펜타아자 비고리 리간드 5- 메틸- 1,2: 8,9- 디시클로헥사노-

3,5,7- 트리아자노난- 1,9- 디아민 니켈(Ⅱ) 착물의 합성

김 성 권

(주)세풍 공학연구소

Synthesis and Characterization of New Ni(Ⅱ) Complex of the Pentaaza Noncyclic ligand 5-Methyl-1,2:8,9-dicyclohexano-3,5,7 -triazanonane-1,9-diamine

Sung Kwon Kim

Engineering R&D Center, Sepoong Paper Co., Ltd.

1.Introduction

Recently, various new types of sterically congested cyclam derivatives have been synthesized, and some very versatile chemistry of their nickel complexes have been studied. For example, the macrocyclic ligand 1[1] and 2[2] have been prepared from 1, 3 - dibromopropane for 1 and methylvinylketone for 2 with cyclohexane - 1, 2 - diamine.

However, most of them were tetraaza macrocycles with cyclohexane rings obtained by nontemplate reactions, and the systhesis of hexaazamacrocycles, that contains two cyclohexne rings on both of the ethylene bridges(2/3 and 9/10 positions of cyclam)and two methyl pendant arms at the uncoordinated nitrogen atom(6 and 13 positions of cyclam) in the fully saturated 14 - membred macrocyclic backbone, by template condensation reactions have not been reported to data. Especially, it has been known that the preparations of the macrocyclic compounds are affected by the structural parameters, such as ring size, substituents, macrocyclic cavity size, degree of ligand unsaturation, and chelate ring sequence[3-6]. Therefore, we have attemped to prepare the new type hexaaza macrocyclic ligand 1. 8-dimethyl-4, 5:11, 12-dicyclohexano -1, 3, 6, 8, 10, 13-hexaazacyclotetradecane(3), that contains two cyclohexane rings and two methyl pendant arms at the 14-memnered macrocyclic backbone, from the condenastion reaction of 2-diaminocyclohexane, formaldehyde, and methylamine in the presence of Ni(Ⅱ) ion. However, we obstained the Ni(Ⅱ) complex of an unexpected noncyclic ligand(4) instead. We report the synthesis and properties of Ni(Ⅱ) noncyclic complex of (4) in this paper.

Ⅱ. Experimental Section

Materials. All chemicals used in synthesis were of reagent grade and were used without further purification. Organic solvents for the spectroscopic measurements were purified according to the literature[7].

Instrumentation. Conductance measurements were performed by using an TOA conductivity meter CM-30ET in conjuction with a conductivity cell with the cell constant of 1.0 cm-1.  Infrared spectrum were recorded with a JASCO IR - 810 spectrophotometer. Electronic absorption spectra were obtained on a Varian Techtron 635 UV/vis spectrophotometer. 13C-NMR spectra were recorded using a Bruker AC 80 FT NMR spectrometer. Elemental analyses were performed by Korea Basic Science Center, Seoul.

Synthesis. Caution! Some of the compounds containing perchlorate anions must be regarded as potentially explosive and should be handled with caution.

[Ni(4)][(ClO4)2. To a stirred methanol(50 ml) solution of NiCl2·6H2O(5.0 g) were added with  cyclohexane-1,2-diamine(5.2g), 36%-aqueous formaldehyde(6.7 g) and methyamine(4.7 g), and the mixture was heated at reflux for 20 hr until a pale-gray suspension solution resulted. The solution was cooled to room temperature until violet precipitated formed. The solid precipitates were filtered, washed with methanol, and dried in vacuum. The pale violet precipitates were dissolved in H2O, and the color of solution was changed instantly from violet to orange. A saturated methanol solution of exess lithium perchlorate or sodium perchlorate was added to the solution, and the mixture was kept in a refrigerator until orange crystals formed. The crystals were filtered, washed with methanol, and dried in vacuo. Yield - 60%.  mp. 240 ℃,  Anal. Calcd for NiC15H31N5Cl2O8: C, 33.29; H, 6.14; N, 12.94.  Found: C, 32.97; H, 6.00; N, 12.52.

[Ni(4)](PF6)2. This complex was prepared by a method similar to that for [Ni(4)](ClO4)2 except that perchlorate(LiClO4 or NaClO4) ion as anion source. 13C NMR(CD3NO2); □ 25.4, 26.2, 33.8, 54.8, 60.6 (cyclohexane rings), 65.0 (N-C-N), 38.7 (N-Me).

Ⅲ. Results and Discussion

Synthesis and properties. Template condensation of cyclohexane-1,2-diamine, methylamine with foraldehyde in the presence of Ni(Ⅱ) ion with the mole ratio of C6H10(NH2)2 : CH2O : CH3NH2 : Ni++ = 2: 4: 2: 1 in methanol solution produced the Ni(Ⅱ) complex of 4, [Ni(C15H31N5)]2+. The Ni(Ⅱ) complex of ligand 3, which was expected initially, was never isolated. It has been known that chelate rings of the macrocyclic ligand with cyclohexane rings are conformationaly rigid[1,8]. Therefore, the formation of [Ni(C15H31N5)]2+ instead of [Ni(3)]2+ is attributable to the rigidity due to the presence of the cyclohexane ring. The proposed synthetic route for the Ni(Ⅱ) pentaaza noncyclic complex of C15H31N5 is similar to that proposed for the synthesis of [Co(NOSemichar)]3+[9].

Complex [Ni(C15H31N5)](ClO4)2 is soluble in polar solvents such as H2O, CH3CN, CH3NO2 or DMF. The noncyclic complex [Ni(C15H31N5)](ClO4)2 is relatively unstable commpared with that of the other Ni(Ⅱ) complexes of the 14 - membered macrocyclic ligands with 5-6-5-6 chelate ring in acidic solutions[10,11]. Spectra of aqueous solution(3.3 x 10-3M) of [Ni(C15H31N5)](ClO4)2 indicated that 55% of the complex decomposed in 1 min upon the addition of HNO3(0.20 M). This stability is partially due to the ligand rigidity and strong interaction(strong bond energy) between the metal ion and the donor atoms of the ligand. The molar conductance and spectral data of the complex sythesized are summarized in Table Ⅰ. The value of molar conductance for the Ni(Ⅱ) complex in aqueous solutions        Table Ⅰ. Spectral and Conductance Data for Pentaaza Ni(Ⅱ) Complex

□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□

complex           ira,b	electronic spectrac,d  □Mc     ref

cm-1	□max, nm(□M-1cm-1)  □-1cm-2M-1

□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□

[Ni(C15H31N5)]  □NH : 3450, 3470   446(20)c, 460(74)d     235     this work

(PF6)2	□NH : 1625

□NH : 3250, 3260

[Ni(1)](NO3)2	□NH : 3260b	440(80)c                         1

[Ni(2)](ClO4)2	□NH : 3185	459(70)c, 463(73)d      205       2

□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□

aMeasured with Nujol mulls, bMeasured with KBr pellets, cMeasured in aqueous solutions at 25℃, dMeasured in CH3NO2.

indicate that the complex is 1:2 electrolyte. The infrared spectra of [Ni(5)](PF6)2 indicate that the complex contains primary and secondary amine groups. The electronic spectra of [Ni(5)]2+ in nitromethane solution shows a broad d-d transition band at 446 nm, indicating the presence of square-planner Ni(Ⅱ)-N4 chromophore[12]. 13C NMR spectra of [Ni(C15H31N5)](PF6)2 measured in CH3NO2-d3 are summarized in experimental section, which show seven carbon peaks as expected for the square-planar geometry of 4. The carbon peaks of cyclohehane rings are observed 25.4, 26.2, 33.8, 54.8, and 60.6 ppm. Peaks at 65.0 and 38.7 ppm are due to the carbons of the N-C-N linkage and pendant methyl group, respectively. From the results of the above spectral and chemical properties together with elemental analysis, the complex is identified as [Ni(C15H31N5)]2+ with square-planner geometry.

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