FAB Mass Spectrometry Research Articles

Interaction of Mn(acac)3 with Asymmetrical Schiff Base Ligands containing an Amido Group

AbstractInteraction of asymmetrical Schiff base ligands H3Ln [where H3Ln are substituted 3–aza–4–(2–hydroxyphenyl)–N– (2–hydroxyphenyl)but–3–enamide] with Mn(acac)3 (acac = acetylacetonate) has been investigated. Two different type of manganese(III) complexes have been obtained depending on the nature of the substituents on the ligand. We have found that ligands containing donor substituents drives to the formation of two different kinds of complexes from the same reaction: Mn(Ln)(H2O)x (1a–5a) and [Mn(HLn)(acac)](H2O)y (1b–5b) (where Ln and HLn signify the ligand in its trianionic and dianionic form, respectively). However, when the substituents are electron withdrawing or poor donor only compounds of the type [Mn(HLn)(acac)](H2O)y (6–10) are obtained. All these compounds have been characterized by elemental analyses, IR and 1H NMR spectroscopy, FAB mass spectrometry, magnetic measurements and molar conductivities. The electrochemical behaviour of these complexes has also been studied.

Estimation of Thermodynamic Parameters on Enantioselective Complexation Equilibria by Temperature-dependent FAB Mass Spectrometry

Abstract The relative thermodynamic parameters, ΔΔG°enan(R/S), ΔΔH°enan(R/S), and ΔΔS°enan(R/S), on the enantioselective host–guest complexation equilibria were estimated easily using the temperature-dependent FAB mass spectrometry coupled with the enantiomer labeled guest method.

Nitrile−Amidine Coupling at Pt(IV) and Pt(II) Centers. An Easy Entry to Imidoylamidine Complexes

Treatment of trans-[PtCl4(RCN)2] (R = Me, Et, Ph, NEt2) with 2 equiv of the amidine PhC(=NH)NHPh in a suspension of MeCN (R = Me), CHCl3 (R = Et, Ph), or in CHCl3 solution (R = NEt2) results in the formation of the imidoylamidine complexes trans-[PtCl4{NH=C(R)N=C(Ph)NHPh}2] (1-4) isolated in good yields (66-84%). The reaction of soluble complexes 3 and 4 with 2 equiv of Ph3P=CHCO2Me in CH2Cl2 (40 degrees C, 5 h) leads to dehydrochlorination resulting in a chelate ring closure to furnish the platinum(IV) chelates [PtCl2{NH=C(R)NC(Ph)=NPh}2] (R = Ph, 5; R = NEt2, 6), accordingly, and the phosphonium salt [Ph3PCH2CO2Me]Cl. Treatment of 5 with 3 equiv of Ph3P=CHCO2Me at 50 degrees C for 5 d resulted in only a 30% conversion to the corresponding Pt(II) complex [Pt{NH=C(NEt2)NC(Ph)=NPh}2] (15). The reduction can be achieved within several minutes, when Ph2PCH2CH2PPh2 in CDCl3 is used. When the platinum(II) complex trans-[PtCl2(RCN)2] is reacted with 2 equiv of the amidine, the imidoylamidinato complexes [PtCl(RCN){NH=C(R)NC(Ph)=NHPh}] (8-11) and [PhC(=NH)NHPh] x HCl (7) are formed. The reaction of trans-[PtCl2(RCN)2] with 4 equiv of the amidine under a prolonged reaction time or treatment of [PtCl(RCN){NH=C(R)NC(Ph)=NHPh}] (8-11) with 2 more equiv of the amidine yields the complex bearing two chelate rings [Pt{NH=C(R)NC(Ph)=NHPh}2] (12-15). The treatment of cis-[PtCl2(RCN)2] (R = Me, Et) with the amidine gives ca. 50-60% yield of [PtCl2{NH=C(R)NHC(Ph)=NHPh}] (16 and 17). All of the platinum compounds were characterized by elemental analyses; FAB mass spectrometry; IR spectroscopy; 1H, 13C{1H}, and 195Pt NMR spectroscopies, and four of them (4, 6, 8, and 15) were also characterized by X-ray crystallography. The coupling of the Pt-bound nitriles and the amidine is metal-mediated insofar as RCN and PhC(=NH)NHPh do not react in the absence of the metal centers in conditions more drastic than those of the observed reactions. The nitrile-amidine coupling reported in this work constitutes a route to the synthesis of imidoylamidine complexes, some of them exhibiting luminescent properties.

Synthesis and characterization of η3-allyl palladium(II) complexes, [(η3-allyl)Pd(S2X)] (X = CNMe2, CNEt2, COEt, PPh2)

The complexes [(η3-C6H9)Pd(η2-S2CNR2)] (R = Me, 1; Et, 2), [(η3-Me2CCMeCH2)Pd (η2-S2COEt)] 3 and [(η3-Me2CCMeCH2)Pd(η2-S2PPh2)] 4 have been synthesized by reaction of [(η3-allyl)Pd(μ-Cl)]2 with NaS2CNR2 (R = Me, Et), KS2COEt and NaS2PPh2. They have been characterized by elemental analysis, FTIR, 1H NMR and FAB mass spectrometry. Spectroscopic studies suggest that sulfur donor ligands are bidentate, forming Pd–S–C–S and Pd–S–P–S palladacycles, an η3-allyl group completing the coordination sphere.

Thermal decomposition of potassium hexanitronickelate(II) hydrate

The thermal decomposition of the complex K 4[Ni(NO 2) 6]·H 2O has been investigated over the temperature range 25–600 °C by a combination of infrared spectroscopy, powder X-ray diffraction, FAB-mass spectrometry and elemental analysis. The first stage of reaction is loss of water and isomerisation of one of the coordinated nitro groups to form the complex K 4[Ni(NO 2) 4(ONO)]·NO 2. At temperatures around 200 °C the remaining nitro groups within the complex isomerise to the chelating nitrite form and this process acts as a precursor to the loss of NO 2 gas at temperatures above 270 °C. The product, which is stable up to 600 °C, is the complex K 4[Ni(ONO) 4]·NO 2, where the nickel atom is formally in the +1 oxidation state.

Synthesis and characterization of η3-allyl palladium(II) complexes with Ph2P(S)CHP(S)Ph2 and OC(CF3)CHCO(C4H3S) co-ligands

The new complexes [(η3-Me2CCMeCH2)Pd{η2-Ph2P(S)CHP(S)Ph2] (1), [(η3-Me2CCMeCH2)Pd{η2-OC(CF3) CHCO(C4H3S)}] (2) and [(η3-CH2CMeCH2)Pd{η2-OC(CF3)CHCO(C4H3S)}] (3) have been synthesized by reacting [(η3-allyl)Pd(μ-Cl)]2 with Ph2P(S)CH2P(S)Ph2 and OC(CF3)CH2CO(C4H3S) in the presence of base. All have been characterized by elemental analysis, FT-IR, 1H-n.m.r and FAB-mass spectroscopy. Spectroscopic studies suggest that both ligands are bidentate, forming six-membered Pd-S-P-C-P-S and Pd-O-C-C-C-O palladacycles, the η3-allyl group completing the coordination sphere.

Synthesis of (1,2,4‐Oxadiazole)palladium(II) Complexes by [2 + 3] Cycloaddition of Nitrile Oxides to Organonitriles in the Presence of PdCl2

AbstractThe reaction between the nitrile oxides 2,4,6‐R3C6H2CNO (R = Me, OMe) andtrans‐[PdCl2(RCN)2], or RCN (R = Me, Et, CH2CN, NMe2, Ph) in the presence of PdCl2, proceeded smoothly under mild conditions and allowed the isolation of the 1,2,4‐oxadiazole complexestrans‐[PdCl2{Na=C(R)‐ON=Cb(C6H2R3)(Na–Cb)}2] (1–8) in 40–85 % yields. In CH2Cl2, the reaction between 2,4,6‐R3C6H2CNO and [PdCl2(MeCN)2] furnishes [PdCl2(ONCC6H2R3)2] (9and10), which are the first representatives of metal compounds where nitrile oxides act as ligands. The 1,2,4‐oxadiazole complexes1–8were characterized by elemental analysis, FAB mass spectrometry, and IR,1H and13C{1H} NMR spectroscopy, while2,3,7, and8were additionally characterized by X‐ray crystallography. The liberation of the heterocyclic species from1–8was successfully performed by substitution reaction either with 1,2‐bis(diphenylphosphanyl)ethane or with an excess amount of Na2S·7H2O in MeOH; the liberated 1,2,4‐oxadiazoles (11–18) were characterized by positive‐ion FAB mass spectrometry and1H and13C{1H} NMR spectroscopy. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

Phosphor-1,1-Diselenolato Metal Complexes of Group 11 and 12

Several copper and silver clusters containing diselenophosphate ligands such as tetranuclear [Cu{Se2P(OR)2}]4, hexanuclear [Ag{Se2P(OR)2}]6, octanuclear [Cu8(μ8-Se)}Se2P(OR)2}6], [Ag8(μ8-Se)}Se2P(OR)2}6], [Cu8(μ8-X)}Se2P(OR)2}6](PF6), [Ag8(μ8-X)}Se2P(OR)2}6](PF6), decanuclear [Ag10(μ10-Se)}Se2P(OR)2}8], undecanuclear [Cu11(μ9-Se)(μ3-X)3}Se2P(OR)2}6], [Ag11(μ9-Se)(μ3-X)3}Se2P(OR)2}6], and dodecanuclear [Cu12(P2Se6)}Se2P(OR)2}8] have been isolated. All these clusters were well characterized in the solid-state and solution phase by elemental analysis, positive FAB mass spectrometry, multinuclear NMR (1H, 31P, and 77Se), and single crystal X-ray diffraction. In addition, tetranuclear zinc clusters [Zn4(μ4-Se){Se2P(OPr)2}6], and [Zn4(μ4-O){Se2P(OR)2}6] (R = Et, iPr) also are synthesized and characterized. Solution studies of both [M{Se2P(OEt)2}2]∞ and [M2{Se2P(OiPr)2}4] (M = Zn, Cd) which display a monomer-dimer equilibrium in solution were performed by VT 31P NMR in CD2Cl2.

Synthesis, spectroscopic characterization and X-ray crystal structures of oxo-bridged oxo(haloaryl) imido hydrotris(3,5-dimethylpyrazolyl)borate molybdenum(V) complexes

Reaction of the oxomolybdenum(V) precursor [MoTp*(O)Cl2] (Tp* = hydrotris(3,5-dimethyl-1-pyrazolyl)borate) with m-fluoroaniline, H2NC6H4F, in toluene afforded the pair of geometric isomers of [MoTp*(O)Cl](µ-O)[MoTp*(Cl)(≡NC6H4F)] (1a, cis; 1b, trans). Similarly the reaction with m-iodoaniline yielded the compound [MoTp*(O)Cl](µ-O)[MoTp*(Cl)(≡NC6H4I)] (2). This is a new synthetic method for preparing Mo–O–Mo bridged oxo(imido) molybdenum(V) species by double deprotonation of the anilines. The complexes were characterized by IR and 1H-NMR. spectroscopy, FAB mass spectrometry, elemental analysis and X-ray crystallography which revealed that the two chloro ligands are trans to each other in 1b and 2, whereas they are cis to each other in 1a. All compounds have Mo–O–Mo linkages and near linear arylimido moieties.

Synthesis, characterization and complexation behavior investigations of novel starburst-like tris-crown ethers

The novel unique structures of starburst-like tris-crown ethers were successfully synthesized from 1,3,5-tri-acryloylhexahydro-1,3,5-triazine (TAHTA) with amino- and aza- crown ethers through Michael addition. The crown ethers contained primary and secondary amine groups such as 2-aminomethyl crown ethers, 4-aminobenzo crown ethers and 1-aza crown ethers. The newly synthesized starburst tris-crown ethers were characterized by elemental analysis, IR, 1H-NMR, 13C-NMR and FAB mass spectroscopy, respectively. The newly synthesized host compounds of tris-crown ethers showed complexation abilities with various sizes of alkali metal cations such as Na+, K+, Rb+ and Cs+. The complexation behavior was examined by 1H-NMR, FAB mass spectroscopy and UV spectroscopy.

New structural features in triphenylphosphinesilver(i) sulfanylcarboxylates

We investigated the reactions of 1.5 : 1 : 1 mole ratio mixtures of triphenylphosphine, silver nitrate and 3-(aryl)-2-sulfanylpropenoic acids H(2)xspa in chloroform/water, where in the acid nomenclature, spa = 2-sulfanylpropenoato and x = p, Clp, mp, diBr-o-hp or f with p = 3-phenyl-, Clp = 3-(2-chlorophenyl)-, mp = 3-methoxyphenyl-, diBr-o-hp = 3-(3,5-dibromo-2-hydroxyphenyl)- and f = 3-(2-furyl)-. The compounds [Ag(PPh(3))(Hpspa)](1), [(AgPPh3)2(xspa)][x = Clp (2), o-mp (3), p-mp (4), diBr-o-hp (5) and f (6)] and [Ag(PPh3)3(Hfspa)](7) were isolated and all except 7 were characterized by IR, Raman and FAB mass spectrometry and by 1H, 13C and 31P NMR spectroscopy. Compound 6 was also characterized by (13)C CP/MAS, and compounds 1 and 6 by (109)Ag NMR spectroscopy. The crystal structures of 1, 2, 3, 4.(CH3)2CO, 5, 6.(CH3)2CO and 7 were determined by X-ray diffraction. has a supramolecular structure based on hydrogen bonding between dinuclear units, and all the other complexes adopt discrete structures. 2, 3, 4.(CH3)2CO, 5, and 6.(CH3)2CO are tetranuclear, and 7 mononuclear. The tetranuclear complexes contain the eight-membered coordination ring Ag4S2O2 (2, 3, 4.(CH3)2CO, 6.(CH3)2CO) or the twelve-membered ring Ag4(CO2)2S2 (5).

Versatility of 2,6-diacetylpyridine (dap) hydrazones in stabilizing uncommon coordination geometries of Mn(ii): synthesis, spectroscopic, magnetic and structural characterization

Five seven- or eight-coordinate manganese complexes of hydrazone ligands have been prepared. Three seven-coordinate neutral Mn(II) complexes: [Mn(dapA2)]n (1), [Mn(dapB2)(H2O)2] (2), [Mn(dapS2)(H2O)2] (3) have been synthesized from the bis-Schiff bases of 2,6-diacetylpyridine: dap(AH)2, dap(BH)2 and dap(SH)2 (AH = anthraniloyl hydrazide, BH = benzoyl hydrazide, SH = salicyloyl hydrazide), respectively. Two eight-coordinate Mn(II) complexes: [Mn(dapS)2] (4) and [Mn(dapB)2].3H2O (5) have been synthesized from the mono-Schiff bases dapBH and dapSH, respectively. The complexes have been characterized by elemental analyses and by IR, UV-Vis., FAB mass, EI mass and EPR spectroscopy. The molecular structures of 1, 3.DMF and 4.DMF have been determined by single-crystal X-ray diffraction. The mono-Schiff bases are monoanionic and the bis-Schiff bases are dianionic. The octa-coordinated mono-Schiff base complex 4 adopts a dodecahedral geometry, while the hepta-coordinated bis-Schiff base complex 1 forms a one-dimensional linear polymeric chain. A weak antiferromagnetic exchange interaction (J=-0.15 cm(-1)) between the Mn(II) ions in is attributed to weak Mn...Mn interaction through the PhNH(2) moiety of the ligand, as indicated by extended-Hückel molecular orbital calculations. A good simulation of the EPR spectrum of a frozen solution (DMSO at 4 K) of compound 1 was obtained with g=2.0, D=0.1 cm(-1), E=0.01 cm(-1). The EPR spectrum of a powdered sample of compound 1 shows a large broadening of the signal, due in part, to the important zero-field splitting of the hepta-coordinated Mn(II) ion.

Synthesis, Solution Behavior, Thermal Stability, and Biological Activity of an Fe(III) Complex of an Artificial Siderophore with Intramolecular Hydrogen Bonding Networks

Previously, an artificial siderophore complex, the iron(III) complex with tris[2-[(N-acetyl-N-hydroxy)glycylamino]ethyl]amine (TAGE), was constructed in order to understand the effect of intramolecular hydrogen bonding interaction on the siderophore function, and its structural characterization in the solid state was reported (Inorg. Chem. 2001, 40, 190). In this paper, the solution behavior of the M(III)-TAGE (M = Fe, Ga) system has been investigated using (1)H NMR, UV-vis, and FAB mass spectroscopies in efforts to characterize the biological implication of hydrogen bonding networks between the amide hydrogens and coordinating aminohydroxy oxygens of the complex. The temperature dependence of (1)H NMR spectra for Ga(III) complex of TAGE indicates that hydrogen bonding networks are maintained in polar solvents such as DMSO-d(6) and D(2)O. The UV-vis spectra of the Fe(III)-TAGE system under various pH conditions have shown that TAGE forms a tris(hydroxamato)iron(III) complex in an aqueous solution in the pH range 4-8. By contrast, tris[2-[(N-acetyl-N-hydroxy)propylamido]ethyl]amine (TAPE; TAGE analogue that is difficult to form intramolecular hydrogen bonding networks), which has been synthesized as a comparison of TAGE, forms both of bis- and tris(hydroxamato)iron(III) complexes in the same pH range. Both the stability constants (log beta(FeTAGE) = 28.6; beta(FeTAGE) = [Fe(III)TAGE]/([Fe(3+)][TAGE(3)(-)])) and pM (-log[Fe(3+)]) value for Fe(III)TAGE (pM 25) are comparable to those of a natural siderophore ferrichrome (log beta = 29.1 and pM 25.2). The kinetic study of the TAGE-Fe(III) system has given the following rate constants: the rate of the ligand exchange reaction between Fe(III)TAGE and EDTA is 6.7 x 10(-4) s(-1), and the removal rates of iron from diferric bovine plasma transferrin by TAGE are 2.8 x 10(-2) and 6.0 x 10(-3) min(-1). These values are also comparable to those of a natural siderophore desferrioxamine B under the same conditions. In a biological activity experiment, TAGE has promoted the growth of the siderophore-auxotroph Gram-positive bacterium Microbacterium flavescens, suggesting that TAGE mimics the activity of ferrichrome. These results indicate that the artificial siderophore with intramolecular hydrogen bonding networks, TAGE, is a good structural and functional model for a natural ferrichrome.

Synthesis, Crystal Structure and Biological Characterization of a Novel Palladium(II) Complex with a Coumarin‐Derived Ligand

AbstractMethyl 2‐methyl‐4‐oxo‐4H‐chromene‐3‐carboxylate (1) was treated with 25% aqueous ammonia to give 3‐(1‐aminoethylidene)‐2H‐chromene‐2,4(3H)‐dione (2). Compound 2 was used as a ligand for the formation of a palladium(II) complex. The structures of the ligand and its palladium complex 3 were determined by IR and 1H NMR spectroscopy, FAB mass spectrometry and elemental analysis. The single‐crystal X‐ray structure of 3 was also solved. Ligand 2 in 20% dioxane solution shows two protonation constants — log β11 = 4.28 ± 0.01 and log β12 = 7.66 ± 0.03. In complex 3 two ligand molecules chelate to the Pd ion through their N and O donors, giving a four‐coordinate PdII center with a cis‐N2O2 donor set. The coordination geometry at PdII is square‐planar with typical values for the distances from the Pd atom to the coordinated atoms. The cytotoxicity of compound 3 was determined on three cancer cell lines. IC50 values of 9.7, 7.8 and 7.8 nM were found for A546, HeLa and K562 cells, respectively, which is notably lower than carboplatin, which shows corresponding IC50 values of 105.98, 73.49 and 60.92 μM. Double‐stranded DNA treated with 3 shows a significant increase in the Δϵ value in the CD spectra, as well as a lower electrophoretic mobility than parent DNA. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

Formation of Novel 1‐D Chains by μ‐Amido Bridging of Dinuclear Manganese(III)‐Schiff Base Complexes

AbstractThree novel neutral manganese(III) complexes of stoichiometry Mn(R‐amsal‐3,5‐di‐tBu)(H2O)n [H3‐R‐amsal‐3,5‐di‐tBu = 3‐aza‐4‐(2‐hydroxyphenyl)‐N‐(2‐hydroxyphenyl)but‐3‐enamide; (R = H, 4‐Me, 5‐tBu)] have been synthesised using potentially trianionic and pentadentate Schiff‐base ligands containing an amide group. Complexes were thoroughly characterised by elemental analysis, FAB mass spectrometry, infrared spectroscopy, magnetic susceptibility measurements and molar conductivities. Recrystallisation of these complexes from methanol yielded single crystals of [Mn2(amsal‐3,5‐di‐tBu)2(MeOH)2]n 1, [Mn2(4‐Me‐amsal‐3,5‐di‐tBu)2(MeOH)2]n 2 and [Mn2(5‐tBu‐amsal‐3,5‐di‐tBu)2(MeOH)2]n 3 with methanol as solvate. Their X‐ray characterisation shows that these complexes consist of infinite one‐dimensional chains with a repeating cyclic dimeric unit, where the amide oxygen atom is bridging two neighbouring manganese(III) ions. Paramagnetic 1H NMR spectroscopy confirmed the presence of MnIII in these complexes, while the cyclic voltammetry studies suggest the possibility of obtaining polynuclear MnIV complexes with this kind of ligand. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

Nucleophilic addition of bifunctional sulfimidosulfides to platinum(IV)-coordinated nitriles

Reactions of the platinum(IV) nitrile complexes [PtCl4(RCN)2] (R = Me, CH2Ph, Ph) with 1,2- and 1,4-PhS(=NH)C6H4SPh in CH2Cl2 afforded addition products of sulfimides and coordinated nitriles, viz., the [PtCl4{NH=C(R)N=S(Ph)(C6H4SPh)}2] complexes. The latter were isolated in 75—90% yields and characterized by elemental analysis, positive-ion FAB mass spectrometry, IR spectroscopy, and 1H and 13C1H NMR spectroscopy. The temperature dependence of the 1H NMR spectra of the model [PtCl4{NH=C(R)N=SPh2}2] complexes (R = Me, Et) in CD2Cl2 studied in a temperature range from +40 to -70 °C demonstrated that E—Z isomerization of the ligands is a dynamic process in a range from +40 to -10 °C. The activation free energy of this process was calculated.

Chloride as Supramolecular Glue: Anion‐Directed Assembly of a 2D Network of MnIII Complexes

AbstractThe Schiff base H4L [where H4L = N,N′‐bis(3‐hydroxysalicylidene)ethane‐1,2‐diamine], containing six potential donor atoms, is able to induce the formation of a novel [MnIII(H2L)(CH3OH)2]Cl (1) complex, which was characterized by elemental analysis, FAB mass spectrometry, IR, 1H NMR and electronic spectroscopy, magnetic measurements, X‐ray diffraction techniques and conductivity measurements. The study of its redox properties by cyclic and normal pulse voltammetry is also reported. The crystal structure of 1 is formed by monomeric cationic MnIII complexes, where the manganese ion is in an octahedral environment and is coordinated in the equatorial plane to the N2O2 donor set of the inner Schiff‐base compartment. The neutral condition of the complex is achieved with the presence of the chloride counterion, which behaves as a multiple acceptor of hydrogen bonds. The chloride is involved in four O−H···Cl bonds, connecting three neighbouring cationic complexes. To the best of our knowledge, this constitutes the first example of self‐assembly of discrete units of MnIII complexes in a 2D network in the solid state through hydrogen bonding, where the anion is acting as a supramolecular glue. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

A nonacoordinated bridging selenide in a tricapped trigonal prismatic geometry identified in undecanuclear copper clusters: syntheses, structures, and DFT calculations.

Undecanuclear copper clusters, [Cu(11)(micro(9)-Se)(micro(3)-Br)(3)[Se(2)P(OR)(2)](6)] (R = Et, Pr, (i)Pr) (1a-c), were isolated along with closed-shell ion-centered cubes, [Cu(8)(micro(8)-Br)[Se(2)P(OR)(2)](6)] (PF(6)) (2a-c) and [Cu(8)(micro(8)-Se)[Se(2)P(OR)(2)](6)] (3a-c), from the reaction of [Cu(CH(3)CN)(4)](PF(6)), NH(4)[Se(2)P(OR)(2)], and Bu(4)NBr in a molar ratio of 2:3:2 in CH(2)Br(2). The molecular formulations of these clusters were confirmed by elemental analysis, positive FAB mass spectrometry, and multinuclear NMR ((1)H, (31)P, and (77)Se). (77)Se NMR spectra of Cu(11) clusters (1a-c) are of special interest as two inequivalent selenium nuclei of the diselenophosphate (dsep) ligand exhibit different scalar coupling patterns with the adjacent phosphorus nuclei. X-ray analysis of 1c reveals a Cu(11)Se core stabilized by three bromide and six dsep ligands. The central core adopts the geometry of a 3,3,4,4,4-pentacapped trigonal prism with a selenium atom in the center. The coordination geometry for the nonacoordinate selenium atom is tricapped trigonal prismatic. The X-ray structure 2a or 2c consists of a cationic cluster in which eight copper ions are linked by six diselenophosphate ligands with a central micro(8)-Br ion. The shape of the molecule is a bromide-centered distorted Cu(8) cube. Each diselenophosphate ligand occupies square faces of the cube and adopts a tetrametallic tetraconnective coordination pattern. Each copper atom of the cube is coordinated by three selenium atoms with a strong interaction with the central bromide ion. Molecular orbital calculations at the B3LYP level of the density functional theory have been carried out to study the Cu-micro(9)-Se interactions for clusters [Cu(11)(micro(9)-Se)(micro(3)-X)(3)[Se(2)P(OR)(2)](6)] (X = Br, I). Calculations show that the formal bond order of each Cu-micro(9)-Se bond is slightly smaller than half of those calculated for the terminal Cu-micro(2)-Se bonds.

Synthesis, Structure, and Catalytic Oxidation Chemistry from the First Oxo−Imido Schiff Base Metal Complexes

The molybdenum oxo-imido complex, [Mo(O)(NtBu)Cl2(dme)] (1), was obtained from the reaction between [MoO2Cl2(dme)] and [Mo(NtBu)2Cl2(dme)]. Reactions between [Mo(O)(NR)Cl2(dme)] (where R = tBu or 2,6-iPr2C6H3) and the disodium Schiff base compounds Na(2)(3,5-tBu2)2salen, Na(2)(3,5-tBu2)2salpen, and Na(2)(7-Me)2salen afforded the first oxo-imido transition metal Schiff base complexes: [Mo(O)(NtBu)[(3,5-tBu2)2salen]] (2), [Mo(O)(NtBu)[(3,5-tBu2)2salpen]] (3), and [Mo(O)(N-2,6-iPr2C6H3)[(7-Me)2salen]] (4), respectively. The compounds [Mo(NtBu)2[(3,5-tBu2)2salpen]] (5) from [Mo(NtBu)2(NHtBu)2] and [Mo(N-2,6-iPr2C6H3)(2)[(7-Me)2salen]](6) from [Mo(N-2,6-iPr2C6H3)(2)(NHtBu)2] (7) are also reported. Compounds 1-7 were characterized by NMR, IR, and FAB mass spectroscopy while compounds 3, 4, and 5 were additionally characterized by X-ray crystallography. In conjunction with tBuOOH as oxidant, compound 3 is a catalyst for the oxidation of benzyl alcohol to benzaldehyde and cis-cyclooctene and 1-octene to the corresponding epoxides.

Synthesis and Spectroscopic Characterization of Dinuclear Calcium Complexes with Oxa‐Aza Macrocyclic Ligands

AbstractThe syntheses of dinuclear calcium perchlorate and/or nitrate complexes by template and direct methods, employing macrocyclic ligands with 18, 20, 22, and 26 membered rings are reported. The presence of pendant arms provide with coordinative NxOy donor atoms in the smaller macrocycles, the high number of donor atoms between 7 and 10, and the dinuclear composition obtained in all the systems examined, point out that in the formed solid complexes both Ca2+ ions could be located inside of the macrocycle cavities. Transmetallation reaction of a lanthanide(III) complex, [L5Sm](ClO4)3·9H2O, with Ca(ClO4)2·xH2O leads the formation of the new dinuclear orange [L5Ca2](ClO4)4·3H2O complex, manifesting the versatility of this macrocyclic cavity.All complexes have been characterized by microanalysis, IR, UV‐vis, 1H NMR spectroscopy, FAB mass spectrometry, FAAS spectroscopy, and conductivity measurements.