The synthesis and characterization of two new 19-vertex metallaborane clusters: [B18H20Ni(η5-C5H5)]−1 and [B18H19(2-THF)Ni(η5-C5H5)]

Two new 19-vertex metallaboranes, [B₁₈H₂₀Ni(η⁵-C₅H₅)][N(CH₃)₄] and [B₁₈H₁₉(2-THF)Ni(η⁵-C₅H₅)], were isolated from the reaction of anti-B₁₈H₂₂ with nickelocene, [Ni(η⁵-C₅H₅)₂], in high yields. The complexes were characterized by multinuclear NMR (¹H, ¹³C, ¹¹B), IR and UV–vis spectroscopy. Single-crystal X-ray diffraction analyses of these new complexes confirmed their structures as 19-vertex conjuncto-metallaborane clusters.     

Synthesis and structure of the cubane type [Fe2Sb(CO)5(η5-C5H5)]4 cluster

The [Fe₂Sb(CO)₅Cp]₄ (Cp=η⁵-C₅H₅) cluster has been obtained by the thermolysis of [Et₄N][{Fe(CO)₄}₂{Fe(CO)₂Cp}SbI]. The structure of the [Fe₂Sb(CO)₅Cp]₄·2toluene solvate has been determined by X-ray analysis. The cluster contains the cubane [Fe₄Sb₄] core. Each Sb serves as a μ₄-ligand between three iron atoms of the core and one of a terminal [Fe(CO)₂Cp] group.     

A convenient method for the synthesis of [Pd{[(η5-C5H3)–CHN–(CH2)2–NMe2]Fe(η5-C5H5)}Cl] and the study of its reactivity with diphosphines

A one-pot method for the preparation of [Pd{[(η⁵-C₅H₃)–CHN–(CH₂)₂–NMe₂]Fe(η⁵-C₅H₅)}Cl] is described. Its X-ray crystal structure and its reactions with the diphosphines Ph₂P–(CH₂)_n–PPh₂ {with n=1 (ddpm) or 2 (dppe)} are also reported.     

Zirconocene complexes of the sterically demanding pentaphenylcyclopentadienyl ligand,CpPRO. Synthesis and characterization of CpPROZrCl3 and CpCpPROZrCl2 (Cp=η5-C5H5; CpPRO=η5-C5(C6H5)5)

The synthesis, characterization and X-ray structures of two zirconium complexes of the bulky pentaphenylcyclopentadienyl ligand, Cp^PRO, are reported. The monocyclopentadienyl 12 electron complex, Cp^PROZrCl₃ (I), has an unusual monomeric structure in the solid state and has short Zr–ligand distances. The Lewis acidity of this complex is manifested in its ability to catalyze the [4+2] cycloadditions of methyl- and ethylmethacrylate to cyclopentadiene. The sandwich complex, Cp^PROCpZrCl₂ (II), has more typical Zr–ligand distances, but has a more parallel arrangement of the two cyclopentadienyl rings.     

Electrochemical anion recognition by redox-responsive unnatural amino acid derivatives; the X-ray crystal structure of N-ferrocenoyl glycine methyl ester, (η5-C5H5)Fe(η5-C5H4)CONHCH2COOMe

N-Ferrocenoyl glycine ester derivatives FcCONHCH₂COOR (Fc=(η⁵-C₅H₅)Fe(η⁵-C₅H₄); R=methyl (1), ethyl (2) and benzyl (3)) have been prepared by coupling ferrocene carboxylic acid to a series of glycine esters using 1,3-dicyclohexylcarbodiimide (DCC), 1-hydroxybenzotriazole (HOBT) and Et₃N in CH₂Cl₂. The electrochemical anion sensing using a platinum microdisk working electrode of these N-ferrocenoyl glycine ester derivatives is reported. The crystal structure of 1 has been determined; principal dimensions are amide N(H)CO 1.229(3) Å, ester CO 1.183(3) Å with N–H⋯OC(amide) as the primary intermolecular hydrogen bond, N⋯O 2.804(3) Å.     

Theoretical study of the reactive intermediate Si2Me4[(η5-C5H4) Fe(CO)2] 2 2−

In two previous papers (Kinget al., J. Organomet. Chem. 19, 327, 1969; Pannellet al., Organometallics 9, 859, 1990), the synthesis and X-ray structure of the two tetramethyl disilyl complexes [(η⁵-C₅H₅) Fe(CO)₂]₂Si₂Me₄ (I) and Si₂Me₄[(η⁵-C₅H₄) Fe(CO)₂CH₃]₂ (II) were reported. ComplexII is obtained fromI [2]. However, attempts to form other derivatives fromI have generally failed. In the chemical process to getII fromI, an intermediate complex, Si₂Me₄[(η⁵-C₅H₄) Fe(CO)₂] ₂ ^2? (III), is probably formed. This is similar to complexII without the two methyl groups bonded to the Fe atoms. Therefore, a theoretical study that may shed some light on the intermediate structure, stability, and reactivity is justified. We have developed theoretical studies consisting of extended Huckel electronic structure calculations on the simulated intermediate geometry. The results obtained from these calculations suggest that it might be stable enough to form during reactions of complexI. The more reactive sites, which suggest reaction alternatives, are pointed out.     

Synthesis of UHMW-PE by a Highly Active Homogeneous System: η5-(C5H5)2Ti(η1-OC(O)C6H5)2/MAO

Summary The complex ⁵-(C₅H₅)₂Ti (¹-OC(O)C₆H₅)₂ was synthesized and activated with MA0 for ethylene polymerization. The resultant polymer is UHMW-PE with a viscosimetric molecular weight of Mv = 6.8 x 10⁶ to 0.7 x 10⁶ g/mol dependent on the temperature of the reaction. The effects of the Al/Ti molar ratio and temperature of the reaction on the catalytic activity and polymer properties were studied.     

Cyclohexadiene-linked clusters: synthesis and molecular structure of [{Os4(CO)8(MeCCMe)(η6-C6H6)}2(μ2-η2:η2-C6H8-1,3)]

The reaction of [Os₄(CO)₉(RCCR)(η⁶-C₆H₆)] (R=Me, Ph) with Me₃NO in the presence of 1,3-cyclohexadiene or 1,4-cyclohexadiene yields the clusters [{Os₄(CO)₈(RCCR)(η⁶-C₆H₆)}₂(μ₂-η²:η²-C₆H₈-1,3)] and [{Os₄(CO)₈(RCCR)(η⁶-C₆H₆)}₂(μ₂-η²:η²-C₆H₈-1,4)], respectively. The molecular structure of [{Os₄(CO)₈(MeCCMe)(η⁶-C₆H₆)}₂(μ₂-η²:η²-C₆H₈-1,3)] has been determined by single crystal X-ray diffraction, and represents the first example of two osmium cluster fragments linked by 1,3-cyclohexadiene through a μ₂-η²:η²-bridge.     

A fast route to the potential biological reagent (η5-C5H4COOH)Re(CO)3 from [NH4] [ReO4]

The rhenium carbonyl carboxylic acid (η⁵-C₅H₄COOH)Re(CO)₃ (Re + 1) is readily accesssible in a rapid fashion starting from perrhenate (Re + 7). This complex can be conjugated to amino acids and proteins opening the way to a robust small radiopharmaceutical.     

Semi-rigid N-para-ferrocenyl(benzoyl)amino-acid esters for biomaterials: synthesis and characterization of Fc-C6H4CONHCH(R)CO2Me where Fc = (η5-C5H5)Fe(η5-C5H4) and R=H,CH3,CH2CH(CH3)2,CH2C6H5 and the X-ray crystal structures of Fc-C6H4CO2Me and the l-alanine derivative Fc-C6H4CONHCH(CH3)CO2Me

A series of N-para-(ferrocenyl)benzoyl amino-acid esters, para-Fc(C₆H₄)CONHCH(R)CO₂CH₃ {Fc = (η⁵-C₅H₅)Fe(η⁵-C₅H₄); R = H, CH₃, CH₂CH(CH₃)₂, CH₂C₆H₅}, 3–6 have been prepared by coupling para-(ferrocenyl)benzoic acid to the amino-acid esters (gly, l-Ala, l-Leu, l-Phe) using the standard 1,3-dicyclohexylcarbodiimide (DCC), 1-hydroxybenzotriazole (HOBt) protocol. The compounds were fully characterized by a range of spectroscopic techniques including FAB-MS. The X-ray crystal structures of the parent para-(ferrocenyl)benzoyl methyl ester, Fc-C₆H₄CO₂Me, 1 and a chiral derivative N-{para-(ferrocenyl)benzoyl}-l-alanine methyl ester, Fc-C₆H₄CONHCH(CH₃)CO₂Me, 4 have been determined.     

Formation of [8,8-η2-{(μ-Cl)2Ru(η6-p-cym)Ph2PCH2PPh2}-nido-8,7-RhSB9H10], a bimetallic derivative of the novel species [8,8-(η2-dppm)-8-(η1-dppm)-nido-8,7-RhSB9H10]

Treatment of [8,8-(η²-dppm)-8-(η¹-dppm)-nido-8,7-RhSB₉H₁₀] (I) with [Ru(η⁶-p-cym)Cl₂]₂ leads to the formation of a new bimetallic complex, [8,8-η²-{(μ-Cl)₂Ru(η⁶-p-cym)Ph₂PCH₂PPh₂}-nido-8,7-RhSB₉H₁₀], (II) containing the group [(μ-Cl)₂Ru(η⁶-p-cym)Ph₂PCH₂PPh₂] that coordinates in a multidentate mode to Rh.     

Synthesis of the sterically constrained ligand precursor cyclopentadienyl-2,6-diphenylbenzene and structure of [(2,6-Ph2–C6H3-η5-C5H4)Zr(NEt2)3]

A Pd-catalysed Stille coupling of 2,6-diphenyliodobenzene with tributylcyclopentadienyltin gave the sterically constrained ligand precursor cyclopentadienyl-2,6-diphenylbenzene (1). Treatment of this precursor with tetrakis(diethylamido)zirconium(IV) gave the three-legged piano-stool complex [(2,6-Ph₂–C₆H₃-η⁵-C₅H₄)Zr(NEt₂)₃] (2). Complex 2 was characterised by ¹H- and ¹³C{¹H}-NMR spectroscopy as well as by X-ray crystallography which showed significant distortions of the three-legged piano-stool geometry as a result of steric interactions with the bulky aryl substituent.     

Sulfur-assisted chloride and triphenylphosphine dissociation of palladium(II) complex [Pd(PPh3)2(η1-SCNMe2)(Cl)]. X-ray structures of [Pd(PPh3)2(η1-SCNMe2)(Cl)], [Pd(PPh3)(Cl)]2(μ,η2-SCNMe2)2, and [Pd(PPh3)2(η2-SCNMe2)][PF6]

Treatment of Pd(PPh₃)₄ with Me₂NC(S)Cl in dichloromethane at −20 °C produces the complex [Pd(PPh₃)₂(η¹-SCNMe₂)(Cl)], 2. Variable temperature ¹H and ³¹P{H} NMR experiments of complex 2 shows the dissociation of either the chloride or the triphenylphosphine ligand to form complex [Pd(PPh₃)₂(η²-SCNMe₂)][Cl], 3 or the dipalladium complex [Pd(PPh₃)Cl]₂(μ,η²-SCNMe₂)₂, 4. The reaction of complex 2 with NaPF₆ affords complex [Pd(PPh₃)₂(η²-SCNMe₂)][PF₆], 5. Complexes 2, 4, and 5 are characterized by X-ray diffraction analyses.     

An unusual o-metallated pyridyl dirhodium(II) complex: [Rh2{μ-(C5H3N)NH(C5H4N)}2{η2-(C5H4N)NH(C5H4N}2]Cl2·CH3OH

Reaction of Rh₂(O₂CMe)₄ and bis(2-pyridyl)amine, Hdpa, followed by addition of CH₂Cl₂ led to replacement of the acetate groups by Hdpa and orthometallation of two Hdpa pyridyl groups. The isolated complex, [Rh₂{μ-(C₅H₃N)NH(C₅H₄N)}₂{η²-(C₅H₄N)NH(C₅H₄N}₂]Cl₂ (1), has been characterized by X-ray crystallography, showing that the complex has two equatorially bound Hdpa groups and two bridging orthometallated dpa anions.     

Hydrothermal synthesis,crystal structure and physical properties of {[Gd(H2O)4(μ2-C6NO2H5)2Gd(H2O)4](μ3-C6NO2H4)2(ZnCl3)2} · 2H2O · 2Cl

A bimetallic 4f–3d tetranuclear complex {[Gd(H₂O)₄(μ₂-C₆NO₂H₅)₂Gd(H₂O)₄](μ₃-C₆NO₂H₄)₂(ZnCl₃)₂} · 2H₂O · 2Cl (1) has been synthesized via hydrothermal reaction and structurally characterized by single-crystal X-ray diffraction. Complex 1 is characterized by a tetranuclear Gd₂Zn₂ structure with the gadolinium and zinc atoms interconnected by isonicotinic acid ligands. The tetranuclear species of {[Gd(H₂O)₄(μ₂-C₆NO₂H₅)₂Gd(H₂O)₄](μ₃-C₆NO₂H₄)₂(ZnCl₃)₂} link to isolated chlorine ions and water molecules via π?π interactions and hydrogen bonds to yield a 3-D supramolecular framework. Photoluminescent investigation reveals that the title complex displays an emission in ultraviolet region. The solid-state diffuse reflectance spectra of 1 reveal the presence of a sharp optical gap of 3.66 eV.     

Molecular structure of [In2(μ,η1-OR)(μ,η2-OR)(η2-OR)3(η1-OR)] R = C2H4NMe2, a pincer ligand

Functional indium [In(OR)₃]_m alkoxides (R = C₂H₄OMe, C₂H₄NMe₂) have been obtained by alcoholysis of In[N(SiMe₃)₂]₃ and characterised by elemental analysis, FT-IR and NMR spectroscopy. The 2-dimethylaminoethoxide was characterised by X-ray diffraction. It corresponds to the association of two InO₆ octahedra giving the unsymmetrical dimer [In₂(μ,η¹-OR)(μ,η²-OR)(η²-OR)₃(η¹-OR)] (2). 2 was used as a pincer ligand toward Cu(acac)₂.     

Thermal dehydration of Y(TFA)3(H2O)3: Synthesis and molecular structures of [Y(μ,η1:η1-TFA)3(THF)(H2O)]1∞ · THF and [Y4(μ3-OH)4(μ,η1:η1-TFA)6(η1-TFA)(η2-TFA)(THF)3(DMSO)(H2O)] · 6THF (TFA = trifluoroacetate)

In order to obtain a better anhydrous precursor for various applications in materials science and catalysis, thermal dehydration reactions of Y(TFA)₃(H₂O)₃ (TFA = trifluoroacetate) (A) were investigated. Thermal treatment of A at different temperatures under vacuum (5 × 10^?2 mm) for several hours failed to give totally anhydrous yttrium trifluoroacetate (as indicated by IR). Two different complexes, a partially dehydrated [Y(μ,η¹:η¹-TFA)₃(THF)(H₂O)]_1∞·THF (1) and a partially hydrolyzed [Y₄(μ₃-OH)₄(μ,η¹:η¹-TFA)₆(η¹-TFA)(η²-TFA)(THF)₃(DMSO)(H₂O)] · 6THF (2), were obtained with good and moderate yield, respectively, by crystallization of two different thermally treated batches of A from THF (or THF + DMSO) at room temperature. More efficient dehydration of A could be achieved at 200 °C in a furnace, the obtained anhydrous yttrium tris-trifluoroacetate giving Y(TFA)₃(THF)₂ (3) on crystallization from THF. All the products were characterized by elemental analyses, FT-IR and ¹H NMR spectroscopy as well as thermo-gravimetric analysis. In addition, single crystal X-ray structures are reported for 1 and 2, which show either a terminal (η¹ and η²) or bridging (μ,η¹:η¹) bonding behavior of the TFA ligand.     

Synthesis of cis- and trans-[M(CN)2(1-CH3-C6H10-NC)4] (M = Fe,Ru) and crystal structure of trans-[Ru(CN)2(1′-CH3-C6H10-NC)4]

The reaction of the metal carbonyls Fe₂(CO)₉ or Ru₃(CO)₁₂ with 1-isocyano-1-methyl-cyclohexane produces the octahedral metal(II) cyano complexes [M(CN)₂(1-CH₃-C₆H₁₀-NC)₄] in good yields. The cis-isomer is not isolated as a pure compound due to rearrangement processes that yield the sterically less crowded trans-isomer. The molecular structure of the trans-isomer of the ruthenium complex shows the expected almost ideal octahedral coordination of the central ruthenium ion with two cyanide and four isocyanide ligands. This reaction again indicates that isocyanides exhibiting quarternary carbon atoms in α-position with respect to the isocyano substituent in general react with di- or trinuclear metal carbonyls to yield cyano complexes with oxidized metal centres and concomitant reductive cleavage of the respective isocyanide.