Quinquedentate Macrocyclic Ligands Research Articles

A Definitive Example of a Geometric “Entatic State” Effect: Electron-Transfer Kinetics for a Copper(II/I) Complex Involving A Quinquedentate Macrocyclic Trithiaether−Bipyridine Ligand

The quinquedentate macrocyclic ligand cyclo-6,6'-[1,9-(2,5,8-trithianonane)]-2,2'-bipyridine ([15]aneS3bpy = L), containing two pyridyl nitrogens and three thiaether sulfurs as donor atoms, has been synthesized and complexed with copper. The CuII/IL redox potential, the stabilities of the oxidized and reduced complex, and the oxidation and reduction electron-transfer kinetics of the complex reacting with a series of six counter reagents have been studied in acetonitrile at 25 degrees C, mu = 0.10 M (NaClO4). The Marcus cross relationship has been applied to the rate constants obtained for the reactions with each of the six counter reagents to permit the evaluation of the electron self-exchange rate constant, k11. The latter value has also been determined independently from NMR line-broadening experiments. The cumulative data are consistent with a value of k11 = 1 x 10(5) M(-1) s(-1), ranking this among the fastest-reacting CuII/I systems, on a par with the blue copper proteins known as cupredoxins. The resolved crystal structures show that the geometry of the CuIIL and CuIL complexes are nearly identical, both exhibiting a five-coordinate square pyramidal geometry with the central sulfur donor atom occupying the apical site. The most notable geometric difference is a puckering of an ethylene bridge between two sulfur donor atoms in the CuIL complex. Theoretical calculations suggest that the reorganizational energy is relatively small, with the transition-state geometry more closely approximating the geometry of the CuIIL ground state. The combination of a nearly constant geometry and a large self-exchange rate constant implies that this CuII/I redox system represents a true geometric "entatic state."

A new NS4 quinquedentate macrocyclic ligand: synthesis, structure and properties of its Ni(ii), Pd(ii), Pt(ii), Cu(ii), Cu(i) and Ag(i) complexesPresented at ISMC-2001 held in Fukuoka, Japan from July 15–20, 2001.Electronic supplementary information (ESI) available: synthetic scheme for macrocyclic complexes 12–17; views of 12, 15 and 16; cyclic voltammograms of 13 and 14. See http://www.rsc.org/suppdata/dt/b2/b206182a/

An aza-thia macrocycle 2,5,14,17-tetrathia[6](1,2)benzeno[6](2,6)pyridinophane (11) and its complexes with Ni(II), Pd(II), Pt(II), Cu(II), Cu(I) and Ag(I) were synthesized and their crystal structures were determined. Ni(II) forms an octahedral complex coordinated to NS3 of the ligand and two chlorine atoms of the metal salt; one of the sulfurs in the ligand is uncoordinated. The crystal structures of [Pd·11][PF6]2 and [Pt·11][PF6]2 confirm a [NS3 + S] coordination in both complexes. NMR spectroscopic studies indicate that only one form of each complex is present in solution. Cu(II), Cu(I) and Ag(I) complexes of the macrocycle adopt a geometry in between a square pyramid and a trigonal bipyramid with NS4 coordination around the metal ions in [Cu·11][ClO4]2, [Cu·11][PF6] and [Ag·11][PF6]. The electronic and redox properties of [Pd·11][PF6]2, [Pt·11][PF6]2 and the copper complexes in acetonitrile have been examined. The complexation behaviour of the macrocycle, 11, has also been studied in solution and found to lack good selectivity towards the selected transition metal ions.

ChemInform Abstract: Transient Template Effect: Chromium(III)‐Directed Syntheses of Metal‐Free Macrocyclic Ligands and Crystal Structure of 1,11‐Bis(2′‐hydroxyethyl)‐4,8;12,16;17,21‐trinitrilo‐1,2,10,11‐tetra‐azacyclohenicosa‐2,4,6,9,12,14,18,20‐octaene Hydrochloride Tetrahydrate.

AbstractThe metal‐free quinquedentate macrocyclic ligands (IV) and (V) are prepared by the use of a Cr(III) transient template as demonstrated for the example (IVa)·HCl·4 H2O (space group P21/n, Z=4).

The transient template effect: chromium(III)-directed syntheses of metal-free macrocyclic ligands and crystal structure of 1,11-bis(2′-hydroxyethyl)-4,8;12,16;17,21-trinitrilo-1,2,10,11-tetra-azacyclohenicosa-2,4,6,9,12,14,18,20-octaene hydrochloride tetrahydrate

A range of metal-free quinquedentate macrocyclic ligands incorporating 2,2′-bipyridine or 1,10-phenanthroline donor groups has been prepared by the use of a chromium(III) transient template. The transient template effect is shown to be due to pH effects resulting from the presence of chromium(III) complexes in aqueous solution, rather than a process in which the open-chain ligands become co-ordinated to the metal centre. The crystal and molecular structure of a free macrocyclic ligand is reported, as is the preparation of some chromium(III) complexes of open-chain and macrocyclic complexes.

X-Ray crystal structure of the pentagonal bipyramidal nickel(II) complex [NiII(L)(H2O)2](BF4)2and the selective stabilisation of the nickel(I) oxidation state by a quinquedentate macrocyclic ligand

The single crystal X-ray structure of the pentagonal bipyramidal nickel(II) complex [NiII(L)(H2O)2](BF4)2 involving the quinquedentate macrocyclic ligand L is reported; electrochemical reduction of a series of related nickel(II) complexes [NiII(L)X2](BF4)2 yields in solution d9 nickel(I) species.

Synthesis and X-ray structure of a cobalt(II) complex of a negatively charged quinquedentate macrocyclic ligand

Reaction of 2,2′-iminobisbenzaldehyde with 2,9-di(1-methylhydrazino)-1,1 0-phenanthroline in the presence of cobalt(II) ions and pyridine leads to the formation of the spin-free title complex [CoL3(py)2]+(py = pyridine). The X-ray structure of the tetraphenylborate salt confirms a seven-co-ordinate, distorted pentagonal-bipyramidal geometry for the metal ion, which is bound equatorially by five nitrogens from the macrocycle and has two pyridine molecules in the axial sites. The complex crystallises in space group P21/n with a= 16.786(4), b= 23.034(4), c= 13.546(3)A, β= 97.09(3)°, and Z= 4. The structure was solved by Patterson and Fourier-difference techniques and refined to R= 0.097 and R′= 0.079 for 2 458 observed reflections.

Iron(II) complexes of a potentially quinquedentate macrocyclic ligand having an ‘N3S2’ donor set and the crystal and molecular structures of a high-spin (S= 2) complex and a low-spin (S= 0) complex

A series of iron(II) complexes of the 17-membered macrocyclic ligand L, having an ‘N3S2’ donor set, derived from the Schiff-base condensation of 2,6-diacetylpyridine with 4,7-dithiadecane-1, 10-diamine, are described. Physical measurements (magnetic, Mössbauer) characterise the complexes as high-spin (S= 2) or low-spin (S= 0) depending on the nature of the associated unidentate ligands (halide, NCS–, MeOH, MeCN, pyridine, or NH3). Single-crystal X-ray structure determinations of two of the complexes reveal a versatility in the conformations and co-ordination modes of the macrocycle. Crystals of the low-spin complex [FeL(NCS)][BPh4](1) are monoclinic with a= 31.640(8), b= 11.019(8), c= 11.155(7)Å, β= 96.40(3)°, Z= 4, and space group P21/a. Crystals of the high-spin complex [FeLCl(HOMe)][ClO4](2) are monoclinic with a= 18.512(11), b= 18.279(12), c= 8.125(9)Å, β= 113.1(2)°, Z= 4, and space group P21/a. The two structures were solved by Patterson and Fourier methods from 2 548 and 1 772 reflections above background measured by diffractometer and refined by full-matrix least squares to R 0.047 and 0.102 respectively. In both (1) and (2), the co-ordination geometry of the metal ion is distorted octahedral. In (1), the macrocycle adopts a ‘wrap-around’ conformation to occupy five of the octahedral sites [Fe–N 1.981(6), 1.870(6), 1.987(7); Fe–S 2.307(3), 2.258(3)Å], the sixth being filled by the nitrogen atom of the –NCS group [1.965(9)Å]. In (2), one sulphur atom of the macrocycle is not bonded to the metal while the other is only weakly co-ordinated [2.806(5)Å]cis to the trimethine nitrogens [Fe–N 2.205(11), 2.092(10), 2.200(12)Å]. The remaining two octahedral sites are occupied by the Cl– ion (trans to the pyridine nitrogen) and the oxygen atom of the MeOH molecule [Fe–Cl 2.304(4), Fe–O 2.205(16)Å]. Possible structures for the remaining complexes of the series including three modifications of [FeL(NCS)2] are considered.

Chemistry of polydentate ligands. Part 6. Synthesis, characterisation, and properties of Group 2B cation complexes with novel quinquedentate macrocyclic ligands

Complexes of quinquedentate macrocyclic ligands with Group 2B cations have been prepared by condensation of 2,6-diformylpyridine and 2,6-diacetylpyridine with 2,9-di(1-methylhydrazino)-1,10-phenanthroline monohydrochloride in the presence of metal-ion templates. Electrical conductivity measurements, i.r. and 1H n.m.r. spectral data are reported and evaluated to show that ring closure rather than polymer formation has occurred. Evidence is presented for some metal ions in the macrocyclic complexes having pentagonal-pyramidal co-ordination geometries. The n.m.r. data are interpreted as indicating the presence of ring currents in the ligands. Hydrogenation of the hydrazone bonds produces two new ligands: the n.m.r. spectra of the zinc (II) complexes demonstrate that these macrocyles are folded. Relative yields of optical isomers of the complex with one of these reduced macrocycles are reported.

Chemistry of polydentate ligands. Part 8. Preparation and properties of iron(II) complexes with quinquedentate macrocyclic ligands. Crystal and molecular structure of a compound where high-spin Fe II sits in the ligand cavity. Electrochemistry of a series of complexes with the macrocycles

Complexes of quinquedentate macrocyclic ligands with FeII have been prepared by condensation of 2,6-diacetylpyridine and 2,6-diformylpyridine with 2,9-di(1-methylhydrazino)-1,10-phenanthroline monohydrochloride in the presence of iron(II) templates. Magnetic susceptibility measurements and Mossbauer parameters show that the complexes are high spin, while chemical evidence indicates that the macrocycles encompass iron(II). This is confirmed by a structure determination on a single crystal of [FeC23H25N7O2][B2F8], which is monoclinic with a= 14.152(3), b= 11.464(11), c= 16.732(5)A, β= 93.56(3)°, Z= 4, space group P21/c. Metal–donor nitrogen distances are 2.100(9), 2.112(8), 2.116(7), 2.242(8), and 2.276(8)A. The co-ordination geometry of the iron(II) is pentagonal bipyramidal with water molecules occupying the axial sites: Fe–O distances are 2.213(7) and 2.194(7)A. This structure is compared with those of high-spin iron(II) complexes of other macrocycles. Cyclic voltammetry data for selected complexes of MnII, FeII, ZnII, and CdII with the ligands are presented: one-electron reductions produce π-anion radicals.

The synthesis, properties, and the crystal and molecular structures of five-co-ordinate copper(I) and silver(I) complexes of a quinquedentate macrocyclic ligand having an ‘N3S2’ donor set

Download options Please wait... Article information DOI https://doi.org/10.1039/DT9800002020 Article type Paper Download Citation J. Chem. Soc., Dalton Trans., 1980, 2020-2027 BibTex EndNote MEDLINE ProCite ReferenceManager RefWorks RIS Permissions Request permissions The synthesis, properties, and the crystal and molecular structures of five-co-ordinate copper(I) and silver(I) complexes of a quinquedentate macrocyclic ligand having an ‘N3S2’ donor set M. G. B. Drew, C. Cairns, S. G. McFall and S. M. Nelson, J. Chem. Soc., Dalton Trans., 1980, 2020 DOI: 10.1039/DT9800002020 To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page. If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page. Read more about how to correctly acknowledge RSC content. Search articles by author Michael G. B. Drew Colin Cairns Stephen G. McFall S. Martin Nelson

Chemistry of polydentate ligands. Part 7. Synthesis, characterisation, and properties of some manganese(II) complexes of quinquedentate macrocyclic ligands based on 1,10-phenanthroline. Crystal and molecular structure of a complex with pentagonal-pyramidal coordination geometry about the Mn II

Complexes of quinquedentate macrocyclic ligands with MnII have been prepared by condensation of 2,6-diformylpyridine and 2,6-diacetylpyridine with 2,9-di(1-methylhydrazino)-1,10-phenanthroline monohydrochloride in the presence of manganese(II) templates. Electrical conductivity and i.r. spectra are reported and evaluated to distinguish between ring closure and polymer formation, while magnetic susceptibility data show the complexes to be high spin. Evidence is presented for co-ordination of unidentate ligands in one axial site thereby completing the pentagonal-pyramidal co-ordination geometry about the MnII ions. This is confirmed by a single-crystal X-ray structure determination of [MnC23H21N7Cl][BF4], which is monoclinic with a= 11.717(8), b= 14.403(9), c= 15.316(9)A, β= 116.42(6)°, Z= 4, space group P21/n. Metal–donor nitrogen bond lengths are 2.167(11), 2.168(11), 2.204(11), 2.312(11), and 2.348(11)A and the metal–chlorine distance is 2.353(6)A. The MnII is 0.53 A out of the N5 donor plane, towards the chlorine. The structure is compared with other pentagonal pyramids and distortions from the symmetric shape are discussed. Structural similarities between the current ligand and porphyrins, particularly in cavity sizes, are noted.

Nickel(II) complexes of quinquedentate macrocyclic ligands and the crystal and molecular structure of the ring-opened hydrolysis product [11-(6-acetyl-2-pyridyl)-3,7,10-triazadodec-10-enylamine-NN′N″N‴N″″]-aquanickel(II) diperchlorate

In contrast to several other first-row transition-metal (and non-transition-metal) ions, NiII is ineffective as a template for the cyclic condensation of 2,6-diacetylpyridine with 4,7-diazadecane-1,10-diamine and related tetraamines to yield quinquedentate macrocyclic ligands. However, nickel(II) complexes of the 17-membered macrocycle L3 may be prepared by replacement of AgI from the complex [AgL3][ClO4]. On the basis of electronic spectra and other physical measurements, these complexes [NiL3(X)][ClO4](X = ClO4, NCS, or N3) are shown to have six-co-ordinate structures in which L3 adopts a new conformation, i.e. one in which it occupies five sites of a distorted octahedron. Replacement of AgI from the cavity of the less flexible 16-membered macrocycle L2 in dry ROH (R = Me or Et) yields distorted octahedral complexes of the new, more flexible, macrocycles L9 or L10 formed by addition of ROH across one azomethine bond of L2. The driving force for these reactions, which do not occur with (pentagonal) complexes of L2 with other metal ions, is believed to arise from a strong preference for the d8 ion for an orthogonal disposition of donor atoms. If the metal exchange is carried out in the presence of water, or if the L9 and L10 complexes are treated with water, a ready hydrolysis occurs to yield octahedral complexes of the ring-opened ligand L11. Crystals of the title complex [NiL11(OH2)][ClO4]2 are monoclinic, with a= 15.292(12), b= 19.807(15), c= 8.432(8)A, β= 106.54(8)°, Z= 4, space group P21/a. 1 514 Reflections above background have been measured by diffractometer and refined by full-matrix least squares to R 0.076. The ligand occupies five sites of a distorted octahedron around the metal ion [Ni–N 2.099(12), 1.999(14), 2.312(13), 2.084(11), and 2.085(12)A]. A water molecule at 2.126(8)A completes the co-ordination sphere.

Crystal structures of a five-co-ordinate copper(II) and a six-co-ordinate cobalt(III) comples containing flexible quinquedentate macrocyclic ligands

Crystal structures of a five-co-ordinate copper(II) and a six-co-ordinate cobalt(III) comples containing flexible quinquedentate macrocyclic ligands

Seven-co-ordination in metal complexes of quinquedentate macrocyclic ligands. Part 6. Magnesium complexes of macrocyclic ligands containing nitrogen and oxygen donor atoms

Reaction of 2,6-diacetylpyridine or 2,6-diformylpyridine with 3,6-dioxaoctane-1,8-diamine in methanol in the presence of MgCl2·6H2O gves complexes [MgL(OH2)2]Cl2·H2O of 15-membered quinquedentate N2O2 macrocycles (L) in high yield. Simple metathetical reactions lead to derivatives containing other anions including neutral complexes having axially co-ordinated thiocyanate. On the basis of various physical properties, the complexes are assigned seven-co-ordinate, probably pentagonal-bipyramidal, structures. Control experiments show that in the absence of a salt of Mg2+ the macrocycles are formed in only small yield or not at all. The Ca2+ ion is ineffective in oromotina the synthesis of these macrocvcles, as is Mg2+ in the synthesis of three related quadridentate N4 and N3O macrocycles.

Crystal structures of four complexes of quinquedentate macrocyclic ligands with novel co-ordination geometries containing five-co-ordinate silver(I), six-co-ordinate cadmium(II), six-co-ordinate mercury(II), and seven-co-ordinate cadmium(II)

Metal complexes of two ‘N5’ macrocyclic ligands are five-co-ordinate (distorted pentagonal plane, M = AgI), six-co-ordinate (distorted pentagonal pyramid, M = CdII or HgII), or seven-co-ordinate (pentagonal bipyramid, M = CdII) depending upon the sizes of the metal ion and macrocycle.

Seven-co-ordination in metal complexes of quinquedentate macrocyclic ligands. Part IV. Crystal and molecular structures of two pentagonal bipyramidal iron (II) complexes

The crystal structures of two iron(II) complexes of stoicheiometry [FeL(NCS)2], where L is a 15- or 16-membered ‘N5’ macrocycle, have been determined. Crystals of (I)(L = C15N5H23) are triclinic with a= 12.923(11), b= 7.165(9), c= 11.673(8)A, α= 93.24(11), β= 90.75(11), γ= 110.40(12)°, Z= 2, space group P. Crystals of (II)(L = C16N5H25) are monoclinic, space group P21/c with a= 7.746(8), b= 11.747(12), c= 24.367(18)A, β= 102.08(12)°Z= 4. The two structures were solved by Patterson and Fourier methods from 1 057 and 1 131 independent reflections above background collected by counter methods and refined to R 0.058 and 0.060, respectively. In both structures, the metal atoms have distorted pentagonal bipyramidal environments with the thiocyanate ligands in axial positions and the five nitrogen aioms of the macrocycle in equatorial positions. The Fe–N bond lengths and the conformations of the girdles are different in the two molecules as a consequence of the extra CH2, group in (II). However, both molecules have similar structures to those of the analogous FeIII cations.

Seven-co-ordination in metal complexes of quinquedentate macrocyclic ligands. Part II. Synthesis, properties, and crystal and molecular structures of some iron(III) derivatives of two ‘N5’ macrocycles

Template synthesis of the sixteen-membered, potentially quinquedentate, macrocycle formed by the Schiff-base condensation of 2,6-diacetylpyridine with 1,9-diamino-3,7-diazanonane (2,3,2-tet) in the presence of iron(II) salts yields a series of iron (III) complexes [Fe(C)X2] Y (C = macrocycle; X = Cl, Br, NCS, or N3; and Y = ClO4 PF6, BPh4, FeCl4, or FeBr4). Spectroscopic, magnetic, and electric conductance measurements characterise the complexes as having high-spin seven-co-ordinate structures similar to those of the previously prepared complexes of the fifteen-membered macrocycle (B) derived from 2,6-diacetylpyridine and 1,8-diamino-3,6-diazaoctane (2,2,2-tet). The crystal and molecular structure of [Fe(C)(NCS)2]ClO4(II) has been determined and that of [Fe(B)(NCS)2]ClO4(I) redetermined. Crystals of (I) are monoclinic, space group P21/c, Z= 4, with a= 8.946(8), b= 14.504(13), c= 18.029(17)A, β= 92.66(9)°. Crystals of (II) are monoclinic, space group P21/a, Z= 4, with a= 17.349(13), b= 12.151(10), c= 12.295(12)A, β= 110.61(9)°. The two structures were solved by Patterson and Fourier methods from 1 531 (I) and 1 473 (II) independent reflections collected by counter methods and refined to R 0.090 (I) and 0.077 (II). In both structures the metal atoms have distorted pentagonal bipyramidal environments with the isothiocyanate ligands in axial positions and the five nitrogen atoms of the macrocycle in equatorial positions. The Fe–N bond lengths and the conformation of the girdles are different in (I) and (II) as a consequence of the different ring sizes. The perchlorate anion in (I) is disordered.