Reactivity of intramolecularly coordinated aluminum compounds to R3EOH (E = Sn,Si). Remarkable migration of N,C,N and O,C,O pincer ligands

The reaction of organoaluminum compounds containing O,C,O or N,C,N chelating (so called pincer) ligands [2,6-(YCH₂)₂C₆H₃]AlⁱBu₂ (Y = MeO 1, ^tBuO 2, Me₂N 3) with R₃SnOH (R = Ph or Me) gives tetraorganotin complexes [2,6-(YCH₂)₂C₆H₃]SnR₃ (Y = MeO, R = Ph 4, Y = MeO, R = Me 5; Y = ^tBuO, R = Ph 6, Y = ^tBuO, R = Me 7; Y = Me₂N, R = Ph 8, Y = Me₂N, R = Me 9) as the result of migration of O,C,O or N,C,N pincer ligands from aluminum to tin atom. Reaction of 1 and 2 with (ⁿBu₃Sn)₂O proceeded in similar fashion resulting in 10 and 11 ([2,6-(YCH₂)₂C₆H₃]SnⁿBu₃, Y = MeO 10; Y = ^tBuO 11) in mixture with ⁿBu₃SnⁱBu. The reaction 1 and 3 with 2 equiv. of Ph₃SiOH followed another reaction path and ([2,6-(YCH₂)₂C₆H₃]Al(OSiPh₃)₂, Y = MeO 12, Me₂N 13) were observed as the products of alkane elimination. The organotin derivatives 4–11 were characterized by the help of elemental analysis, ESI-MS technique, ¹H, ¹³C, ¹¹⁹Sn NMR spectroscopy and in the case 6 and 8 by single crystal X-ray diffraction (XRD). Compounds 12 and 13 were identified using elemental analysis,¹H, ¹³C, ²⁹Si NMR and IR spectroscopy.     

Diorganotin(IV) compounds containing 2-(Et2NCH2)C6H4 moieties: Configurational stability in solution and solid state structures

Hypercoordinated diorganotin(IV) dichloride, [2-(Et₂NCH₂)C₆H₄]₂SnCl₂ (1), was prepared by reacting [2-(Et₂NCH₂)C₆H₄]Li with SnCl₄. Halide-exchange reactions between 1 and the appropriate potassium halides gave [2-(Et₂NCH₂)C₆H₄]₂SnX₂ [X = F (2), Br (3), I (4)]. Reaction of 1 with excess of Na₂S gave the cyclo-[{2-(Et₂NCH₂)C₆H₄}₂SnS]₂ (5). The solution behavior of the title compounds in solution was investigated by multinuclear (¹H, ¹³C, ¹⁹F and ¹¹⁹Sn) NMR spectroscopy, including variable temperature studies. Single-crystal X-ray diffraction analysis revealed for all compounds intramolecular N → Sn coordination thus resulting in distorted octahedral (C,N)₂SnX₂ configurations. Planar chirality is observed as result of the non-planarity of the SnC₃N rings; all compounds, however, crystallizing as racemates. The isomers are linked by extensive hydrogen bonds to give different supramolecular architectures in the crystals of compounds 1, 3 and 4.     

Two novel Keggin tungstocobaltates grafted by cobaltII complex group(s): K[Co(phen)2(H2O)]2[HCoW12O40]·2H2O and [Co(2,2′-bipy)3]1.5{[Co(2,2′-bipy)2(H2O)][HCoW12O40]}·0.5H2O

Two novel inorganic–organic hybrid compounds composed of Keggin tungstocobaltate framework and cobalt(II)–N coordination complexes, K[Co(phen)₂(H₂O)]₂[HCoW₁₂O₄₀]·2H₂O (1) (phen = 1,10-phenanthroline) and [Co(2,2′-bipy)₃]_1.5{[Co(2,2′-bipy)₂(H₂O)][HCoW₁₂O₄₀]·0.5H₂O (2) (bipy = bipyridine), have been synthesized under hydrothermal conditions by directly using Keggin POMs as starting materials, which were characterized by elemental analyses, IR, TG analyses and X-ray single crystal diffraction. Crystal data for compound 1: C₄₈H₄₁Co₃KN₈O₄₄W_12, triclinic, space group P-1, a = 10.918(5) Å, b = 13.401(5) Å, c = 13.693(5) Å, α = 69.291(5)°, β = 71.568(5)°, γ = 78.421(5)°, V = 1768.9(12) Å³, Z = 1; for compound 2: C₁₃₀H₁₀₄Co₇N₂₆O₈₃W_24, orthorhombic, space group, C2/c, a = 46.839(9) Å, b = 14.347(3) Å, c = 26.147(5) Å, α = β = γ = 90°, V = 17,570(6) Å³, Z = 4. Compound 1 exhibits a pseudo-1D chainlike structure, in which potassium ions act as linkages of Keggin unit doubly grafted by [Co(phen)₂(H₂O)] complex. Compound 2 represents a [Co(2,2′-bipy)₂(H₂O)]²⁺ mono-grafted Keggin tungstocobaltate derivative with 1.5[Co(2,2′-bipy)₃]²⁺ countercations. The cyclic voltammetric behavior of 1-CPE is similar to the parent 3-CPE, but the cyclic voltammetric behavior of Co^II shows a little difference. Variable-temperature magnetic susceptibility measurement of compound 1 demonstrates the presence of antiferromagnetic interactions.     

Structure and magnetic properties of 3-oxyl-4,4,5,5-tetramethyl-2-oxoimidazolidin-1-olates

The paramagnetic salts (NH₃Bu^t)1 and [K(NH₂Bu^t)₂]1, where 1 is the 3-oxyl-4,4,5,5-tetramethyl-2-oxoimidazolidin-1-olate anion, were isolated for the first time in the individual state. The crystal structure of [K(NH₂Bu^t)₂]1 involves polymer chains formed by hydrogen bonding between anions 1 and [K₂(NH₂Bu^t)₄]²⁺ cation dimer fragments. The magnetic properties of [K(NH₂Bu^t)₂]1 are well described by the quasi-isolated dimer model with spins S = 1/2 coupled by weak exchange interactions via [K₂(NH₂Bu^t)₄]² fragments in polymer chains.     

Solvothermal synthesis and crystal structure of the Mo(VI)-bridged helical chain containing Mo2(V) dimers: (C4H12N2)2[(MoV2O4)(MoVIO4)(C2O4)2]·2H2O

A new molybdenum complex (C₄H₁₂N₂)₂[(Mo^V₂O₄)(Mo^VIO₄)(C₂O₄)₂]·2H₂O, was solvothermally synthesized and characterized by single-crystal X-ray diffraction. The structure of the compound consists of oxalate acid-coordinated mixed-valent [Mo^V₂O₄][Mo^VIO₄] helical chains and protonated piperazine cations. The helical chains are built up from the [Mo^V₂O₄] units and [Mo^VIO₄] tetrahedral. The central axis about helical chain is a 2-fold screw axis. The compound crystallizes in the space group P2₁/n of monoclinic system with a = 11.396(2) Å, b = 14.107(3) Å, c = 15.805(3) Å, β = 102.09(3)°, V = 2484.6(9) Å³, Z = 4. Other characterizations by elemental analysis, IR, and thermal analysis for this compound are also given.     

A unique 2-D hollow sheet structure and magnetic behavior of a cyanide- and triamine-bridged MnIICrIII ferrimagnet

A 2-D cyanide- and triamine-bridged Mn^IICr^III ferrimagnet, [Mn₃(dien)₂(H₂O)₂][Cr(CN)₆]₂ · 4H₂O (1), has been prepared by the combination of Mn²⁺, diethylenetriamine (dien) co-ligand and [Cr(CN)₆]³⁻. This compound forms a unique 2-D hollow sheet structure constructed by 1-D ribbon networks on the basis of triamine (dien)-bridged trinuclear Mn^II units. Compound 1 readily looses all lattice water molecules and irreversibly changes to a dehydrated form, [Mn₃(dien)₂(H₂O)₂][Cr(CN)₆]₂ (1a), in the air. Cryomagnetic studies of 1 and 1a reveal an antiferromagnetic interaction between Cr^III and Mn^II ions, and an unusual long-range ferrimagnetic ordering below 30 K (1) and 40 K (1a) with multiple magnetic phase changes below T_C. MCD spectra of 1a show a strong Faraday ellipticity associated with the LMCT band of the Cr–CN below 300 nm. Faraday ellipticity is remarkably enhanced below T_C in line with the characteristics long-range ferrimagnetic ordering.     

Dimeric and monomeric palladium(II) parent-amido (NH2) complexes: Synthesis,characterization, and reactivity

The treatment of [PdL₃(NH₃)]OTf (L₃ = (PEt₃)₂(Ph) (1), (2,6-(Cy₂PCH₂)₂C₆H₃) (3)) with NaNH₂ in THF afforded dimeric and monomeric parent-amido palladium(II) complexes with bridging and terminal NH₂, respectively, anti-[Pd(PEt₃)(Ph)(μ-NH₂)]₂ (2) and Pd(2,6-(Cy₂PCH₂)₂C₆H₃)(NH₂) (4). The dimeric complex 2 crystallizes in the space group P2₁/n with a = 13.228(2) Å, b = 18.132(2) Å, c = 24.745(2) Å, β = 101.41(1)°, and Z = 4. It has been found that there are two crystallographically independent molecules with Pd(1)–Pd(2) and Pd(3)–Pd(4) distances of 2.9594 (10) and 2.9401(9) Å, respectively. The monomeric amido complex 4 protonates from trace amounts of water to give the cationic ammine species [Pd(2,6-(Cy₂PCH₂)₂C₆H₃)(NH₃)]⁺. Complex 4 reacts with diphenyliodonium triflate ([Ph₂I]OTf) to give aniline complex [Pd(2,6-(Cy₂PCH₂)₂C₆H₃)(NH₂Ph)]OTf (5). Reaction of 4 with dialkyl acetylenedicarboxylate (DMAD, DEAD) yields diastereospecific palladium(II) vinyl derivative (Z)–(Pd(Cy₂PCH₂)₂C₆H₃)(CR = CR(NH₂)) (R = CO₂Me (6a), CO₂Et (6b)). Reacting complexes 6a and 6b with p-nitrophenol produces (Pd(Cy₂PCH₂)₂C₆H₃)(OC₆H₄–p-NO₂) (8) and cis-CHR = CR(NH₂), exclusively.     

New α,ω-dicarboxylate coordination polymers with 4,4′-bipyridine: Cu(bpy)(C5H6O4), Zn(bpy)(C5H6O4), Zn(bpy)(C6H8O4) and Mn(bpy)(C8H12O4) · H2O

Four 4,4′-bipyridine α,ω-dicarboxylate coordination polymers Cu(bpy)(C₅H₆O₄) (1), Zn(bpy)(C₅H₆O₄) (2), Zn(bpy)(C₆H₈O₄) (3) and Mn(bpy)(C₈H₁₂O₄) · H₂O (4) have been synthesized and structurally characterized by single crystal X-ray diffraction methods (bpy = 4,4-bipyridine, (C₅H₆O₄)²⁻ = glutarate anion, (C₆H₈O₄)²⁻ = adipate anion, (C₈H₁₂O₄)²⁻ = suberate anion). Their crystal structures are featured by dimeric metal units, which are co-bridged by 4,4′-bipyridine ligands and dicarboxylate anions such as glutarate, adipate and suberate anions to generate 2D layers with a (4,4) topology in 1, 2 and 4 as well as to form 3D frameworks in 3. Two 3D frameworks in 3 interpenetrate with each other to form a topology identical to the well-known Nb₆F₁₅ cluster compound. Over 5–300 K, the paramagnetic behavior of 4 follows the Curie–Weiss law χ_m(T − Θ) = 4.265(5) cm³ mol⁻¹ with the Weiss constant Θ = −6.3(2) K. Furthermore, the thermal behavior of 3 and 4 is also discussed.     

Structure and magnetic properties of a novel copper diphosphonate with pillared layered structure:: Cu2(H2O)2{O3PCH2N(C2H4)2NCH2PO3}

Compound Cu₂(H₂O)₂{O₃PCH₂N(C₂H₄)₂NCH₂PO₃} (1) has a pillared layered structure in which the organic groups of N,N′-piperazinebis(methylenephosphonate) are sandwiched between the inorganic layers. Compared with other copper phosphonates with layered or pillared layered structures, the inorganic layer in 1 is unique in that each {CPO₃} tetrahedron is corner-shared with three {CuO₄N} square pyramids through three oxygen donors. Ferromagnetic interactions are mediated between the metal centers. Crystal data: Pbca, a=10.0830(16) Å, b=9.4517(15) Å, c=13.218(2) Å, V=1259.7(3) Å³, Z=4.     

Synthesis of heteronuclear (MoRu2) clusters from 16-electron half-sandwich complexes (p-Cymene)Ru[E2C2(B10H10)] (E = S,Se)

The heterometallic cluster complexes {(p-Cymene)Ru[S₂C₂(B₁₀H₁₀)]}Mo(CO)₂{(CO)₃Ru[S₂C₂(B₁₀H₁₀)]} (2) and {(p-Cymene)Ru[Se₂C₂(B₁₀H₁₀)]}₂Mo(CO)₂ (3) (p-Cymene = η⁶-4-isopropyl-toluene) have been synthesized from the reactions of 16-electron half-sandwich ruthenium 1,2-dichalcogenolate carborane complexes (p-Cymene)Ru[E₂C₂(B₁₀H₁₀)] (E = S(1a), Se(1b)) with Mo(CO)₃(Py)₃ in the presence of BF₃ · Et₂O. The complexes of 2 and 3 were characterized by elemental analysis and IR, NMR spectra. The molecular structure of 2 has been characterized by single-crystal X-ray diffraction analysis. Complex 2 is unsymmetrical and the two Ru–Mo single bonds (2.7893(14), 2.8189(13) Å) are each supported by a symmetrically bridging o-carborane-1,2-dithiolato ligand.     

Synthesis,structure and magnetic properties of 2-D and 3-D [cation]{M[Au(CN)2]3} (M = Ni, Co) coordination polymers

In order to study the templating effect of the cation and the resulting impact on the magnetic properties, reactions of M(II) salts with [cation][Au(CN)₂] were conducted, yielding a series of coordination polymers of the form [cation]{M[Au(CN)₂]₃} (cation = ⁿBu₄N⁺, PPN⁺ (bis(triphenylphosphoranylidene)ammonium); M = Ni(II) and Co(II)). The structures of ⁿBu₄N{M[Au(CN)₂]₃} and PPN{M[Au(CN)₂]₃} (M = Ni and Co) contain two distinct 3-D anionic frameworks of {M[Au(CN)₂]₃}⁻, hence the framework was sensitive to the cation, but not to the identity of the metal center. In ⁿBu₄N{M[Au(CN)₂]₃}, the metal centers are connected by [Au(CN)₂] units to form six 2-D (4, 4) rectangular grids that are fused through the M centers to yield a complex three-dimensional framework which accommodates the ⁿBu₄N⁺ cations. In PPN{M[Au(CN)₂]₃}, the framework adopts a simpler non-interpenetrated Prussian-blue-type pseudo-cubic array, with the PPN⁺ cations occupying each cavity; no reduction in dimensionality occurs despite the large cation size. In the presence of water, {Co(H₂O)₂[Au(CN)₂]₂} · ⁿBu₄N[Au(CN)₂] was obtained, a 2-D layered polymer that contains neutral sheets of {Co(H₂O)₂[Au(CN)₂]₂} which are separated by ⁿBu₄N[Au(CN)₂] layers; aurophilic interactions of 3.4250(13) Å and hydrogen-bonding connect the layers. The magnetic properties of all compounds were investigated by SQUID magnetometry. The Ni(II) polymers have similar magnetic behaviour, which are dominated by zero-field splitting with very weak antiferromagnetic interactions at low temperature (D ∼ 2–3 cm⁻¹, zJ < 1 cm⁻¹). The magnetic behaviour of all of the Co(II) polymers were found to be very similar, and dominated by single-ion effects (i.e. a large first-order orbital contribution). No significant magnetic coupling is observed in any of these coordination polymers, suggesting that the [Au(CN)₂] bridging unit behaves as a poor mediator of magnetic exchange in these high-dimensionality systems.     

Heterofunctionalized phosphines derived from (2-formylphenyl)diphenylphosphine and their reactions with oxorhenium(V) complexes

Reactions of [ReOCl₃(PPh₃)₂] with a potentially tridentate Schiff base derived from (2-formylphenyl)diphenylphosphine and 2-aminophenol, HL¹P, (HL¹P = Ph₂PC₆H₄-2-HCN(C₆H₄-2-OH)) result in a rapid decomposition of the Schiff base and the formation of a large number of hitherto non-identified metal-containing species, while from similar reactions with the analogoue phosphine oxide HL¹PO, (HL¹PO = Ph₂P(O)C₆H₄-2-HCN(C₆H₄-2-OH)) products of the compositions [ReOCl₂(PPh₃)(L¹PO)] (1) and [Re(NC₆H₄-2-OH)Cl₃(PPh₃)₂] (2) could be isolated. The structure of 2 is an experimental proof of the preceding, metal-induced cleavage of the C–N double bond. A subsequent reaction of the released 2-aminophenol forms the final phenylimido ligand.Reduction of HL¹P with NaBH₄ gives the phosphine amine H₂L²P (H₂L² = Ph₂P(C₆H₄-2-CH₂NH(C₆H₄-2-OH))) in good yield. Reactions of H₂L²P with common oxorhenium(V) complexes result in the formation of the stable rhenium(V) complex [ReOCl₂(HL²P)] (3) with a facially coordinated HL²P^? ligand.     

Mono(amidinate) rare earth metal bis(alkyl) complexes: Synthesis,structure and their activity for l-lactide polymerization

Alkane elimination reaction between Ln(CH₂SiMe₃)₃(THF)₂ (Ln = Y, Lu) with one equivalent of the amidines with different steric demanding HL ([CyC(N-2,6-ⁱPr₂C₆H₃)₂]H (HL₁), [CyC(N-2,6-Me₂C₆H₃)₂]H (HL₂), [PhC(N-2,6-Me₂C₆H₃)₂]H (HL₃)) in THF afforded a series of mono(amidinate) rare earth metal bis(alkyl) complexes [CyC(N-2,6-ⁱPr₂C₆H₃)₂]Ln(CH₂SiMe₃)₂(THF) (Ln = Y (1), Lu (3)), [CyC(N-2,6-Me₂C₆H₃)₂]Ln(CH₂SiMe₃)₂(THF)₂ (Ln = Y (4), Lu (6)), and [PhC(N-2,6-Me₂C₆H₃)₂]Y(CH₂SiMe₃)₂(THF)₂ (7) in 75–89% isolated yields. For the early lanthanide metal Nd, THF slurry of NdCl₃ was stirred with three equiv of LiCH₂SiMe₃ in THF, followed by addition of one equiv of the amidines HL₁ or HL₂ gave an “ate” complex [CyC(N-2,6-ⁱPr₂C₆H₃)₂]Nd(CH₂SiMe₃)₂(μ-Cl)Li(THF)₃ (2) in 48% yield and a neutral [CyC(N-2,6-Me₂C₆H₃)₂]Nd(CH₂SiMe₃)₂(THF)₂ (5) in 52% yield, respectively. They were characterized by elemental analysis, FT-IR, NMR spectroscopy (except for 2 and 5 for their strong paramagnetic property). Complexes 2, 3, 4 and 5 were subjected to X-ray single crystal structure determination. These neutral mono(amidinate) rare earth metal bis(alkyl) complexes showed activity towards l-lactide polymerization to give high molecular weight and narrow molecular weight distribution polymers.     

Synthesis and characterization of thiosemicarbazone derivatives of 2-chloro-4-hydroxy-benzaldehyde and their rhenium(I) complexes

N-Thioamide thiosemicarbazone derived of 2-chloro-4-hydroxy-benzaldehyde (R = H, HL¹; R = Me, HL² and R = Ph, HL³) have been prepared and their reaction with fac-[ReX(CO)₃(CH₃CN)₂] (X = Br, Cl) in chloroform gave the adducts [ReX(CO)₃(HL)] (1a X = Cl, R = H; 1a′ X = Br, R = H; 1b X = Cl, R = CH₃; 1b′ X = Br, R = CH₃; 1c X = Cl, R = Ph; 1c′ X = Br, R = Ph) in good yield. Complexes 1a′ and 1b’ were also obtained by the reaction of HL¹ and HL³ with [ReBr(CO)₅] in toluene.All the compounds have been characterized by elemental analysis, mass spectrometry (FAB), IR and ¹H NMR spectroscopic methods. Moreover, the structures of HL², HL³ and 1a·H₂O were also established by X-ray diffraction. In 1a, the rhenium atom is coordinated by the sulphur and the azomethine nitrogen atoms, forming a five-membered chelate ring, as well as three carbonyl carbon and chloride atoms. The resulting coordination polyhedron can be described as a distorted octahedron.The study of the crystals obtained by slow evaporation of methanol and DMSO solutions of the adducts 1a′ and 1b, respectively, showed the formation of dimer structures based on rhenium(I) thiosemicarbazonates [Re₂(L¹)₂(CO)₆]·3H₂O (2a)·3H₂O and [Re₂(L²)₂(CO)₆]·(CH₃)₂SO (2b)·2(CH₃)₂SO. Amounts of these thiosemicarbazonate complexes [Re₂(L)₂(CO)₆] (2) were obtained by reaction of the corresponding free ligands with [ReCl(CO)₅] in dry toluene.In 2a·3H₂O and 2b·2(CH₃)₂SO the dimer structures are established by Re–S–Re bridges, where S is the thiolate sulphur from a N,S-bidentate thiosemicarbazonate ligand. In both structures the rhenium coordination sphere is similar; the dimers are in the same diamond Re₂S₂ face.     

Supramolecular chemistry and the control of the crystallization behavior by the choice of the counter-ion. Part 11. The stereochemistry and crystallization architecture of [(tren)Co(NO2)2]A (I), [(tren)Co(ox)]A (II), [(en)2Co(ox)]A (III) and [trans-(pn)2Co(NO2)2]A (IV), with A = [trans-(NH3)2Co(NO2)4]

In continuation of studies carried out previously [I. Bernal, Inorg. Chim. Acta 96 (1985) 99; I. Bernal, Inorg. Chim. Acta (1986) 121; I. Bernal, E.O. Schlemper, C.K. Fair, Inorg. Chim. Acta 115 (1986) 25; I. Bernal, Inorg. Chim. Acta 101 (1985) 175; I. Bernal, J. Cetrullo, J. Coord. Chem. 20 (1989) 237], we have now expanded the nature and number of cations associated with the [trans-(NH₃)₂Co(NO₂)₄] anion in order to better document when, and how, this helical propeller species crystallizes as a conglomerate.[(tren)Co(NO₂)₂][trans-(NH₃)₂Co(NO₂)₄] (I) crystallizes as a racemate in space group P2₁/n with cell constants of a = 15.8900(2), b = 19.7800(3), c = 26.6200(4) Å, β = 101.970(3)°, z = 15.[(tren)Co(ox)][trans-(NH₃)₂Co(NO₂)₄] (II) crystallizes as a racemate in space group I2/a with cell constants of a = 21.592(11), b = 7.050(4), c = 26.46(2) Å, β = 93.09(6)°, z = 8.[(en)₂Co(ox)][trans-(NH₃)₂Co(NO₂)₄] (III) crystallizes as a racemate in space group P2₁/n with cell constants of a = 6.4740(1), b = 22.8950(6), c = 13.1660(3) Å, β = 97.3310(10)°, z = 4.[trans-(pn)₂Co(NO₂)₂][trans-(NH₃)₂Co(NO₂)₄] (IV) also crystallizes as a racemate in space group P(¯1; no. 2) with cell constants of a = 6.508(2), b = 8.829(5), c = 9.851(5) Å, α = 72.84(2), β = 80.15(3), and γ = 81.45(6)°, z = 1.The most notable results are as follows: (1) all four compounds studied are racemates unlike the previously studied [cis-Co(en)₂(NO₂)₂][trans-(NH₃)₂Co(NO₂)₄] [I. Bernal, Inorg Chim Acta 101 (1985) 175] (V) and K[trans-(NH₃)₂Co(NO₂)₄] (VI) that crystallize as conglomerates. Nevertheless, they share certain crystalline features, which are readily observed in their packing diagrams.In all the four cases the new data were collected at 295 K and 120 K, using Mo Kα radiation; the former with a Nonius CAD-4 diffractometer and the latter with a Nonius CCD instrument. Of primary interest to us are the changes in packing caused by repeated changes in the charge compensating cations. Comparisons with the packing observed previously in [cis-Co(en)₂(NO₂)₂][trans-(NH₃)₂Co(NO₂)₄] (V) and K[trans-(NH₃)₂Co(NO₂)₄] (VI) are made since, at the time of publications of those early papers, no detailed study of the packing characteristics of these anions was published and the existing graphic software were primitive compared with the current packages. This oversight is remedied below.     

Dinuclear ruthenium(I) complexes of the type [Ru2(CO)4L2] with carboxylate or 2-pyridonate ligands: Evaluation as catalysts for olefin cyclopropanation with diazoacetates

Dinuclear ruthenium(I,I) carboxylate complexes [Ru₂(CO)₄(μ-OOCR)₂]_n (R = CH₃ (1a), C₃H₇ (1b), H (1c), CF₃ (1d)) and 2-pyridonate complex [Ru₂(CO)₄(μ-2-pyridonate)₂]_n (3) catalyze efficiently the cyclopropanation of alkenes with methyl diazoacetate. High yields are obtained with terminal nucleophilic alkenes (styrene, ethyl vinyl ether, α-methylstyrene), medium yields with 1-hexene, cyclohexene, 4,5-dihydrofuran and 2-methyl-2-butene. The E-selectivity of the cyclopropanes obtained from the monosubstituted alkenes and the cycloalkenes decreases in the order 1b > 1a > 1d > 1c. The cyclopropanation of 2-methyl-2-butene is highly syn-selective. Several complexes of the type [Ru₂(CO)₄(μ-L¹)₂]₂ (4) and (5), [Ru₂(CO)₄(μ-L¹)₂L²] (L² = CH₃OH, PPh₃) (6)–(9) and [Ru₂(CO)₄(CH₃CN)₂(μ-L¹)₂] (10) and (11), where L¹ is a 6-chloro- or 6-bromo-2-pyridonate ligand, are also efficient catalysts. Compared with catalyst 3, a halogen substituent at the pyridonate ligand affects the diastereoselectivity of cyclopropanation only slightly.     

Complexes derived from the copper(II) perchlorate/maleamic acid/2,2′-bipyridine and copper(II) perchlorate/maleic acid/2,2′-bipyridine reaction systems: Synthetic,reactivity, structural and spectroscopic studies

A systematic investigation of the reactions of Cu(ClO₄)₂ · 6H₂O with maleamic acid (H₂L) in the presence of 2,2′-bipyridine (bpy) has been carried out. The chemical and structural identity of the products depends on the solvent, the absence or presence of external hydroxides in the reaction mixture and the molar ratio of the reactants. Various reaction schemes have led to the isolation of the complexes [Cu₂(HL)₂(bpy)₂(H₂O)₂](ClO₄)₂ (1), [Cu₂(HL)₂(bpy)₂(H₂O)₂](ClO₄)₂ · 2H₂O (1 · 2H₂O), [Cu(L′′)(bpy)]_n · 2nH₂O (2 · 2nH₂O), [Cu₂(L′′)(bpy)₂(H₂O)₂]_n(ClO₄)_2n · 0.5nH₂O (3 · 0.5nH₂O), [Cu₂(L′′)₂(bpy)₂] · 2MeOH (5 · 2MeOH), [Cu₂(L′)₂(bpy)₂(ClO₄)₂] (6) and [Cu(ClO₄)₂(bpy)(MeCN)₂] (7b), where L′′^2? and L′^? are the maleate(?2) and monomethyl maleate(?1) ligands, respectively. The HL^? ion has been transformed to L′′^2? and L′^? in the known compounds 2 · 2nH₂O and 6, respectively, via metal ion-assisted processes involving hydrolysis (2 · 2nH₂O) and methanolysis (6) of the primary amide group. The reaction that leads to 6 takes place through the formation of the mononuclear complex [Cu(ClO₄)₂(bpy)(MeOH)₂] (7a), whose structure was assigned on the basis of its spectral similarity with the structurally characterized complex 7b. The structures of the cations in 1 and 1 · 2H₂O consists of two Cu^II atoms bridged by the carboxylate groups of the two HL^? ligands, each exhibiting the less common η² coordination mode; a chelating bpy molecule and a H₂O ligand complete square pyramidal coordination at each metal centre. The structure of the dinuclear repeating unit in the 1D coordination polymer 3 · 0.5nH₂O consists of two Cu^II atoms bridged by two syn,syn η¹:η¹:μ₂ carboxylate groups belonging to two L′′^2? ions; each ligand bridged two neighboring [Cu^II,II₂] units thus promoting the formation of a helical chain. The structure of the dinuclear molecule of complex 5 · 2MeOH consists of two Cu^II atoms bridged by two η² carboxylate groups from two L′′^2? ligands; the second carboxylate group of each maleate(?2) ligand is monodentately coordinated to Cu^II, creating a remarkable seven-membered chelating ring. The L′^? ion behaves as a carboxylate-type ligand in 6, with the carboxylate group being in the familiar syn,syn η¹:η¹:μ₂ coordination mode; a chelating bpy molecule and a coordinated ClO₄^? complete five-coordination at each Cu^II centre. The crystal structures of the complexes are stabilized by various H-bonding patterns. Characteristic IR bands of the complexes are discussed in terms of the known structures and the coordination modes of the ligands.     

Six-coordinate uranium complexes featuring a bidentate anilide ligand

The synthesis of a new bidentate anilide ligand and four uranium amide complexes utilizing the ligand are reported. The secondary aniline HN[R]Ar_MeL (R = C(CD₃)₂CH₃, Ar_MeL = 2-NMe₂-5-MeC₆H₃) is prepared by condensation of H₂NAr_MeL and acetone-d₆ followed by alkylation of the resulting imine with MeLi. The ligand precursors (Et₂O)Li(N[R]Ar_MeL) and K(N[R]Ar_MeL) are prepared through deprotonation of HN[R]Ar_MeL with n-BuLi and KH, respectively. Treatment of UI₃(THF)₄ with (Et₂O)Li(N[R]Ar_MeL) (2 equiv) provides the uranium(III) -ate complex Li[I₂U(N[R]Ar_MeL)₂] (Li[1]), while treatment of UI₃ with three equiv. of K(N[R]Ar_MeL) provides the neutral uranium(III) complex U(N[R]Ar_MeL)₃ (2). Both uranium(III) complexes are susceptible to 1e oxidation, as is demonstrated by the syntheses of the uranium(IV) derivatives I₂U(N[R]Ar_MeL)₂ (1) and [U(N[R]Ar_MeL)₃][OTf] ([2][OTf]; OTf = CF₃SO₃). The spectroscopic and X-ray structural characterization of all four uranium complexes is described. The structures of 2 and [2][OTf] exhibit a large degree of steric pressure about the uranium center, effectively preventing the [2]⁺ ion from achieving a seven-coordinate structure.     

An unprecedented two-dimensional polymeric [Zn(OOC–C6H4–COO)2]n2−[+H3N–(CH2)3–NH3+]n system bearing one-dimensional chain of zinc(II) bis(phthalate) dianions held by propane-1,3-diammonium cations: Crystal structure,thermal and fluorescent properties

A novel zinc(II) phthalate compound, [Zn{C₆H₄(COO)₂}₂]_n²⁻[NH₃–(CH₂)₃–NH₃]_n²⁺, 1 which contains four different phthalate moieties coordinated to the Zn(II) ion through one each of their carboxylate moieties in a η¹-form and each phthalate moiety acting as a bridging unit with an overall tetrahedral geometry around the metal ion has been prepared and structurally characterized. The structure is unique in the sense that the dianionic moieties [Zn{C₆H₄(COO)₂}₂]²⁻ form an infinite one-dimensional network composed of 14-membered cyclic units interconnected in a way that they are disposed alternatively in almost perpendicular planes. The dicationic [NH₃–(CH₂)₃–NH₃]²⁺ units are seen to hold these one-dimensional chains by strong coulombic and hydrogen bond interaction, resulting in an infinite two-dimensional layered structure of 1. The compound is thermally stable up to 250 °C. Above this temperature it loses one equivalent of phthalate moiety along with the diammonium unit to yield Zn(II) phthalate. The thermodynamic and kinetic parameters associated with this process could be evaluated using Coats–Redfern equation which shows the activation energy E_a for the process as 305.0 kJ mol⁻¹, the frequency factor A as 1.49 × 10¹¹ s⁻¹ and the entropy change ΔS as −35.90 JK⁻¹ mol⁻¹. Fluorescent emission properties of 1 was studied by exciting the compound at 380 nm and also at 322 nm which were found to be the two λ_max corresponding to absorptions of the molecule. Interestingly, the compound gave same type of emission spectra showing a maximum around 444 nm on exciting at these two different wavelengths, indicating that the molecule comes to the first excited state from the higher excited state by a fast non-radiative process before it exhibits singlet emission to come to the ground state.     

Synthesis of new substituted benzaldazine derivatives,hydrogen bonding-induced supramolecular structures and luminescent properties

Syntheses of three benzaldazine compounds 1–3 with the general formula Ar₁(CH = N–N = HC)Ar₂ (Ar₁ = Ar₂ = 2-OH-3,5-^tBu₂C₆H₂ (1), Ar₁ = Ar₂ = 2-BrC₆H₄ (2), Ar₁ = ortho-C₆H₄(NHC₆H₃-Me₂-2,6), Ar₂ = C₆H₄F-2 (3)) are described. All compounds were characterized by elemental analysis, ¹H NMR, ¹³C NMR, IR spectroscopy and single-crystal X-ray crystallography. The different supramolecular structures were obtained through different weak interactions (C ? H···O, O ? H···N and π···π interactions for 1; C ? H···Br and Br···Br interactions for 2; C ? H···F and C ? H···N interactions for 3). Compound 1 shows solvent-dependent fluorescent properties with blue to green emission on the increasing of the solvent polarity. Compounds 2, 3 show blue photoluminescence in different solvents.