Transition Metal Complexes of Derivatized Chiral Dihydro-1,2,4-triazin-6-ones. Template Synthesis of Nickel(II) Tetraaza-(4N-M) Complexes Incorporating the Triazinone Moiety

Corresponding Author: Ahmad S. Abushamleh, Hashemite University Department of Chemistry, P.O. Box 150459, Zarqa, Jordan 750 Transition Metal Complexes of Derivatized Chiral Dihydro-1,2,4-triazin-6-ones. Template Synthesis of Nickel(II) Tetraaza-(4N-M) Complexes Incorporating the Triazinone Moiety Ahmad S. Abushamleh, Marwa M. Al-Aqarbeh, and Vector Day Department of Chemistry, Hashemite University, P.O. Box 150459, Zarqa, Jordan X-Ray Crystallography Laboratory, Department of Chemistry, University of Kansas Lawrence, Kansas 66045-7582, USA

Attempts to introduce Pd 2+ ion instead of Ni 2+ in (4) resulted in a square-planar palladium(II) complex where the two oxime ligands (2) are coordinated unsymmetrically and thus not allowing the expected carbon-carbon coupling to take place (5) [5] .This has occurred probably due to the larger size of the Pd 2+ ion In addition, the reaction of oxime (2) with copper(II) acetate gave complex (6) in minute quantities, apparently because toluene was eliminated from it giving rise to complex (7), (Scheme 3). The crystal structure of (7) was proved by X-ray crystallorgraphy and found to be slightly distorted square-pyramidal geometry [6] . This geometry was surprisingly supported by the presence of a chlorine atom bonded to the copper center. The source of this chlorine atom is not definitely known but it could be from the chlorinated solvent used in the preparation and crystallization processes [7] .
Since the overall aim of this work is to incorporate the triazinone moiety into a real macrocyclic ring system, we attempted a new synthetic route and that is the reaction of the triazinone compounds with suitable diamines in the presence of the transition metal cation, i.e.,template effect synthesis [8] .

RESULTS AND DISCUSSION
It has been observed that in order for the carboncarbon coupling between the benzylic carbon of one triazinone ligand and the chiral carbon center of the other to take place, the two oxime ligands must coordinate in a symmetrical way (e.g. compound 4). This has initiated the idea of linking the two triazinone moieties from the bottom, using a suitable diamine, assuming that the carbon-carbon coupling will link them from the top. As such this should produce a macrocyclic ring system of a tetraaza-type (4N-M). Thus, two types of the 3-acetyl triazinones (compounds 8) and three types of diamines were used, these are: 1,3-diaminopropane, o-phenylenediamine, and ethylenediamine. The reaction of two moles of the triazinone (8a) with one mole of 1,3-diaminopropane in the presence of one mole of nickel(II) acetate is expected to produce compound 9a or 9`b (Scheme 4). The nature of the product depends on whether cyclization, via carboncarbon coupling, has taken place or not. The resulting complex, however, is diamagnetic indicating square planar geometry for Ni 2+ . It is also neutral in 10 -3 M DMF solution. The IR spectral data are not diagnostic for such compounds. The elemental analyses indicate, most likely, an open-chain structure (9a). Similarly, two moles of the triazinone(8b) were reacted with one mole of 1,3-diaminopropane in the presence of one mole nickel(II) acetate. The produced oily/gummy product was purified until it was solid. The solid was recrystallized from hot aqueous methanol and the results of elemental analyses were consistent with structure 9b which is neutral in 10 -3 M DMF solution. Magnetic measurements showed that 9b is diamagnetic. In an attempt to grow crystals of 9b, several organic solvents were tried. The crystals used in the X-ray crystallographic analysis for the determination of the structure depicted in Fig. 1 were grown from acetone. When a sample of 9b was recrystallized from dichloromethane, a much deeper color crystals were obtained. These deep color crystals are most likely compound 12 (Scheme 5), results of elemental analyses are consistent with structure 12 (for Ni C 32 H 27 N 8 O 2 Calcd: C 62.57, H 4.40, N 18.25%; Found: C 62.26, H 4.56, N 18.05%). Compound 12 is also diamagnetic and neutral in DMF. Attempts to grow crystals of the compound are still going on to prove the structure further by X-ray work.
The same synthetic roots (with minor variations) were employed when o-phenylenediamine and ethylenediamine were used to prepare compounds 10a, 10b and 11a, 11b, respectively (Scheme 4). Apparantly, macrocyclic closure was not observed in these complexes, however, work is still going on to elucidate their structural features.

CRYSTAL STRUCTURE DETERMINATION OF 9B
Crystals suitable for X-ray crystallographic analysis were grown from acetone. The structure shown in Fig.  1 was determined at the X-Ray Crystallography Laboratory, University of Kansas, USA. The absolute configuration that is shown was determined experimentally using anomalous dispersion of the Xrays.

EXPERIMENTAL
Melting points (uncorrected) were determined using a Gallenkamp melting point apparatus in one-end glass capillaries. The magnetic moments were measured for finely ground solid samples at ambient temperature using a Johnson Matthey Magnetic Susceptibility Balance. Elemental analyses were performed on an Euro EA3000 Elemental Analyzer (Euro Vector), at the Department of Chemistry, Hashemite University, Jordan.

Synthesis of 1-phenylhyrazono-1-chloroacetone (Ph-NH-N=C(Cl)-C(O)-CH 3 )(Hydrazonoyl Chloride)
General procedure: • Preparation of benzenediazonium chloride PhN 2 + Clsolution: Aniline (0.1 mol) in 80 ml of 1:1 H 2 O/conc. HCl was cooled to about 0°C in an ice bath with stirring. Then a solution of sodium nitrite (7.6 g/25 mL H 2 O) was added dropwise. Stirring was continued for 30 min. This preparation was done according to reference 8 and the solution was used as it is in the next step. H Ph continued for 15 minutes. The crude solid product was collected by suction filtration and washed several times with cold water and then with little petroleum ether, dried and recrystallized from chloroform / petroleum ether. Yield = 15.1g (79%); mp 140-14°C ; literature mp. 141-142 °C [9] .

Synthesis of: L-3-Acetyl-5-methyl-1-phenyl-4,5dihydro -[1,2,4]triazin-6-one(8a):
This compound was prepared via direct interaction between 1-chloro-1phenylhydrazono-2-propanone (hydrazonoyl chloride) and L-alanine methyl ester hydrochloride in the presence of triethylamine, according to the following general procedure: To a stirred solution of the hydrazonoyl chloride (20 mmol) in 50 mL of CHCl 3 , a solution of the appropriate amino acid ester hydrochloride (20 mmol) in 50mL of methanol was added. The mixture was cooled to about 0°C and triethylamine (18 mL, 0.17 mol) in 10 mL of methanol was added dropwise keeping the temperature not higher than 5°C . The reaction mixture was kept under continuous stirring at 0°C for 2-3 h. and then at ambient temperature for 24 hours. The solvent was then removed in vacuo, and the residue was washed with water. The resulting crude solid product was then collected and recrystallized from aqueous ethanol. The product was obtained in the form of prismatic crystals, 78% yield, mp 114-115°C.

N,N´-Bis [(1-phenyl-5-methyl-4,5-dihydro-6-oxo-1,2,4-triazin-3-yl)-ethylidene] propane-1,3-diamine nickel (II) , (9a):
The acetyl compound (8a) (1.39g, 6 mmol) and nickel acetate tetrahydrate (0.75 g, 3 mmol) in 80 mL of absolute ethanol were stirred at room temperature for few minutes. 1,3-diaminopropane (0.24 g, 3.25 mmol) in absolute ethanol (20 mL) was added dropwise over a period of 10 min. The reaction mixture was brought to reflux under constant stirring for about 70 hours. During the first few hours the reaction mixture assumed dark green color which changed to red then to brown color. This color persisted until the end of the reflux time. The solvent was removed in vacuo, and a gummy residue was obtained. This was treated with hot aqueous ethanol and left aside to solidify. The The acetyl compound (8b), (1.84g, 6 mmol) and nickel acetate tetrahydrate (0.75 g, 3 mmol) in 80 mL of absolute ethanol were stirred at room temperature for few minutes. Ethylenediamine (0.20g, 3.33 mmol) in absolute ethanol (20 mL) was added dropwise over a period of 10 minutes. The reaction mixture was brought to reflux under constant stirring for about 3 days. During the first few hours the reaction mixture assumed red color ans this color persisted until the end of the reflux time. The solvent was removed in vacuo, and an oily residue was obtained. This was treated with hot aqueous ethanol and left aside to solidify and the solid was recrystallized from acetone. Yield =1.35g (65%), mp > 330°C