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The bicyclic hexaamine "cage" ligand Me(8)tricosaneN(6) (1,5,5,9,13,13,20,20-octamethyl-3,7,11,15,18,22-hexaazabicyclo[7.7.7]tricosane) is capable of encapsulating octahedral metal ions, yet its expanded cavity allows the complexed metal to adopt a variety of geometries comprising either hexadentate or pentadentate coordination of the ligand. When complexed to Cu(II) the lability of the metal results in a dynamic equilibrium in solution between hexadentate- and pentadentate-coordinated complexes of Me(8)tricosaneN(6). Both [Cu(Me(8)tricosaneN(6))](ClO(4))(2) (6-coordinate) and [Cu(Me(8)tricosaneN(6))](S(2)O(6)) (5-coordinate) have been characterized structurally. In weak acid (pH 1) a singly protonated complex [Cu(HMe(8)tricosaneN(6))](3+) has been isolated that finds the ligand binding as a pentadentate with the uncoordinated amine being protonated. vis-NIR and electron paramagnetic resonance (EPR) spectroscopy show that the predominant solution structure of [Cu(Me(8)tricosaneN(6))](2+) at neutral pH comprises a five-coordinate, square pyramidal complex. Cyclic voltammetry of the square pyramidal [Cu(Me(8)tricosaneN(6))](2+) complex reveals a reversible Cu(II/I) couple. All of these structural, spectroscopic, and electrochemical features contrast with the smaller cavity and well studied "sarcophagine" (sar, 3,6,10,13,16,19-hexaazabicyclo[6.6.6]eicosane) Cu(II) complexes which are invariably hexadentate coordinated in neutral solution and cannot stabilize a Cu(I) form.

The racemic C3 hexadentate cage complex, [Pt(Me5-tricosatrieneN6)]Cl4 (1,5,9,13,20-pentamethyl-3,7,11,15,18,22-hexaazabicyclo[7.7.7]tricosa-3,14,18-triene)platinum(IV) tetrachloride), was synthesised stereospecifically and regiospecifically from a reaction of the bis-triamine template [Pt(tame)2]Cl4 (bis[1,1,1-tris(aminomethyl)ethane]platinum(IV) tetrachloride) with formaldehyde and then propanal, in acetonitrile under basic conditions. Largely, one racemic diastereoisomer was obtained in a surprisingly high yield (∼ 50%), even though the molecule has seven chiral centres. The origins of the stereoselective synthesis are addressed. The crystal structure of [Pt(Me5-tricosatrieneN6)](ZnCl4)1.5Cl·2H2O showed that all three imines were attached to one tame fragment with a chiral amine site (ΛSSS, ΔRRR) and a chiral methine carbon site (ΛRRR, ΔSSS) on each ligand strand. The PtN64+ moiety had a slightly distorted octahedral configuration with the two types of Pt–N bonds related to the imine and the amine donors, 2.050(7) and 2.072(6) A, respectively. Treatment with sodium borohydride (15 s, 20 °C) at pH ∼ 12.5 reduced the imine groups, but not the Pt(IV) ion, producing a C3 saturated ligand complex [Pt(Me5-tricosaneN6)]Cl4 ((1,5,9,13,20-pentamethyl-3,7,11,15,18,22-hexaazabicyclo[7.7.7]tricosane)platinum(IV)tetrachloride). X-ray crystallographic analysis showed that the average Pt–N bond distance in the cation increased upon imine reduction to 2.10 (av) A. The cyclic voltammograms of the two cage complexes displayed irreversible two-electron reduction waves in aqueous media and a ∼ 0.3 V shift to more positive potentials compared to that of the smaller cavity sar (3,6,10,13,16,19-hexaazabicyclo[6.6.6]icosane) analogue. After reduction, net dissociation of one strand of the cage was also evident, to give unstable square planar Pt(II) macrocyclic products.

Rac.-p-(tris(2-aminoethyl)amine-2-(nitromethyl)ornithine)cobalt(III) trichloride (2d) was obtained by a simple three-step procedure from ornithine using cobalt template chemistry. p-(Tris(2-aminoethyl)amine-ornithine)cobalt(III) trichloride (2a) was obtained from tris(2-aminoethyl)amine (tren) and (S)-ornithine in the presence of cobalt(II), which was oxidised to cobalt(III) during the reaction. Complex 2a was selectively oxidised with thionyl chloride–dimethyl formamide to p-(tris(2-aminoethyl)amine-dehydro-ornithine)cobalt(III) trichloride 2b. Complex 2c, in which reaction of thionyl chloride–dimethyl formamide has also occurred at the δ-amine of ornithine, was obtained at longer reaction times. Complex 2b reacted with nitromethane anion to give rac.-p-(tris(2-aminoethyl)amino-2-(nitromethyl)ornithine)cobalt(III) trichloride (2d). The amino acid rac.-2-(nitromethyl)ornithine (1b) was released by reducing complex 2d with aqueous ammonium sulfide. Complex 2d was expected to release 2-(nitromethyl)ornithine (1b) in hypoxic cells, where the amino acid could act as an inhibitor of ornithine decarboxylase. Preliminary data indicated that complex 2d was weakly cytotoxic in one cell type studied.

The Hg2+aq- and HgCl+aq-assisted aquations of [PtCl4]2- (1), [PtCl3(H2O)]- (2), cis-[PtCl2(H2O)2] (3), trans-[PtCl2(H2O)2] (4), [PtCl(H2O)3]+ (5), [PtCl3Me2SO]- (6), trans-[PtCl2(H2O)Me2SO] (7), cis-[PtCl(H2O)2Me2SO]+ (8), trans-[PtCl(H2O)2M32SO]+ (9), trans-[PtCl2(NH3)2] (10), and cis-[PtCl2(NH3)2] (11) have been studied at 25.0 degrees C in a 1.00 M HClO4 medium buffered with chloride, using stopped-flow and conventional spectrophotometry. Saturation kinetics and instantaneous, large UV/vis spectral changes on mixing solutions of platinum complex and mercury are ascribed to formation of transient adducts between Hg2+ and several of the platinum complexes. Depending on the limiting rate constants, these adducts are observed for a few milliseconds to a few minutes. Thermodynamic and kinetics data together with the UV/vis spectral changes and DFT calculations indicate that their structures are characterized by axial coordination of Hg to Pt with remarkably short metal-metal bonds. Stability constants for the Hg2+ adducts with complexes 1-6, 10, and 11 are (2.1 +/- 0.4) x 10(4), (8 +/- 1) x 10(2), 94 +/- 6, 13 +/- 2, 5 +/- 2, 60 +/- 6, 387 +/- 2, and 190 +/- 3 M-1, respectively, whereas adduct formation with the sulfoxide complexes 7-9 is too weak to be observed. For analogous platinum(II) complexes, the stabilities of the Pt-Hg adducts increase in the order sulfoxide << aqua < ammine complex, reflecting a sensitivity to the pi-acid strength of the Pt ligands. Rate constants for chloride transfer from HgCl+ and HgCl2 to complexes 1-11 have been determined. Second-order rate constants for activation by Hg2+ are practically the same as those for activation by HgCl+ for each of the platinum complexes studied, yet resolved contributions for Hg2+ and HgCl+ reveal that the latter does not form dinuclear adducts of any significant stability. The overall experimental evidence is consistent with a mechanism in which the accumulated Pt(II)-Hg2+ adducts are not reactive intermediates along the reaction coordinate. The aquation process occurs via weaker Pt-Cl-Hg or Pt-Cl-HgCl bridged complexes.

The syntheses of a cobalt(III) complex, 2, containing N-(2-pyridylmethyl)urea and of six complexes, 3, containing phenyl-substituted N-2-pyridylmethyl-N'-(X)phenylureas (where X = 4-H, 4-CH(3), 4-Br, 3-Cl, 4-CF(3), and 4-NO(2)), have been accomplished by reaction of [(en)(2)Co(OSO(2)CF(3))(2)](CF(3)SO(3)) with the urea ligands in tetramethylene sulfone. The complexes have been characterized by UV-vis, FTIR, (1)H NMR, and (13)C NMR spectra along with elemental analysis. Also, X-ray crystallographic analysis of 2 confirms that the urea ligand chelates as a bidentate through the pyridyl nitrogen atom and the endo deprotonated, urea nitrogen atom to form a stable five-membered ring. Crystals of the perchlorate salt of 2 were monoclinic, space group P2(1)/c with a = 9.743(1) Å, b = 13.924(3) Å, c = 15.006(4) Å, beta = 97.07(1) degrees, and Z = 4. Reflection data (3454) with I = 3sigma(I) were refined to conventional R factors of 0.037 and 0.051. In acidic solution (0.05-1.00 M HCl at 55 degrees C), the phenyl-substituted complexes undergo hydrolysis to form the bis(ethylenediamine)(2-picolylamine-N,N')cobalt(III) ion, 4, aniline, and CO(2). The hydrolysis kinetics of the phenyl-substituted complexes were studied by UV-vis spectroscopy (I = 1.00 M HCl/LiCl). At 55 degrees C the observed rate constants fit the rate law k(obsd) = kK[H(+)]/(1 + K[H(+)]). It is proposed that the protonated urea eliminates aniline to give a coordinated isocyanate intermediate that hydrolyzes rapidly to the pyridyl methylamine complex and CO(2) via the carbamate complex. Since all of the studies of this kind to date appear to involve the NCO intermediate, it raises the prospect that urease also functions by a similar path and that urease should be tested with NCO(-) as a substrate.

Treatment of the two CoIII-hexaamine complexes [Co(taci)2]3+ and [Co(tmca)2]3+ (taci = 1,3,5-triamino-1,3,5-trideoxy-cis-inositol, tmca = all-cis-2,4,6-trimethoxycyclohexane-1,3,5-triamine) in CH3CN with NEt3 and excess paraformaldehyde gave the corresponding hexamethylideneimino (hmi) derivatives [Co(taci)2-hmi]3+ and [Co(tmca)2-hmi]3+ in excellent yield. Both hexaimines were stable in acidic aqueous solution and were isolated as solid compounds. They were characterized by elemental analyses, 13C NMR, 1H NMR, IR, and visible spectroscopy, mass spectrometry, and single-crystal X-ray analyses. [Co(taci)2-hmi]Cl3·6H2O crystallizes in the monoclinic space group C2/m, C18Cl3CoH42N6O12, Z = 2, a = 13.046(2) A, b = 9.802(2) A, c = 12.332(2) A, β = 118.42(1)°. [Co(tmca)2-hmi](HSO4)3 crystallizes in the monoclinic space group C2/c, C24CoH45N6O18 S3, Z = 4, a = 14.087(3) A, b =15.890(3) A, c = 15.502(3) A, β = 95.27(3)°. Subsequent treatment of [Co(taci)2-hmi]3+ with nitromethane and base resulted in the formation...

The ability of available molecular mechanics programs to calculate structures and relative energies of metal complexes is examined via a comparative study of five different force fields: Molmec, Momec91(H), Momec91(C), Xnviron, and Spartan. The method used for assessing the validity of the force fields showed that four of the force fields were able to reproduce successfully the structures of various Co(III) hexaamine cations determined by X-ray analysis, even when these structures were considerably distorted. In certain cases, the calculated relative steric energies were not reliable. Small variations in force fields parameters sometimes led to large changes in the calculated steric energies, and in some instances, in the order of steric strain for different isomers. The most notable changes occurred when metal-dependent parameters were altered.

The H+- and Cl--assisted dissociation kinetics and the stabilities of the complexes [Hg(sar)](2+) and [Hg((NH2)(2)-sar)](2+) (sar = 3,6,10,13,16,19-hexaazabicyclo[6.6.6]icosane and (NH2)(2)-sar = 1,8-diamino-sar) were determined. The Hg2+ dissociation rates depend on both the proton and the chloride ion concentrations. H+ competes with the metal ion for dissociated amine groups, and Cl- competes with the amine for vacant coordination sites. The rate laws are complicated. For the [Hg(sar)](2+) system (0.1 less than or equal to [H+] less than or equal to 1.0 M, 0.01 less than or equal to [Cl-] less than or equal to 1.0 M, I = 2.0 M (NaO3SCF3), 25.0 degrees C) the observed rate law is upsilon(-Hg2+) = (a + b[Cl-])[H+][Hg(sar)(2+)]/(1 + c[Cl-]), with a = 35(3) M-1 s(-1), b = 2.9(4) x 10(3) M-2 s(-1), and c = 33(5) M-1. For the [Hg((NH3)(2)-sar)](4+) system (0.001 less than or equal to [H+] less than or equal to 1.0 M, 0.01 less than or equal to [Cl-] less than or equal to 1.0 M, I = 1.0 M (LiClO4), 25.0 degrees C) the observed rate law is upsilon(-Hg2+) = (a + b[H+] + c[H+](2))[Cl-][Hg((NH3)(2)-sar)(4+)])/((1 + d[Cl-])(1 + e[H+])), with a = 0.056(6) M-1 s(-1), b = 8(3) M-2 s(-1), c = 5(3) M-3 s(-1), d = 1.3(4) M-1, and e = 1.1(5) x 10(2) M-1. Intimate mechanisms for the dissociation reactions are proposed. Using iodide ion or sar ligand as competing ligands and the reported values for the stabilities of HeI3- and HgI42- the stability constants at 25.0 degrees C were determined for [Hg(sar)](2+) (10(28.1(1)) M-1), [Hg(sar)I](+) (10(29.1(1)) M-2), [Hg((NH2)(2)-sar)I](+) (10(28.5(1)) M-2), and [Hg(cyclam)I](+) (10(30.8(1)) M-2) (cyclam = 1,4,8,11-tetraazacyclotetradecane) with [OH-] = 0.1 M, I = 0.5 M (NaClO4) and for [Hg((NH2)(2)-sar)](2+) (10(26.4(3)) M-1) with [OD-] = 0.1 M, I = 0.1 M (NaOD).

[Fe(tmca)2]3+ and [Co(tmca)2]3+ (tmca = all-cis-2,4,6-trimethoxycyclohexane-1,3,5-triamine) were prepared and characterized by elemental analyses, NMR, and FAB+ mass spectrometry and by spectroscopic methods (UV−vis). Magnetic susceptibility measurements established a low-spin d5 electron configuration for the FeIII hexaamine complex. In aqueous solution, cyclic voltammetry revealed a quasi reversible one electron reduction for both complexes with MIII/MII redox potentials of +0.16 and −0.30 V (vs SHE), respectively. The two compounds [M(tmca)2]Cl3·5H2O·EtOH (C20H58Cl3MN6O12, M = Fe, Co) are isostructural. They both crystallize in the triclinic space group P1, Z = 2. Fe complex: a = 10.338(3) A, b = 13.062(4) A, c = 14.042(4) A, α = 80.20(2)°, β = 72.07(2)°, γ = 69.11(2)°. Co complex: a = 10.307(3) A, b = 13.066(2) A, c = 14.029(2) A, α = 80.14(1)°, β = 72.18(2)°, γ = 69.55(2)°. The ligand tmca is compared with the unsubstituted 1,3,5-triamino-1,3,5-trideoxy-cis-inositol (taci) and the N-methylated 1,3...

This paper describes aspects of the synthesis of cage complexes in relation to their prospects for use in biology. The means of attaching peptides, cholestane, paraffin tails and aromatic residues are outlined. Also, the properties of some of these molecules, especially a new class of detergents, a new polymer able to capture metal ions, the selectivity of the cages for metal ions and the DNA intercalating properties of aromatic residues attached to the cages are discussed.

A study of high- and low-spin cobalt(II) derivatives having hexadentate encapsulated ligands known as ‘sar’ is reported (sar = 3,6,10,13,16,19-hexaazabicyclo(6.6.6)icosane). The chemically prepared derivatives have well defined EPR spectra at 4 K especially in the g = 9 region, and were clearly high-spin Co(II). However, when the Co II centres were prepared by radiation-induced electron addition to the Co(III) complex at 77 K, a low-spin species was initially formed with g values in the free-spin region. These were converted into the normal high-spin form on annealing to ∼ 115 K.

Complexation of the penta-, hexa- and hepta-N-methylated derivatives of the macrobicyclic hexaamine sar (3,6,10,13,16,19-hexaaza-bicyclo[6.6.6]icosane) with nickel(II) and copper(II) is reported. Unlike their analogous hexadentate-coordinated [M(sar)](2+) complexes, the Cu(II) and Ni(II) complexes of N-Me(5)sar, N-Me(6)sar and N-Me(7)sar(+) show the ligands coordinating only as tetradentates, both in the solid state and in solution. The X-ray crystallographic analyses of [Ni(N-Me(5)sar)](ClO4)(2), orthorhombic, space group P2(1)2(1)2(1), a 9.915(2), b 10.694(2), c 25.549(6) Angstrom, Z = 4; {[Ni(HN-Me(6)sar)](ClO4)(3).2H(2)O}(3), triclinic, space group P $($) over bar$$ 1, a 14.160(2), b 17.739(4), c 21.617(5) Angstrom, alpha 75.20(2), beta 89.72(2), gamma 68.31(1)degrees, Z = 2; [Ni(N-Me(7)sar)](ClO4)(3), orthorhombic, space group P2(1)2(1)2(1), a 10.752(2), b 13.410(2), c 21.643(3) Angstrom, Z = 4; [Cu(N-Me(5)sar)](ClO4)(2), orthorhombic, space group P2(1)2(1)2(1), a 10.005(1), b 10.524(1), c 25.731(2) Angstrom, Z = 4 and [Cu(N-Me(7)sar)](ClO4)(3).0.5H(2)O, orthorhombic, space group P2(1)2(1)2(1), a 11.337(2), b 12.802(2), c 22.170(2) Angstrom, Z = 4, are reported. The Ni(II). complexes exhibit marked solvent, temperature and pH-dependent electronic spectra as a result of high-spin/low-spin equilibria. Molecular mechanics calculations indicate that hexadentate coordination of N-Me(6)sar to metal ions such as Cu(II) and Ni(II) will be unfavorable as a result of severe steric strain.

The cage complexes [Co{(NMe(2))(2)sar}](3+) and [Co{(NMe(2),Me)sar}](3+) (sar = sarcophagine = 3,6,10,13,16,19 hexaazabicyclo[6.6.6]icosane; (NMe(2))(2)sar 1,8-bis(dimethylamino)sarcophagine; (NMe(2),Me)sar 1-(dimethylamino)-8-methylsarcophagine) are obtained by methylation of amino substituents on the parent cage complexes using formaldehyde and formic acid. Further methylation with methyl iodide in dimethyl sulfoxide, or with dimethyl sulfate in N,N-dimethylformamide, converts the dimethylamino substituents to trimethylammonium substituents and essentially inverts the circular dichroism (CD) spectrum in comparison to that of the protonated parent cage complex, [Co{(NH3)(2)sar}](5+). A combination of NMR and electronic spectroscopic measurements indicates that the inversion of the CD spectra is due to conformational inversions in the 1,2-ethanediamine rings from mainly a lel conformation in [Co{(NH3)(3)sar}](5+) to an obs conformation in [Co{(NMe(3))(2)sar}](5+), (without inversion at any of the seven stereogenic centers; Co plus six coordinated amines). This ob(3) conformation was identified in the solid state by an X-ray crystallographic analysis of [Co{(NMe(3))(2)sar}](NO3)(5).3H(2)O: monoclinic, P2(1)/n, a 14.382(4) Angstrom, b = 14.604(3) Angstrom, c 16.998(6) Angstrom, beta = 100.28(3)degrees, Z= 4. The electron self-exchange rate constant of the [Co((NMe(3))2sar)](5+/4+) redox couple (+0.05 V vs NHE, 0.011(1) M(-1) s(-1) at 25 degrees C, I = 0.2 M (NaCl)) is a factor of 2 smaller than that of the [Co((NH3)2sar)](5+/4+) couple under the same conditions and is the slowest electron-transfer rate so far measured for a hexaamine cage complex of this type. However, it is still much faster than those of the parent [Co(en)(3)](3+/2+) and [Co(NH3)(6)](3+/2+) couples. This paper also provides hard evidence for the conformations of other Co(III) cage complexes in solution as well as the solid state.

The encapsulation of transition metal ions by hexa-amine ligands of the sarcophagine type permits their electronic and spectroscopic properties to be studied in a magnetically dilute and kinetically inert environment. In particular, the saturated nature of the amine yields a cryptand of the innocent kind so that the ligand field absorption of the metal containing cages is not obscured by intense charge transfer bands. This paper presents the results of magnetic, vis-UV spectroscopic and NMR measurements on a series of hexa-aza Werner complexes of encapsulated divalent iron performed over a range of temperature. The data reveal that both low-spin and high-spin isomers of the iron(II) cages coexist in solution. The temperature dependence of the physical parameters is characteristic of a spin equilibrium between molecular states of 1A1g and 5T2g origin.

The three monodentate pentaamminecobalt(III) linkage isomers of glycinamide have been synthetized and characterized by visible and 1 H and 13 C NMR spectroscopy and microanalysis. A nitrile-bonded ammonioacatonitrile complex was synthesized, it reacts in liquid ammonia to produce the amidine-bonded aminoacatamidine complex while in aqueous base it hydrolyzes to the amido-N-bonded glyanamida ion. Both [(NH 3 ) 5 CoNHCOCH 2 NH 2 ] 2+ and [(NH 3 ) 5 CoNHC(OH)CH 2 NH 3 ] 2+ have been isolatad

Electron transfer kinetics for the reduction of spinach plastocyanin and horse cytochrome c by several cobalt-cage complexes have been determined. The reduction of plastocyanin by [Co((N(CH 3 ) 3 ) 2 -sar)] 4+ shows saturation kinetics with K Co(II) = (1.5±0.2)×10 3 M -1 , and κ' et =4.0±0.2 s -1 . This reaction is stereoselective (κ Δ /κ Δ = 1.7) and the stereoselectivity is independent of ionic strength.

The reaction of [NH4]2[OsBr6] with neat 1,2-ethanediamine (en) yields cis-[Os(en-H)2(en)]Br2, which is recrystallized as cis-[Os(en-H)2(en)]I·Br in 40–50% yield. [Os(en)3]Br3·2H2O is obtained from the filtrate in ∼ 40% yield by the addition of EtOH, to give a recovery of ∼ 90% of osmium 1,2-ethanediamine complexes. This cis[Os(en-H)2(en)]2+ complex protonates to form [Os(en-H)(en)2]3+ and both OsIV complexes have been characterized by 1H and 13C NMR, IR and UV-Vis spectroscopies. Since the NH exchange rate for the doubly deprotonated OsIV complex is slow at the amido sites their cis relationship is maintained. The OsIV complexes are reduced readily to [Os(en)3]3+ by a variety of reductants. A reversible OsIII/II couple is observed at −0.52 V versus NHE in 0.1 M NaCF3SO3. All of these complexes are oxidized in air to form [Os(en)2(diim)]2+ (diim=ethanediimine) and [Os(en)(diim)2]2+ as the eventual product. The latter were characterized by 1H and 13C NMR, UV-Vis and IR spectroscopy. The mechanism of the dehydrogenation reaction is discussed in detail, in relation to related Fe and Ru amine chemistry.

The electrochemical reduction of [Cu II (sar)] 2+ ion 1 in aqueous solution is essentially irreversible and leads to extrusion of Cu from the cage, leaving the organic framework intact. This extrusion process also appeared to be very rapid on the cyclic voltammetry time scales available (up to 200 V/s). We were prompted, therefore, to look at the reduction process by pulse radiolysis over a shorter time scale (ns→10 ms) using the hydrated electron in order to probe for the events which lead to extrusion of the metal ion in such a facile way

Chelate complexes derived from 2-imino carboxylato ligands contain both electrophilic and nucleophilic sites for reaction. To explore both the utility and control of these properties, reactions of the simple pyruvate imine complex [(NH 3 ) 4 Co(NH=C(CH 3 )CO 2 )] 2+ with a variety of polyfunctional molecules have been examined. Diethyl oxaloacetate reacts to provide a substituted pyridine, showing that the previously observed reaction of the complex with biacetyl to give a pyrroline can be varied to provide to other heterocycles

The oxidation of bis(1,2-ethanediamine)(sarcosinato)cobalt(III) ion with SOCl2 in dimethylformamide gave the N-methylthiooxamato complex as the final product. The results, along with others, implicate the acid chloride chelate, a sulfine, and the methyl thiooxamato chelate as intermediates en route. The thiooxamato sulfur atom retains a nucleophilic capability and adds readily to cyclohexene in the thionyl chloride-dmf reaction medium to give an unusual imido hydroxycyclohexane thioester complex. Various results, including those in this paper, indicate that the chelated acid chloride readily loses an alpha-carbon proton and the resulting carbanion captures SOCl+. Elimination of HCl yields the sulfine and further addition of SOCl+, eliminations, and rearrangement yield chelated thiooxamate, which reacts even further under the pseudo-Vilsmeier conditions to the N-methyloxamato chelate complex.

The redox potentials, E 1/2 , for the reversible cobalt (III/II) redox couples of complexes of substituted macrobicyclic ligands derived from 3,6,10,13,16,19-hexaazabicyclo[6.6.6]icosane show a substantial variation with the type of substituent. The variation was subjected to a Hammett type treatment yielding a series of inductive or polar substituent constants σ E that correlate with the organic substituent constants obtained by a variety of other methods

Solvent-dependent formal potentials, Ef, and reaction entropies, for four reversible Co(III)/(II) couples featuring macrobicyclic cage ligands have been obtained. These are utilized, together with corresponding data for other Co(III)/(II) and Ru(III)/(II) amine couples and for M(III)/(II) polypyridine couples, to unravel effects on the redox thermodynamics arising from specific ligand-solvent and other interactions. The solvent dependencies of Ef (vs. ferrocenium-ferrocene) for each redox couple are fitted by using a multiparameter approach, incorporating various well-known empirical quantities describing solvent basicity, acidity, polarity, and internal ordering. For most amine couples, solvent basicity appears to play a prevailing role, associated with interactions involving the amine hydrogens, although solvent polarity also exerts a substantial, albeit less solvent-dependent, influence upon EfD.

The redox behavior of nitro groups bonded in the apical positions of sar (sar=3,6,10,13,16,19-hexaazabicyclo[6.6.6]icosane) cage complexes is very diverse. Nitroso, hydroxylamine, amine, and nitro radical anions result as primary products from such reductions, depending on the type of reductant, pH, solvent, and the amount of reductant supplied. The ultimate reduction products with Zn/HCl as the reductant contain amine substituents, whereas reductions with Sn 2+ /HCl or S 2 O 4 2− , or electrochemical reductions at a Hg-pool electrode, yield hydroxylamine-substituted cage complexes as the ultimate products

The temperature dependence of the magnetic susceptibility (4.2-300 K) is reported for a series of crystalline salts of first-row transition-metal ions encapsulated by hexaamine ligands of the sar type where sar =3,6,10,13,16,19-hexaazabicyclo [6.6.6] icosane

The phosphodiester metal ion complexes (ethyl 4-nitrophenyl phosphato)pentaammineiridium(III) and bis(4-nitrophenyl phosphato)pentaammineiridium(III) have been synthesized and their reactivities under basic conditions studied. Both complexes react predominantly via intramolecular attack of a deprotonated coordinated ammonia to liberate 4-nitrophenolate ion. The rate constant for intramolecular attack of amido ion is enhanced considerably relative to the reactivity of the uncoordinated substrate under the same conditions

Treatment of the cobalt(III) complex of the hexadentate tripodal N(3)S(3) ligand ten (4,4',4' '-ethylidynetris(3-thiabutan-1-amine) with propanal and paraformaldehyde under basic conditions, followed by borohydride reduction and reoxidation of the metal center, leads largely to the encapsulated (red) metal complex cation [Co(Me(2)-N(3)S(3)sar)](3+) (Me(2)-N(3)S(3)sar = 1,8-dimethyl-3,13,16-trithia-6,10,19-triazabicyclo[6.6.6]icosane). Unexpectedly, significant amounts of the homologous (yellow) complex cation [Co(Me(2)-N(3)S(3)absar)](3+) (Me(2)-N(3)S(3)absar = 1,8-dimethyl-3,13,16-trithia-6,10,19-triazabicyclo[6.6.5]nonadecane) were also obtained. This macrobicyclic complex has a contracted cavity resulting from a cap containing one fewer methylene units than Me(2)-N(3)S(3)sar. The structures of both cobalt(III) complexes have been determined by X-ray crystallography. [Co(Me(2)-N(3)S(3)sar)]Cl.ZnCl(4).H(2)O crystallizes in the cubic space group P2(1)3 with Z = 4, a = 13.9683(11) Å. [Co(Me(2)-N(3)S(3)absar)](ClO(4))(3).0.5CH(3)CN.0.5H(2)O crystallizes in the triclinic space group Ponemacr; with Z = 4, a = 12.036(4) Å, b = 15.932(9) Å, c = 17.212(14) Å, alpha = 64.93(7) degrees, beta = 72.77(5) degrees, gamma = 88.91(7) degrees. The surprising structural rearrangement is examined, along with the spectral and redox properties of both cobalt complexes. The influence of the reduced cavity size in the absar type cage is reflected in a shift of the bands in the electronic spectrum of both the cobalt(II) and cobalt(III) complexes to higher energy, and a more negative value for the Co(III/II) redox potential. The demetalation of the complexes is also described.

The mechanisms of oxidative ligand dehydrogenation in high-valent ruthenium hexaamine complexes of bidentate 1,2-ethanediamine (en) and tridentate 1,1,1-tris(aminomethyl)ethane (tame) are elucidated in detail. In basic aqueous solution, [Ru(III)(tame)(2)](3+) undergoes rapid initial deprotonation (pK(III) = 10.3). This is followed by a pH-dependent disproportionation step involving either [Ru(III)(tame)(2)-H(+)](2+) + [Ru(III)(tame)(2)](3+) (k(1d) = 8300 M(-)(1) s(-)(1)) or two singly deprotonated [Ru(III)(tame)(2)-H(+)](2+) ions (k(2d) = 3900 M(-)(1) s(-)(1)). The products are [Ru(II)(tame)(2)](2+) and either the singly deprotonated species [Ru(IV)(tame)(2)-H(+)](3+) (pK(IV) = 8.2) or the doubly deprotonated [Ru(IV)(tame)(2)-2H(+)](2+). These Ru(IV) complexes undergo spontaneous dehydrogenation to give the imine [Ru(II)(imtame)(tame)](2+) (imtame = 1,1-bis(aminomethyl)-1-(iminomethyl)ethane), with first-order rate constants of k(1im) = 320 s(-)(1) and k(2im) = 1.1 s(-)(1), respectively. In the [Ru(III)(en)(3)](3+) system, the initial deprotonation (pK(III) = 10.4) is followed by the corresponding disproportionation reactions (k(1d) = 9000 M(-)(1) s(-)(1), k(2d) = 3800 M(-)(1) s(-)(1)). The complex [Ru(IV)(en)(3)-H(+)](3+) (pK(IV) = 8.9) and its deprotonated counterpart, [Ru(IV)(en)(3)-2H(+)](2+), undergo dehydrogenation to give [Ru(II)(imen)(en)(2)](2+) (imen = 2-aminoethanimine) with first-order rate constants of k(1im) = 600 s(-)(1) and k(2im) = 1.0 s(-)(1), respectively. In the light of this analysis, the disproportionation and ligand oxidation of the [Ru(III)(sar)](3+) ion are reexamined (k(1d) = 4 x 10(7) M(-)(1) s(-)(1), k(2d)/= 2 x 10(7) M(-)(1) s(-)(1), pK(IV) = 2.0, k(1im) = 17 s(-)(1), k(2im) = 5 x 10(-)(4) s(-)(1) at 25 degrees C). While the disproportionation to Ru(II) and Ru(IV) has been recognized in such systems, the complexity of the paths has not been realized previously; the surprising variation in the rates of the intramolecular redox reaction (from days to milliseconds) is now dissected and understood. Other facets of the intramolecular redox reaction are also analyzed.

The success of positron emission tomography (PET) in personalised medicine and drug development requires radioisotopes that provide high quality images and flexible chemistry for a broad application. 64Cu is arguably one of the most suitable PET isotopes for imaging with the evolving target agents, but there are not many appropriate chelating agents for 64Cu and this has limited its wider application. The bi-functional chelator, SarAr is known to bind 64Cu2+ quantitatively (i.e. one metal per ligand present) and rapidly (2 min) at 10(-6) M over a range of pH (4-9). In this paper the conjugation of SarAr to the whole and fragmented antibody is described. Conjugation of the SarAr to the protein does not impair its coordination of the 64Cu. It complexes the 64Cu2+ rapidly, quantitatively and essentially irreversibly at pH 5. Animal studies show that the 64Cu-SarAr-immunoconjugates maintain their specificity for the target and are stable in vivo. Also, SarAr is a platform technology, is easy to use in a kit formulation and is readily adaptable for the wider application in 64Cu PET imaging.

Etude des reactions de transfert d'electron des complexes de sipulerate et sarcophagine. Influence de la stereochimie sur les constantes de vitesse

Acid hydrolysis of the ester function in Δ-(−)589-β2-(RR)-[Co (trien) (glyOEt) Cl]2+ ((−)-1) produces optically pure Δ-(−)589-(RR)-[Co (trien) (glyOH)Cl]2+ ((−)-4). Hg2+ induced removal of chloride in (−)-4 follows the rate law kobs = kHg [Hg2+] with kHg = (1.36 ± 0.03) × 10−2 M−1s−1, 25°, μ=1.0, and produces optically pure Δ-(−)589-β2-(RR)-[Co(trien) (glyO)]2+ ((−)-2). Competition by NO occurs in this reaction ([NO], 1M, 3%) indicating a path whereby external nucleophiles (YNO, H2O) compete with the intramolecular carboxylate function for an intermediate of reduced coordination number. Rapid ring closure to 2 must ensue for Y H2O. Base hydrolysis of chloride in (±)-1 produces (±)-2 together with its diastereoisomer β2-(RS, SR)-[Co(trien) (glyO)]2+, ((±)-3), in which one secondary amine function has an inverted configuration. 2 and 3 incorporate 18O-labelled solvent into the Co-O position of the coordinated carboxylate moiety (2: 9.0%; 3: 12.3%) indicating that at least part of the product arises via intramolecular hydrolysis in β2-hydroxo ethylglycinate intermediates (Fig. 4). Base hydrolysis of (−)-4 follows the rate law Kobs = kOH[OH−] with kOH = (6.3 ± 0.6) × 10−4M−1 S−1, 25°, μ = 1.0 producing (−)-2 (37-45%) and (−)-3 (63-55%), the ratio being somewhat medium dependent. Competition by added N (1M) occurs using (±) -4 forming β2-(RR, SS)-[Co (trien) (glyO)N3]+ (∼2%) and β2-(RS, SR)-[Co (trien) (glyO)N3]+ (∼ 13%). Mutarotation at the secondary nitrogen centre is shown to occur after the rate determining loss of Cl− in 1 and 4 and before the formation of 2 and 3. It is concluded that this secondary nitrogen is the site of deprotonation in the reactive conjugate bases of 1 and 4, and possible mechanisms for the mutarotation process are considered.

L'oxydation par le chlore du centre S dans les complexes [Co(en) 2 (NH 2 CH(R)CH 2 S)] 2+ . Formation d'un sulfonate chelate [Co(en) 2 (NH 2 CH(CO 2 H)CH 2 SO 2 O] 2+ . Stereochimie des transpositions

Synthese au coordinat hexadente tris(amino-2 ethyl)-1,4,7 triaza-1,4,7 cyclononane et de [CoL] 3+ . Synthese des complexes ou L est egalement: amino-9 hexaazatricyclodocosane, heptaazatricyclodocosane. Etude de configuration et electrochimique

Il semblerait ne pas y avoir de relation entre la loi de vitesse et la distribution des produits pour l'hydrolyse basique de [(NH 3 ) 5 CoX] n+ en presence d'anions Y m−

Le compose cristallise dans le systeme monoclinique, groupe P2 1 /c avec Z=4. Coordination octaedrique autour du cation. Etude electrochimique et photochimique

L'hydrolyse du β-alaninate d'isopropyle dans le complexe [Co(en) 2 (β-alaO-i-Pr)] 3+ a lieu par attaque sovolytique sur le centre carbonyle, donnant [Co(en) 2 (β-alaO)] 2+ . Cinetique. Catalyse par HCO 3 − , HPO 4 2− , imidazole, glycinate d'ethyle

La decomposition de Ni(tach) 2 2+ (tach=cyclohexane triamine) en Ni(tach)(H 2 O) 3 2+ est du 1er ordre. La constante de vitesse depend beaucoup de l'acide. Etude RX du complexe du titre