Willem G. Haanstra

Transition metal complexes of two related pyrazole containing ligands:3,6-dimethyl-1,8-(3,5-dimethyl-1-pyrazolyl)-3,6-diazaoctane (ddad) and 1,4-bis(2-ethyl-(3,5-dimethyl-1-pyrazolyl))-piperazine (bedp). Synthesis, spectroscopy and X-ray structures

Abstract Several coordination compounds with the ligand 3,6-dimethyl-1,8-(3,5-dimethyl-1-pyrazolyl)-3,6-diaza- octane (ddad) were obtained: (Cu, Ni)(ddad)(BF 4 ) 2 , Co(ddad)(H 2 O)(BF 4 ) 2 , (Co, Ni, Cu, Zn) 2 (ddad)Cl 4 , Co 3 (ddad) 2 (NCS) 6 and Cu 2 (ddad)(NCS) 3 . Five X-ray structures were obtained, viz. of [Cu(ddad)](BF 4 ) 2 , [Ni(ddad)](BF 4 ) 2 , Ni(ddad)(NCS) 2 , [Ni(bedp)](H 2 O)(BF 4 ) 2 and [Cu(bedp)](H 2 O)(BF 4 ) 2 , but the data did not allow the calculation of very accurate bond lengths. However, the basic coordination geometries were obtained in all cases. The coordination by the ligands is square planar, while Ni(ddad)(NCS) 2 contains additional trans coordinating thiocyanate anions. The asymmetric unit of [Cu(ddad)](BF 4 ) 2 contains two almost identical [Cu(ddad)] 2+ species. The coordination of the copper atoms in both molecules is intermediate between tetrahedral and square planar. One molecule [Cu(ddad)] 2+ is the (R,R) diastereoisomer of the ligand and the other is the (S,S) diastereoisomer. The chloride compounds are, except for Ni(II), all dinuclear with MN 2 Cl 2 chromophores. The nickel(II) compound contains square planar Ni(ddad) 2+ cations and tetrahedral NiCl 4 2- anions. The thiocyanate compound of Ni(II), which is isomorphous with the corresponding Zn(II) compound, has octahedral MN 2 N 2 ′N 2 ″ chromophores. The cobalt compound crystallizes as [Co(ddad)(NCS)] 2 Co(NCS) 4 with five coordinate cobalt in the cation. With copper thiocyanate ddad forms the mixed-valence compound Cu 2 (ddad)(NCS) 3 , with [Cu(ddad)] 2+ and [Cu(NCS) 3 ] 2- . With the ligand, 1,4-bis(2-ethyl-(3,5-dimethyl-l-pyrazolyl))-piperazine (bedp) the compounds [(Ni, Cu)Coedp)](H 2 O)(BF 4 ) 2 , (Ni, CO)Coedp)(NCS) 2 , Zn 2 (bedp)(NCS) 4 , (Ni, Co, Cu, Zn) 2 (bedp)Cl 4 and Cu 2 (bedp)(NCS) 3 were obtained. The chloride compounds form dinuclear compounds (similar to ddad) with MN 2 Cl 2 chromophores. However, in addition to the green form of [Ni(bedp)][NiCl 4 ] a purple isomer Ni 2 (bedp)Cl 4 , with a tetrahedral NiN 2 Cl 2 chromophore, was obtained. The ligand field spectra of Ni(bedp)(NCS) 2 and the isomorphous cobalt compound show typical octahedral chromophores. With copper thiocyanate a mixed-valence compound was formed, with a structure likely to be similar to the corresponding ddad compound, viz. [Cu(II)(bedp)][Cu(I)(SCN) 3 ].

Unusual chelating properties of the ligand 1,8-bis(3,5-dimethyl-1-pyrazolyl)-3,6-dithiaoctane (bddo). Crystal structures of Ni(bddo)(NCS)2, Zn(bddo)(NCS)2 and Cd2(bddo)(NCS)4

The synthesis and characterization of the ligand 1,8-bis(3,5-dimethyl-1-pyrazolyl)-3,6-dithiaoctane (bddo) and its co-ordination compounds with zinc, cobalt, nickel, and cadmium thiocyanate are described. The general formula is M(bddo)(NCS)2 with M = Ni, Co, or Zn. With cadmium, Cd2(bddo)(NCS)4 was found. X-Ray structure determinations were performed on crystals of the compounds Zn(bddo)(NCS)2, Ni(bddo)(NCS)2, and Cd2(bddo)(NCS)4. The cobalt compound was found to be isomorphous to the zinc compound. The compound Zn(bddo)(NCS)2 crystallizes from ethanol in the orthorhombic space group Pbcn with unit-cell dimensions a= 9.521(1), b= 14.835(5), c= 16.840(4)A, for Z= 4. The structure was refined to R= 0.058 and R′= 0.069 for 1 072 unique reflections with I > 2σ(I). The compound consists of chains of zinc atoms linked by ligand molecules. The zinc ion is tetrahedrally co-ordinated by two pyrazole nitrogen atoms and two thiocyanate nitrogen atoms. The sulphur atoms of the ligand bddo do not co-ordinate. The compound Ni(bddo)(NCS)2 crystallizes from ethanol in the tetragonal space group P41212 with a= 9.370(3), c= 26.524(7)A, for Z= 4. The structure was refined to R= 0.041 and R′= 0.034 for 1 441 unique reflections with I > 3σ(I). The compound consists of monomeric units of octahedral nickel(II) ions with a trans,cis,cis-NiN2N′2S2 chromophore. The compound Cd2(bddo)(NCS)4 crystallizes from ethanol in the triclinic space group P with a= 8.695(3), b= 9.083(5), c= 10.008(3)A, β= 91.10(3), β= 99.34(3), γ= 108.23(2)°, for Z= 1. The structure was refined to R= 0.029 and R′= 0.033 for 2 794 unique reflections with I > 3σ(I). The cadmium ions are octahedrally co-ordinated with a CdNSN′2S′2 chromophore. Each cadmium ion is linked to two other cadmium ions by double thiocyanate bridges and to a third cadmium ion by one ligand molecule in such a manner that a two-dimensional structure results.

Copper coordination compounds of the ligand 1,6-bis(3,5-dimethyl-1-pyrazolyl)-2,5-dithiahexane (bddh). X-ray structures of [Cu(bddh)]2(BF4)2, [Cu(bddh)Cl]2CuCl4 and [Cu(bddh)(3,5-dimethylpyrazole)](BF4)2

Abstract The new ligand 1,6-bis(3,5-dimethyl-1-pyrazolyl)-2,5-dithiahexane (bddh) rendered the following coordination compounds with copper(I) and copper(II) salts: Cu(bddh)(NO3)2, [Cu(bddh)(H2O)](BF4)2, [Cu(bddh)Cl]2CuCl4, [Cu(bddh)(Hdmpz)](BF4)2 (Hdmpz=3,5-dimethylpyrazole), [Cu(bddh)Cl]BF4, [Cu(bddh)]2(BF4)2, Cu(bddh)Cl and Cu(bddh)Br. The compound [Cu(bddh)Cl]2CuCl4 crystallizes from ethanol in the monoclinic space group Cc, with a=19.018(4), b=14.840(3), c=14.963(3) A, β=100.24(2), V=4158 Ap3, Z=4 and Dcalc=1.63 g cm−3. The refinement using 5145 measured and 1826 observed (F>2σ(F)) reflections resulted in the R values 0.062 (R) and 0.068 (Rw). The asymmetric unit consists of two [Cu(bddh)Cl]+ cations and a CuCl42− anion. The copper(II) atom in [Cu(bddh)Cl]+ cation is coordinated by two pyrazole nitrogen atoms in trans position (1.991(9) and 1.98(1) A), two thioether atoms in cis position (2.422(3) and 2.480(3) A) and one chloride atom (2.249(4) A) in a distorted trigonal bipyramid with the nitrogen donors on axial positions and the two sulfurs and chloride in the equatorial plane. The tetrahedral CuCl42− anion lies in disorder. The compound [Cu(bddh)(Hdmpz)](BF4)2 crystallizes from ethanol in the monoclinic space group P21/c, with a=18.360(3), b=9.419(3), c=16.068(2) A, β= 100.29(1), V=2734 A3, Z=4 and Dcalc=1.55 g cm−3. The refinement using 6883 measured and 2326 observed (F>2σ(F)) reflections resulted in the R values 0.055 (R) and 0.061 (Rw). The asymmetric unit consists of a [Cu(bddh)(Hdmpz)]2+ cation and two tetrafluoroborate anions. The copper(II) atom is coordinated by three pyrazole nitrogen atoms (1.987(6) and 1.962(6) A; Hdmpz: 1.977(6) A) and two sulfur atoms (2.478(2) and 2.404(3) A) in a distorted trigonal bipyramid, with the ligand pyrazole groups on axial positions. The copper(I) compound [Cu(bddh)]2(BF4)2 crystallizes from ethanol in the monoclinic space group C2/c, with a=22.679(2), b=12.766(2), c=14.213(2) A, β=106.69(1), V=3942 A3, Z=8 and Dcalc=1.55 g cm−3. The refinement using 1495 observed (F>2.5σ(F)) reflections resulted in the R values 0.049 (R) and 0.082 (Rw). The cationic part of the compound is dinuclear with C2 symmetry. The copper(I) ions are 4.603(3) A apart. Each copper(I) ion is coordinated by a pyrazole nitrogen atom at 2.067(6) A and two thioether atoms at 2.426(2) and 2.333(3) A from one ligand and by a pyrazole nitrogen at 1.980(8) A of another ligand in a strongly distorted tetrahedral fashion. Spectroscopic results strongly suggest that the compounds [Cu(bddh)(H2O)](BF4)2 and [Cu(bddh)Cl]BF4 contain the trigonal bipyramidal [Cu(bddh)A] unit (A=anion), as present in [Cu(bddh)Cl]2CuCl4 and [Cu(bddh)(Hdmpz)](BF4)2. The compounds Cu(bddh)Cl and Cu(bddh)Br are IR and X-ray isomorphous.

Coordination compounds of the ligand 1,6-bis(3,5-dimethyl-1-pyrazolyl)-2,5-dithiahexane (bddh) with divalent nickel, cobalt and zinc salts. X-ray crystal structure of Co(bddh)(NCS)2

Abstract The N 2 S 2 ligand 1,6-bis(3,5-dimethyl-1-pyrazolyl)-2,5-dithiahexane (abbreviated bddh) forms the coordination compounds (Co, Ni, Zn)(bddh)Cl 2 , (Ni, Co)(bddh)(NCS) 2 and [Ni(bddh)(NO 3 ) 2 ](H 2 0) 2 . The X-ray crystal structure of Co(bddh)(NCS) 2 was determined at room temperature: tetragonal, space group P4 1 2 1 2, a = b =9.083(1), c =26.447(3) A, α=β=γ=90.0°, Z =4. The structure was solved by Patterson methods and refined by least-squares calculations to the residual R values of 0.038 ( R ) and 0.021 ( R w ) and the goodness-of-fit of 2.27 for 4808 measured, 2313 independent and 1999 observed ( F ρ4.0σ(F)) reflections. The cobalt(II) ion is in a distorted octahedral CoN 2 N′ 2 S 2 geometry, in agreement with its ligand field spectrum. The ligand chelates through two pyrazole N atoms in trans position and the two sulfur atoms in cis position. The thiocyanate anions coordinate through the N atoms in a cis position. The Co-donor distances are 2.119(2) (N-pyrazole), 2.579(1) (S) and 2.026(3) (N-thiocyanate) A. The ligand field spectra of the nickel compounds agree with octahedral coordination of the metal ion. IR spectroscopy of [Ni(bddh)(NO 3 ) 2 ](H 2 O) 2 strongly suggests that both nitrate anions are monodentate and the water molecules are present in the crystal lattice. The compounds (Co, Zn)(bddh)Cl 2 are X-ray isomorphous and the ligand field spectrum of Co(bddh)Cl 2 shows a CoN 2 Cl 2 chromophore.

Coordination behavior of the ligand 1,9-bis(3,5-dimethyl-1-pyrazolyl)-3,7-dithianonane (bddn) towards first-row transition metals. X-ray structure of [Cu(bddn)(H2O)](BF4)2

Abstract The synthesis and characterization of the ligand 1,9-bis(3,5-dimethyl-1-pyrazolyl)-3,7-dithianonane (bddn) and its coordination compounds, viz. [M(L)(X) 2 ] where M is Co 2+ , Zn 2+ ; X is Cl − , Br − , NCS − , and [Cu(L)(H 2 O)](BF 4 ) 2 are described. The X-ray structure of [Cu(bddn)(H 2 O)](BF 4 ) 2 has been determined. The compound crystallizes from ethanol in the monoclinic space group P 2 1 / c with unit-cell parameters a =18.508(5), b =9.253(3), c =15.743(5) A, β=107.91(3)°, V =2565.5 A 3 , D calc =1.57 g/cm 3 for Z =4. The structure was refined to R =0.099 and R w =0.116 for 1841 unique reflections with I >σ( I ). The copper(II) ion is coordinated by two pyrazole nitrogen donors, two thioether donors and a water molecule in a trigonal bipyramidal environment, with the two pyrazoles in an unusual cis position. The donor atoms at the axial positions area nitrogen and a sulfur, the equatorial plane donors are nitrogen, sulfur and the oxygen atom. From the ligand field spectra, the infrared patterns and the X-ray powder patterns it was concluded that the structures of the cobalt(II)- and zinc(II)-containing compounds are structurally similar to Zn(bddo)(NCS) 2 , a previously reported chain like structure with an MN 2 N′ 2 chromophore, in which the ligand S atoms do not bind to the metal ion.

Co-ordination compounds with the N2S-donor ligand 1,5-bis(3,5-dimethylpyrazol-1-yl)-3-thiapentane

With the ligand 1,5-bis(3,5-dimethylpyrazol-1-yl)-3-thiapentane (bdtp) the compounds [M(bdtp)-(NCS)2](M = Co or Zn), [Ni(bdtp)(NCS)2(H2O)], Cu(bdtp)(F)(BF4), M(bdtp)Cl2(M = Co or Cu), Zn(bdtp)Cl2·0.5EtOH, M(bdtp)(NO3)2(M = Co or Cu), Cu(bdtp)X (X = Br or Cl), [Cu(bdtp)]BF4·H2O and Ag(bdtp)(NO3) have been isolated. X-Ray single-crystal structures of [Co(bdtp)(NO3)2], Cu(bdtp)Br and Ag(bdtp)(NO3) were determined. The compound [Co(bdtp)(NO3)2] crystallizes in the monoclinic space group P21/n, with a= 8.984(2), b= 15.342(3), c= 14.888(3)A, β= 107.28(2)°, Z= 4 and R 0.038 for 2727 observed [F > 2σ(F)] reflections. The cobalt(II) atom is pseudo-octahedrally co-ordinated by three ligand donors, one mono- and one di-dentate. The Co–N [2.072(3) and 2.083(3)A] and Co–S bond lengths [2.584(1)A] are normal. The compound Cu(µ(bdtp)Br crystallizes in the monoclinic space group P21/n, with a= 9.017(2), b= 14.09(2), c= 13.660(3)A, β= 97.80(2)°, Z= 4 and R 0.040 for 1655 observed reflections. The pseudo-tetrahedral co-ordination environment of the copper(I) atom is made up by two pyrazole nitrogens [2.120(5) and 2.014(5)A], one thioether [2.461(2)A] and one bromide [2.432(1)A]. The ligand acts as a link between two successive copper centres, resulting in a polymeric compound structurally isomorphous to Cu(bdtp)Cl. The compound Ag(bdtp)(NO3) crystallizes in the monoclinic space group P21/n, with a= 18.710(4), b= 8.828(2), c= 11.162(5)A, β= 103.13(3)°, Z = 4 and R 0.038 for 2346 observed reflections. The structure, with bridging ligands, is similar to that of Cu(bdtp)Br. The silver(I) atoms are co-ordinated, in a very distorted-tetrahedral fashion, by two nitrogens [2.483(5) and 2.216(4)A], one thioether [2.571(2)A] and a monodentate nitrate anion [2.503(5)A].

Unusual behaviour of the thioether function of the ligand 1,8-bis(3,5-dimethyl-1-pyrazolyl)-3,6-dithiaoctane (bddo) towards transition-metal salts. X-Ray structures of a green and a red modification of [Cu(bddo)Cl2]

Co-ordination compounds of the new ligand 1,8-bis(3,5-dimethyl-1 -pyrazolyl)-3,6-dithiaoctane (bddo) with MCl2(M = Fe, Mn, Ni, Co, Zn, Cu, or Cd), MBr2(M = Mn, Co, Ni, or Zn), Cu(BF4)2, and CuX (X = BF4, NCS, Cl, Br, or I) are described. The general formula for the divalent metal is [M(bddo)X2] and for copper(I), [Cu2(bddo)X2]. With CuCl2 two modifications were obtained. The green modification of [Cu(bddo)Cl2] crystallises in space group P21/n with a= 9.019(2), b= 28.671(5), c= 8.431(2)A, β= 113.65(2)°, R= 0.055, and R′= 0.066 for 1 578 unique reflections [I > 2σ(I)]. The compound consists of Cu(bddo)Cl2 units. The copper atom is co-ordinated by two pyrazole nitrogens and two chloride atoms, in trans positions, in a distorted square-planar geometry. The red modification of [Cu(bddo)Cl2] crystallises in space group Pbcn with a= 9.397(4), b= 15.093(4), c= 15.142(4)A, Z= 4, R= 0.069, and R′= 0.089 for 864 unique reflections [I > σ(I)]. This compound consists of CuCl2 units linked together by ligand molecules, thus forming chains with distinct C2 symmetry perpendicular to the chain axis. The copper atom is co-ordinated in a distorted-tetrahedral geometry by two pyrazole nitrogens and two chloride atoms in cis positions. The sulphur atoms do not participate in the co-ordination, although molecular-mechanics calculations show that the ligand bddo is not sterically hindered to form tetradentate mononuclear chelates, i.e. with a MN2S2 chromophore. The structures of the other divalent metal halides were established as being very similar to that of the red modification. For [Cu(bddo)(BF4)2] semi-co-ordination of one or both tetrafluoroborates is indicated by the i.r. spectrum. Solid-state 13C n.m.r. spectra of the copper(I) compounds indicate that the S atoms show significant shifts, suggesting co-ordination. In the thiocyanate and iodide compounds both thioether sulphurs co-ordinate in an identical manner, whereas in the chloride and bromide compounds they co-ordinate in a different manner.

Cyclic Voltammetric Behaviour of Some Copper Complexes with a BIS(Pyrazole)BIS(Thioether)Ligand

The cyclic voltammetric behaviour of four mononuclear copper(II) complexes and one binuclear copper(I) complex with the N2S2 ligand 1,6-bis(3,5-dimethyl-l-pyrazolyl)-2,5-dithiahexane (bddh) was studied. Their oxidation-reduction properties will be discussed in terms of the possible relevance of these complexes as models of the Type 1 site of the blue-copper proteins.