Metal Moiety Research Articles

Up to Seven‐Component Adducts by Unprecedented Multiple Alkyne and Carbonyl Insertions in the Metal–Carbon Bond of Chromium Alkoxy Alkynyl Carbene Complexes

Chromium alkoxy alkynyl Fischer carbene complexes react with symmetrical internal alkynes to form new and different organometallic species, which result from consecutive insertions of several alkyne units and carbonyl groups into the metal-carbon bond. The insertion sequence can be controlled and, by slight modification of the reaction conditions, it can be directed to the preparation of either seven- or five-component adducts. Three molecules of alkyne, two carbonyl groups, the carbene ligand and the chromium metal moiety partake in the creation of seven new carbon-carbon bonds and two five-membered carbocycles in the first case while four new carbon-carbon bonds, a sigma Cr--C(sp(2)) bond and a cyclopentadienyl moiety are built in the second case. Evidence that five-component chromium complexes are intermediates in the formation of seven-component adducts is provided; they are also able to insert a unit of a different internal alkyne which confers more diversity to the seven-component adducts. The presence of the sigma Cr--C(sp(2)) bond has also been exploited to develop the synthesis of both cyclopentene-fused and novel spiro-cyclopentenones as well as symmetrical biscyclopentenones. Finally, the isolation of six-component adducts, when tolane was employed as the initial alkyne, provides further support to the proposed mechanism.

The studies of complex formation of metal borides in the reaction system of epoxidation of 1-octene with tert-butyl hydroperoxide by IR spectroscopy

The complex formation of molybdenum and vanadium borides in the reaction system of 1-octene epoxidation with tert-butyl hydroperoxide by infrared spectroscopic analysis was studied. It was shown that 1-octene formed complex with metal moiety in a case of molybdenum boride and with boron moiety in a case of vanadium boride.

Stepwise synthesis of peripherally dimetallated metallo-tetraazaporphyrins with linear and bent motifs

Two new dinuclear and two new trinuclear complexes of 2,3,7,8,12,13,17,18-octakis(methylthio)tetraazaporphyrinatomagnesium(II), [Mg(OMTTAP)] were synthesized using a convenient stepwise process. These complexes possess (bpy)2RuII and Cp(PPh3)RuII metal moieties directly attached to the β-positions in the [Mg(OMTTAP)] through thioether chelation. Complexes were characterized using 1H-n.m.r., u.v.–vis and mass spectroscopic data. The peripheral binding of the two RuII units significantly influenced redox potentials of the OMTTAP core by lowering E1/2 for the OMTTAP centered oxidation and reduction processes, both, as evident from their cyclic voltammograms. The stepwise synthesis reported here demonstrates success of a convenient strategy to obtain hybrid, trimetallic, redox active chromophores with linear and bent motifs.

Dynamic Stereochemical Rearrangements in Chiral Organometallic Complexes

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Influence of Single Impurity Atoms on the Structure, Electronic, and Magnetic Properties of Ni5Clusters

With a gradient-corrected density functional method, we have studied computationally the influence of single impurity atoms on the structure, electronic, and magnetic properties of Ni5 clusters. The square-pyramidal isomer of bare Ni5 with six unpaired electrons was calculated 23 kJ/mol more stable than the trigonal bipyramid in its lowest-energy electronic configuration with four unpaired electrons. In a previous study on the cluster Ni4, we had obtained only one stable isomer with an O or an H impurity, but we located six minima for ONi5 and five minima for HNi5. In the most stable structures of HNi5, the H atom bridges a Ni-Ni edge at the base or the side of the square pyramid, similarly to the coordination of an H atom at the tetrahedral cluster Ni4. The most stable ONi5 isomers exhibit a trigonal bipyramidal structure of the Ni5 moiety, with the impurity coordinated at a facet, (micro3-O)Ni5, or at an apex edge, (micro-O)Ni5. We located four stable structures for a C impurity at a Ni5 cluster. As for CNi4, the most stable structure of the corresponding Ni5 complex comprises a four-coordinated C atom, (micro4-C)Ni5, and can be considered as insertion of the impurity into a Ni-Ni bond of the bare cluster. All structures with C and five with O impurity have four unpaired electrons, while the number of unpaired electrons in the clusters HNi5 varies between 3 and 7. As a rough trend, the ionization potentials and electron affinities of the clusters with impurity atoms decrease with the coordination number of the impurity. However, the position of the impurity and the shape of the metal moiety also affect the results. Coordination of an impurity atom leads to a partial oxidation of the metal atoms.

Controlled assembly of two novel 3D hexad-supporting Keggin-polyoxometalate derivatives: {[Cu(4,4′-bipy)] 3[H nXW 12O 40]}[4,4′-bipy]·2H 2O (X = P, n = 0; X = Si, n = 1)

Two novel three-dimensional (3D) hexad-supporting organic–inorganic hybrid compounds based on the Keggin POMs modified by copper(I) transition metal and N-ligand organic moiety, {[Cu(4,4′-bipy)] 3[PW 12O 40]}[4,4′-bipy]·2H 2O ( 1) and {[Cu(4,4′-bipy)] 3[HSiW 12O 40]}[4,4′-bipy]·2H 2O ( 2) (bipy = bipyridine), have been synthesized under hydrothermal conditions by directly using Keggin POMs as starting materials. The two compounds are isomorphous and crystallized in the space group P 1 ¯ . They represent an important example of the family of polyanion-supported transition-metal solids, in which POMs covalently link six transitional metal-complex fragments. It is also interesting that the 3D structure constructed by hexad-supporting {[Cu(4,4′-bipy)] 3[H n XW 12O 40]} subunits presents 1D channels in which neutral 4,4′-bipy molecules are located. They exhibit similar redox behavior, undergoing two one-electron reversible redox processes.

Neutral and Cationic Cyclopentadienyliron Macromolecules Containing Azo Dyes

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Metallomics—the future of atomic spectroscopy?

Metallomics is defined as the study of metals and metal species, and their interactions, transformations, and functions in biological systems. The full complement of metals and metal moieties (free and bound) is accordingly known as the metallome. The terms are relatively new ones, first coined by R.J.P. Williams of Oxford University and Hiroki Haraguchi of Nagoya University early in the present millennium. Metallomics is a new moniker for the field of bioinorganic chemistry, extending and broadening that discipline much as genomics has done for genetics, and is appositely harmonious with other ''ohmics'' terms like genomics, proteomics, and metabolomics. Metallomics is also distinguished from other terms (e.g. speciation) by consideration of the global role of all metals/metalloids in a system.

Cleavage of double-strand DNA by zinc complexes of dicationic 2,2′-dipyridyl derivatives

Two highly charged zinc complexes, [Zn(L1)3](ClO4)8.4H2O (1) and [Zn(L2)2Br](ClO4)5.H2O (2) (L1 = 5,5'-di(1-(triethylammonio)methyl)-2,2'-dipyridyl and L2= 5,5'-di(1-(tributylammonio)methyl)-2,2'-dipyridyl) were synthesized and structurally characterized by crystallography. The zinc atom in 1 shows a distorted octahedral sphere. Variable-pH NMR studies on 1 demonstrated that the saturated six-coordinated [Zn(L1)3]8+ species can partially change into five-coordinated [Zn(L1)2(H2O)]6+ species in aqueous solution. The zinc atom in 2 shows a distorted trigonal-bipyramidal sphere. The average distance of the coordinated Br atom to the cationic N atom in 2 is ca 5.9 A, which is comparable to that of adjacent phosphodiesters in the DNA (ca. 6 A). Both complexes exhibited high nuclease activities towards cleavage of supercoiled plasmid DNA with the activity being the maximum under physiological pH. The effective DNA cleavage may be attributed to the strong electrostatic interaction of the metal moiety and two positive pendants with phosphodiester groups of nucleic acid.

Dynamic stereochemical rearrangements in chiral organometallic complexes

Organometallic complexes have long been known to display a wide variety of dynamic stereochemical processes. Classic examples of such processes include the exchange of axial and equatorial environments in trigonal bipyramidal complexes, such as Fe(CO)(5), and the migration of the metal moiety round the periphery of the cyclopentadiene ring in eta(1)-bound Cp complexes. The systematic study of fluxional processes is of interest because it can not only help provide a detailed, quantitative 'picture' of the bonding between the metals and ligands involved, but it can also help to rationalise chemical reactivity patterns. The introduction of chirality into organometallic complexes, usually in the form of a non-racemic chiral ligand, has led to an explosion in the importance such species, particularly with regard to their applications in organic functional group transformations. The presence of a chiral centre can also provide an excellent spectroscopic handle on the complex in question, enabling both novel fluxional processes to be observed and new light to be shed on old (unresolved) problems. In this critical review (101 references) the literature on metal-centred fluxional rearrangements in chiral transition and main group organometallic complexes is reviewed, complementing the recent review by Faller (see reference 8).

Induced Super-halogen Behavior of Metal Moieties in Halogen-Doped Clusters: LinI(-) and AlnI(-), n = 13, 1, 2, 3

A comparative density functional theory (DFT) study of a series of neutral and negative-ionic lithium and aluminum clusters doped with iodine atom is presented. The I atom is found to preserve the same position at Li13 with and without the negative charge and Li13 to vary its shape from prolate to oblate with changing spin state of Li13I. Both the Mulliken and natural charges are considered, the natural-charge separation between the metal and halogen moieties being generally much larger (except for Al13I-). In LinI-, the additional electron is strongly localized on the metal moiety starting from n = 1, even though the electron affinity of Lin is much smaller than that of I. Such a super-halogen behavior of Lin is induced by highly electronegative iodine making the two components charged in LinI and leading to a charge-dipole interaction with the additional electron. In AlnI-, similar factors result in Aln being more negative than I already for n = 3, even though the electron affinity of I is higher, the effect escalating for n = 13.

One-Dimensional Coordination Polymers of Dihydrobis(1,2,4-triazol-1-yl)borate Ruthenium(II) Complex

Increasing interest in coordination and organometallic polymers lies in the various intriguing properties of welldesigned inorganic polymer materials. A variety of attempts have been made to synthesize multidentate ligands which can bridge various metal centers. Ambidentate poly(triazolyl)borate ligands [HnB(tz)4-n] − (n = 1 and 2, tz = 1,2,4triazol-1-yl) are good candidates for multidimensional network topologies. It was revealed that both the exodentate (4-position) and endodentate (2-position) nitrogen atoms of the triazolyl rings have comparable electron density to coordinate competitively to metal centers from the theoretical calculation and the N NMR study. It was frequently observed that the poly(triazolyl)borate ligands induce metal ions to form multidimensional coordination polymers through the coordinations of exodentate N atoms whose electron density is higher than the endodentate N atoms. However, in the case of [HB(tz)3] −, tridentate chelated monomers M[η-HB(tz)3]2 (M = Fe, Co, Cu and Zn) are exclusively isolated, and these results are explained by a combination of chelate and kinetic effect. Discrete Ag and Cu complexes bearing a bidentate dihydrobis(1,2,4triazolyl)borate through endodentate coordination such as Cu(L)n[η-H2B(tz)2] (L = aryl phosphines, n = 1 or 2), Ag(L)2[η-H2B(tz)2] (L = aryl phosphines), Ag(dppf)[ηH2B(tz)2] (dppf = 1,10-bis(diphenylphosphino)ferrocene) and their polymeric derivatives were recently reported. In these cases, however, the dihydrobis(1,2,4-triazolyl)borate ligands coordinate to the same type of ions to constitute 1D homometallic polymer networks. In order to develop efficient heterometallic polymeric systems whose physicochemical properties can be systematically tuned, we are pursuing to prepare discrete mononuclear complexes bearing anionic dihydrobis(1,2,4-triazolyl)borate ligands through endodentate coordinations instead of exodentate coordinations. Discrete complexes having a ligand (or ligands) through a bidentate coordination of the two endodentate N atoms could potentially serve as metalloligands for the engineering of 1D modular structure through additional coordinations of the exodentate N atoms to two other transition metal moieties. Recently we were able to prepare discrete mononuclear Fe[HB(tz)3]2·ClO4 and Ag(L)(PPh3) (L = hydrotris(3,5-dimethyl-4-(4-pyridyl)pyrazolyl)borate) to use them as building blocks for novel 3D or 2D functional networks. On the other hand, the reaction between Mn(TPP)·ClO4 and K[H2B(tz)2] only afforded a discrete mononuclear Mn(TPP)(H2O)[η-H2B(tz)2] instead of 1D polymeric structures because of a steric bulk of TPP ligand (TPP is 5,10,15,20-tetraphenylporphine). Here we report a new metalloligand having a dihydrobis(1,2,4-triazolyl)borate, RuH(CO)(PPh3)2[η-H2B(tz)2] (1) and its successful applications to 1D supramolecular systems through self-assembly. Because 1 might have catalytic activities for the hydrogenation of ketones and aldehydes under hydrogen atmosphere, the 1D polymers of 1 could be used as recyclable heterogeneous catalysts. The compound 1 was obtained in good yield from the reaction of RuHCl(CO)(PPh3)3 10 with K[H2B(tz)2] 2 (Figure 1). The compound 1 was fully characterized by H and P{H} NMR, IR, and elemental analysis. A triplet resonance signal of the hydride ligand from H NMR and a singlet peak of two P atoms from P{H} NMR clearly indicate that the proposed structure of 1 which is an ideal geometry as a metalloligand. The entire coordination environment is same to the crystallographically characterized RuH(CO)[P(p-Tolyl)3]2[η-H2B(tz)2] and RuH(CO)(AsPh3)2[η-H2B(pz)2] (pz is pyrazol-1-yl). Unlike other insoluble dihydrobis(triazolyl)borate derivatives, the monomer 1 shows a good solubility in halogenated hydrocarbon solvents. The reactions of 1 with 1 or 2 equivalent Cu(OAc)2·H2O afford well-defined 1D heterometallic polymers {[Cu2(OAc)4][1][Cu(η-OAc)2][1]}n (2) and {[1][Cu2(OAc)4]·(CH2Cl2)2}n (3), respectively, which contain lantern-type dicopper moieties, Cu2(OAc)4. 12 Single crystal x-ray crystallographic studies of 2 and 3 confirm the

Star‐Shaped Molecules Containing Polyalkynyl Groups with Metal Moieties on Benzene and Triphenylene Cores

AbstractA series of star‐shaped molecules with a silyl group and an aromatic core surrounded by extended π conjugative arms has been synthesized by the use of Sonogashira coupling methods. They show excellent fluorescence intensity with high quantum yield. These molecules undergo desilylation in the presence of nBu4NF to give terminal polyalkynyl compounds. By incorporating metal moieties such as palladium, platinum and gold into these compounds, star‐shaped molecules can be obtained. Photophysical properties of these molecules are investigated spectroscopically in solution. These star‐shaped molecules are characterized by IR, NMR (1H, 31P and 13C) spectroscopy, as well as MALDI‐TOF mass spectrometry. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

A fluorescence enhancement-based sensor using glycosylated metalloporphyrin as a recognition element for levamisole assay

A fluorescence sensor based on the supermolecular recognition by glycosylated metalloporphyrin for levamisole (LEV) assay is reported. For the preparation of a LEV-sensitive active material, 5, 10, 15, 20-tetrakis[2-(2, 3, 4, 6-tetraacetyl-beta-D-glucopyranosyl)-1-O-phenyl] porphyrin and its metal complexes were synthesized and used in an optode membrane prepared by including glycosylated metalloporphyrin in chitosan matrice. The immobilized glycosylated metalloporphyrin is shown to be weakly fluorescent as a result of the inhibiting of the electron tansfer by central metal. The fluorescence enhancement of the metalloporphyrin modified optode membrane by LEV is based on the complexation with the central metal moiety of metalloporphyrin and weakening the inhibiting of the electron tansfer for metalloporphyrin. The glycosylated metalloporphyrin/chitosan optode membrane showed excellent selectivity toward LEV with respect to a number of interferents and exhibited stable response. The calibration graph obtained with the proposed sensor was linear over the range of 1.3x10(-5)-3.5x10(-7)ML(-1), with a detection limit of 3.5x10(-7)ML(-1) for LEV. The prepared sensor is applied for the determination of LEV in pharmaceutical preparations and the results agreed with the values obtained by the pharmacopoeia method.

Hydrothermal synthesis, crystal structure and properties of a 3D-framework polyoxometalate assembly: [Ag(4,4′-bipy)](OH){[Ag(4,4′-bipy)] 2[PAgW 12O 40]}·3.5H 2O

A 3D framework assembly based on the Keggin tungstophosphate POM with silver (I) transition metal and N-ligand organic moiety and of formula [Ag(4,4′-bipy)](OH){[Ag(4,4′-bipy)] 2[PAgW 12O 40]}·3.5H 2O ( 1) (bipy=bipyridine) has been synthesized by hydrothermal method and structurally characterized. The crystal of 1 belongs to triclinic, space group P-1, Mr = 3857.27 , a = 10.2741 ( 3 ) Å , b = 11.3723 ( 4 ) Å , c = 14.0161 ( 5 ) Å , α = 85.7249 ( 5 ) ° , β = 72.8795 ( 5 ) ° , γ = 79.9543 ( 5 ) ° , V = 1540.61 ( 9 ) Å 3 , Z = 1 , D calc = 4.158 Mg m - 3 . The final statistics based on F 2 are GOF=1.045, R 1 = 0.0326 and w R 2 = 0.0843 for I > 2 σ ( I ) . X-ray diffraction analysis revealed that the molecular structure of 1 consists of a neutral fragment {[Ag I(4,4′-bipy)] 2[PAg IW VI 12O 40]}, [Ag I(4,4′-bipy)] + cation, hydroxide anion and lattice water molecules. The {[Ag I(4,4′-bipy)] 2[PAg IW VI 12O 40]} subunits are interconnected through Ag(I) with bipyridine ligands, both surface bridging and terminal oxygen atoms of polyoxoanions (POMs) to represent a novel three-dimensional (3D) polymer with 1D elliptic channels. Meanwhile, the [Ag I(4,4′-bipy)] + cations are also linked each other to form 1D chains, and embedded in 1D elliptic channels.

Synthesis of norbornenes containing cationic mono‐ and di(cyclopentadienyliron)arene complexes and their ring‐opening metathesis polymerization

AbstractA number of classes of polynorbornenes containing cationic iron moieties within their side chains were prepared via ring‐opening metathesis polymerization with a ruthenium‐based catalyst. The iron‐containing polymers displayed excellent solubility in polar organic solvents. The weight‐average molecular weights of these polymeric materials were estimated to be in the range of 18,000–48,000. Thermogravimetric analysis of these polymers showed two distinct weight losses. The first weight loss was in the range of 204–260 °C and was due to the loss of the metallic moieties, whereas the second weight loss was observed at 368–512 °C and was due to the degradation of the polymer backbone. Cyclic voltammetry studies of the iron‐containing polymers showed that the 18 e− cationic iron centers underwent a reduction to give the neutral 19 e− complexes at half‐wave potential (E1/2) = −1.105 V. Photolysis of the metallated polymers led to the isolation of the norbornene polymers in very good yields. Differential scanning calorimetry studies showed a sharp increase in the glass‐transition temperatures up to 91 °C when rigid aromatic side chains were incorporated into the norbornene polymers. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3053–3070, 2006

Stereoretentive Elimination and Trans-olefination of the Dicationic Dipalladium Moiety [Pd2Ln]2+ Bound on 1,3,5-Trienes

The reaction of [Pd(2)(CH(3)CN)(6)][BF(4)](2) (1) with 1,3,5-hexatriene, 1,6-diphenyl-1,3,5-hexatriene (DPHT), or 2,2,9,9-tetramethyl-3,5,7-decatriene (DBHT) afforded bi-eta(3)-allyldipalladium complexes 3, 4, or 5. The reaction of 1 and DBHT proceeded in a stereospecific (syn) manner when the reaction was carried out in CD(2)Cl(2) under aerobic conditions, while a mixture of two diastereomers was formed under N(2) atmosphere. The two diastereomers (5-E,Z,E-antifacial and 5-E,E,E-antifacial) formed from DBHT were isolated, and the structure of 5-E,Z,E-antifacial, which was kinetically formed from the reaction of 1 and (E,E,E)-DBHT, was determined by X-ray diffraction analysis. Addition of phosphine ligands (PPh(3) or dppm) to the dinuclear adduct 5-E,Z,E-antifacial or 5-E,E,E-antifacial in acetonitrile resulted in the stereospecific (syn) elimination of [Pd(2)(PPh(3))(2)(CH(3)CN)(4)][BF(4)](2) (2) or [Pd(2)(dppm)(2)(CH(3)CN)(2)][BF(4)](2) (6). During the PPh(3)-induced dinuclear elimination, the phosphine adducts 7 that retain bi-eta(3)-allyldipalladium structure were observed initially. The phosphine adduct generated from 5-E,E,E-antifacial was isolated and structurally characterized by X-ray diffraction analysis. The reaction of 1 and DPHT in CH(2)Cl(2) afforded unique dipalladium sandwich compounds [Pd(2)(mu-eta(3):eta(3)-DPHT)(2)][BF(4)](2) (8). Interconversion between the sandwich complexes and half-sandwich complexes occurred in a stereoretentive manner. The structure of the sandwich complex 8-E,Z,E formed from 4-E,E,E-antifacial and (E,Z,E)-DPHT was determined by X-ray diffraction analysis. Transfer of the dipalladium moiety [Pd(2)(CH(3)CN)(4)](2+) from DPHT ligand of 4-E,E,E-antifacial onto DBHT ligand proceeded in a stereoretentive manner. The observed stereoretentive dinuclear process is featured by the pairwise behavior of two palladium atoms sitting on the triene pi-plane. In the dinuclear elimination, the two Pd atoms that are initially in the divalent state and bound on the opposite faces (antifacial) come to the synfacial positions to form a Pd-Pd bond prior to dissociation. These results represent the unique property of conjugated olefin as the multidentate ligands for metal-metal moieties.

Allergenicity and cross‐reactivity of naphthenic acid and its metallic salts in experimental animals

The allergenicity and the cross-reactivity of naphthenic acid (NA) and its metallic salts were evaluated in experimental animals. In the guinea pig maximization test, sensitizing skin reactions were observed with cobalt naphthenate (CoN), zinc naphthenate (ZnN) and NA, but not with copper naphthenate, with CoN being the most potent sensitizer. Animals sensitized with 1 naphthenic compound cross-reacted to the other 3 as well. Furthermore, animals in the CoN-sensitized group reacted to the relevant metallic salt cobalt chloride (CoCl2). A dose-response study using the CoN-sensitized group showed that the concentration of CoCl2 required to elicit a skin reaction of similar extent in comparison with CoN was more than 10 times higher, when skin-reaction scores were compared on the basis of cobalt content. In the local lymph node assay, significant increases in stimulation index values without skin irritation were observed with CoN and ZnN, where the former was more potent than the latter. Although CoN is a reported skin sensitizer, this study showed that skin allergenicity of naphthenic compounds is not restricted solely to CoN. In addition, the results suggest the main antigenic determinant of naphthenic compounds to be the structure of NA, even though metal moieties modulate their allergenicity.

Double-strand DNA cleavage by copper complexes of 2,2′-dipyridyl with electropositive pendants

Two highly charged cationic copper(II) complexes have been synthesized and characterized structurally and spectroscopically: [Cu(L1)2(Br)](ClO4)5 (1) and [Cu(L2)2(Br)](ClO4)5 (2) (L1= 5,5'-di(1-(triethylammonio)methyl)-2,2'-dipyridyl cation and L2= 5,5'-di(1-(tributylammonio)methyl)-2,2'-dipyridyl cation bidentate ligands). X-Ray structures show that Cu(II) ions in both complexes have a trigonal-bipyramidal CuN4Br-configuration. Two nitrogen atoms of the electropositive pendants and coordinated bromine atom basically array in a straight line. Their close distances of N[dot dot dot]Br atoms are 5.772 and 5.594 A, respectively, which is comparable to that of adjacent phosphodiesters in B-form DNA (ca. 6 A). In the absence of reducing agent, supercoiled plasmid DNA cleavage by the complexes has been performed and their hydrolytic mechanisms have been investigated. The pseudo-Michaelis-Menten kinetic parameters (kcat), 4.15 h(-1) for 1, 0.43 h(-1) for 2 and 0.61 h(-1) for [Cu(bipy)(NO3)2], were obtained. This result indicates that 1 exhibits markedly higher nuclease activity than its corresponding analogues. The high ability of DNA cleavage for 1 is attributed to the effective cooperation of the metal moiety and two positive pendants since the array of linear tri-binding sites matches with one of three phosphodiester backbones of nucleic acid.

Synthesis and characterization of some organo-all-tin dendrimers with different peripheral substituents

The synthesis of the first all-tin-dendrimer Sn[(CH 2) 4SnPh 3] 4 ( 2) results from complete hydrostannation of tetra(but-3-enyl)stannane ( 1) with triphenyltin hydride. Selective cleavage of one phenyl group from each dendron of 2 with anhydrous HCl results in Sn[(CH 2) 4Sn(Cl)Ph 2] 4 ( 3), which on treatment with LiAlH 4 yields the corresponding hydride derivative Sn[(CH 2) 4Sn(H)Ph 2] 4 ( 4) containing four reactive Sn–H bonds. The cyclopentadienyl derivative Sn[(CH 2) 4Sn(C 5H 5)Ph 2] 4 ( 5) as well as the transition metal substituted derivatives Sn[(CH 2) 4Sn{Co(CO) 4}Ph 2] 4 ( 6), Sn[(CH 2) 4Sn{Fe(CO) 2C 5H 5}Ph 2] 4 ( 7), and Sn[(CH 2) 4Sn{Mn(CO) 5}Ph 2] 4 ( 8) have been prepared by coupling of 3 with the appropriate Grignard or sodium derivatives of the transition metal moieties. The new compounds were characterized by elemental analyses, IR, 1H-, 13C- and 119Sn NMR spectroscopy and MALDI-TOF mass spectrometry.