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)₂and Cd₂(bddo)(NCS)₄

Abstract

The synthesis and characterization of the ligand 1,8-bis(3,5-dimethyl-l -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), with M = Ni, Co, or Zn. With cadmium, Cd,( bddo) (NCS), was found. X-Ray structure determinations were performed on crystals of the compounds Zn(bddo) (NCS),, Ni(bddo) (NCS),, and Cd,(bddo)(NCS),. The cobalt compound was found to be isomorphous to the zinc compound. The compound Zn(bddo) (NCS), 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 > 2cr(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), crystallizes from ethanol in the tetragonal space group P4,2,2 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 > 30(1). The compound consists of monomeric units of octahedral nickel (11) ions with a trans,cis,cis-NiN,N',S, chromophore. The compound Cd2( bddo) (NCS), crystallizes from ethanol in the triclinic space group P i with a = 8.695 (3), & = 9.083(5), c = 1 0.008(3) A, 0: = 91 .I 0(3), p = 99.34(3), y = 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 > 30(/). The cadmium ions are octahedrally co-ordinated with a CdNSN' ,S' , 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.Chelating ligands with a possibility to generate an MN2S2 chromphore have been of increasing interest in recent years for a variety of reasons. On one hand synthetic analogues for the active site of blue copper proteins (and metallo substituted derivatives) have stimulated the design, synthesis, and study of azole-thioether chelating ligands. O n the other hand an interest had developed towards chelating ligands containing a weak donor (sulphur) and a strong donor (nitrogen).Early results have indicated that thioether sulphur atoms can be forced to chelate to metal ion^,^.^ whereas such donor atoms as such do hardly bind to metal ions. An important parameter seems to be the chelate ring size and therefore we have set up a programme towards a set of ligands containing the N2S2 donor set, with pyrazoles and imidazoles as the N donor and thioether as the S donor. The first example of such a new ligand is 1,8-bis(3,5-dimethyl-1 -pyrazolyl)-3,6-dithiaoctane (abbreviated as bddo). Molecular models of this ligand suggest that a tetrahedral MN2S2 chromophore can be formed. To obtain more insight into the ...

Synthesis, Characterisation, and X‐ray Crystal Structure of New NiII, PdII, and PtII Complexes of Tridentate Pyrazole‐Based Ligands with an NOS‐Donor Set

“…In this respect, 2-(3,5-dimethyl-1H-pyrazol-1-yl)ethyl 4-methylbenzenesulfonate [9] on treatment with 2-mercaptoethanol gave thpd and 1-(2-mercaptoethyl)-3,5-dimethylpyrazole [10] on treatment with 3-chloro-1-propanol gave thhd (Scheme 1). These ligands were characterised by elemental analysis, MS spectrometry, and infrared, 1 [11] and Pt II [12] ) produced four chloro complexes whose elemental analyses agree with the formula [MCl 2 in acetonitrile.…”

“…2-(3,5-Dimethyl-1H-pyrazol-1-yl)ethyl 4-methylbenzenesulfonate [9] and 1-(2-mercaptoethyl)-3,5-dimethylpyrazole [10] were prepared according to published methods, as were samples of [PdCl 2 (CH 3 CN) 2 ] [11] and [PtCl 2 (CH 3 CN) 2 ]. [12] Analyses (C, N, H, S) were performed in our analytical laboratory on a Carlo Erba CHNS EA-1108 instrument.…”

Zinc 3,5-dimethylpyrazolate complexes: synthesis and structural studies. The crystal and molecular structure of [Zn2(dmpz)4(Hdmpz)2]

“…A report by Driessen et al describes a compound in which the zinc centre is "tetrahedrally" coordinated by two 33-dimethylpyrazolyl moieties, one neutral 3,5-dimethylpyrazole, and a nitrate anion (12); Venveij et al report a zinc complex in which the zinc is coordinated by the N2 atoms of two 3-methyl-5-phenylpyrazole molecules and two bromide anions in a distorted tetrahedral fashion (13); and Haanstra et al describe a novel structure consisting of chains of zinc atoms linked by a bridging 1,8-bis(3,5-dimethylpyrazoly1)-3,6-dithiaoctane ligand (14). Of more than passing interest to the present study is a report on the binding of pyrazole in crystalline binary and tertiary complexes of liver alcohol dehydrogenase (15).…”

Synthesis of New Palladium(II) Complexes Containing Hemilabile N‐(Alkylamino)pyrazole Ligands: Spectroscopic Analysis and Crystal Structure of [PdCl(ddae)]Cl·H2O {ddae = Bis[2‐(3,5‐dimethyl‐1‐pyrazolyl)ethyl]ethylamine}

“…The precursor 3,5-dimethyl-1-[2-(p-tosyloxy)ethyl]pyrazole was prepared as described in the literature. [8] …”

“…This new method is also useful to develop two new ligands that had not been described previously: bis[2-(3,5-dimethyl-1-pyrazolyl)ethyl]-isopropylamino (ddai) and bis[2-(3,5-dimethyl-1-pyrazolyl)-ethyl]tert-butylamino (ddat), neither of which could be synthesised by the same method that was used in the literature for ddae. Synthesis of the three ligands consists of the treatment of 3,5-dimethyl-1-(2-toluene-p-sulfonyloxyethyl)pyrazole [8] with the appropriate primary amine (ddae: ethylamine; ddai: isopropylamine; ddat: tert-butylamine) in the presence of sodium hydroxide in water.…”