Synthesis and X-ray Structure of Zn(bpeae)ZnCl₃(bpeae = 2-{Bis-[2-(3,5-dimethyl-pyrazol-1-yl)-ethyl]amino}ethoxy)

2003 Bulletin of the Korean Chemical Society (Print)  
Coordination chemistry of zinc with chelate ligands containing nitrogen and/or oxygen donors is of considerable interest as a model of enzymes such as carbonic anhydrase [NNN] 1 and thermolysin [NNO]. 2 A variety of coordination possibilities such as the variability and flexibility of functional ligands in relevant coordination spheres for zinc could provide highly interesting reactions, structures and catalyst chemistry. 3 Although transition metal complexes of the ligands,
more » ... hyl]amine (bpea), 4-6 bis[2-(3,5-dimethyl-1-pyrazolyl)ethyl]ether 5,6 and bis[2-(3,5-dimethyl-1-pyrazolyl)ethyl]sulfide 6 having commonly three-coordinated Tshape, N 3 -donor ligand are known, the zinc complexes of their ligands were still limited. 4a,4b,4d We have focused on the design and synthesis of N-substituted pyrazole derivative ligand in order to gain better understandings of the controlling electronic effects and coordination numbers from the reaction of those ligands with ZnCl 2 in a structural model of trigonal-bypramidal Cl 2 ZnN 3 or ClZnN 3 O complex. Herein, we report the synthesis and structural properties of the Zn(II) complex of the bpeae as a new type of tetradentate ligand. Experimental Section All chemicals were all reagent-grade and all solvents were freshly distilled prior to use. The bpea was prepared as described in the literature. 4c,5a 1 H NMR spectra were obtained with a Varian 300-NMR Spectrometer at ambient temperature and chemical shifts were referenced to internal tetramethylsilane. Elemental analyses were performed at the Chemical Analysis Laboratory of Center for Scientific Instruments in Kyungpook National University. 2-{Bis-[2-(3,5-dimethyl-pyrazolyl-1-yl)-ethyl]amino}ethanol (bpeaeH). To the solution of bpea (7.03 g, 26.9 mmol) in acetone (70 mL) was added slowly 2-bromoethanol (5.01 mL, 67.2 mmol) and subsequently triethylamine (9.34 mL, 67.2 mmol) with stirring at room temperature. The solution was refluxed for 2 weeks and then the resulting solution was filtered, dried and extracted with dichloromethane, washed four times with brine, dried with MgSO 4 and evaporated in vacuo to afford a yellow oil. Yield: 5.01 g (61%). 1 H NMR (CDCl 3 ): δ 5.68 (s, 4-H-Pz), 3.76 (t, NCH 2 CH2-Pz, J = 6.3, 6.3 Hz), 3.48 (t, NCH 2 CH2OH, J = 4.5, 4.8 Hz), 2.80 (t, NCH2CH 2 -Pz, J = 6.3, 6.3 Hz), 2.62 (t, NCH2CH 2 OH, J = 4.8, 4.8 Hz), 2.12 (s, CH 3 -Pz), 2.08 (s, CH 3 -Pz). [Zn(bpeae)(ZnCl3)]·CH2Cl2. To a suspension of NaH (0.163 g, 6.50 mmol) in dry THF was added a solution of bpeaeH (1.97 g, 6.45 mmol) in THF. The mixture was refluxed for 1 day and the resulting suspension gradually converted into a yellow clear solution. To the resulting solution was added a solution of ZnCl 2 (1.76 g, 12.90 mmol) in methanol (25 mL) and was precipitated a white solid after several minutes. The mixture was stirred for 1 day at ambient temperature, the solution was filtered and the solvent was removed in vacuo to give a white solid. The product was washed with ether and dried in vacuo. The recrystallization of a white solid in dichloromethane gave colorless crystals within a week. Yield: 1.8 g (51%). Anal. (DMSO-d 6 ): δ 5.72 (s, 4-H-Pz), 3.80 (t, NCH 2 CH2-Pz, J = 6.6, 6.9 Hz), 3.35 (t, NCH 2 CH2O, J = 6.0, 5.7 Hz), 2.75 (t, NCH2CH 2 -Pz, J = 6.9, 6.6 Hz), 2.55 (t, NCH2CH 2 O, J = 6.0, Table 1. Details of the X-ray crystal analyses of [Zn(bpeae) (ZnCl3)] · CH2Cl2 Empirical formula C16H26Cl3N5OZn2.CH2Cl2 Formula weight 626.43 Crystal system Monoclinc Space group P21/c a (Å) 9.2536(7) b (Å) 17.499(1) c (Å) 16.119(2) β ( o ) 108.821(7) V (Å 3 ) 2455.0(4) Z 4 dcalc. (mg/m 3 ) 1.695 µ (mm −1 ) 2.518 F(000) 1272 Reflections collected/unique 5226/4725 [R(int)=0.0104] Data/restraints/parameters 4725/0/272 Goodness-of −fit on F 2 1.002 Final R indices [I > 2σ(I)] a R = 0.0372, wR = 0.1127 Largest diff. Peak and hole 0.961 and −0.725 e/Å 3 a R = Σ||Fo| − |Fc|| / Σ|Fo|. wR = [Σ{w(Fo 2 − Fc 2 ) 2 }/ Σ{w(Fo 2 ) 2 }] ½ . w −1 = [σ 2 (Fo 2 ) + (aP) 2 + bP] where P = [Fo 2 + 2Fc 2 ]/3.
doi:10.5012/bkcs.2003.24.4.521 fatcat:dzqpmc3rbba2zbczotdmrqldlu