[MoFe3S4]3+ and [MoFe3S4]2+ cubane clusters containing a pentamethylcyclopentadienyl molybdenum moiety

A series of organometallic molybdenum/iron/sulfur clusters of the general formula [Cp¹MoFe₃S₄L_n]^m (Cp¹ = η⁵-C₅Me₅; L = S^tBu, SPh, Cl, I, n = 3, m = 1−; L_n = I₂(P^tBu₃), m = 0; L = 2,6-diisopropylphenylisocyanide (ArNC), n = 7, m = 1+) have been synthesized. A cubane cluster (PPh₄)[Cp¹MoFe₃S₄(S^tBu)₃] (2) was isolated from a self-assembly reaction of Cp¹Mo(S^tBu)₃ (1), FeCl₃, LiS^tBu, and S₈ followed by cation exchange with PPh₄Br in CH₃CN, while an analogous cluster (PPh₄)[Cp¹MoFe₃S₄(SPh)₃] (3) was obtained from the Cp¹MoCl₄/FeCl₃/LiSPh/PPh₄Br reaction system or from a ligand substitution reaction of 2 with PhSH. Treatment of 2 with benzoyl chloride gave rise to (PPh₄)[Cp¹MoFe₃S₄Cl₃] (4), which was in turn converted to (PPh₄)[Cp¹MoFe₃S₄I₃] (5) by the reaction with NaI. A neutral cubane cluster Cp¹MoFe₃S₄I₂(P^tBu₃) (6) was generated upon treating 5 with P^tBu₃. Although reduction of 4 by cobaltocene under the presence of ArNC resulted in a disproportionation of the cubane core to give Fe₄S₄(ArNC)₉Cl (7), a similar reduction reaction of 5 produced [Cp¹MoFe₃S₄(ArNC)₇]I (8), where the MoFe₃S₄ core was retained. The crystal structures of 4–6, and 8 were determined by the X-ray analysis.     

Ruthenium-catalyzed intramolecular cyclization of hetero-functionalized allylbenzenes

Intramolecular addition of heterofunctionalities to CC double bonds without β-hydride elimination was investigated and catalyzed by ruthenium complexes. The combination of RuCl₃ · nH₂O (10 mol%) and 3 equiv. of AgOTf acted as a catalyst for cyclization of 2-allylphenol (1a) to 2,3-dihydro-2-methylbenzofuran (2a) in good yield in the presence of Cu(OTf)₂ as a co-catalyst and PPh₃ as a ligand. This catalyst system also catalyzed the cyclization of 2-allylbenzoic acid to lactone in 91% yield. Then, a new catalyst system (RuCp¹Cl₂)₂ (1.0 mol%)/4AgOTf/4PPh₃, was found to be more active even in the absence of Cu(OTf)₂. Furthermore, this catalysis was applied to asymmetric reaction of 2-allylphenol (1a). When using TolBINAP as a ligand, over 60% e.e. was achieved.     

Synthesis and characterization of organophosphine/phosphite stabilized N-silver(I) succinimide: crystal structure of [(Ph3P)3 · AgNC4H4O2]

Six organophosphine/phosphite stabilized N-silver(I) succinimide complexes of the type L_n · AgNC₄H₄O₂ (L = PPh₃; n = 1, 2a; n = 2, 2b; n = 3, 2c; L = P(OEt)₃; n = 1, 2d; n = 2, 2e; n = 3, 2f) have been prepared by reacting [AgNC₄H₄O₂], which can be synthesized from succinimide and excessive Ag₂O in boiling water, with triphenylphosphine or triethylphosphite in dichloromethane under a nitrogen atmosphere. These complexes were obtained in high yields and characterized by elemental analysis, ¹H, ¹³C{H} NMR, IR spectroscopy and thermal analysis (TG and DSC). The molecular structure of 2c has been determined by X-ray single crystal analysis, in which the silver atom is in a distorted tetrahedral geometry.     

Synthesis,X-ray structure and reactivity of μ-(CF3COO)2-[Mo(N-2,6-i-Pr2-C6H3)(CHCMe2Ph)(OOCCF3)(Et2O)]2, the first Bis(trifluoroacetate) derivative of a Schrock catalyst

Reaction of Mo(N-2,6-i-Pr₂-C₆H₃)(CHCMe₂C₆H₅)(OSO₂CF₃)(DME) (DME = 1,2-dimethoxyethane) with 2 equiv. of CF₃COOK yields μ-(CF₃COO)₂-[Mo(N-2,6-i-Pr₂-C₆H₃)(CHCMe₂Ph)(OOCCF₃)(Et₂O)]₂ (1). Compound 1 crystallizes in the orthorhombic space group Pna2₁ with a = 17.2485(3), b = 17.0336(3), c = 25.4031(5) Å, α = β = γ = 90°, V = 7463.5(2) Å³, Z = 4. In contrast to alkoxide based Schrock type initiators, 1 is virtually inactive in numerous metathesis reactions including ring-closing metathesis (RCM) and homo metathesis reactions, the cyclopolymerization of 1,6-heptadiynes, and even ring-opening metathesis polymerization (ROMP) of norborn-2-ene. However, addition of quinuclidine results in the in situ formation of 1a (Mo(N-2,6-i-Pr₂-C₆H₃)(CHCMe₂C₆H₅)(OOCCF₃)₂(quinuclidine) which displays moderate activity in ROMP, cyclopolymerization of 1,6-heptadiynes and RCM. Theoretical investigations carried out on the B3LYP/LACVP¹ level provide substantial explanation for these findings.     

A family of dodecanuclear Mn11Ln single-molecule magnets

A series of four isostructural dodecanuclear complexes [Mn^III₉Mn^II₂Ln^III(O)₈(OH)(piv)₁₆(NO₃)(CH₃CN)]·xCH₃CN·yC₇H₁₆ (piv = pivalate; x = ½, y = ¾, Ln = Tb (1); x = 2, y = ½, Ln = Dy (2), Ho (3), and Y (4)) has been prepared for which the structural motif described as ‘a lanthanide ion nested in a large manganese shell’ is observed. All compounds show out-of-phase signals in their ac susceptibilities, and their single-molecule magnet behaviour was confirmed by single-crystal micro-SQUID studies of 1-3 which show hysteresis loops of molecular origin at T < 1.0 K. The SMM behaviour observed in compounds 1-3 is more pronounced than that for 4, which contains the diamagnetic Y^III ion. This is principally the result of ferromagnetic coupling between the paramagnetic anisotropic Ln^III ions (Tb^III, Dy^III and Ho^III) and the manganese shell, which enhances the total spin ground state of the complexes.     

Diiron chelate complexes relevant to the active site of the iron-only hydrogenase

A novel unsymmetrically disubstituted propanedithiolate compound [Fe₂(CO)₄(κ²-dmpe)(μ-pdt)] (1) (pdt = SCH₂CH₂CH₂S, dmpe = Me₂PCH₂CH₂PMe₂) was synthesized by treatment of [Fe₂(CO)₆(μ-pdt)] with dmpe in refluxing THF. Compound 1 was characterized by single-crystal X-ray diffraction analysis. Protonation of 1 with HBF₄·Et₂O in CH₂Cl₂ gave at room temperature the μ-hydrido derivative [Fe₂(CO)₄(κ²-dmpe)(μ-pdt)(μ-H)](BF₄)] (2). At low temperature, ¹H and ³¹P–{¹H} NMR monitoring revealed the formation of a terminal hydride intermediate 3. Comparison of these results with those of a VT NMR study of the protonation of symmetrical compounds [Fe₂(CO)₄L₂(μ-pdt)] [L = PMe₃, P(OMe)₃] suggests that in disubstituted bimetallic complexes [Fe₂(CO)₄L₂(μ-pdt)], dissymmetry of the complex is required to observe terminal hydride species. Attempts to extend the series of chelate compounds [Fe₂(CO)₄(κ²-L₂)(μ-pdt)] by using arphos (arphos = Ph₂AsCH₂CH₂PPh₂) were unsuccessful. Only mono- and disubstituted derivatives [Fe₂(CO)_6−n(Ph₂AsCH₂CH₂PPh₂)_n(μ-pdt)] (n = 1, 4a; n = 2, 4b), featuring dangling arphos, were isolated under the same reaction conditions of formation of 1. Compound 4b was structurally characterized.     

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.     

Synthesis,spectroscopy and structures of halogen and sulfur-bridged dinuclear silver(I) complexes with N1-substituted thiophene-2-carbaldehyde thiosemicarbazone

The reactions of silver(I) halides (Cl or Br) with thiophene-2-carbaldehyde N¹-methyl thiosemicarbazone (HttscMe) in the presence of Ph₃P (1:1:1 molar ratio) yield halogen-bridged dimers, [Ag₂(μ-X)₂(η¹-S-HttsMe)₂(PPh₃)₂] (X = Cl, 1; Br, 2). The use of 2,2′-bipyridine in lieu of Ph₃P in the reaction of silver(I) chloride with HttscMe yields the sulfur-bridged dimer, [Ag₂(μ-S-HttscMe)₂(η¹-HttsMe)₂] · 2CHCl₃ 3. The substituents have altered the nature of bridge between the two silver atoms. The Ag···Ag separation (3.4867(5) Å) in complex 3 is less than that in the halogen-bridged dimers (3.734(4) Å 1; 3.746(5) Å 2). Unlike PPh₃ the co-ligand 2,2′-bipyridine did not coordinate to the silver center, but was necessary for crystallization in the reaction with the thio-ligand. NMR spectroscopy revealed that the complexes remained unchanged in the solution state (CDCl₃).     

Synthesis of ligands based on naphthalene peri-substituted by Group 15 and 16 elements and their coordination chemistry

The synthetic aspects of chemistry of ligands based on naphthalene peri-substituted by heavier Group 15 elements (P, As, Sb, Bi) or Group 16 elements (S, Se, Te) are discussed in this review. An overview of coordination chemistry of these ligands is also given. In general, the area is dominated by bis(phosphines) Nap(PR₂)₂ and dithiolates Nap(SR)₂ (Nap = naphthalene-1,8-diyl), and most of the ligands act with chelating rigid C₃-backbones. Whilst all known bis(phosphine) complexes with Ni, Pd and Pt contain unmodified Nap(PR₂)₂ moieties, the reactions with a variety of metal carbonyls sometimes result in P–C bond cleavage within the ligand. A range of gold complexes with Nap(PR₂)₂ ligands have been investigated for material applications. NapP₂ ligands other than phosphines are also described, these include 1,2-diphosphaacenaphthenes, bis(phosphonites) and bis(phosphine oxides). Group 16 peri-dichalcogenolates used as ligands include NapS₂, NapSe₂ and NapSSe systems, but no tellurium congeners. Heterodentate ligands discussed in this review include those with NapPN, NapPO, NapPS, NapPF, NapPC and NapSN motifs. Ligands with heavier Group 15 donor atoms (NapAs₂, NapSb₂) are also reported. All possible oxides of the dithioles (monooxide to tetraoxide) as ligands are also discussed. Areas of interest for further work are outlined.     

Preparation and reaction of phosphorus peri-bridged naphthalenes and their adducts with Lewis acids

The reaction of dilithionaphthalene with R₂NPCl₂ (R = ⁱPr and Et) gave diisopropylamino-naphtho[1,8-bc]phosphete 3a and its diethyl analog 3b (phosphorus versions of single-atom peri-bridged naphthalene). The nature of the strained four-membered ring thus formed was examined by treating 3a with four types of electrophiles, BH₃, elemental sulfur, methyltriflate, and a metal fragment W(CO)₅, all of which gave the corresponding electrophile adducts with the strained ring retained. X-ray analysis was performed for 3b and all of the above adducts, showing that the trigonal plane of the amino group was commonly oriented almost perpendicular to the naphthalene plane, which was rationally understood on the basis of the favorable overlap between the lone pair orbital of the sp² nitrogen center and the σ¹ orbital(s) of the two P–C bonds. In addition, when the W(CO)₅ adduct, W(3a)(CO)₅, was treated with Pt(PPh₃)₄ and then with a CO gas, its four-membered ring was expanded to give a tungsten–platinum heterodinuclear complex having a five-membered platina–phospha heterocycle.     

Long-distance electronic interaction in a molecular wire consisting of a ferrocenyl–ethynyl unit bridging two [(η5-C5H5)(dppe)M] metal centers

Several multinuclear ferrocenyl–ethynyl complexes of formula [(η⁵-C₅H₅)(dppe)M^II?CC–(fc)_n–CC–M^II(dppe)(η⁵-C₅H₅)] (fc = ferrocenyl; dppe = Ph₂PCH₂CH₂PPh₂; 1: M^II = Ru²⁺, n = 1; 2: M^II = Ru²⁺, n = 2; 3: M^II = Ru²⁺, n = 3; 4: M^II = Fe²⁺, n = 2; 5: M^II = Fe²⁺, n = 3) were studied. Structural determinations of 2 and 4 confirm the ferrocenyl group directly linked to the ethynyl linkage which is linked to the pseudo-octahedral [(η⁵-C₅H₅)(dppe)M] metal center. Complexes of 1–5 undergo sequential reversible oxidation events from 0.0 V to 1.0 V referred to the Ag/AgCl electrode in anhydrous CH₂Cl₂ solution and the low-potential waves have been assigned to the end-capped metallic centers. The solid-state and solution-state electronic configurations in the resulting oxidation products of [1]⁺ and [2]²⁺ were characterized by IR, X-band EPR spectroscopy, and UV–Vis at room temperature and 77 K. In [1]⁺ and [2]²⁺, broad intervalence transition band near 1600 nm is assigned to the intervalence transition involving photo-induced electron transfer between the Ru³⁺ and Fe²⁺ metal centers, indicating the existence of strong metal-to-metal interaction. Application of Hush’s theoretical analysis of intervalence transition band to determine the nature and magnitude of the electronic coupling between the metal sites in complexes [1]⁺ and [2]²⁺ is also reported. Computational calculations reveal that the ferrocenyl–ethynyl-based orbitals do mix significantly with the (η⁵-C₅H₅)(dppe)Ru metallic orbitals. It clearly appears from this work that the ferrocenyl–ethynyl spacers strongly contribute in propagating electron delocalization.     

Mono- and di-nuclear complexes of thiosemicarbazones with copper(I): Synthesis,spectroscopy and structures

Reactions of copper(I) halides with a series of thiosemicarbazones, namely, benzaldehyde thiosemicarbazone (R¹R²CN–NH–C(S)–NH₂, R¹ = Ph, R² = H; Hbtsc), 2-benzoylpyridine thiosemicarbazone (R¹ = Ph, R² = py; Hbpytsc), and acetone thiosemicarbazone (R¹ = R² = Me; Hactsc), in the presence of PPh₃ has formed dimeric complexes, viz. sulfur bridged [Cu₂(μ-S-Hbtsc)₂Br₂(PPh₃)₂]·2H₂O (1), iodo-bridged [Cu₂(μ-I)₂(η¹-S-Hbtsc)₂(PPh₃)₂] (2), and heterobridged [Cu₂(μ₃-S,N³-Hactsc)(η¹-Br)(μ-Br)(PPh₃)₂] (3), as well as mononuclear complexes [CuX(η¹-S-Hbpytsc)(PPh₃)₂]·CH₃CN (X = Br, 4; Cl, 5). Complexes 1, 2, 4 and 5 involve thiosemicarbazone ligands in η¹-S bonding mode while in compound 3, ligand acts in N³, S-chelation-cum-S-bridging mode (μ₃-S,N³ mode). The intermolecular interactions such as, N²H?X, HN¹H?X (X = S, Br, Cl), CH?π interactions lead to 2D networks. All the complexes have been characterized with the help of elemental analyses, IR, ¹H, and ³¹P NMR spectroscopy, and single crystal X-ray crystallography. The role of a solvent in alteration of nuclearity and bonding modes of complexes has been highlighted.     

Magnetic properties of hybrid organo-inorganic copper(II) oxovanadate(V) phosphate and phosphonate bridged systems

The hybrid organo-inorganic compounds [Cu₄(bipy)₄V₄O₁₁(PO₄)₂]nH₂O (n ∼ 5) (1), [Cu₂(phen)₂(PO₄)(H₂PO₄)₂(VO₂) · 2H₂O] (2) and [Cu₂(phen)₂(O₃PCH₂PO₃)(V₂O₅) (H₂O)]H₂O (3) which present different bridging forms of the phosphate/phosphonate group, show different bulk magnetic properties. We herein analyze the magnetic behaviour of these compounds in terms of their structural parameters. We also report a theoretical study for compound (1) assuming four different magnetic exchange pathways between the copper centres present in the tetranuclear unit. For compound (1) the following J values were obtained J₁ = +3.29; J₂ = −0.63; J₃ = −2.23; J₄ = −46.14 cm⁻¹. Compound (2) presents a Curie–Weiss behaviour in the whole range of temperature (3–300 K), and compound (3) shows a maximum for the magnetic susceptibility at 64 K, typical for antiferromagnetic interactions. These data where fitted using a model previously reported in the literature, assuming two different magnetic exchange pathways between the four copper(II) centres, with J₁ = −30.0 and J₂ = −8.5 cm⁻¹.     

Synthesis,characterization and catalytic behaviors of neutral nickel complexes: Arylnickel N-alkyl-6-(1-(arylimino)ethyl)picolinamide

A series of novel neutral nickel complexes, aryl (phenyl or naphthyl) nickel N-alkyl-6-(1-(arylimino)ethyl)picolinamides, were synthesized and characterized by NMR and IR spectroscopy and elemental analysis. Single-crystal X-ray diffraction analyses of the complexes C2, C3 and C7 reveal distorted square-planar geometry along with the molecular structure of one free ligand L1. On activation with diethylaluminum chloride (Et₂AlCl), the nickel complexes exhibited moderate catalytic activities for ethylene oligomerization, and the catalytic activity was up to 2.45 × 10⁵ g mol^?1(Ni) h^?1 in the presence of 1 equiv. PPh₃. Moreover, these complexes also exhibit moderate activities for Kumada–Corriu reaction and polymerization of methyl methacrylate.     

Organo-aluminum,zinc and magnesium derivatives of the imidotris(amido)phosphate Me3SiNP(NHtBu)3

Reactions of (^tBuHN)₃PNSiMe₃ (1) with the alkyl-metal reagents dimethylzinc, trimethylaluminum and di-n-butylmagnesium yield the monodeprotonated complexes [MeZn{(N^tBu)(NSiMe₃)P(NH^tBu)₂}] (2), [Me₂Al{(N^tBu)(NSiMe₃)P(NH^tBu)₂}] (3) and [Mg{(N^tBu)(NSiMe₃)P(NH^tBu)₂}₂] (4), respectively. Attempts to further deprotonate complex 2 with n-butyllithium or di-n-butylmagnesium result in nucleophilic displacement of the methylzinc fragment by lithium or magnesium. The two remaining amino protons of 3 are removed by reaction with di-n-butylmagnesium to give a heterobimetallic complex in which the coordination sphere of magnesium is completed by two molecules of THF (5 · 2THF) or one molecule of TMEDA (5 · TMEDA). Reaction of complex 3 with 1 equiv. of n-butyllithium followed by treatment of the product with di-n-butylmagnesium yields the complex {Me₂Al[(N^tBu)(NSiMe₃)P(N^tBu)₂]MgBu} Li · 4THF (6 · 4THF), the first example of a triply deprotonated complex of 1 containing three different metals. Reaction of complex 5 with iodine results in cleavage of an Al–Me group to give {MeIAl[(N^tBu)(NSiMe₃)P(N^tBu)₂Mg]} (7). Complexes 5 · 2THF, 5 · TMEDA, 6 · 4THF and 7 have been characterized in solution by multinuclear (¹H, ¹³C, ³¹P and ⁷Li) NMR spectroscopy, while the solid-state structures of 2, 4 and 5 · 2THF have been determined by X-ray crystallography.     

Pentamethylcyclopentadienyl ruthenium(II) complexes of para-substituted N-(pyrid-2-ylmethylene)-phenylamine ligands: syntheses,spectral and structural studies

The reaction of [(η⁵-C₅Me₅)Ru(PPh₃)₂Cl] (1) with acetonitrile in the presence of excess NH₄PF₆ leads to the formation of the cationic ruthenium(II) complex [(η⁵-C₅Me₅)Ru(PPh₃)₂(CH₃CN)]PF₆ (2). The complex (2) reacts with a series of N,N′ donor Schiff base ligands viz. para-substituted N-(pyrid-2-ylmethylene)-phenylamines (ppa) in methanol to yield pentamethylcylopentadienyl ruthenium(II) Schiff base complexes of the formulation [(η⁵-C₅Me₅)Ru(PPh₃)(C₅H₄N-2-CHN-C₆H₄-p-X)]PF₆ [3a]PF₆–[3f]PF₆, where C₅Me₅ = pentamethylcylopentadienyl, X = H, [3a]PF₆, Me, [3b]PF₆, OMe, [3c]PF₆, NO₂, [3d]PF₆, Cl, [3e]PF₆, COOH, [3f]PF₆. The complexes were isolated as their hexafluorophosphate salts. The complexes were fully characterized on the basis of elemental analyses and NMR spectroscopy. The molecular structure of a representative complex, [(η⁵-C₅Me₅)Ru(PPh₃)(C₅H₄N-2-CHN-C₆H₄-p-Cl)]PF₆ [3e]PF₆, has been established by X-ray crystallography.     

Synthesis,electrochemical behavior and X-ray crystal and molecular structures of [Fe(diene)(CO)2PPh3] (diene=chalcone,sorbic acid)

The compounds [Fe(ch)(CO)₂PPh₃] (1) (ch=chalcone) and [Fe(sba)(CO)₂PPh₃] (2) (sba=sorbic acid) were prepared by irradiating the tetracarbonyltriphenylphosphineiron(0) complex in benzene in the presence of ch or sba. The compounds were characterized by infrared and ³¹P NMR spectroscopies. Their electrochemical behavior was investigated by cyclic voltammetry and the results suggest that their oxidations occur by more than one electrochemical step, producing free ch and sba, free PPh₃ and solvated Fe(III). It was observed that sba ligand contributes more effectively to the stabilization of metal center in these complexes. The X-ray crystal and molecular structures of 1 and 2 were determined; it was shown that the Fe atom adopts a distorted octahedral coordinated geometry in which three of the sites are occupied by the ch or sba ligand. The [Fe(ch)(CO)₂PPh₃] complex is a monomer and the unit cell of complex 2 contains exist two identical and crystallographically independent molecules of [Fe(sba)(CO)₂PPh₃] which are linked by short hydrogen bonds OH· · ·O     

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.     

Two highly unsymmetrical tetradentate (N3O) Schiff base copper(II) complexes: Template synthesis,structural characterization,magnetic and computational studies

Two new copper(II) complexes, [Cu₂(L¹)₂](ClO₄)₂ (1) and [Cu(L²)(ClO₄)] (2), of the highly unsymmetrical tetradentate (N₃O) Schiff base ligands HL¹ and HL² (where HL¹ = N-(2-hydroxyacetophenone)-bis-3-aminopropylamine and HL² = N-(salicyldehydine)-bis-3-aminopropylamine) have been synthesised using a template method. Their single crystal X-ray structures show that in complex 1 two independent copper(II) centers are doubly bridged through phenoxo-O atoms (O1A and O1B) of the two ligands and each copper atom is five-coordinated with a distorted square pyramidal geometry. The asymmetric unit of complex 2 consists of two crystallographically independent N-(salicylidene)-bis(aminopropyl)amine-copper(II) molecules, A and B, with similar square pyramidal geometries. Cryomagnetic susceptibility measurements (5–300 K) on complex 1 reveal a distinct antiferromagnetic interaction with J = ?23.6 cm^?1, which is substantiated by a DFT calculation (J = ?27.6 cm^?1) using the B3LYP functional. Complex 1, immobilized over highly ordered hexagonal mesoporous silica, shows moderate catalytic activity for the epoxidation of cyclohexene and styrene in the presence of TBHP as an oxidant.     

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.