Segregated aromatic π-π stacking interactions involving fluorinated and non-fluorinated benzene rings: Cu(py)2(pfb)2 and Cu(py)2(pfb)2(H2O) (py = pyridine and pfb = pentafluorobenzoate)

The syntheses, physical characterization and crystal structures of two new molecular copper(II) complexes of composition [Cu(C₅H₅N)₂(C₇F₅O₂)₂] (1) and [Cu(C₅H₅N)₂(C₇F₅O₂)₂(H₂O)] (2) (C₅H₅N = py = pyridine and C₇F₅O₂⁻ = pfb = pentafluorobenzoate) are reported. Single-crystal X-ray structure determinations revealed that in 1, the Cu²⁺ ion, which lies on a crystallographic inversion centre, is coordinated to two py molecules and two oxygen atoms from two monodentate pfb anions, resulting in a trans-CuN₂O₂ square planar geometry. In 2, the Cu²⁺ ion is also coordinated to two py and two pfb species in addition to a water molecule in the apical site of a distorted CuN₂O₃ square pyramid. In the crystal packing, both 1 and 2 show segregated aromatic π-π stacking interactions in which (py + py) and (pfb + pfb) ring-pairings are seen, but no (py + pfb) pairings occur. Crystal data: 1: C₂₄H₁₀CuF₁₀N₂O₄, M_r = 643.88, space group , a = 8.0777 (3) Å, b = 8.0937 (3) Å, c = 10.5045 (5) Å, α = 90.916 (3)°, β = 93.189 (2)°, γ = 118.245 (3)°, V = 603.36 (4) Å³, Z = 1. 2: C₂₄H₁₂CuF₁₀N₂O₅, M_r = 661.90, space group , a = 7.5913 (5) Å, b = 15.6517 (6) Å, c = 21.1820 (14) Å, α = 95.697 (4)°, β = 94.506 (2)°, γ = 91.492 (4)°, V = 2495.2 (3) Å³, Z = 4.     

Centrosymmetric [Mn2(CO)6(μ-thpymS)2] (thpymS = tetrahydropyrimidine-2-thionato) as a synthon to mixed-metal clusters

Reaction of [Mn₂(CO)₉(NCMe)] with tetrahydropyrimidine-2-thione (thpymSH) at 25 °C furnishes the mono- and dinuclear complexes [Mn(CO)₄(κ¹:η¹-SCNHC₃H₆NCO)] (2) and [Mn₂(CO)₆(μ-thpymS)₂] (1), respectively. Carbon-nitrogen coupling is observed in compound 2 resulting in the formation of κ¹:η¹-SCNHC₃H₆NCO ligand while compound 1 adopts a centrosymmetric structure. Reaction of 1 with [Os₃(CO)₁₀(NCMe)₂] at 80 °C affords the mixed Mn-Os cluster [MnOs₃(CO)₁₃(μ₃-thpymS)] (3) which possesses a butterfly skeleton of four metal atoms whereas with Ru₃(CO)₁₂ at 110 °C gives the mixed Mn-Ru complex [MnRu₃(CO)₁₄(μ₄-S)(κ¹:η¹-thpym)] (4). In contrast, treatment of 1 with Fe₃(CO)₁₂ at 80 °C furnishes two triiron complexes [Fe₃(CO)₉(μ₃-S)(μ₃-κ¹:η¹-C₄H₆N₂)] (5) and [Fe₃(CO)₈(μ₃-S)₂(η¹-C₄H₈N₂)] (6). The former also results from the direct reaction of thpymSH with Fe₃(CO)₁₂ and reacts with H₂S to afford 6. The molecular structures of all these new complexes have been determined by X-ray diffraction studies.     

Reactions of Cu3(dppm)3(μ3-OH)(ClO4)2 (dppm = bis-(diphenylphosphino) methane) with Soft Heterocumulenes

The reaction of [Cu₃(dppm)₃(μ₃-OH)](ClO₄)₂ (1) with heterocumulenes (XCS; X = NPh, NMe and S) has been studied. The μ₃-OH ligand inserts into PhNCS and MeNCS only in the presence of methanol. Insertion products are formed in accord with earlier observations made with copper(I)-aryloxides. On heating, the insertion products convert to a S bridged cluster [Cu₄(dppm)₄(μ₄-S)](ClO₄)₂ (8), having a tetrameric core. However, in the reaction with CS₂, 1 is converted to 8 even at room temperature in the presence of methanol. On the other hand, the dimeric complex [Cu₂(dppm)₂(CH₃CN)₄](ClO₄)₂, reacts with CS₂ to give (diphenylphosphinomethyl)-diphenylphosphine sulfide, Ph₂P-CH₂-P(S)Ph₂ (dppmS), which forms the complex [Cu(dppmS)₂]ClO₄ (9). A single crystal X-ray crystallographic study of 9, the first copper(I) complex of dppmS has been taken up to confirm the mono-oxidation of the dppm ligand and the nuclearity of the complex. Reactions of complex 1 with heterocumulenes and with elemental sulfur, are compared.     

Insertion reaction of elemental sulfur into the Ln–C bond: Synthesis and characterization of [(C5H4SiMe2Bu)2Ln(μ-SR)]2 (R = Me,Ln = Yb,Er, Dy,Y; R = Bu,Ln = Yb,Dy)

Treatment of (C₅H₄SiMe₂^tBu)₂LnR with 1 equiv of elemental sulfur in toluene at ambient temperature gives dimeric complexes [(C₅H₄SiMe₂^tBu)₂Ln(μ-SR)]₂ [R = Me, Ln = Yb (1), Er (2), Dy (3), Y (4); R = ⁿBu, Ln = Yb (5), Dy (6)]. All these complexes have been characterized by elemental analysis, IR and mass spectroscopies. The structures of complexes 1, 3, 5 and 6 are also determined through X-ray single crystal diffraction analysis, indicating that only one sulfur atom from elemental sulfur inserts into Ln–C σ-bond.     

[M(dipicH2)(H2O)3], M = Ni,Cu, Zn (dipicH2 = dipicolinic acid) – A combined crystallographic,spectroscopic and computational study

Cationic metal complexes of dipicolinic acid (dipicH₂) are stabilized by [Ce(dipic)₃]²⁻ ions in the three isomorphous crystals [M(dipicH₂)(OH₂)₃][Ce(dipic)₃] · 3H₂O (M = Ni, 1; Cu, 2; Zn, 3). Magnetic dilution provided by the bulky anions leads to well-resolved EPR spectra in polycrystalline samples of 2. The cations have 4+2 coordination, the carbonyl atom of the carboxylic acid groups coordinating weakly from trans positions. In the case of 2 this steric distortion is augmented by Jahn–Teller distortion. All the three structures are satisfactorily modelled by calculations based on density functional theory (DFT). The switch of the Jahn–Teller axis upon deprotonation of the complex, leading to the neutral species Cu(dipic)(H₂O)₃, is also reproduced by DFT. Electronic transition energies as well as the g-tensor component of the d⁹ complex obtained are in good agreement with experiment. However, the calculated hyperfine coupling constants are in error. DFT also fails to satisfactorily account for the electronic transition in the d⁸ ion in 1.     

Trimetallic complexes containing 1,1′-Rc′(CC)2 units [Rc′ = ruthenocene-1,1′-diyl, Ru(η-C5H4-)2]

Reactions between 1,1′-(Me₃SiCC)₂Rc′ [Rc′ = ruthenocen-1,1′-diyl, Ru(η-C₅H₄-)₂] and RuCl(PP)Cp′ in the presence of KF gave 1,1′-{Cp(PP)RuCC}₂Rc′ [Cp′ = Cp, PP = PPh₃1, P(m-tol)₃2, dppe 3, dppf 4; Cp′ = Cp^∗, PP = dppe 5]. Compounds 1 and 2 react with tcne to give two diastereomers a/b of the allylic (vinylcarbene) complexes 6 and 7, while methylation of 5 gave the bis-vinylidene [1,1′-{Cp^∗(dppe)RuCCMe}₂Rc′](BPh₄)₂ (8). The X-ray structures of 4, 6b and 8 have been determined. Cyclic voltammograms indicate that there is some electronic communication between the ruthenium end-groups through the Rc′ centre.     

Syntheses and crystal structures of [Bu3SbCr(CO)5], [Bu3BiM(CO)5] (M = Cr, W), and [Bu3BiMnCp′(CO)2] (Cp′ = η-C5H4CH3)

Syntheses and crystal structures of [^tBu₃SbCr(CO)₅] (1), [^tBu₃BiM(CO)₅] [M = Cr (2), W (3)] and [^tBu₃BiMnCp′(CO)₂] (4) (Cp′ = η⁵-C₅H₄CH₃) are reported.     

Germylene and stannylene (Me2NCH2CH2O)2E as strong σ-donor ligands for transition metal complexes [ML(CO)n] (E = Ge, Sn; M = Cr, Mo, W, n = 4 or 5; M = Fe, n = 4). Synthesis, spectroscopic and theoretical study

A series of germylene and stannylene (Me₂NCH₂CH₂O)₂E (E = Ge, 1; E = Sn, 2) complexes of group 6 metals and iron carbonyls L·M(CO)_n (M = Cr, Mo, W, n = 5 (3-8), n = 4 (9, 10); M = Fe, n = 4 (11, 12)) were prepared. These complexes were characterized by ¹H, ¹³C NMR, FTIR and elemental analysis. Ligand properties of 1 and 2 were compared to PPh₃ and dmiy (N,N′-dimethylimidazolin-2-ylidene) using theoretical calculations (PBE/TZ2P) and FTIR. Ligand dissociation energies increase in the order Ph₃P < 2∼1 < dmiy, while donor strength rise in the order PPh₃ < dmiy < 2 < 1.     

Di- and tri-nuclear molybdenum-palladium complexes bearing strong π-acceptor “P-N-P” ligands, MeN{P(OR)2}2 (R = CH2CF3 or Ph)

The dipalladium complexes, [PdCl(μ-MeN{P(OR)₂}₂)]₂ (R = CH₂CF₃, 1a; Ph, 1b) react with [Mo₂(η⁵-C₅H₅)₂(CO)₆] in boiling benzene to afford the molybdenum-palladium heterometallic complexes, [(η⁵-C₅H₅)(CO)Mo(μ-MeN{P(OR)₂}₂)₂PdCl] (R = CH₂CF₃, 3a; Ph, 3b), [(η⁵-C₅H₅)Mo(μ₃-CO)₂(μ-MeN{P(OR)₂}₂)₂Pd₂Cl], (R = CH₂CF₃, 5a; Ph, 5b), [(η⁵-C₅H₅)(Cl)Mo(μ₂-CO)(μ₂-Cl)(μ-MeN{P(OR)₂}₂)PdCl], (R = CH₂CF₃, 6a; Ph, 6b) and also the mononuclear complex [Mo(CO)Cl(η⁵-C₅H₅)(κ²-MeN{P(OR)₂}₂)], (R = Ph, 4b). These complexes have been separated by column chromatography and are characterised by elemental analysis, IR, ¹H, ³¹P{¹H} NMR data. The structures of 1a, 3a, 4b, 5b and 6a have been confirmed by single crystal X-ray diffraction. The CO ligands in 5b and 6a adopt a semi-bridging mode of bonding; the Mo-CO distances (1.95-1.97 Å) are shorter than the Pd-CO distances (2.40-2.48 Å). The Pd-Mo distances fall in the range, 2.63-2.86 Å. The reaction of [Mo₂(η⁵-C₅H₅)₂(CO)₆] with MeN{P(OPh)₂}₂ in toluene gives [Mo₂(CO)₄(η⁵-C₅H₅)₂(κ¹-MeN{P(OPh)₂}₂)₂] (2) in which the diphosphazane acts as a monodentate ligand.     

Syntheses, structures, and dynamic properties of M(CO)2(η-C3H5)(en)(X) (M = Mo, W; X = Br, N3, CN) and [(en)(η-C3H5)(CO)2M(μ-CN)M(CO)2(η-C3H5)(en)]Br (M = Mo, W)

Mononuclear compounds M(CO)₂(η³-C₃H₅)(en)(X) (X = Br, M = Mo(1), W(2); X = N₃, M = Mo(3), W(4); X = CN, M = Mo(5), W(6)) and cyanide-bridged bimetallic compounds [(en)(η³-C₃H₅)(CO)₂M(μ-CN)M(CO)₂(η³-C₃H₅)(en)]Br (M = Mo (7), W(8)) were prepared and characterized. These compounds are fluxional and display broad unresolved proton NMR signals at room temperature. Compounds 1-6 were characterized by NMR spectroscopy at −60 °C, which revealed isomers in solution. The major isomers of 1-4 adopt an asymmetric endo-conformation, while those of 5 and 6 were both found to possess a symmetric endo-conformation. The single crystal X-ray structures of 1-6 are consistent with the structures of the major isomer in solution at low temperature. In contrast to mononuclear terminal cyanide compounds 5 and 6, cyanide-bridged compounds 7 and 8 were found to adopt the asymmetric endo-conformation in the solid state.     

Synthesis and molecular structure of new heterometal alkoxide clusters Ln2Na8(OCH2CF3)14(THF)6 (Ln = Sm, Y, Yb): Highly active catalysts for polymerization of ε-caprolactone and trimethylene carbonate

The new polynuclear heterometal alkoxide clusters Ln₂Na₈(OCH₂CF₃)₁₄(THF)₆ (Ln = Sm 1, Y 2, Yb 3) have been synthesized by the reaction of anhydrous LnCl₃ with 7 equiv. of NaOCH₂CF₃ in 68–75% yields. Crystal structural analysis revealed clusters 1–3 are isomorphous composed of two cubanes and a double open cubane, with one face of an Ln₁Na₂O₄ open cubane capped by an additional Ln₁O₂ layer. Clusters 1–3 show extremely high activity for the polymerization of ε-caprolactone (ε-CL) and trimethylene carbonate (TMC). The reactivity is much higher than those found for the monometallic alkoxides lanthanide complexes previously reported. The dependence of catalytic activity on lanthanide metals is observed: Yb ≈ Y < Sm for ε-CL and Yb < Y < Sm for TMC. The polymers obtained with these clusters all show a unimodal molecular weight distribution with moderate molecular weight distributions (M_w/M_n = 1.4–1.7), indicating that clusters 1–3 can really be used as single-component catalysts. The bimetallic cooperation and the coordination–insertion mechanism were proposed.     

Syntheses, structures, and dynamic properties of M(CO)2(η-C3H5)(L-L)(NCBH3) (M = Mo, W; L-L = dppe, bipy, en)

Compounds M(CO)₂(η³-C₃H₅)(L-L)(NCBH₃) (L-L = dppe, M = Mo(1), W(2); L-L = bipy, M = Mo(3), W(4); L-L = en, M = Mo(5), W(6)) were prepared and characterized. The single crystal X-ray analyses of 2-6 revealed that the cyanotrihydroborate anion bonds to the metal through a nitrogen atom, the open face of the allyl group being pointed toward the two carbonyls (endo-isomer). In compounds 2, 5, and 6, the two donor atoms of the bidentate ligand occupy equatorial and axial positions, respectively. In the solid state structures of compounds 3 and 4 both nitrogen atoms of the bipy ligand occupy equatorial positions. The NMR spectroscopy reveals a fluxional behavior of compounds 1, 2, 5, and 6 in solution. Although the fluxional behavior of compounds 5 and 6 ceased at about −40 °C, that of compound 1 could not be stopped even at −90 °C. Their low temperature conformations are consistent with their solid state structures. Both the endo- and exo-isomers coexist in solution for compounds 3 and 4.     

Synthesis, X-ray crystal structure, and reactivity of Pd2(μ-dotpm)2 (dotpm = bis(di-ortho-tolylphosphino)methane)

Alkylation of PdCl₂(dotpm) (dotpm = bis(di-ortho-tolylphosphino)methane) with n-butyllithium produces the binuclear Pd(0) complex Pd₂(μ-dotpm)₂ and the elimination byproducts 1-butene, cis-2-butene, trans-2-butene, butane, and octane. The dibutyl complex, Pd(dotpm)(n-Bu)₂, is presumed to be the reaction intermediate. The crystal structure of Pd₂(μ-dotpm)₂ reveals that the methylene groups of the bridging dotpm ligands are located on opposite sides of the Pd₂P₄ unit, forming an 8-membered ring that is in an elongated chair conformation. The four phosphorus atoms are not coplanar, and the P1-P2-P3-P4 ring has a torsion angle of 13.8°, which minimizes the spatial interactions among the o-tolyl rings. The Pd-Pd bond distance is 2.8560(6) Å, which indicates that there is a weak “closed-shell” bonding interaction between the d¹⁰-d¹⁰ metal centers. Each palladium atom has a nearly linear geometry, and the eight methyl groups of the dotpm ligands shield the open coordination sites on the metal centers. Four methyl groups shield the metal atoms above and below the Pd₂P₄ ring cavity, and four methyl groups block the open metal sites outside of the Pd₂P₄ ring. The Pd₂(μ-dotpm)₂ complex readily undergoes oxidative addition of dichloromethane to form the rigid A-frame complex Pd₂Cl₂(μ-CH₂)(μ-dotpm)₂.     

Polymeric assembling through reciprocal metal-η-arene π-interactions: Synthesis and X-ray characterization of [Hg(RPhNNNPhR′)2Py]2 (R = NO2, R′ = F), an asymmetric bis diaryl-substituted triazenide-pyridinyl complex of Hg(II)

Hg(SCN)₂ reacts with 3-(2-fluorophenyl)-1-(4-nitrophenyl)triazene in tetrahydrofuran in the presence of triethylamine to give orange crystals of [Hg^II(RPhNNNPhR′)₂Py]₂ (R = NO₂, R′ = F), a new polymeric triazenide-pyridinyl complex of Hg(II) with reciprocal metal-η²-arene π-interactions. The crystal structure belongs to the triclinic space group , and the lattice of [Hg^II(RPhNNNPhR′)₂Py]₂ can be viewed as a supramolecular unidimensional assembling of tectonic [Hg^II(RPhNNNPhR′)₂Py] units linked through intermolecular metal-arene π interactions and non-classical C-H?O hydrogen bonding.     

Synthesis and characterization of mono and polymeric cyclopalladated compounds: Crystal and molecular structure of [{Pd(dmba)(ONO2)}2(μ-pz)] · H2O (pz = pyrazine)

In the treatment of cyclometallated dimer [Pd(dmba)(μ-Cl)]₂ (dmba = N,N-dimethylbenzylamine) with AgNO₃ and acetonitrile the result was the monomeric cationic precursor [Pd(dmba)(NCMe)₂](NO₃) (NCMe = acetonitrile) (1). Compound 1 reacted with m-nitroaniline (m-NAN) and pirazine (pz), originating [Pd(dmba)(ONO₂)(m-NAN)] (2) and [{Pd(dmba)(ONO₂)}₂(μ-pz)] · H₂O (3), respectively. These compounds were characterized by elemental analysis, IR and NMR spectroscopy. The IR spectra of (2–3) display typical bands of monodentade O-bonded nitrate groups, whereas the NMR data of 3 are consistent with the presence of bridging pyrazine ligands. The structure of compound 3 was determined by X-ray diffraction analysis. This packing consists of a supramolecular chain formed by hydrogen bonding between the water molecule and nitrato ligands of two consecutive [Pd₂(dmba)₂(ONO₂)₂(μ-pz)] units.     

Soluble {[Rh2(μ-OOCCH3)2(dbbpy)2][BF4]}n molecular wire and [Rh2(μ-OOCCH3)2(dbbpy)2L2] complexes; dbbpy = 4,4′-di-tert-butyl-2,2′-bipyridine: Synthesis and physicochemical characterization

Binuclear Rh(II) compounds [Rh₂(μ-OOCCH₃)₂(dbbpy)₂(H₂O)₂](CH₃COO)₂ (1) (dbbpy = 4,4′-di-tert-butyl-2,2′-bipyridine), [Rh₂(μ-OOCCH₃)₂(dbbpy)₂(H₂O)₂](BF₄)₂·H₂O·CH₃CN (2), [Rh₂(CH₃COO)₂(C₁₈H₂₄N₂)₂(CH₃CN)₂](BF₄)₂·4CH₃CN (3) and {[Rh₂(μ-OOCCH₃)₂(dbbpy)₂][BF₄]}_n (4) have been synthesized and characterized with spectroscopic methods. Structure of complex 3 has been determined using X-ray crystallography. Rhodium atoms in compound 3 have distorted octahedral coordination with O and N atoms in equatorial positions and Rh atom and CH₃CN molecule in axial coordination sites. Reduction of rhodium(II) compounds with aqueous 2-propanol leads to the formation of polymetallic compound {[Rh₂(μ-OOCCH₃)₂(dbbpy)₂][BF₄]}_n (4) containing [Rh₂]³⁺ core. Compound 4 shows strong antiferromagnetic properties, μ = 0.18–1.73 M.B. in the range 1.8–300 K, J = −597 cm⁻¹. Electrochemistry of compounds 3 and 4 in CH₃CN has been investigated. Compound 4 exhibits a poorly reversible oxidation system at E_1/2 = −0.92 V (ΔE_p = 0.19 V) and in solution in DMF is slowly oxidized to 3 even in total absence of oxygen. Complex 3 is irreversibly oxidized to Rh(III) compound at E_pa = 1.48 V and irreversibly reduced at E_pc = −1.02 V to lead to the unstable polynuclear complex 4 in CH₃CN.     

Theoretical insight into stereodynamics of the O(D) + H2 (v = 0–3, j = 0) → OH + H reaction: A quasiclassical trajectory (QCT) study

In this work, the reaction O(¹D) + H₂ → OH + H has been theoretically studied using the quasiclassical trajectory (QCT) method developed by Han and co-workers. All the quasiclassical trajectory calculations are performed on the DK (Dobbyn and Knowles) potential energy surface (PES). The vector correlation information on the reaction O(¹D) + H₂ → OH + H has been obtained. It has been demonstrated that the product alignment is sensitive to the reactant vibrational quantum number (v) at collision energy of 19 kcal/mol. Moreover, with increasing the value of v, backward scattering becomes weaker and forward scattering becomes stronger.     

A series of multinuclear homo- and heterometallic complexes with bridging tellurolato ligands derived from [CpIr(CO)(TeTol)2] (Cp = η-C5Me5, Tol = p-tolyl)

Reactions of [Cp^∗Ir(CO)(TeTol)₂] (1; Tol = p-tolyl) with certain organometallic Pd(II), Pt(II), Ir(III), Rh(III), and Ru(II) species afforded IrPd, IrPt, IrPt₂, Ir₂, IrRh, IrRu₃, and IrRu complexes having tellurolato-bridged dinuclear or trinuclear cores. This finding demonstrates that 1 is a versatile precursor to synthesize a variety of multinuclear homo- and heterometallic μ-tellurolato complexes, whose chemistry is still less advanced as compared with that of μ-thiolato complexes.