O-Disiyano sübstitüe yeni bir dioksim türevi sentezi ve komplekslerinin incelenmesi

Abstract

ÖZET Geçiş metalleri ile kararlı kompleksler oluşturan viç-dioksimlerin B,2 vitamini için model bileşik olarak kullanılması biyokimyasal önemini son derece artırmıştır. Değişik fonksiyonel gruplar taşıyan yeni ligandların hazırlanması pekçok araştırmanın esasım oluşturmaktadır. Bu çalışmada sodyum siyanür ve karbon sülfür gibi basil maddelerden çıkarak iki adımda elde edilen diliyomaleonilril disodyum tuzu ile anti- dikloroglioksimin reaksiyonundan hem yjç-dioksim, hem de 1,2-disiyano grubu taşıyan yeni bir ligand olan l,4-ditiya-2,3-disiyano-4,5-bis(hidroksiimino)siklo-heksa-2-en (LH2) sentez edilmiştir. Dietileter, kloroform ve etilalkolde çok iyi çözünen bu bileşik, kütle spektrumunda moleküler iyon pikini e/z 226'da göstermiştir. İR spektrumunda O-H, C=N ve N-0 gruplarına ait gerilme titreşimlerini sırasıyla 3260, 2210, 1620 ve 1010 cm`1 'de göstermiştir. 'H NMR spektrumunda anli-formundaki O-H gruplarım gösteren tek bir pik 13.04 ppnı'de ortaya çıkmıştır. LH2'ııin ııikcl(II) ve kobalt(II) ile oluşturduğu metal/ligand oranı 1:2 olan kompleksleri [Ni(LH)2 ve Co(LH)2] kırmızı-kahverengi ve kahverengidir. Komplekslerin İR speklrumları serbest OH titreşimlerinin kaybolduğunu, O-H... O köprüsüne atfedilebilecek geniş bir bandın 1710 cm`1 civarında çıktığını, C=N titreşimlerin de ise önemli bir değişimin olmadığım göstermekledir.

SUMMARY Transition metal chemistry of oximes which starts with the early work of Tschugaeff on the reaction of dimelhylglyoxime with d8 metal ions is one of the most significant events of coordination chemistry. Variations on the structure of thc'ligand and on the central metal ions have been rapidly increased. The bidentate nature of vic-dioximates has been proposed even in the early works and has been accepted generally without further criticsm. However, the chelate ring size remained uncertain for few decades and incorrect seven-membered and six-membered structures were proposed until x-ray single crystal analyses were carried out which clearly proved the 5-membered chelates with two hydrogen bridges. vic-dioxime complexes have yielded through the decades a never-ending scries of interesting chemistry. The chemistry of ligands having additional functions other than the oxime moiety has become the goal of many chemists all over the world. The structure, stability and reactivity of molecules in analytical, biochemical or technical applications have been the fundamental aims of research in this field. The structures of oxime and vic-dioxime ligands have been extensively studied by x-ray diffraction techniques. The dimensions of the oxime group in number of compounds have been determined and these values are very close to the calculated C=N (1.27 A0) and N-0 (1.44 A`) distances based on covalent radii and electro negativity. For the O-II bonds, the calculated values are around 1.02 A°. As ligand, simple oximo group is capable of bonding through nitrogen and/or oxygen atomy. The vast majority of complexes actually contain bonds between metal ion and the donor nitrogens. The bonding modes can be briefly summarized as follows: In all these structures, oxime group coordinates as it is or in the form of deprotonated conjugate base. VllThe coordination efficiency of the two neighboring oxime groups (i.e. vicinal dioximes) is far above that of simple oximes and the best known example of vic- dioximes is dimethylglyoxime. This ligand group has been divided into three subgroups according to the orientation of -OH functions with respect to each other: namely and, amphi and şyn : These three isomers have been differentiated by spectroscopic methods and by their interaction with metal ions. The anti-dioximes form two five-membered chelates and two hydrogen bridges with a planar MN4 core. The amphi derivative is liable to form N.O-coordinated six-membered chelates without any 0-H...0 bridges. The third isomer (syn) does not form any complex under ordinary conditions. O-H- O rVY C = N-0 N= C `O- N= C OH O- H- O The results of structure analyses on the metal complexes of anti-vic-dioxime indicate that N-0 distance is considerably shortened and C=N lenghth is not much affected when compared with those of the free ligands. The intramolecular hydrogen bridged O O distances are found to occur upward from 2.4 A°. When O O separation becomes larger than 2.5 A0, the H atom is usually situated unsymmetrically at about 1 A0 from one of the two oxygen atoms. For a given ligand 0....0 distance increases in the order of Ni<Pd<Pt paralleling increase in atomic radii. VlllThe reaction of anti-dichloroglyoxime or an active reagent derived from it by treating with aqueous sodium carbonate solution at low temperatures, namely dicyan- di-N-oxide, with amines and thiols have been extensively used to prepare new diamino-glyoxime derivates. These new ligands contain another functional group in addition to the vic-dioxime moiety, so multinuclear compounds have been prepared. yjc-Dioxime ligands with ferrocene units can be taken as an example for these multinuclear compounds. A number of bisglyoxime complexes with crown ether rings as substituents have been reported by Bekaroğlu and coworkers. The synthesis of these complexes was achieved by reacting mono or dichloroglyoxime with subtituted all oxa-,monoaza-,or diaza-crown ethers in ethanol in the presence of NaHC03. The 'II NMR, 13C NMR and IR spectra are not significantly affected by complexation of alkali ions to crown ethers. Extraction experiments of alkaline picrate salts from aqueous solutions into a dichloromethane layer containing the bis glyoxime complex showed a high extraction efficiency of K+, which may be due to sandwiching of the K+ by two crown ether rings. r~/ »°-N>r XtX Disodium salt of dithiomaleonitrile (1) prepared relatively easily from simple starting materials sodium cyanide and carbondisulfide in two steps, has been recently used extensively for the synthesis of porphyrazine derivatives after alkylation of the thiolate groups. In these reactions, the cis-conformation of dicyano-function has been used to carry of the cyclotetramerization. IXNaS^/CN NaS -`^CN C,H,7S^XN C,H7S---^-.CN Rswsi SR N---M.-..N Nv`vN M R=C,H7 In the present work, our aim has been to prepare a vic-dioxime ligand simultaneously carrying dicyano-substituents. Dithiomaleonitrile disodium salt(l) and anti-dichloroglyoxime have been chosen as the starting materials, cis-conformation of thiolates in 1 is especially suitable for the condensation of these two reactants in 1:1 ratio to for a six-membered ring. Since 1 is already in the salt form, there is no need to add any base to the reaction medium. l,4-Dithia-2,3-dicyano-4,5-bis(hydroxyimino)cyclo-hexa-2-ene(LH2)issoluble in chloroform, diethyl ether and ethanol. Elemental analysis results of LH2 closely follow the theoretical values. In the GC Mass spectrum, molecular ion peak (M+) is at m/e 226. In the IR spectrum, stretching vibrations of O-H, C=N and N-0 groups appear at 3260, 1620 and 1010 cm`1, respectively. These relatively intense peaks are the characteristic absorptions for oxime groups. Another IR active group in the spectrum of LH2 is C=N and its streching vibrations come out at 2210 cm`1 which is a typical value for nitrile groups bound to unsaturated carbons. In the 'H NMR spectrum of LH2, the single peak in the low field can be easily attributed to oxime protons. At the same time, it is a strong evidence for the anti-conformation of oximes in LH2, while amphi-derivatives give two peaks in this region. The anti- structure is further confirmed by the formation of reddish-brown complexes with Ni2+ salts which is typical for square planar MN4 core containing vic-dioximates. NCv/SNa NC^SNa CI NOH V CI^NOH NC /zsv NOH NC' xs NOHIn order to prepare Ni(II) and Co(II) complexes of LH2, the ethanol solution of the ligand was treated with the metal salt and dilute ammonia or NaOH solution was added to adjust the pH. For the dark-brown Ni(LH)2 and brown Co(LH)2 complexes, metal/ligand ratio is 1:2 as expected. These complexes are only slightly soluble in pyridine and dimethylsulfoxide. The general appearence of the IR spectra of both complexes is very similar. The OH-stretching vibration of LH2 around 3250 cm`1 has dissappeared. A broad peak around 1710 cm`1 corresponding to 0-H...0 bridges comes out. The vibrations of the cyano groups do not show appreciable change after complexation, so we might conclude that no interaction between cyano groups and the metal ion is present. O-H- O NC YSV/ /VY* NC AA// X S'^CN O- H- O XI