in refluxing cyclohexane at 81°C gave $[\hbox{Os}_{3}\hbox{(CO)}_{8}(\upmu\hbox{-}\upeta^{2}\hbox{-C}_{9}\hbox{H}_{5} \hbox{(4-Me)N})(\upeta^2\hbox{-SC}(\hbox{NMe}_2\hbox{NCH}_2\hbox{Me})(\upmu \hbox{-H})_2]$ (2) and $[\hbox{Os}_{3}\hbox{(CO)}_{9}(\upmu\hbox{-}\upeta^{2}\hbox{-C}_{9}\hbox{H}_{5}\hbox{(4-Me)N})(\upeta^1\hbox{-SC}(\hbox{NMe}_2)_2)(\upmu\hbox{-H})]$ (3). In contrast, a similar reaction of the corresponding quinoline compound $[\hbox{Os}_{3}\hbox{(CO)}_{9}(\upmu_{3}\hbox{-}\upeta^{2}\hbox{-C}_{9}\hbox{H}_{6}\hbox{N})(\upmu\hbox{-H})]$ (4) with tetramethylthiourea afforded $[\hbox{Os}_{3}\hbox{(CO)}_{9}(\upmu\hbox{-}\upeta^{2}\hbox{-C}_{9}\hbox{H}_{6}\hbox{N})(\upeta^{1}\hbox{-SC(NMe}_{2})_{2})(\upmu\hbox{-H)}]$ (5) as the only product. Compound 2 contains a cyclometallated tetramethylthiourea ligand which is chelating at the rear osmium atom and a quinolyl ligand coordinated to the Os₃ triangle via the nitrogen lone pair and the C(8) atom of the carbocyclic ring. In 3 and 5, the tetramethylthiourea ligand is coordinated at an equatorial site of the osmium atom, which is also bound to the carbon atom of the quinolyl ligand. Compounds 3 and 5 react with PPh₃ at room temperature to give the previously reported phosphine substituted products $[\hbox{Os}_{3}\hbox{(CO)}_{9}(\upmu \hbox{-}\upeta^{2}\hbox{-C}_{9}\hbox{H}_{5}\hbox{(4-Me)N)(PPh}_{3})(\upmu\hbox{-H)}]$ (6) and $[\hbox{Os}_{3}\hbox{(CO}_{9}(\upmu \hbox{-}\upeta^{2}\hbox{-C}_{9}\hbox{H}_{6}\hbox{N)(PPh}_{3})(\upmu\hbox{-H)}]$ (7) by the displacement of the tetramethylthiourea ligand.     

Reaction of alkyne cluster Os3(μ-CO)(CO)9(μ3-η1:η1:η2-Me3SiC2Me) with HC≡CCOOMe. Molecular and crystal structures of Os3(CO)9{μ3-η1:η1:η2:η2-C(SiMe3)C(Me)C(COOMe)CH× and Os3(CO)8{μ3-η1:η1:η4:η1-C(SiMe3)C(Me)C(H)C(COOMe)CH× complexes

Reaction of the cluster Os₃(μ-CO)(CO)₉(μ₃-η¹:η¹:η²-Me₃SiC₂Me) with HC≡CCOOMe in benzene at 70 °C results in Os₃(CO)₉{μ₃-η¹:η¹:η²:η²-C(SiMe₃)C(Me)C(COOMe)CH× (5), Os₃(CO)₉{μ₃-η¹:η¹:η²:η²-C(SiMe₃)C(Me)C(H)C(COOMe)CH× (6), Os₃(CO)₉{μ-η¹:η¹:η⁴-C(SiMe₃)C(Me)C(H)C(COOMe)CH× (7), and Os₃(CO)_δ{μ₃-η¹:η¹:η⁴:η¹-C(SiMe₃)C(Me)C(H)C(COOMe)× complexes (8), containing an osmacyclopentadiene moiety. Complexes5–8 were characterized by¹H NMR and IR spectroscopy. The structure of clusters5 and8 was confirmed by X-ray analysis. Complex7 is formed from cluster5 as a result of a new intramolecular rearrangement and complex8 is obtained by decarbonylation of compound6. Complex8 adds PPh₃ to give Os₃(CO)_δ(PPh₃){μ-η¹:η¹:η⁴-C(SiMe₃)C(Me)C(H)C(COOMe)×.     

KINETICS AND MECHANISM FOR INTRAMOLECULAR ISOMERIZATION OF HRu3 (μ3-η3-EtSCCMeCMe)(CO)9 TO Ru3(μ-SEt) (μ3-η3-CCMeCHMe)(CO)9

Abstract

The kinetics for isomerization of HRu₃ (μ₃-η³-EtSCCMeCMe)(CO)₉ TO Ru₃(μ-SEt) (μ₃-η³-CCMeCHMe)(CO)₉, were determined. The overall process involves C[sbnd]H elimination, C[sbnd]S and Ru[sbnd]Ru bond cleavage and Ru₂(μ-S) bond formation. Activation parameters were determined from the temperature dependence (ΔH^? = 127(3) kJ/mol, ΔS^?= 56(11) J/mol-K) and from the pressure dependence (0[sbnd]207 MPa, ΔV^? ₀ +12.7(1.1) cm³/mol, Δβ^? = +0.037(0.012) cm³/(mol-MPa)) of the rate constant. The data are consistent with an intramolecular reaction involving significant metal-metal or carbon-sulfur bond cleavage in the transition state. The activation volume is too large to be accommodated by C[sbnd]H elimination alone and CO dissociation is not involved.     

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.     

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 the η1:η6-C6H5Cr(CO)3 ligand into the cyclopentadienyl ring during metallation of the η5-C5H5(CO)2Fe η1:η6-C6H5Cr(CO)3 binuclear complex

It was found that the ¹⁶-C₆H₅Cr(CO)₃ ligand migrates into the cyclopentadienyl ring when the ⁵-C₅H₅(CO)₂Fe ¹⁶-C₆H₅Cr(CO)₃ binuclear complex is metallated with BuⁿLi. Under the same conditions, no migration of the phenyl ligand in the ⁵-C₅H₅(CO)₂Fe ¹-C₆H₅ complex was observed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 325–326, February, 1994.     

Density functional calculations of the structures and bond energies of Cr(CO)6 and (η6-C6H6) Cr(CO)2(CX) (X=O,S) complexes

Summary Quantum chemical calculations based on density functional theory have been performed on Cr(CO)₆, (⁶-C₆H₆)Cr(CO)₃ and (⁶-C₆H₆)Cr(CO)₂(CS) at the local and nonlocal level of theory using different functionals. Good agreement is obtained with experiment for both optimized geometries and metal-ligand binding energies. In particular, a comparison of metal-arene bond energies calculated for the (⁶-C₆H₆)Cr(CO)₃ and (⁶-C₆H₆)Cr(CO)₂(CS) complexes correlates well with kinetic data demonstrating that substitution of one CO group by CS leads to an important labilizing effect of this bond, which may be primarily attributed to a larger -backbonding charge transfer to the CS ligand as compared with CO.     

Stereoselective synthesis of key (η6-arene)Cr(CO)3 complexes to acorenone and acorenone B

Direct diastereoselective chromium complexation of meta-methoxy benzylalcohol derivatives was achieved by the introduction of Me₃,Si group, and the benzylic acetoxyl groups of the complexes were substituted with stereochemical retention to lead the key complexes to acorenone and acorenone B.