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Research demonstrates that chiral bidentate mercury ligands can be prepared by reacting mercury cyanide and bis(trifluoromethyl)phosphane. Data indicate that yield of the compounds is quantitatively significant with 18 valence electron complexes exhibiting thermal stability.

Research demonstrates formation of a P--H bond by the reductive coupling of bridging phosphides and terminal hydride ligand during the reaction between platinum clusters and hydride ligands. Data indicate that reaction gives rise to thermally unstable protonated kinetic intermediates.

Crystallographic analysis demonstrates that among the third transition series element gold(III) and its derivatives of 2-(diphenylphosphino)-aniline, the compound gold(III)-N displays unusual reactivity and gold(I)-gold(III) interactions.

Research demonstrates synthesis of polyamine macrocycles incorporating dipyridine units containing different binding moities, a pentaamine chain and a dipyridine moiety. The molecular architecture exhibits two separated binding zones, the macrocyclic cavity, and an external dipyridine unit

X-ray crystallographic, Mossabauer, EPR Raman, and magnetic susceptibility analyses demonstrate that [(THF)(TPP)Mn-N-FePc(H(sub)2O)](I(sub)5).2THF is isostructural with the iron-iron complex whereas in [(TPP)Mn(sup)IV-N-Fe(sup)IIIPc, oxidation occurs at one of the two macrocycles. Data indicate that the former compound represents a heteroleptic and heterobimetallic mu-nitrido bridged species.

The synthesis of the macrocycle ion sensor ligand involves seven steps and exhibits temperaure dependency. Results show that the conjugated macrocyclic ligand detects cobalt, nickel, copper, and zinc and fluorescence emission of zinc. Data suggest that the ligand binds metal ions in a tetrahedral coordination geometry.

We have previously reported the experimental rotational barriers about the M-S bonds of 16[e.sup.-] bent metallocene monothiolates [([[eta].sup.5]-[C.sub.5][H.sub.5]).sub.2]Zr(Cl)(SR) (R = C[H.sub.3], C[H.sub.2]C[H.sub.3], CH[(C[H.sub.3]).sub.2], C[(C[H.sub.3]).sub.3]] (1a-d): 32, 33, 35, and 26 kJ [mol.sup.-1], respectively. The ground-state orientation about the Zr-S bonds of 1 that maximizes S(p[pi]) [vector] M(d[pi]) bonding (Cl-Zr-S-R [approximately equal to] 90[degrees]) also maximizes Cp [left and right arrow] R (Cp = [[eta].sup.5]-[C.sub.5][H.sub.5]) steric interaction, whereas the rotational transition-state orientation (Cl-Zr-S-R [approximately equal to] 0[degrees]) is one that minimizes S(p[pi]) [vector] M(d[pi]) bonding and maximizes Cl [left and right arrow] R steric interaction. Deviation from a ground-state orientation that is ideal for S(p[pi]) [vector] M(d[pi]) bonding might be expected as the size of the R-group and Cp [left and right arrow] R steric interaction increases. The present study employs hybrid density function computational methods to reproduce the experimental rotational barriers. The computational rotational barriers decrease in the order 1a (R = C[H.sub.3]) > 1b (R = C[H.sub.2]C[H.sub.3]) > 1c (R = CH[(C[H.sub.3]).sub.2]) at low temperature. However, opposing enthalpic factors reverse this trend at higher temperatures. The aberrant trend (unexpectedly low rotational barrier) that is observed for the 1d (R = C[(C[H.sub.3]).sub.3]) derivative is due to dominant ground-state steric (enthalpic) effects. We conclude the thiolate ligand of 1d is misdirected in the ground-state with respect to the other thiolate derivatives. Key words: misdirected ligands, metallocene, thiolate, structure, bonding, dynamics.

Four complexes of cobalt(II) with lacunary polyoxotungstate ligands, [alpha]-[[P[W.sub.11][O.sub.39]Co([H.sub.2]O)].sup.5-], [alpha]-[[Si[W.sub.11][O.sub.39]Co([H.sub.2]O)].sup.6-], [[alpha].sub.1]-, and [[alpha].sub.2]-[[[P.sub.2][W.sub.17][O.sub.61] Co([H.sub.2]O)].sup.8-] have been examined as potential precursors to substitutionally inert derivatized polytungstates that are stable in aqueous solution at near neutral pH. Replacement of the terminal water ligand by pyridine is readily achieved and the rates of exchange between bound and free pyridine were determined from NMR line widths at temperatures between 24 and 48[degrees]C. Oxidation to the aquacobalt(III) and pyridinecolbalt(III) polytungstates occurs at potentials between +0.64 V (for [[alpha].sub.1]-[[P.sub.2][W.sub.17] [O.sub.61]Co(py)].sup.8-]) and +1.00 V (for [[alpha].sub.2]-[[[P.sub.2] [W.sub.17][O.sub.61]Co([H.sub.2]O)].sup.8-]). The cobalt(III) complexes (with the exception of ([alpha]-[[P[W.sub.11][O.sub.39]Co ([H.sub.2]O)].sup.4-] which undergoes slow reduction by the solvent) were prepared by controlled potential electrolysis and by oxidation with potassium perdisulfate. The rates of pyridine substitution on the aquacobalt(III) complexes were determined and follow the sequence [[alpha].sub.1]-[[[P.sub.2][W.sub.17][O.sub.61]Co([H.sub.2]O)].sup.7-] (~0.5 [M.sup.-1] [S.sup.-1]) [much greater than] [[alpha].sub.2]-[[[P.sub.2][W.sub.17][O.sub.61]Co([H.sub.2]O)].sup.7-] [[alpha]-[[Si[W.sub.11][O.sub.39]Co([H.sub.2]O)].sup.5-]. Cesium salts of [[alpha].sub.1]-[[[P.sub.2][W.sub.17][O.sub.61 [Co.sup.III](L)].sup.7-] (L = pyrazine, 4,4'-bipyridine, isonicotinic acid, and the ethyl ester of isonicotinoylglycylglycine) and the "dumbbell" 2:1 complex with bridging 4,4'-bipyridine were isolated and characterized by cyclic voltammetry and [sup.1]H NMR spectroscopy. Key words: lacunary polyoxotungstates, cobalt, ligand substitution, kinetics, redox.

The transmetalation reaction of the aryllithium compound [[Li(NCN)]. sub.2] (NCN is the monoanionic "pincer" ligand [[[C.sub.6][H.sub.3][(C [H.sub.2]N[Me.sub.2]).sub.2]-2,6].sup.-]) with the cyclometalated arylplatinum complex [PtCl(NCN)] afforded the bisaryl platinum(II) complex [Pt[(NCN).sub.2]] (3) containing one [[eta].sup.3]-N,C, N-terdentate and the other [[eta].sup.1]-C-monodentate-bonded pincer ligand. Spectroscopic analyses on 3 suggest that [[eta].sup.3] to [[eta].sup.1] interconversion of the ligand binding mode (or vice versa) is inhibited. Two independent X-ray structure determinations on crystals of 3 revealed the existence of a rare polymorph containing one and three crystallographically independent molecules, respectively, in the unit cell. A similar transmetalation reaction with lithium and platinum complexes containing heteroleptic NC[N.sup.RR'] ligands (NC[N.sup.RR'] is [[[C.sub.6][H.sub.3](C[H.sub.2]NRR')-2,6].sup.-] with R = R' = Me or R = Me, R' = Et) pointed to the formation of a heterodinuclear cationic bisaryl platinum lithium species as an intermediate of a preequilibrium to the final transmetalation products, involving, rapid transcyclometalation (TCM) reactions. These TCM reactions comprise the exchange of the monoanionic NC[N.sup.RR'] ligands between the platinum(II) and lithium centers. A consequence of the latter properties is that the strong Pt--N bonds in [PtX(NCN)] complexes are considerably weakened by the presence of [Li.sup.+] cations. Key words: transmetalation, transcyclometalation (TCM), platinum, bisaryl complex, polymorphism.

A series of cationic and dicationic Ru-arene complexes with Binap (1a) and MeO-Biphep (1b) have been prepared. [sup.13]C NMR studies are shown to be useful in connection with recognising the 6e-bonding mode of 1a and 1b in the dications [Ru(1a or 1b)([[eta].sup.6]-arene)][(Sb[F.sub. 6]).sub.2] (8, 9). Reaction of 8, 9 with: (a) ([Bu.sub.4]N)([Ph.sub.3] Si[F.sub.2]) leads to a cyclometallated product which arises via P--C bond breaking and P--F bond making; (b) methanol provides a straightforward synthesis of the corresponding hydrides. [sup.13]C NMR p-cymene chemical shifts are reported. Key words: P--C bond cleavage, 6e donors, cyclometallation, hydrides, [sup.13]C NMR.

The trans-[RuS[O.sub.4][(N[H.sub.3]).sub.4](L)]Cl complexes, (L = nicotinamide (nia), L-histidine (L-hist), 4-picoline (4-pic), 4-chloropyridine (4-Clpy), isonicotinamide (isn), pyrazine (pyz), 4-aminopyridine (4-N[H.sub.2]py), 4-cyanopyridine (4-CNpy), pyridine (py), imidazole (Him), and water ([H.sub.2]O)), were characterized by elemental analysis cyclic voltammetry, UV-vis, IR, and electron paramagnetic resonance spectroscopies. From the four v (S[O.sup.2-.sub. 4]) observed only [v.sub.3] and [v.sub.4] split in two bands each for the sulfate unidentate coordination. The values of [DELTA]/[xi] parameters, extracted from g values, allow us to write the following order of increasing [pi]-donation ability: pyz < (py, 4-CNpy, 4-Clpy. 4-pic, isn, nia) < Him < L-hist < 4-N[H.sub.2]py. The intense absorption in the 317-347 nm ([epsilon] ~ 2.3-5.6 x [10.sup.3] [M.sup.-1] [cm.sup.-1]) region was tentatively assigned to sulfate-to-metal charge transfer (LMCT) and the absorption in the range of 230-270 nm ([epsilon] ~ 2 - 6 x [10.sup.3] [M.sup.-1] [cm.sup.-]) assigned to an internal (IL) [pi]-[[pi].sup.*] transition in the heterocyclic ligands. The rate for the sulfate aquation in trans-[[RuS[O.sub.4][(N[H.sub.3]).sub.4]L].sup.0] complexes was evaluated through chronopotentiometric measurements and are in the 2.6 [s.sup.-1] (chloropyridine) to 20 [s.sup.-1] (pyrazine) range. The S[O.sup.2-.sub.4] is aquated in trans-[[Ru.sup.III]S[O.sub.4][(N [H.sub.3]).sub.4](4-pic)]Cl at the specific rate constant of (1.4 [+ or -] 0.4) x [10.sup.-5] [s.sup.-1], which is very much slower than in trans-[[Ru.sup.II]S[O.sub.4][(N[H.sub.3]).sub.4](4-pic)] (5.4 [s.sup.-1]). The X-ray crystal structure data show that the Ru--Cl (2.3444(9) [Angstrom]) and Ru--N[H.sub.3] (2.100(2) [Angstrom]) mean distances in trans-[RuCl[(N[H.sub.3]).sub.4](4-pic)][Cl.sub.2]* [H.sub.2]O are similar to the ones observed in other tetraammineruthenium(III) complexes. Key words: ruthenium, sulfate, ammines.

The synthesis and characterization of complexes [[(P.sup.[intersection]]P).sub.2]Rh][hfacac] (P[intersection]]P = chelating bidentate phosphine ligand [R.sub.2]P[(C[H.sub.2]).sub.n] P[R.sub.2] (2a-g), hfacac = hexafluoroacetylacetonate anion) (4) is reported. The molecular structures of 4a (R = Ph, n = 1) and 4f (R = Cy, n = 2) in the solid state were determined by single-crystal X-ray diffraction. The complexes crystallize in the monoclinic space groups C2/c (No. 15) and P[2.sub.1]/n (No. 14), respectively. No coordinative interaction between the rhodium center of the cation [[(P.sup.[intersection]]P).sub.2])Rh].sup.+] (4[a.sup.+], 4[f.sup.+]) and the hfacac anion is evident in either cases. In the crystal structure of 4a, hydrogen bonds between the oxygen atoms of the hfacac anion and methylene protons of the C[H.sub.2] bridges of the phosphine ligand lead to highly symmetric chains of regularly alternating cations and anions. The coordination geometry around the rhodium center in 4[a.sup.+] is ideally square-planar, whereas 4[f.sup.+] is significantly distorted towards a tetrahedron with an angle between the two [P.sub.2]Rh moieties of 18.6[degrees]. The cation 4[b.sup.+] (R = Cy, n = 1) was investigated in form of the tetrafluoroborate salt for comparison. The compound [[{[Cy.sub.]P(C[H.sub.2])P[Cy.sub.]}.sub.2]Rh] [B[F.sub.4]] crystallizes as a THF solvate (4b') in the triclinic space group P [bar]1 (No. 2) containing ideally square-planar [[(P.sup.[intersection]]P).sub.2])Rh].sup.+] cations. Key words: rhodium, chelating ligands, coordination modes, 1,3-diketonates, phosphorus ligands.

Reaction enthalpies of (COD)Ru[(allyl).sub.2] (COD = [[eta].sup.4]-1,5-cyclooctadiene; allyl = 2-methylpropenyl) with a series of bidentate phosphines (dppm, dppf, dppe, dppb, dppp, depe, dmpe) have been measured by anaerobic solution calorimetry. The relative stability of the resulting complexes is strongly influenced by the electronic donor properties of the bidentate phosphine ligand. Reactions involving ligands that are better [sigma] donors result in higher enthalpy values and, therefore, more thermodynamically stable complexes. Additionally, the synthesis and characterization of two new ruthenium allyl complexes Ru[(allyl).sub.2](dppf) (3) and Ru[(allyl).sub.2](depe) (8) and the X-ray crystal structure of 3 are reported. Key words: ruthenium, allyl, solution calorimetry, thermodynamics, X-ray structure.

The coordination chemistry of phenoxide ligands, such as [C.sub.6] [H.sub.5][O.sup.-], 4-(C[H.sub.3])-[C.sub.6][H.sub.4][O.sup.-], 3,5-[(C[H.sub.3]).sub.2]-[C.sub.6][H.sub.3][O.sup.-], 2,6-[(tert-butyl).sub.2]-[C.sub.6][H.sub.3][O.sup.-]-, 2,6-[(C[H.sub.3]).sub.2]-[C.sub.6][H.sub.3]0-, to Mn(II) has been investigated because of the possible implication of Mn(II)-phenoxide complexes as intermediates in the phenylphosphate carboxylase enzyme, a protein which catalyses the selective carboxylation of phenylphosphate to 4-OH-benzoic acid using C[O.sub.2]. We report here the synthesis and characterization of [[CpMn([[eta].sup.5]-OAr)(THF)].sub.2] (ArO = [C.sub.6][H.sub.5] [O.sup.-], 4-(C[H.sub.3])-[C.sub.6][H.sub.4][O.sup.-], 3,5-[(C[H.sub.3]).sub.2]-[C.sub.6][H.sub.3][O.sup.-], 2,6-[(C[H.sub.3]).sub.2]-[C.sub.6][H.sub.3][O.sup.-]) and [CpMn([[eta].sup.5]-ArO)] (ArO = 2,6-[(tert-butyl).sub.2]-[C.sub.6] [H.sub.3][O.sup.-] and 2,6-[(CH.sub.3]).sub.2]-[C.sub.6][H.sub.3] [O.sup.-]) complexes, the first examples of mixed-sandwich complexes with Cp and phenate as [pi]-ligands. The latter bear the 2,6-substituted phenoxide [pi]-coordinated to the [[Mn(Cp)].sup.+] moiety. The different mode of bonding of the phenoxide ligands to Mn(II), substantiated by [sup.1]H NMR and electron spin resonance (ESR) spectroscopy, is controlled by the steric hindrance of substituents at the 2- and 6-position. The reactivity of the [pi]-bonded ligand towards C[O.sub.2] is also reported as a quite rare example of nucleophilic attack at the cumulene by the ring-carbon of the phenoxide, which is driven by electron density localization at the 4-position generated upon [pi]-coordination to Mn(II). Key words: Mn(II)-complexes, phenoxide ligands, [sup.1]H NMR spectroscopy, ESR spectroscopy, reaction with carbon dioxide.

The synthesis of the cationic hydridotris(pyrazolyl)borate iridium(III) complex [Tp(P[Me.sub.3])IrMe(ClC[H.sub.2]Cl)][[BAr.sub.f]] (2-C[H.sub.2][Cl.sub.2]) is reported. Spectroscopic characterization of 2-C[H.sub.2][Cl.sub.2] in C[H.sub.2][Cl.sub.2] solution indicates that exchange of bound C[H.sub.2][Cl.sub.2] with free C[H.sub.2][Cl.sub.2] is slow on the NMR time scale. Under 50 atm (1 atm = 101.325 kPa) of [N.sub.2], the C[H.sub.2][Cl.sub.2] in 2-C[H.sub.2][Cl.sub.2] is displaced by [N.sub.2] to yield [Tp(P[Me.sub.3])IrMe(N2)][[BAr.sub.f]] (2-[N.sub.2]). The stronger nucleophile C[H.sub.3]CN reacts rapidly with 2-C[H.sub.2][Cl.sub.2] to produce [Tp(PMe3)IrMe(NCCH3)][BArf] (4). A kinetic study was performed on C[H.sub.2][C1.sub.2] substitution in 2-C[H.sub.2][Cl.sub.2] by C[D.sub.3]CN. The data are most consistent with dissociative loss of C[H.sub.2][C1.sub.2] to generate the unsaturated species ([Tp(P[Me.sub.3])IrMe][[BAr.sub.f]]) which then reacts with C[D.sub.3]CN to generate [Tp(P[Me.sub.3]) IrMe(NCC[D.sub.3])] [[BAr.sub.f]]. Further evidence for a dissociative mechanism was obtained by comparison of ligand substitution rates for the Tp complexes with the analogous [Tp.sup.Me2] complexes ([Tp.sup.Me2] = hydridotris(3,5-dimethylpyrazolyl)borate). The relevance of these substitution experiments to C--H activation by cationic iridium(III) complexes is discussed. Key words: iridium, hydridotris(pyrazolyl)borate, methylene chloride and dinitrogen complexes, dissociative substitution.

The chelate complex [Ru[Cl.sub.2][{[kappa].sup.2](P,O)-i-[Pr.sub.2] PC[H.sub.2]C[H.sub.2]OMe}.sub.2]] (1) reacted, in the presence of C[F.sub.3]S[O.sub.3]Ag, with 1 equiv of [C.sub.6][H.sub.4]([C [equivalent to] CH).sub.2.sup.-p] (4) to afford the mononuclear vinylidene compound [RuCl(C=CH[C.sub.6][H.sub.4.sup.-p-]C [equivalent to]CH) {[[kappa].sup.2](P,O)-i-[Pr.sub.2]PC[H.sub.2] C[H.sub.2]OMe}.sub.2]](C[F.sub.3]S[O.sub.3] (3). From 1 and 0.5 equiv of 4, the binuclear bis(vinylidene) complex [RuCl{[[kappa].sup.2] (P,O)-i-[Pr.sub.2]PC[H.sub.2]C[H.sub.2]OMe}.sub.2]](C=CH[C.sub.6] [H.sub.4.sup.-p-]CH=C)RuCl{[[kappa].sup.2](P,O)-i-[Pr.sub.2]PC[H.sub.2] C[H.sub.2]O[Me.}.sub.2]((C=H[C.sub.6][H.sub.4.sup.-p]CH=C) RuCl{[[kappa].sup.2](P,O)-i-[Pr.sub.2]PC[H.sub.2]C[H.sub.2]OMe}.sub.2]] ((C[F.sub.3]S[O.sub.3]).sub.2]] (6) was obtained. The related compound [[RuCl{[[kappa].sup.2](P,O)-i-[Pr.sub.2]PC[H.sub.2] C[H.sub.2]OMe}.sub.2]] (C=CH[C.sub.6][H.sub.4.sup.-m]CH=C)RuCl {[[kappa].sup.2](P,O)-i-[Pr.sub.2]PC[H.sub.2]C[H.sub.2]OMe}.sub.2]] (C[F.sub.3]S[O.sub.3]).sub.2] (7) was prepared from 1, 0.5 equiv of [[C.sub.6][H.sub.4](C [equivalent to] CH).sub.2.sup.-m]] (5), and silver triflate. The reaction of 2 or 3 with [[RhCl(P-i-[Pr.sub.3]).sub.2]2]] (8) in the molar ratio of 2:1 yields, by addition of the 14-electron fragment [[RhCl(P-i-[Pr.sub.3]).sub.2]2]] to the uncoordinated C--C triple bond, the heterobinuclear complexes [RuCl{[[kappa].sup.2](P,O)-i-[Pr.sub.2] PC[H.sub.2]C[H.sub.2]OMe}.sub.2](C=CH[C.sub.6][H.sub.4.sup.-m/p] C [equivalent to] CH)[[RhCl(P-i-[Pr.sub.3]).sub.2]2]][(C[F.sub.3] S[O.sub.3]) (9, 10) which slowly rearrange at room temperature to give the bis(vinylidene) isomers [RuCl{[[kappa].sup.2](P,O)-i-[Pr.sub.2] PC[H.sub.2]C[H.sub.2]OMe}.sub.2](C=CH[C.sub.6][H.sub.4.sup.-m/p]CH=C) RuCl(P-i-[Pr.sub.3]).sub.2]2](C[F.sub.3]S[O.sub.3]) (11, 12). Key words: ruthenium, rhodium, vinylidene complexes, alkyne complexes, phosphine complexes.

This review focuses on the catalytic asymmetric dialkylzinc addition to aldehydes to obtain ligands of diverse structures and catalysts with high enantioselectivity for the organozinc addition to carbonyl compounds. Discussion on the catalytic asymmetric reactions of alkyl, aryl, alkenyl, and alkynylzincs with aldehydes and chiral catalysts is presented.

The aromatic group substituents of the two silanediols influence the hydrogen bonding with diol molecules. The N-bonded silanediol forms two types of hexameric clusters in the solid state, whereas the other silanediol exist as cyclic hydrogen-bonded dimers, transforming into polymeric structure by further intermolecular hydrogen bonding.

Research demonstrates the synthesis of a tetradentate diamide ligand containing pendant benzimidazole groups. Data indicate that the reduction of copper(II) complex to copper(I) complex is accompanied with simultaneous oxidation of quinol and catechol, mimicking met-tyrosinase activity of catecholase enzymes.

Research describes the synthesis and reactivity of the C(sub)3 symmetric ligands, the phosphite derivatives of the tripodal-linked phenolic compounds and their arsenite derivatives. Data indicate that the metal complexes are C(sub)3 symmetric, rigid, and bulky and exhibit a very high stability for hydrolysis and oxidation.

Results reveal that the allylic substitution with P-chiral diphosphine ligands exhibiting C(sub)2-symmetry induces enantioselectivities to the tune of 99% ee. Data indicate that the reaction efficiency depends on the substrate structure, nucleophile type, backbone constitution, and the pattern of substitution of the chiral phosphorus donors.

Research discusses metal-radical strategy for preparing dinuclear nickel(II), chromium(III), and copper(II) complexes employing bis(semiquinone) ligand. Data reveal that the synthesized complexes exhibit septet, quintet, and quintet electronic states, respectively.

Research demonstrates the redox reactions of bis(hydroxoruthenium) complexes in relation to the acid-base equilibrium reactions of the hydroxo groups. Results include the catalytic activity between these complexes and bipyridine analogue complexes and the role of quinone of the bis(hydroxoruthenium) complexes in the oxidation of water.

Research discusses coordination chemistry aspects of Te(IV) compounds obtained from NMR spectroscopic studies. Data demonstrate a rapid exchange of -Cl and -OR ligands and the mechanism for the exchange of -OR groups between Te(IV) centers.

Research demonstrates that the alpha-diimine enhances the photostability of the coordination and organometallic compounds. Data indicate that at absolute temperature of 80, the photostability extends from four microseconds to one millisecond due to an inefficient decay to the sigma-bond-to-ligand charge transfer state.

Research discusses the cyano-bridged mixed-valence compounds in terms of their electron coupling in the supramolecular donor/acceptor pair facilitated by the acidic nature of the cyanide ligands. Data demonstrate that the electronic spectra of the compounds reveal a single intervalent absorption band for every nondegenerate iron transition.

Results show that the reactivity of copper(I) complexes towards oxygen and nitric oxide is mediated by tris(pyrazolyl)hydro- borate ligands. Data point out that modification of the ligands in which the cycloaddition of CH(sub)3CN to a pyrazolyl unit ryields a heterocyclic ring system.

Research discusses structural aspects of charge-transfer (CT) compounds of transition metal complexes that exhibit electrochemical reduction reactions. Data indicate that the redox state of the coordinated ligands determines the mixed-valence state of the chromium module of the CT compounds.

Research presents the reactions and structural configurations of the reduction of heteroleptic lanthanide compounds by lanthanide metals. Majority of the compounds exhibit nearly identical unit cell volumes suggesting that they may be isomorphous with lanthanide ions bridged by PhnnPh ligands.

Results show that the trigonal bipyramidal technetium(III)mixed-ligand complexes are diamagnetic thereby facilitating structural analysis by NMR. Data indicate that the electron density at the metal center is increased with geometry changing from square pyramidal to trigonal bipyramidal.

Research demonstrates a methodology for the synthesis of polyheterocyclic alcohols and derivatives. Data reveal that the cyclobutane consists of a longest bond as determined by X-ray crystal structural analysis.

The accurate calculation of the energetics of electrostatistically driven binding of amino acid residues to other amino acids or to synthetic molecules is significant in many physiological and technological processes. It is concluded that commonly used continuum methods are inadequate for describing fine differences in the binding of similarly charged ligands to a target protein.

Results describe the syntheses and structure of two three-dimensional manganese(II) coordination polymers using m-pyridinecarboxylate ligands. Data show that both polymers are topologically similar and antiferromagnetic in nature as revealed by X-ray diffraction and magnetic studies.

Results demonstrate the formation of a 2:1 coordination complex between a trifunctional ligand and plutonium(IV) and its structural determination using single-crystal X-ray diffraction technique. Data indicate that both solution and solid forms of the complex exhibit the same plutonium(IV) chromophore.

Research describes the physico-chemical characteristics of heterocyclic monodentate nitrogen ligands in relation to ruthenium complexes and their fluxionl behaviors in solution by using (sup)1H nuclear magnetic resonance spectroscopy. Data indicate that different ruthenium complexes have different fluxional behaviors in solution and the smallest ligand exhibits the fastest exchange kinetics.

Research discusses the synthesis of an unique trinuclear ligand system, H(sub)4(PDK) in a multistep protocol using two molecules of Kemp's triacid and one molecule of porphyrin as building blocks. The ligand system is used against porphyrin-based diamine bis(Kemp's triacid)-imide. Data indicate hydrogen bonding interactions between Kemp's triacid units occur.

Application of sulfonamide/Schiff base ligands to asymmetric catalysis is explored as shown in the catalytic asymmetric cyclopropanation of allylic alcohols. Results indicate that the ligands mediate the cyclopropanation of trans allylic with good yields and enantioselectivity.

Results reveal that the D-mannose and D-allose ligands in the carbohydrate-platinum(IV) complexes exhibit an unusual furanose form. Furthermore, the metal complexation imposes structural constraints on the monosaccharide leading to J-coupling behavior of carbon of the furanose rings.

The syntheses of unique C(sub)2-symmetric chiral bisoxazoline ligands from enantiomerically pure 2-amino alcohols are presented. The Ligands possess only two ortho-substituents at the biphenyl backbone and complex with metal ions. The axis-unfixed biaryl backbone of the ligands contributes to the higher catalytic activity and enantioselectivity of the major complex of the bisoxazoline ligands.

Optically active 2-amino-2'-diphenylphosphino-1,1'-binaphthyls having various functional groups, such as amino, alkoxycarbonylamino, acylamino, mono- and dialkylamino, and sulfonylamino at C2 position were prepared. The key intermediate of the above aminophosphines was 2-carbamoyl-2'-diphenylphosphinyl-1,1'-binaphthyl synthesized from optically active 2-cyano-2'-diphenylphosphinyl-1,1'-binaphthyl. The transformation of the carbamoyl group to an amino group was effected by the Hofmann reaction. Key words: aminophosphine ligand, Hofmann reaction, optically active phosphine ligand.

Research describes the synthesis of N,S-chelates that function as ligands for the iridium-(I)-catalyzed transfer hydrogenation of prochiral ketones. Data indicate that the aminosulfide is the best ligand for controlling asymmetric iridium-catalyzed transfer hydrogenation of prochiral ketones.

Research describes the synthesis and characterization of two new heteroatom-bridged bis(benzo-12-crown-4ehter)s and diselenides together with their silver-selectivities behavior and structure-selectivity relationship in the silver-ion-selective electrodes in terms of steric and electronic effects of the nitro groups.

The synthesis of optically pure and active 1,2-bis(pentafluorophenyl)ethane-1,2-diols (1R,2R) and (1S,2S) using lipase-catalyzed transesterification derived cyanohydrin intermediates (R)- and (S)- is described. X-ray structural data of the naproxen ester of the intermediates indicate that they exhibit well-ordered packing structure with pentafluorophenyl and the 6-methoxynaphthyl groups exhibiting face-to-face stacking interactions and end-to-end parallel contacts.

Research describes the synthesis of porphyrazinediols, their conversion into solitaire complexes, and chemical oxidation of the polydentate noninnocent macrocycles. Results demonstrate that porphyrazinediols are a novel class of redox-active ligands whose diol chelating group is directly attached at the beta-positions of the macrocycle.

Research has been conducted on the preparation of the phospholanes and the corresponding diastereomers. The displacement of the dimesylate with dilithium-phosphide reagents is discussed.

Results demonstrate structure-reactivity relationships of zinc complexes with two heteroscorpionate ligands and influence of the latter in the activity of zinc metalloproteins.

Structural analysis of the two new cross-bridged tetraazamacrocyclic complexes reveals that the ligand skeletons within them are identical. Data further show that the complexes have kinetic stability under harsh conditions.

Thionitrosyl complexes, together with -SCN and N2, were produced from the reaction between [OsVI(tpm)(Cl)2(N)](PF6) (tpm = tris(1-pyrazolyl)methane) (1) or OsVI(Tp)(Cl)2(N) (Tp = hydrotris(1-pyrazolyl)borate anion) (2) and CS2 + N3- in acetone. Analysis shows that such complexes exhibit versatile and extensive redox chemistry in [OsII(tpm)(Cl)2(NS)]+. The ability of the NS group to move a S atom to PPh3 was revealed by the reaction between [OsII(tpm)(Cl)(NS)]+ (3b) and PPh3(eq 3).

Two major structural distortions were identified which influence the photophysical properties of [Cu(NN)2]+ complexes. The first distortion, which enhances the physical properties of such complexes, entails the relative orientation of the two phenanthroline ligands. It happens due to copper(II) ion's preferences for a square-planar coordination environment. The second distortion, meanwhile, entails a single ligand which can be reduced by using substituents that increase the pie-delocalization.

Sulfur atom situated as part of a flexible ring system exhibited stronger coordination with cyclic phosphates and cyclic phosphites than the oxygen atom of a sulfone group. The comparative donor action observed were found to be unrelated with the electronegativity of the ligands. Experimental results illustrates donor action's potential importance in nearby amino acid residues which are found in the active sites of phosphoryl transfer enzymes.