Yeni makrosiklik vic-dioksimlerin sentezi ve komplekslerininin incelenmesi

Abstract

viç-dioks imler geçiş metalleri ile verdikleri stabil kompleksler nedeniyle şelat teşkil edici olarak kullanılması grubumuz tarafından yapılan çalışmaların önemli bir bölümünü oluşturmaktadır. Literatürde bilinen makrosiklik yapıdaki vic-dioksim ligantların sayısı oldukça sınırlıdır ve makro halka bünyesindeki hetero atomlar O, N, S veya bunların ikili karışımlarından ibarettir. Burada donor grupların türüne bağlı olarak metal iyonlarıyla etkileşim farklılk göstermektedir. Sadece N ve S donor grupları mevcut olduğunda geçiş metalleri ile kompleks oluştururken N ve 0 karışımından oluşan makro halka sadece alkali metallerle kısmen etkileşmektedirler. Bu çalışmanın amacı makrosiklik vic- dioksimlerde halkayı oluşturarak üç tür hetero atomu N2S20 şeklinde bir araya getirmektedir. Bu çalışmada çıkış maddesi olarak O-aminotiofenolden çıkılarak ilk kademede bis(2-klor etil) eter ile reaksiyona sokulmuş daha sonra ele geçen ürün diklorglioksim ile muamele edilerek yeni bir ligand (8, 9); (14f 15)-Dibenzo ll,12-bis(hidroksiimino) 1,7,4,10,13 ditiaoksadiazasiklopentadekan (LH2) elde edilmiştir. Daha sonra bu liganddan çıkılarak Ni (II), Co (II) ve U02 (VI) kompleksleri ilk defa izole edilmiştir. Elde edilen yeni bileşiklerin yapısı elementel analiz yanında, İR, NMR ve kütle spektrumları yardımıyla aydınlatılmıştır.

The name oxime may be considered to be derived from oxy-imine, C=NOH. The oxime group is amphiprotic with a slightly basic nitrogen and a mildly acidic hydroxyl group. Werner explained the observed isomerism of oximes on the basis of differences in "spatial arrangement" of the groups atteched to the C=N moiety. The most significant early discovery in the chemistry of metal oximates was the reaction between nickel (II) salts and dimethylglyoxime, which is the best known example of a vicinal dioxime (abbreviated as vic-dioxime). The discoverer Tschugaeff correctly identified the bidentate nature of vic-dioximes. However, the chelate ring size remained uncertain and went through the incorrect seven- and six-membered formulations before the correct five-membered ring was fully established. Interesting historical accounts of oximes are well documented. Oximes are generally represented by structure (JJ, but the alternative nitrone structure (J2) was debated actively as late as 1952. Neutron diffraction work on dimethylglyoxime definitely established the presence of 0- H bonds (1.02±0.04°A) in it. Structure (JL.) is now usually accepted for the oximes, which are generally assopiated in the solid state via 0-H...N hydrogen bonds of length ~ 2.8 °A. The calculated C=N and N-0 distances based on covalent radii and electronegativity date are 1.27 and 1.44°A respectively. Actual experimental values for C=N distances lie within ± 0.02°A of the calculated figure, but the observed N-0 distances are generally lower and lie in the range of 1.40±0.02°A vi As a ligand, the oxime group is potentially ambidentate with possibilities of coordination through nitrogen and/or oxygen atom(s), as depicted in (2.)~(§J* Although a good number of oxygen -bonded complexes are known, the coordination in actual practice generally occurs through nitrogen. In the latter cases, coordination can occur through the oxime or its conjugate base, as depicted by putting the hydrogen atom in parenthesis in (3) ; in (4J, one oxime molecule is coordinating as such WKxle the second one does so in the form of conjugate base, with the single hydrogen atom shared as 0....H....0. Simple oximes are ligands which have merely one oxime group as the only coordination site; the simplest examples of these are acetaldoxime (Hado) and acetoxime (Hato). Hieber and Leutert showed in 1927-29 that such oximes yield complexes of the type M ( oxime )nX2( where n is usually 2 or 4 and X a halogen) with copper (II), nickel (II) and cobalt (II) salts. The three-dimensionel crystal structure of Ni(Hado)«Cl2 has shown the molecule to be of trans octahedral NiN4Cl2 type, with the NiN* fragment being planar and the oxime protons being hydrogen -bonded with the coordinated chloride ions intramolecularly. The work has been extenced to the synthesis of the corresponding Ni(cyclohexanone oxime )«C12 complex, which also indicated an octahedral structure, with the oxime being bonded through nitrogen only. Complexes ML«X2 and M'L2X2(M « Ni11, Co11 ; L=acetaldoxime or benzaldoxime and X=C1 or Br) have been prepared and characterized on the basis conductivity, magnetic moment, IR and electron spectra data. A number of planar platinum (II) complexes, [Pt(oxime)2(NH3)2]Cl2 and [Pt (oxime )«]C12, have been isolated, which have been shown to function as stronger protonic acids than the corresponding free oximes; in some cases neutralized species such as [Pt(Hato) (ato)2] can be readily obtained. vii Dimeric compounds with the formula [M(ato)Me2]2, where M=B, Al or Ga, with the "ato" (acetoximato) group bridging have been reported. Similary, in the trimetic palladium (II) complexes [ Pd(acetato) acetoximato ) ]3, both the acetato and acetoximato groups have been shown to bridge the three palladium atoms which constitue an equilateral triangle. The best known example of a vic-dioxime is dimethylglyoxime (7.) (H2DMG), which gives the well-known red nickel complex (B) with Ni2+ in ammoniacal solution. The detailed structures of a fairly large of metal vic- dioximates are known from X-ray investigations. The important features, apart from NA planar binding, are the strong 0...H...0 hydrogen bondings and the stacking of the planar units parallel to each other in the crystal, in the cases of Ni11 and Pd11 complexes in general. Metal-metal interactions in chains have reported in number of similar compounds. 8 A special mention may be made of cobalt complexes; the [Co(HDMG)2]n± (n=0,l) has been named "cobaloxime" by analogy with "cobalamin" which is another name of vitamin B12. Depending upon the metal and its oxidation state, structures of the type (11) may accommodate additional ligands on one or both [e.g.Rh(HDMG)2Cl(PPh3) ] the etial positions, perpendicular to the plane of (.11). Ideally (11) should have the symmetry D^, but it is often found to biT lower due to distortions arising out of the peculiarities in bonding or crystal packing. The C=N distance (~1.30°A) in most of these vic-dioximates is almost the same as in parent dioximes, but the N-0 distances are generally lowered to ~1.34°A from ~1.40°A in the free ligands. The structural details along with supporting spectral evidence have been well summarized in a recent review. Selectively and analytical applications of dimethylglyoxime and related ligands have also been extensively studied. A series of chiral bis-dioximato complexes of Fe11, Co11, Ni11 and Pd11 have been described from three viii geometrical isomers (a, £ and b ) of D-camphorguinone dioxime (Hcdq) and two (J5 and 5) of L-nopinoquinone dioxime (Hnqd). Opposite Cotton effects around 20.000 cm*1 have been observed for Co(a-cqd)2.H20 and Co( 8-nqd)2.H20 indicating their "quasi-enantiomeric" stereochemistries. Although square-planer configuration is customarily considered classical for vic-dioximate of nickel (II), attempts have been made repeatedly over the years for preparing the above complexes in other configurations also. By employing weakly polar solvents and some other variations, success has been claimed in the preparation of mono(dioxime) complexes of nickel (II). The dichloro- bis(l,2-cyclohexanedione dioximato)nickel(II) has been shown to have an octahedral vie structure. Examples of tris (dioxime) complexes of transition metals in general and of bivalent atoms in particular are rare and structural details of only a tris (dioxime) complex of cobalt (III) are known. The crystal structure of tris ( 1, 2-cyclohexanedione dioximo ) nickel ( II ) sulfate dihydrate has been elucidated to confirm the structures with 3:1 ligand/metal ratio. The number of macrocyclic vic-dioxime ligands reported in the literature is rather few and the heteroatoms of these macro rings are usually 0,N,S, or binary mixtures of these donor groups. Depending upon the nature of the donor group the interaction of macrocycles with metal ions shows different tendencies: When only N and S groups are present, they prefer to complex with transition metal ions, while in the case of N and 0 mixtures, only partial interaction with alkali metal ions occurs. In the present work, we have planned to bring together three of these donor groups (N2S20) with the oxime moiety for the first time on the same ligand molecule. The synthetic work starded with the chlorination of OH group in diethyleneglycol. For this purpose diethyleneglycol was dissolved in pyridine and treated with S0C12 to obtain bis (2-chloroethyl) ether with a high yield ( ~ % 85 ). The reaction of this compound with o- mercaptoaniline in a basic medium gave 1,5- bis(2'aminophenilthio)-3-oxapentane, which was a viscous liquid at room temperature and which was converted into crystaline hydrochloride salt by treatment with HC1 gas in inert solution. xx "d 'SM In order to obtain the desired macrocyclic vic- dioxime ligand with N2S20 donors in the macro ring, the diamino compound can be reacted with either cyanogen-di-N- oxide or with anti-dichloroglyoxime. In the first one, cyanogen-di-N-oxide, which was obtained by treating anti- dichloroglyoxime with a strong base and subsequently extracting the mixture with dichlorome thane or toluene was added into the diamino-compound, but the product was an olygomer rather than a raacroring formed by 1:1 condensation of the two reactants. The latter method made use of the reaction of diamino-compound with anti- dichloroglyoxime directly in the presence of NaHC03. Here bicarbonate ions were consumed to neutralize HC1 formed during the reaction, while sodium ions showed template effect to complate the cyclomerization. Also gradual addition of anti-dichloro-glyoxime provided dilute conditions which also resulted with 1:1 condensation of the two reactants to from the desired product. OH ci^N / Gl.Xn \ OH OH / \ OH Ni (II), Co (II) and U02 (VI) complexes of this novel ligand, namely ( 8, 9 ) ; ( 14, 15 ) -dibenzo-11, 12- bis ( hydroxy imino) -1, 7,4, 10, 13-dithiaoxadiazocyclopenta- decane (LH2). The metal/ligand ratio for the first raw transition metal ions Co and Ni is 1:2, but for the uranyl ion 1:1. These results indicate that the usual N,N- coordinated planar vic-dioximate complexes are formed with Ni (II) and Co (II). The uranyl complex can be postulated as an N,0-coordinated n-hydroxo complex of 2:2 metal/ligand ratio as encountered in same other dioxime ligands. xi The structures of the novel compounds have been elucidated by using suitable spectral techniques such as IR, lH NMR,, Mass spectra along with elementel analysis. M = Ni(II) and Co(II) H OH u \f