C-H activation of arenes and heteroarenes by early transition metallaborane, [(Cp*Ta)2B5H11] (Cp* = η5-C5Me5)

C-H activation of arenes and heteroarenes has been achieved by a hydrogen rich tantalaborane cluster [(Cp*Ta)(2)B(5)H(11)] that leads to the formation of C-H functionalized products. Furthermore, we examined the reaction of substituted thiophene and pyrrole derivatives with tantalaborane which provided a convenient and efficient route to regio-defined C-H functionalized heteroarenes.     

A homometallic tricapped cubane cluster: [(Cp*Mo)4B4H4(μ4-BH)3] (Cp* = η5-C5Me5)

The reaction of [Cp*MoCl(4)] with an excess of LiBH(4), followed by thermolysis with tellurium powder in toluene, afforded a tricapped cubane cluster, [(Cp*Mo)(4)B(4)H(4)(μ(4)-BH)(3)] (1), which represents an unprecedented metal-rich metallaborane cluster with a cubane core containing 58 cluster valence electrons (cve) and three metal-metal bonds.     

Combined experimental and theoretical investigation into C-H activation of cyclic alkanes by Cp'Rh(CO)2 (Cp' = η5-C5H5 or η5-C5Me5)

Fast time-resolved infrared spectroscopic measurements have allowed precise determination of the rate of C-H activation of alkanes by Cp'Rh(CO) {Cp' = η(5)-C(5)H(5) or η(5)-C(5)Me(5); alkane = cyclopentane, cyclohexane and neopentane (Cp only)} in solution at room temperature and allowed the determination of how the change in rate of oxidative cleavage varies between complexes and alkanes. Density functional theory calculations on these complexes, transition states, and intermediates provide insight into the mechanism and barriers observed in the experimental results. Unlike our previous study of the linear alkanes, where activation occurred at the primary C-H bonds with a rate governed by a balance between these activations and hopping along the chain, the rate of C-H activation in cyclic alkanes is controlled mainly by the strength of the alkane binding. Although the reaction of CpRh(CO)(neopentane) to form CpRh(CO)(neopentyl)H clearly occurs at a primary C-H bond, the rate is much slower than the corresponding reactions with cyclic alkanes because of steric factors with this bulky alkane.     

A beneficial kinetic effect of an η(5)-C5Me4H ligand

C-H activation of benzene at 26 °C by (η(5)-C(5)Me(5))W(NO)(CH(2)CMe(3))(η(3)-CH(2)CHCHMe) results after 4 h in the production of five new organometallic complexes, only two of which are isomers of the desired (η(5)-C(5)Me(5))W(NO)(C(6)H(5))(η(3)-CH(2)CHCHMe) compound. In contrast, the identical reaction involving the η(5)-C(5)Me(4)H analogue affords only the phenyl complexes during the first 24 h, thereby facilitating their isolation in good yields. This striking difference in reactivity can be attributed to the lesser steric demands of the η(5)-C(5)Me(4)H ligand that result in its complexes reacting at a significantly slower rate.     

Triphospha-Ferrocenes as Ligands. Crystal Structures of [Fe(η5-C5Me5)(η5-C2 TBu2P3)M(CO)5)], (M= Cr,MO, W) and the Novel ruthenium and Nickel Complexes [Fe(η5-C5Me5) (η5-C2 TBu2P3)Ru3(CO)9] and [Fe(η5-C5Me5)(η5-C2 tBu2P3)Ni(Co)2]2

Abstract

Syntheses and structures of penta- and hexaphosphorus analogues of ferrocene have been described recently¹. Unlike their simple ferrocene analogues, these complexes have further ligating potential towards other transition metal centres by virtue of the availability of the ring phosphorus lone-pair electrons that are not involved in the η⁵-coordination. We now describe the first examples of coordination compounds of the triphospha-ferrocene [Fe(η⁵-C₅Me₅) (η⁵-C₂ ^tBu₂P₃]. In the ruthenium complex [Fe(η⁵-C₅Me₅)(η⁵-C₂ ^tBu₂P₃) Ru₃(CO)₉] ² two adjacent phosphorus atoms of the η⁵-C₂ ^tBu₂P₃ ring are interlinked by a ruthenium carbonyl cluster in which all three ruthenium atoms interact with the phosphorus atoms. The tetrametallic nickel complex [Fe(η⁵-C₅Me₅)(η⁵-C₂ ^tBu₂P₃)Ni(CO)₂]₂ ³ represents the first example of intermolecular interlinkage of two phospha-ferrocene systems by two metal centres.     

DFT studies of the methyl exchange reaction between Cp2M-CH3 or Cp*2M-CH3 (Cp = C5H5, Cp* = C5Me5, M = Y, Sc, Ln) and CH4. Does M ionic radius control the reaction?

The activation energies for the methyl exchange reactions between Cp2M-CH3 and H-CH3 have been calculated for M = Sc, Y and representative metals of the lanthanide family (La, Ce, Sm, Ho, Yb and Lu) with DFT(B3PW91) calculations with large-core pseudopotentials for M. The sigma-bond metathesis reactions are calculated to have lower activation energies for early lanthanides than for late lanthanides and any of group 3 metals. The relative activation barriers are analyzed using the NBO charge distributions in the reactant and in the transition states. It is shown that the methane needs to be polarized in the transition state as H((+delta))-CH3((-delta)) by the reactant, because this sigma-bond metathesis is best viewed as heterolytic cleavage of methane, leading to a proton transfer between two methyl groups in the field of an electropositive M metal. Early lanthanides, which are involved in strongly ionic metal-ligands bonds are thus associated with the lowest activation energies. The ionic radius and the steric effects influence the relative rates of reaction for the complexes of Sc, Y and Lu. In agreement with earlier works of Sherer et al., the experimental reactivity trends found by Tilley are reproduced best with Cp*2M-CH3 (Cp* = C5Me5) rather than Cp2M-CH3 (Cp = C5H5) because the steric bulk of C5Me5 deactivates most the complex where the metal has the smallest ionic radius (Sc). While the steric effects and the influence of the metal ionic radius cannot be neglected, these factors are not the only ones involved in determining the activation barriers of the sigma-bond metathesis reaction.     

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.     

不对称型双核半夹心结构铁化合物Cp′2Fe2(CO)3Se2C2B10H10 (Cp′=η5-C5H4Me)的合成、表征及结构

用碳硼烷的含硒锂盐Li2Se2C2B10H10 (1)与单茂羰基铁的氯化物Cp′Fe(CO)2Cl(2)反应得到不对称型双核半夹心结构铁的化合物Cp′2Fe2(CO)3Se2C2B10H10(3). X射线单晶结构分析表明其中一个铁原子是手性的, 而且两个铁原子之间没有相互作用.     

A mild,phosphine-assisted synthesis of (η-C5Me5)Ta(CO)4. Isolation and crystal structure of intermediate (η-C5Me5)TaCl2(CO)2(PMe3)

Mild, reductive carbonylation of (C₅Me₅)TaCl₄ in the presence of trimethylphosphine gives (C₅Me₅)Ta(CO)₄ in 47% yield. The intermediate (C₅Me₅)TaCl₂- (CO)₂(PMe₃) has been isolated from the reaction of (C₅Me₅)TaCl₂(PMe₃)₂ with carbon monoxide and its crystal structure determined (space group P2₁2₁2₁).     

Coordination chemistry of [Cp*Fe(η5-P3C2tBu2)] (Cp* = η5-C5Me5) with copper(I) halides – Formation of oligomeric and polymeric compounds

The reaction of the 1,2,4-triphosphaferrocene [Cp*Fe(η⁵-P₃C₂tBu₂)] (1) with CuX (X = Cl, Br, I) in a 1:1 stoichiometric ratio leads to the formation of the oligomeric compounds [{Cu(μ-X)}₆(μ₆-X)Cu(MeCN)₃{μ,η²-(Cp*Fe(η⁵-P₃C₂tBu₂))}₂{μ₃,η³-(Cp*Fe(η⁵-P₃C₂tBu₂))}] (X = Cl (2), Br (3)) and [{Cu(μ-I)}₃{Cu(μ₃-I)}₃Cu(μ₆-I){μ,η²-(Cp*Fe(η⁵-P₃C₂tBu₂))}₃{η¹-(Cp*Fe(η⁵-P₃C₂tBu₂))}] (4) revealing Cu(I) halide cages surrounded by 1,2,4-triphosphaferrocene moieties. The reaction of [Cp*Fe(η⁵-P₃C₂tBu₂)] with CuI in a 1:4 stoichiometry leads to the formation of the two-dimensional polymer [{Cu(μ-I)}₄{Cu(μ₃-I)(MeCN)}₂{μ₃,η³-(Cp*Fe(P₃C₂tBu₂))}]_n (5). The oligomeric compounds show dynamic behavior in solution monitored by ³¹P NMR spectroscopy. All compounds are additionally characterized by single crystal X-ray diffraction.     

Insertions of nitriles and pyridine into the ZrSi bond of (η5-C5H5)(η5-C5Me5)Zr[Si(SiMe3)3]Me

The zirconium silyl complex CpCpZr[Si(SiMe₃)₃]Me (1; Cp = η⁵-C₅H₅; Cp = η⁵-C₅Me₅) reacts with nitriles RCN (R = Me, CHCH₂, Ph) to form the azomethine derivatives CpCpZr[NC(R)Si(SiMe₃)₃]Me (2, R = Me; 3, R = CHCH₂; 4, R = Ph). Pyridine reacts with 1 to give a 75% yield of CpCpZr[NC₅H₅Si(SiMe₃)₃]Me (5), which results from 1,2-addition of the ZrSi bond of 1 to pyridine. These reactions provide the first examples of nitrile and pyridine insertions into a transition metal-silicon bond. The related silyl complexes Cp₂Zr[Si(SiMe₃)₃]Me and CpCpZr[Si(SiMe₃)₃]Cl are much less reactive toward nitriles and pyridine.     

Synthesis,characterization, and reactivity of the neutral metal formyl (η5-C5Me5)(CO)2(PPh3)MoCHO. A new route to monocationic secondary alkoxycarbene complexes [(η5-C5Me5)(CO)2(PPh3)Mo(CHOE)]+ X− (E = H,Me)

(η⁵-C₅Me₅)(CO)₂(PPh₃)MoCHO (2) one of the few isolated neutral metal formyls, reacts with the electrophilic reagents (CF₃COOH and CH₃SO₃F without disproportionation to give the secondary carbene complexes [(η⁵-C₅Me₅)(CO)₂(PPh₃)Mo(CHOE)]⁺ X⁻ (E = H, X = CF₃COO (4); E = Me, X = PF₆ (5)).     

钛配合物Cp2TiL,Cp2Ti2Cl2(μ-O)和Cp4Ti4Cl4(μ-O)4的合成与晶体结构研究(Cp=η5-C5H5,L=2,6-吡啶二羧酸盐)

利用溶剂热的方法将Cp2TiCl2(Cp=η5-C5H5)与2,6-吡啶二羧酸钠(L)反应,不同的反应时间得到了2个具有不同晶体空间群的化合物Cp2TiL(1a和1b),而在常温或低温下,Cp2TiCl2或CpTiCl3同羧酸盐或亚胺反应却得到了双核或四核氧桥联的钛化合物。     

[(η5-C5Me5)WS3Cu3Br2(PPyPh2)2]四核簇合物的合成和晶体结构

以2[(η5-C5Me5)WS3(CuBr)3]2和diphenyl-2-pyridylphosphine (PPyPh2)在乙腈中反应得到标题化合物[(η5-C5Me5)WS3Cu3Br2(PPyPh2)2], 对该产物进行了元素分析、 IR、 UV-Vis和1H NMR 谱表征, 并测定了晶体结构. 该化合物晶体属三斜晶系, P1空间群, 晶胞参数: a=1.545 9(7) nm, b=1.62 0(1) nm, c=1.018 0(2) nm, α=94.18(3)°, β=97.38(3)°, γ=111.81(4)°, V=2.327(2) nm3, Z=2, Dc=1.84 g*cm-3, F(000)=1 260, μ=57.77 cm-1, 最终偏离因子R=0.029. 此簇合物结构可视为由一个[(η5-C5Me5)WS3]单元和3个Cu组成的开口立方烷, 其中2个Cu是畸变四面体配位, 第3个Cu是近似三角平面配位. W-Cu(1), W-Cu(2) 和W-Cu(3)距离分别为0.270 41(9), 0.273 27(8), 0.267 85(9) nm.     

Structure and bonding analysis of dimethylgallyl complexes of iron, ruthenium, and osmium [(η5-C5H5)(CO)2M(GaMe2)] and [(η5-C5H5)(Me3P)2M(GaMe2)

Density functional theory calculations have been performed for the dimethylgallyl complexes of iron, ruthenium, and osmium [(η(5)-C(5)H(5))(L)(2)M(GaMe(2)] (M = Fe, Ru, Os; L = CO, PMe(3)) at the DFT/BP86/TZ2P/ZORA level of theory. The calculated geometry of the iron complex [(η(5)-C(5)H(5))(CO)(2)Fe(GaMe(2))] is in excellent agreement with structurally characterized complex [(η(5)-C(5)H(5))(CO)(2)Fe(Ga(t)Bu(2))]. The Pauling bond order of the optimized structures shows that the M-Ga bonds in these complexes are nearly M-Ga single bond. Upon going from M = Fe to M = Os, the calculated M-Ga bond distance increases, while on substitution of the CO ligand by PMe(3), the calculated M-Ga bond distances decrease. The π-bonding component of the total orbital contribution is significantly smaller than that of σ-bonding. Thus, in these complexes the GaX(2) ligand behaves predominantly as a σ-donor. The contributions of the electrostatic interaction terms ΔE(elstat) are significantly smaller in all gallyl complexes than the covalent bonding ΔE(orb) term. The absolute values of the ΔE(Pauli), ΔE(int), and ΔE(elstat) contributions to the M-Ga bonds increases in both sets of complexes via the order Fe < Ru < Os. The Ga-C(CO) and Ga-P bond distances are smaller than the sum of van der Waal radii and, thus, suggest the presence of weak intermolecular Ga-C(CO) and Ga-P interactions.     

B-Alkylation and Arylation of [(η5-C5Me5Mo)2B5H9]: Synthesis and Characterization of Isomeric [(η5-C5Me5Mo)2B5H9-nRn] (When R = n-Bu, n = 2, 1; R = Ph, n = 2, 1)

Abstract  Reaction of [(η⁵-C₅Me₅Mo)₂B₅H₉], 1 with 5-fold excess of n-BuLi at −70 °C followed by excess of RI (R = n-Bu or Ph) at room temperature yielded B-R inserted metallaboranes [(η⁵-C₅Me₅Mo)₂B₅H₈R] (2: R = n-Bu, 5: R = Ph), [(η⁵-C₅Me₅Mo)₂B₅H₇R₂] (3, 4: R = n-Bu; 6, 7: R = Ph). Isolated yields of mono-alkyl/arylated species are better than di-alkyl/arylated ones. All the new cluster compounds have been characterized by IR, ¹H, ¹¹B, ¹³C NMR and mass spectroscopy as simple substitution derivatives of [(η⁵-C₅Me₅Mo)₂B₅H₉] and the structural types of one of these species, 2 was established by X-ray crystallographic analysis. Graphical Abstract  Reaction of [(η⁵-C₅Me₅Mo)₂B₅H₉], with 5-fold excess of n-BuLi at −70 °C followed by excess of RI (R = n-Bu or Ph) at room temperature yielded B-R inserted metallaboranes [(η⁵-C₅Me₅Mo)₂B₅H_9-nR_n] (When R = n-Bu, n = 2, 1; R = Ph, n = 2, 1).      

Synthesis and structures of bridged diruthenium complexes (E)[η5-C5H4)Ru(CO)]2(μ-CO)2 (E = Me2Ge,Me2SiOSiMe2, Me2SiOSiMe2OSiMe2)

A series of bridged diruthenium complexes (E)[(⁵-C₅H₄)Ru(CO)]₂(-CO)₂ (E = Me₂Ge (2); Me₂SiOSiMe₂ (3); Me₂SiOSiMe₂OSiMe₂ (4)) has been prepared by reacting Ru₃(CO)₁₂ with Cp₂E in refluxing heptane. The molecular structures of (2) and (4) have been determined by X-ray diffraction.     

The reductive dimerization of [W(NCMe)(MeC2Me)2(η-C5H5)]+: Synthesis and X-ray structure of the novel bis(metallacyclopentadiene) complex [W2(μ-σ,σ,η2,η2-C4Me4)2(η-C5H5)2]

Treatment of [W(CO)(MeC₂Me)₂(-C₅H₅)][PF₆] with ONMe₃ in acetonitrile yields [W(NCMe)(MeC₂Me)₂(-C₅H₅)][PF₆] which undergoes irreversible reduction at a Pt electrode in THF. Sodium amalgam reduction of [W(NCMe) (MeC₂Me)₂(-C₅H₅)][PF₆] gives orange crystals of [W₂(µ-,, ², ²-C₄Me₄)₂ (-C₅H₅)₂] X-ray studies on which reveal pairwise alkyne coupling and a novel bis(metallacyclopentadiene) structure.Dedicated to Professor L. F. Dahl on the occasion of his 65th birthday.