Heterometallic architectures based on the combination of heteroleptic copper and cobalt complexes with silver salts

A strategy for the formation of heterometallic coordination polymers based on novel copper(II) and cobalt(III) heteroleptic complexes (acacCN)Cu(dpm) and (acacCN)Co(dpm)(2) (acacCN = 3-cyanoacetylacetonate; dpm = dipyrrin) is presented. Using dipyrrins appended with a p- or m-pyridyl group, dpm-4py and dpm-3py, four novel copper and cobalt complexes were prepared and characterized both in solution and in the solid state. These two classes of complexes show different electrochemical properties upon investigation by cyclic voltammetry in CH(2)Cl(2). While the copper complexes show only irreversible reduction processes, the voltammogram of the cobalt species reveals the presence of two quasi-reversible reductions. In the solid state, the copper(II) compounds self-assemble to form one-dimensional architectures upon coordination of the peripheral pyridyl group to the copper center, as characterized by single-crystal X-ray diffraction. Owing to the filled coordination sphere of the octahedral cobalt centers, the (acacCN)Co(dpm-py)(2) compounds crystallize as isolated molecules. Upon reaction with silver salts, these complexes form crystalline heterometallic architectures with different organization and dimensionality, depending on the nature of the metal center and the position of the nitrogen atom in the pyridyl group. The two copper complexes lead to the formation of trinuclear species, {[(acacCN)Cu(dpm-py)](2)Ag}(+), resulting from coordination of the pyridyl groups to the silver cations. However, while meta-functionalized complexes self-assemble into an extended architecture via weak interaction of the peripheral nitrile of the acacCN ligand to the Ag(+) cation, this interaction is not present in the para-functionalized analogue. In both networks based on the Ag(BF(4)) salt, coordination of the tetrafluoroborate anion to the silver center in the rather rare chelate mode is observed. Upon assembly of the cobalt metallatectons with silver salts, two-dimensional (2D) coordination polymers are obtained in crystalline form, resulting, however, from different sets of interactions. Indeed, no coordination of the peripheral nitrile of the acacCN ligand is observed in the network incorporating the m-pyridyl-appended dpm; coordination of the pyridyl groups to the silver center and d(10)-d(10) interactions lead to a 2D architecture. In the case of the para analogue, a 2D honeycomb network is observed owing to coordination of the Ag(I) ion to two pyridyl nitrogen atoms and to one peripheral nitrile group of a acacCN ligand. This latter polymer represents a geometrical hybrid of the networks reported in the literature based on homoleptic Co(dpm-4py)(3) and Cr(acacCN)(3) complexes.     

Pd2X2(dpm)2(X＝NCO-,CH3CO2-,SCN-,NO3-;dpm＝Ph2PCH2PPh2配合物与H2S反应的NMR研究

采用NMR方法考察了室温和低温(-78～60℃)下Pd₂X₂(dpm)₂(X=NCO^-,CH₃CO₂^-,SCN^-和NO₃^-,dpm=Ph₂PCH₂PPh₂)与H₂S在CD₂Cl₂或CDCl₃中的反应。结果表明,在X=NCO^-和CH₃CO₂^-的情况下,H₂S优先与这些Pd配合物的阴离子作用生成相应的共轭酸HX和Pd₂(SH)₂(dpm)₂,后者在H₂S存在下又进一步转化为Pd₂(SH)₂(dpm)₂(μ-S);当X=SCN^-和NO₃^-时,反应则生成结构可能为[Pd₂(H)(SH)(μ-SH)(dpm)₂]⁺的双核Pd配合物。     

Short metal-metal separations in a highly luminescent trimetallic Ag(I) complex stabilized by bridging NHC ligands

Reaction of 1,3-bis(2-pyridinylmethyl)-1H-imidazolium salt, [H(pyCH(2))(2)im]X (X = BF(4)(-) or Cl(-)), with silver oxide in acetonitrile readily yields yellow-brown [((pyCH(2))(2)im)(2)Ag]X, 1.BF(4) or 1.Cl. The chloride salt crystallizes with 3.650 A intermolecular Ag...Ag interactions while 1.BF(4) shows no short intermolecular interaction. Addition of excess Ag(BF(4)) produces the homoleptic carbene bridged trimetallic species, [(mu-NHC)(3)Ag(3)](BF(4))(3), 2. This species contains very short Ag-Ag separations between 2.7249(10) and 2.7718(9) A. In solution, these complexes are photoluminescent.     

Ru and Os complexes containing a P,N-donor heterotopic ligand: the effect of solvent on stereochemistry

Ruthenium and osmium complexes of the general formula MCl 2(PyP) 2 (where PyP is the P,N- donor ligand 1-(2-diphenylphosphinoethyl)pyrazole) were synthesized from MCl 2(PPh 3) 3 (where M = Ru or Os). Three of the five possible stereoisomers of RuCl 2(PyP) 2 were synthesized and characterized in solution by multinuclear NMR spectroscopy, and the structure of these in the solid state was determined by X-ray crystallography. Two of the analogous Os isomers were also synthesized. It was found that different solvents induced isomerization between these stereoisomers, indicating either lability of the chloride anion or hemilability of the PyP ligand. Bimetallic complexes of the general formula [Ru(mu-Cl)(PyP) 2] 2[X] 2 were synthesized from chloride abstraction from RuCl 2(PyP) 2 using either silver (X = OSO 2CF 3, BF 4) or sodium (X = BPh 4) salts. The osmium analogue of the Ru bimetallic complexes, [Os(mu-Cl)(PyP) 2] 2[BPh 4] 2, was also synthesized. Solid-state structures were obtained using X-ray crystallography for the osmium bimetallic complex and the ruthenium bimetallic complex where X = OSO 2CF 3. The hemilability of PyP was demonstrated through the synthesis of RuCl 2(CO)(kappa (1)- P-PyP)(kappa (2)- P, N-PyP), which contains one pendant PyP ligand, bound through the P-donor atom.     

Highly phosphorescent iridium complexes containing both tridentate bis(benzimidazolyl)-benzene or -pyridine and bidentate phenylpyridine: synthesis, photophysical properties, and theoretical study of Ir-bis(benzimidazolyl)benzene complex

Novel mixed-ligand Ir(III) complexes, [Ir(L)(NwedgeC)X]n+ (L = N/\C/\N or N/\N/\N; X = Cl, Br, I, CN, CH3CN, or -CCPh; n = 0 or 1), were synthesized, where N/\CwedgeN = bis(N-methylbenzimidazolyl)benzene (Mebib) and bis(N-phenylbenzimidazolyl)benzene (Phbib), N/\N/\N = bis(N-methylbenzimidazolyl)pyridine (Mebip), and N/\C = phenylpyridine (ppy) derivatives. The X-ray crystal structures of [Ir(Phbib)(ppy)Cl] and [Ir(Mebib)(mppy)Cl] [mppy = 5-methyl-2-(2'-pyridyl)phenyl] indicate that the nitrogen atom of the ppy ligand is located trans to the coordinating carbon atom in Me- or Phbib, while the coordinating carbon atom in ppy occupies the trans position of Cl. [Ir(Mebip)(ppy)Cl]+ showed a quasireversible Ir(III/IV) oxidation wave at +1.05 V, while the Ir complexes, [Ir(Mebib)(ppy)Cl], were oxidized at +0.42 V versus Fc/Fc+. The introduction of an Ir-C bond in [Ir(Mebib)(ppy)Cl] induces a large potential shift of 0.63 V in a negative direction. Further, the oxidation potential of [Ir(Mebib)(Rppy)X] was altered by the substitution of R, R', and X groups. Compared to the oxidation potential, the first reduction potential revealed an almost constant value at -2.36 to -2.46 V for [Ir(L)(ppy)Cl] (L = Mebib and Phbib) and -1.52 V for [Ir(Mebip)(ppy)Cl. The UV-vis spectra of [Ir(Mebib)(R-ppy)X] show a clear singlet metal-to-ligand charge-transfer transition around 407 approximately 425 nm and a triplet metal-to-ligand charge-transfer transition at 498 approximately 523 nm. [Ir(Mebip)(ppy)Cl]+ emits at 610 nm with a luminescent quantum yield of Phi = 0.16 at room temperature. The phosphorescence of [Ir(Mebib)(ppy)X] was observed at 526 nm for X = CN and 555 nm for X = Cl with the high luminescent quantum yields, Phi = 0.77 approximately 0.86, at room temperature. [Ir(Phbib)(ppy)Cl] shows the emission at 559 nm with a luminescent quantum yield of Phi = 0.95, which is an unprecedentedly high value compared to those of other emissive metal complexes. Compared to the luminescent quantum yields of the Ir(ppy)2(L) derivatives and [Ir(Mebip)(ppy)Cl]+, the neutral Ir complexes, [Ir(L)(R-ppy)X] (L = Me- or Phbib), reveal very high quantum yields and large radiative rate constants (kr) ranging from 3.4 x 10(5) to 5.5 x 10(5) s(-1). The density functional theory calculation suggests that these Ir complexes possess dominantly metal-to-ligand charge-transfer and halide-to-ligand charge-transfer excited states. The mechanism for a high phosphorescence yield in [Ir(bib)(ppy)X] is discussed herein from the perspective of the theoretical consideration of radiative rate constants using perturbation theory and a one-center spin-orbit coupling approximation.     

Synthesis and dehydrative condensation of square-planar mono- and dinuclear hydroxopalladium complexes with the hydrotris(3,5-diisopropylpyrazolyl)borato ligand (TpiPr2), TpiPr2(Py)Pd-OH,and (mu-OH)2[PdTpiPr2(H2O)]2

Mono- and dinuclear hydroxopalladium complexes (kappa 2-TpiPr2,X)(py)Pd-OH (1; X = H, Br) and (mu-OH)2[Pd(kappa 2-TpiPr2)(H2O)]2 (2) are prepared by base hydrolysis of the corresponding chloride complexes (kappa 2-TpiPr2,X)(py)Pd-Cl (3) and (mu-Cl)2[Pd(kappa 3-TpiPr2)]2 (4), respectively. Functionalization of the OH part in 1 is effected via dehydrative condensation with protic substrates (H-A) to give a series of substituted products, (kappa 2-TpiPr)(py)Pd-A (5), and treatment of the dinuclear complex 2 with excess acetic acid affords the mononuclear diacetato complex 6, (kappa 2-TpiPr2-H)Pd(OAc)2(HOAc). Complexes 1-4 and 6 have been characterized crystallographically, and it is revealed that complexes 2 and 6 involve cyclic hydrogen-bonding interaction among the nitrogen atom of the pendent noncoordinated pyrazolyl group, the hydrogen atom in the protic part of the ligand (OH, AcOH), and, in the case of 2, an external water molecule.     

Synthesis and electrochemical studies of diiron complexes of 1,8-naphthyridine-based dinucleating ligands to model features of the active sites of non-heme diiron enzymes

A bis(mu-carboxylato)(mu-1,8-naphthyridine)diiron(II) complex, [Fe2(BPMAN)(mu-O2CPhCy)2](OTf)2 (1), was prepared by using the 1,8-naphthyridine-based dinucleating ligand BPMAN, where BPMAN = 2,7-bis[bis(2-pyridylmethyl)aminomethyl]-1,8-naphthyridine. The cyclic voltammogram (CV) of this complex in CH2Cl2 exhibited two reversible one-electron redox waves at +296 mV (DeltaE(p) = 80 mV) and +781 mV (DeltaE(p) = 74 mV) vs Cp2Fe+/Cp2Fe, corresponding to the FeIIIFeII/FeIIFeII and FeIIIFeIII/FeIIIFeII couples, respectively. This result is unprecedented for diiron complexes having no single atom bridge. Dinuclear complexes [Fe2(BPMAN)(mu-OH)(mu-O2CPhCy)](OTf)2 (2) and [Mn2(BPMAN)(mu-O2CPhCy)2](OTf)2 (3) were also synthesized and structurally characterized. The cyclic voltammogram of 2 in CH2Cl2 exhibited one reversible redox wave at -22 mV only when the potential was kept below +400 mV. The CV of 3 showed irreversible oxidation at potentials above +900 mV. Diiron(II) complexes [Fe2(BEAN)(mu-O2CPhCy)3](OTf) (4) and [Fe2(BBBAN)(mu-OAc)2(OTf)](OTf) (6) were also prepared and characterized, where BEAN = 2,7-bis(N,N-diethylaminomethyl)-1,8-naphthyridine and BBBAN = 2,7-bis[2-[2-(1-methyl)benzimidazolylethyl]-N-benzylaminomethyl]-1,8-naphthyridine. The cyclic voltammograms of these complexes were recorded. The M?ssbauer properties of the diiron compounds were studied.     

Proton-driven self-assembled systems based on cyclam-cored dendrimers and [Ru(bpy)(CN)4]2-

1,4,8,11-tetraazacyclotetradecane (cyclam), which is one of the most extensively investigated ligands in coordination chemistry, in its protonated forms, can play the role of host toward cyanide metal complexes. We have investigated the acid-driven adducts formed in acetonitrile-dichloromethane (1:1 v/v) solution by [Ru(bpy)(CN)4](2-) with 1,4,8,11-tetrakis(naphthylmethyl)cyclam (1) and a dendrimer consisting of a cyclam core appended with 12 dimethoxybenzene and 16 naphthyl units (2). [Ru(bpy)(CN)4](2-), 1, and 2 exhibit characteristic absorption and emission bands, in distinct spectral regions, that are strongly affected by addition of acid. When a solution containing equimolar amounts of [Ru(bpy)(CN)4](2-) and 1 or 2 is titrated by trifluoroacetic acid, or when [Ru(bpy)(CN)4](2-) is titrated with (1.2H)2+ or (2.2H)2+, [[Ru(bpy)(CN)4](2-).(2H+).1] or [[Ru(bpy)(CN)4](2-).(2H+).2] adducts are formed in which the fluorescence of the naphthyl units is strongly quenched by very efficient energy transfer to the metal complex, as shown by the sensitized luminescence of the latter. The [[Ru(bpy)(CN)4]2-.(2H+).1] and [[Ru(bpy)(CN)4](2-).(2H+).2] adducts can be disrupted (i) by addition of a base (1,4-diazabicyclo[2.2.2]octane), yielding the starting species [Ru(bpy)(CN)4](2-) and 1 or 2, or (ii) by further addition of triflic acid, with formation of (1.2H)2+ or (2.2H)2+ and protonated forms of [Ru(bpy)(CN)4](2-). It is shown that upon stimulation with two chemical inputs (acid and base) both [[Ru(bpy)(CN)4](2-).(2H+).1] and [[Ru(bpy)(CN)4](2-).(2H+).2] exhibit two distinct optical outputs (a naphthalene-based and a Ru(bpy)-based emission) that behave according to an XOR and an XNOR logic, respectively.     

Investigation of structural and biological properties of N-heterocyclic carbene silver(I) and palladium(II) complexes

abstract

Computational investigations were done on bis(1-allyl-3-benzyl-2,3-dihydro-1H-benzo[d]imidazol-2-yl)silver(I), bis(1-benzyl-3-butyl-2,3-dihydro-1H-benzo[d]imidazol-2-yl)silver(I), bis(1-allyl-3-benzyl-2,3-dihydro-1H-benzo[d]imidazol-2-yl)dibromidepalladium(II), and bis(1-benzyl-3-butyl-2,3-dihydro-1H-benzo[d]imidazol-2-yl)dibromidepalladium(II) complexes. Related complexes were optimized at different six calculation levels which are HF/6-31G(LANL2DZ), HF/6-31G(d,p)(LANL2DZ), B3LYP/6-31G(LANL2DZ), B3LYP/6-31G(d,p)(LANL2DZ), M062X/6-31G(LANL2DZ) and M062X/6-31G(d,p)(LANL2DZ) levels in vacuo. IR and NMR spectrum are calculated and examined in detail. Energy diagram of molecular orbitals, contour diagram of frontier molecular orbitals, molecular electrostatic potential maps and the harmonic surface of related molecules are examined in detail. Finally, interactions between mentioned complexes and related proteins (1BNA, 1JNX, and 2ING) are investigated in detail. As a result, it is found that biological and anti-cancer properties of silver N-heterocyclic carbene complexes are higher than those of palladium complexes.     

Formation of ammonia in the reactions of a tungsten dinitrogen with ruthenium dihydrogen complexes under mild reaction conditions

Treatment of cis-[W(N2)2(PMe2Ph)4] (5) with an equilibrium mixture of trans-[RuCl(eta 2-H2)(dppp)2]X (3) with pKa = 4.4 and [RuCl(dppp)2]X (4) [X = PF6, BF4, or OTf; dppp = 1,3-bis(diphenylphosphino)propane] containing 10 equiv of the Ru atom based on tungsten in benzene-dichloroethane at 55 degrees C for 24 h under 1 atm of H2 gave NH3 in 45-55% total yields based on tungsten, together with the formation of trans-[RuHCl(dppp)2] (6). Free NH3 in 9-16% yields was observed in the reaction mixture, and further NH3 in 36-45% yields was released after base distillation. Detailed studies on the reaction of 5 with numerous Ru(eta 2-H2) complexes showed that the yield of NH3 produced critically depended upon the pKa value of the employed Ru(eta 2-H2) complexes. When 5 was treated with 10 equiv of trans-[RuCl(eta 2-H2)(dppe)2]X (8) with pKa = 6.0 [X = PF6, BF4, or OTf; dppe = 1,2-bis(diphenylphosphino)ethane] under 1 atm of H2, NH3 was formed in higher yields (up to 79% total yield) compared with the reaction with an equilibrium mixture of 3 and 4. If the pKa value of a Ru(eta 2-H2) complex was increased up to about 10, the yield of NH3 was remarkably decreased. In these reactions, heterolytic cleavage of H2 seems to occur at the Ru center via nucleophilic attack of the coordinated N2 on the coordinated H2 where a proton (H+) is used for the protonation of the coordinated N2 and a hydride (H-) remains at the Ru atom. Treatment of 5, trans-[W(N2)2(PMePh2)4] (14), or trans-[M(N2)2(dppe)2] [M = Mo (1), W (2)] with Ru(eta 2-H2) complexes at room temperature led to isolation of intermediate hydrazido(2-) complexes such as trans-[W(OTf)(NNH2)(PMe2Ph)4]OTf (19), trans-[W(OTf)(NNH2)(PMePh2)4]OTf (20), and trans-[WX(NNH2)(dppe)2]+ [X = OTf (15), F (16)]. The molecular structure of 19 was determined by X-ray analysis. Further ruthenium-assisted protonation of hydrazido(2-) intermediates such as 19 with H2 at 55 degrees C was considered to result in the formation of NH3, concurrent with the generation of W(VI) species. All of the electrons required for the reduction of N2 are provided by the zerovalent tungsten.     

Areneruthenium(II) 4-acyl-5-pyrazolonate derivatives: coordination chemistry, redox properties, and reactivity

Areneruthenium(II) molecular complexes of the formula [Ru(arene)(Q)Cl], containing diverse 4-acyl-5-pyrazolonate ligands Q with arene = cymene or benzene, have been synthesized by the interaction of HQ and [Ru(arene)Cl(micro-Cl)]2 dimers in methanol in the presence of sodium methoxide. The dinuclear compound [{Ru(cymene)Cl}2Q4Q] (H2Q4Q = bis(4-(1-phenyl-3-methyl-5-pyrazolone)dioxohexane), existing in the RRuSRu (meso form), has been prepared similarly. [Ru(cymene)(Q)Cl] reacts with sodium azide in acetone, affording [Ru(cymene)(Q)N3] derivatives, where Cl- has been replaced by N3-. The reactivity of [Ru(cymene)(Q)Cl] has also been explored toward monodentate donor ligands L (L = triphenylphosphine, 1-methylimidazole, or 1-methyl-2-mercaptoimidazole) and exo-bidentate ditopic donor ligands L-L (L-L = 4,4'-bipyridine or bis(diphenylphosphino)propane) in the presence of silver salts AgX (X = SO3CF3 or ClO4), new ionic mononuclear complexes of the formula [Ru(cymene)(Q)L]X, and ionic dinuclear complexes of the formula [{Ru(cymene)(Q)}2L-L]X2 being obtained. The solid-state structures of a number of complexes were confirmed by X-ray crystallographic studies. Their redox properties have been investigated by cyclic voltammetry and controlled potential electrolysis, which, on the basis of their measured RuII/III reversible oxidation potentials, have allowed the ordering of the bidentate acylpyrazolonate ligands according to their electron-donor character and are indicative of a small dependence of the HOMO energy upon the change of the monodentate ligand. This is accounted for by DFT calculations, which show a relevant contribution of acylpyrazolonate ligand orbitals to the HOMOs, whereas that from the monodentate ligand is minor.     

Gold and silver complexes with the ferrocenyl phosphine FcCH2PPh2

Linear gold(I) and silver(I) complexes with the ferrocenyl phosphine FcCH2PPh2 [Fc = (eta5-C5H5)Fe(eta5-C5H4)] of the types [AuR(PPh2CH2Fc)], [M(PPh3)(PPh2CH2Fc)]OTf, and [M(PPh2CH2Fc)2]OTf (M = Au, Ag) have been obtained. Three-coordinate gold(I) and silver(I) derivatives of the types [AuCl(PPh2CH2Fc)2] and [M(PPh2CH2Fc)3]X (M = Au, X = ClO4; M = Ag, X = OTf) have been obtained from the corresponding gold and silver precursors in the appropriate molar ratio, although some of them are involved in equilibria in solution. The crystal structures of [AuR(PPh2CH2Fc)] (R = Cl, C6F5), [AuL(PPh2CH2Fc)]OTf (L = PPh3, FcCH2PPh2), [Au(C6F5)3(PPh2CH2Fc)], and [Ag(PPh2CH2Fc)3]OTf have been determined by X-ray diffraction studies.     

Impact of variations in design of flexible bitopic bis(pyrazolyl)methane ligands and counterions on the structures of silver(I) complexes: dominance of cyclic dimeric architecture

The new ligands 1,1,4,4-tetra(1-pyrazolyl)butane [CH(pz)(2)(CH(2))(2)CH(pz)(2), L2] and 1,1,5,5-tetra(1-pyrazolyl)pentane [CH(pz)(2)(CH(2))(3)CH(pz)(2), L3] have been prepared to determine the structural changes in silver(I) complexes, if any, that accompany the lengthening of the spacer group between two linked bis(pyrazolyl)methane units. Silver(I) complexes of both ligands with BF(4)(-) and SO(3)CF(3)(-) as the counterion have the formula [Ag(2)(micro-L)(2)](counterion)(2). These complexes have a cyclic dimeric structure in the solid state previously observed with the shorter linked ligand CH(pz)(2)CH(2)CH(pz)(2). Similar chemistry starting with AgNO(3) for L2 yields a complex of the empirical formula [Ag(2)[micro-CH(pz)(2)(CH(2))(2)CH(pz)(2)](3)](NO(3))(2) that retains the cyclic dimeric structure, but bonding of an additional ligand creates a coordination polymer of the cyclic dimers. In contrast, coordination of the nitrate counterion to silver in the complex of L3 leads to the formation of the coordination polymer of the empirical formula [Ag(micro-CH(pz)(2)(CH(2))(3)CH(pz)(2))]NO(3). All six new complexes have extended supramolecular structures based on noncovalent interactions supported by the counterions and the functional groups designed into the ligands.     

Controlled hydrolysis of lanthanide complexes of the N-donor tripod tris(2-pyridylmethyl)amine versus bisligand complex formation

The reaction of the lanthanide salts LnI3(thf)4 and Ln(OTf)3 with tris(2-pyridylmethyl)amine (tpa) was studied in rigorously anhydrous conditions and in the presence of water. Under rigorously anhydrous conditions the successive formation of mono- and bis(tpa) complexes was observed on addition of 1 and 2 equiv of ligand, respectively. Addition of a third ligand equivalent did not yield additional complexes. The mono(tpa) complex [Ce(tpa)I3] (1) and the bis(tpa) complexes [Ln(tpa)2]X3 (X = I, Ln = La(III) (2), Ln = Ce(III) (3), Ln = Nd(III) (4), Ln = Lu(III) (5); X = OTf, Ln = Eu(III) (6)) were isolated under rigorously anhydrous conditions and their solid-state and solution structures determined. In the presence of water, 1H NMR spectroscopy and ES-MS show that the successive addition of 1-3 equiv of tpa to triflate or iodide salts of the lanthanides results in the formation of mono(tpa) aqua complexes followed by formation of protonated tpa and hydroxo complexes. The solid-state structures of the complexes [Eu(tpa)(H2O)2(OTf)3] (7), [Eu(tpa)(mu-OH)(OTf)2]2 (8), and [Ce(tpa)(mu-OH)(MeCN)(H2O)]2I4 (9) have been determined. The reaction of the bis(tpa) lanthanide complexes with stoichiometric amounts of water yields a facile synthetic route to a family of discrete dimeric hydroxide-bridged lanthanide complexes prepared in a controlled manner. The suggested mechanism for this reaction involves the displacement of one tpa ligand by two water molecules to form the mono(tpa) complex, which subsequently reacts with the noncoordinated tpa to form the dimeric hydroxo species.     

A computational insight into a metal mediated pathway for the ring-opening polymerization (ROP) of lactides by an ionic {(NHC)2Ag}(+)X(-) (X = halide) type N-heterocyclic carbene (NHC) complex

A metal mediated coordination-insertion pathway for the ring-opening polymerization (ROP) of L-lactide by an ionic {(NHC)(2)Ag}(+)X(-) (X = halide) type silver complex of N-heterocyclic carbene (NHC) has been investigated using the density functional theory (DFT) method. A clear insight into the lactide insertion process could be obtained by modeling two consecutive monomer addition steps with the first one mimicking chain initiation with the second representing a propagation step. In particular, in each of the cycles, the reaction initiates with the formation of a lactide coordinated species, [1+LL] and [2+LL] that transforms into a metal bound cyclic lactide intermediate, I([1+LL]→2) and I([2+LL]→3), which subsequently ring opens to give the lactide inserted products, 2 and 3. The estimated overall activation barrier for the initiation step is 42.0 kcal mol(-1) while the same for the propagation step is 31.5 kcal mol(-1). Studies on higher monomer insertions showed a decrease in the relative product energies as anticipated for an addition polymerization pathway.     

Three novel interpenetrating diamondoid networks from self-assembly of 1,12-dodecanedinitrile with silver(I) salts

The self-assembly of 1,12-dodecanedinitrile (ddn) with various silver salts (NO(3)(-), PF(6)(-), AsF(6)(-), ClO(4)(-)) afforded new polymeric coordination networks with the general formula [Ag(ddn)(2)]X. All these species contain interpenetrating diamondoid nets showing interesting features: with X=NO(3)(-) the cationic [Ag(ddn)(2)](+) network exhibits the highest interpenetration (tenfold) ever found within diamondoid nets exclusively based on coordinative bonds. When X=PF(6)(-) or AsF(6)(-) an eightfold diamondoid network is obtained that shows an unusual [4+4] mode of interpenetration, instead of the "normal" set of eight nets equally translated along a principal axis of the adamantanoid cages. The polymeric species that forms with X=ClO(4)(-) is a fourfold interpenetrating diamondoid network; the lower degree of interpenetration in this case is related to the conformation assumed by the flexible ddn ligands.     

Structural comparison of copper(I) and copper(II) complexes with tris(2-pyridylmethyl)amine ligand

Copper(I) complexes with the tris(2-pyridylmethyl)amine (TPMA) ligand were synthesized and characterized to examine the effect of counteranions (Br(-), ClO(4)(-), and BPh(4)(-)), as well as auxiliary ligands (CH(3)CN, 4,4'-dipyridyl, and PPh(3)) on the molecular structures in both solid state and solution. Partial dissociation of one of the pyridyl arms in TPMA was not observed when small auxiliary ligands such as CH(3)CN or Br(-) were coordinated to copper(I), but was found to occur with larger ones such as PPh(3) or 4,4'-dipyridyl. All complexes were found to adopt a distorted tetrahedral geometry, with the exception of [Cu(I)(TPMA)][BPh(4)], which was found to be trigonal pyramidal because of stabilization via a long cuprophilic interaction with a bond length of 2.8323(12) ?. Copper(II) complexes with the general formula [Cu(II)(TPMA)X][Y] (X = Cl(-), Br(-) and Y = ClO(4)(-), BPh(4)(-)) were also synthesized to examine the effect of different counterions on the geometry of [Cu(II)(TPMA)X](+) cation, and were found to be isostructural with previously reported [Cu(II)(TPMA)X][X] (X = Cl(-) or Br(-)) complexes.     

The coordination chemistry of selenophosphite ligands. Synthesis and characterization of heterometallic tetranuclear clusters [M{CpFe(CO)(2)P(Se)(OR)(2)}(3)](PF(6)) (M = Cu, Ag; R = (n)Pr, (i)Pr) and [Cu(mu-X) {CpFe(CO)(2)P(Se)(O(i)Pr)(2)}](2) (X = Cl, Br)

A neutral selenium donor ligand, [CpFe(CO)(2)P(Se)(OR)(2)] is used for the construction of Cu(I) and Ag(I) complexes with a well-defined coordination environment. Four clusters [M{CpFe(CO)(2)P(Se)(OR)(2)}(3)](PF(6)), (where M = Cu, R = (n)Pr, ; R = (i)Pr, and M = Ag, R = (n)Pr, ; R = (i)Pr, ) are isolated from the reaction of [M(CH(3)CN)(4)(PF(6))] (where M = Cu or Ag) and [CpFe(CO)(2)P(Se)(OR)(2)] in a molar ratio of 1 : 3 in acetonitrile at 0 degrees C. The reaction of [CpFe(CO)(2)P(Se)(O(i)Pr)(2)] with cuprous halides in acetone produce two mixed-metal, Cu(I)(2)Fe(II)(2) clusters, [Cu(mu-X) {CpFe(CO)(2)P(Se)(O(i)Pr)(2)}](2) (X = Cl, ; Br, ). All six clusters have been fully characterized spectroscopically ((1)H, (13)C, (31)P, and (77)Se NMR, IR), and by elemental analyses. X-Ray crystal structures of and consist of discrete cationic clusters in which three iron-selenophosphito fragments are linked to the central copper or silver atom via selenium atoms. Both clusters and crystallize in the noncentrosymmetric, hexagonal space group P6[combining macron]2c. The coordination geometry around the copper or silver atom is perfect trigonal-planar with Cu-Se and Ag-Se distances, 2.3505(7) and 2.5581(7) A, respectively. X-Ray crystallography also reveals that each copper center in neutral heterometallic clusters and is trigonally coordinated to two halide ions and a selenium atom from the selenophosphito-iron moiety. The structures can also be delineated as a dimeric unit which is generated by an inversion center and has a Cu(2)X(2) parallelogram core. The dihedral angle between the Cu(2)X(2) plane and the plane composed of Cp ring is found to be 24.62 and 84.58 degrees for compound and , respectively. Hence the faces of two opposite Cp rings are oriented almost perpendicular to the Cu(2)X(2) plane in , but are close to be parallel in . This is the first report of the coordination chemistry of the anionic selenophosphito moiety [(RO)(2)PSe](-), the conjugated base of a secondary phosphine selenide, which acts as a bridging ligand with P-coordination on iron and Se-coordination to copper or silver.     

Synthesis and structural characterization of double metal cyanides of iron and zinc: catalyst precursors for the copolymerization of carbon dioxide and epoxides

Several synthetic approaches for the preparation of double metal cyanide (DMC) derivatives of iron(II) and zinc(II) are described. These include (1) metathesis reactions of ZnCl(2) or ZnI(2) with KCpFe(CN)(2)CO in aqueous solution, (2) reactions of KCpFe(CN)(2)CO and its phosphine-substituted analogues with Zn(CH(3)CN)(4)(BF(4))(2) and subsequent displacement of acetonitrile at the zinc centers by the addition of a neutral (phosphine) or anionic (phenoxide) ligand, and (3) reactions of the protonated HCpFe(CN)(2)(phosphine) complexes with Zn(N(SiMe(3))(2))(2), followed by the addition of phenols. All structures are based on a diamond-shaped planar arrangement of the Fe(2)(CN)(4)Zn(2) core with various appended ligands at the metal sites. Although attempts to replace the iodide ligands in [CpFe(mu-CN)(2)PPh(3)ZnI(THF)](2) with acetate using silver acetate failed, two novel cationic mixed-metal cyanide salts based on the [CpFe(PPh(3))(mu-CN)(2)Zn(NC(5)H(5))](2)(2+) framework were isolated from pyridine solution and their structures were defined by X-ray crystallography. The anionic ligand bound to zinc in these derivatives, which serve as an anionic polymerization initiator, was shown to be central to the catalytic copolymerization reaction of CO(2)/epoxide to provide polycarbonates and cyclic carbonates. The structurally stabilized phosphine-strapped complexes [CpFe(mu-CN)(2)Zn(X)THF](2)(mu-dppp), where X = I or phenolate, were shown to be thermally stable under the conditions (80 degrees C) of the copolymerization reaction by in situ infrared spectroscopy. Both of these derivatives were proposed to serve as mimics for the heterogeneous DMC catalysts in the patent literature, with the derivative where the initiator is a phenolate being more active for the production of polycarbonates.     

O-confused oxaporphyrin--an intermediate in formation of 3-substituted 2-oxa-21-carbaporphyrins

[Reaction: see text]. A condensation of 2,4-bis(phenylhydroxymethyl)furan with pyrrole and p-toluylaldehyde in the presence of ethanol formed 5,20-diphenyl-10,15-di(p-tolyl)-2-oxa-3-ethoxy-3-hydro-21-carbaporphyrin [(H,EtO)OCPH]H2. The new carbaporphyrinoid has 1H NMR features of an aromatic molecule, including the upfield shift of the inner H(21) atom (-5.48 ppm). Addition of acid removes the ethoxy substituent and converts [(H,EtO)OCPH]H2 into the dication of "true" O-confused oxaporphyrin {[(H)OCPH]H3}2+ via an exocyclic C(3)-O bond cleavage followed by an elimination of the ethoxy group as determined by 1H NMR. Addition of ethanol, water, or pyrrole converts {[(H)OCPH]H3]2+ into [(H,EtO)OCPH]H2, [(H,OH)OCPH]H2, or pyrrole appended O-confused porphyrin [(H,pyrrole)OCPH]H2, respectively. The reaction of [(H,OEt)OCPH]H2 with silver(I) acetate yields a stable Ag(III) complex [(H,OEt)OCP]AgIII substituted at the C(3) position by the ethoxy group and hydrogen. Coordination through the nitrogen donors is reflected by the presence of 107/109Ag scalar splitting seen for the selected -H pyrrolic signals. Addition of TFA to [(H,OEt)OCP]AgIII produces a weakly aromatic O-confused porphyrin complex {[(H)OCP]AgIII}+. In the course of this reversible process the tetrahedral-trigonal rearrangements originate at the C(3) atom but extend its consequences on the whole structure. Insertion of silver into the hydroxy analogue of [(H,OEt)OCPH]H2, i.e., [(H,OH)OCPH]H2, was accompanied by ligand oxidation, yielding carbaporpholactone which contains the lactone functionality instead of the regular furan moiety embedded in the carbaporphyrin ligand of [(O)OCP]AgIII. The structure was determined by X-ray crystallography. The macrocycle is only slightly distorted from planarity, and silver(III) is located in the NNNC plane.