96556-05-7

Basic information

• Product Name: 1,4,7-TRIMETHYL-1,4,7-TRIAZACYCLONONANE
• Synonyms: OCTAHYDRO-1,4,7-TRIMETHYL-1H-1,4,7-TRIAZONINE;1,4,7-Trimethyl-1,4,7-triazacycl;1,4,7-trimethyl-1,4,7-triaazacyclononane;1,4,7-Trimethyl-1,4,7-triazacyclononane,min.97%;1,4,7-Trimethyl-1,4,7-triazacyclononane, min. 97%;1,4,7-Trimethyl-1,4,7-triazacyclononane (stabilized with NaHCO3);1,4,7-Trimethyloctahydro-1H-1,4,7-triazonine;N,N',N''-Trimethyl-1,4,7-triazacyclononane
• CAS NO: 96556-05-7
• Molecular Formula: C₉H₂₁N₃
• Molecular Weight: 171.28
• Product Categories: Crown Ethers;Functional Materials;Macrocycles for Host-Guest Chemistry;Chelation/Complexation Compounds;Crown Ethers;Synthetic Reagents;organic amine;Macrocyclics/Ligand;Achiral Nitrogen;Cy-N
• Mol File: 96556-05-7.mol
• Article Data: 10

Chemical Properties

• Boiling Point: 208℃
• Flash Point: 155 °F
• Appearance: pale yellow/liquid
• Density: 0.884 g/mL at 25 °C(lit.)
• Vapor Pressure: 0.221mmHg at 25°C
• Refractive Index: n20/D 1.473(lit.)
• Storage Temp.: 2-8°C
• PKA: 8.69±0.20(Predicted)
• Sensitive: moisture sensitive
• BRN: 4174812
• CAS DataBase Reference: 1,4,7-TRIMETHYL-1,4,7-TRIAZACYCLONONANE(CAS DataBase Reference)
• NIST Chemistry Reference: 1,4,7-TRIMETHYL-1,4,7-TRIAZACYCLONONANE(96556-05-7)
• EPA Substance Registry System: 1,4,7-TRIMETHYL-1,4,7-TRIAZACYCLONONANE(96556-05-7)

Safety Data

• Hazard Codes: C,Xi
• Statements: 34
• Safety Statements: 26-36/37/39-45
• RIDADR: UN 3267 8/PG 2
• WGK Germany: 3
• F: 10-34
• HazardClass: 8
• PackingGroup: III
• Hazardous Substances Data: 96556-05-7(Hazardous Substances Data)

Usage

Uses

Useful ligand for preparing transition metal complexes.

InChI:InChI=1/C9H21N3/c1-10-4-6-11(2)8-9-12(3)7-5-10/h4-9H2,1-3H3

Synthetic route

N,N',N-tris(p-toluenesulfonyl)-1,4,7-triazacyclononane (52667-89-7) → N,N',N''-trimethyl-1,4,7-triazacyclononane (96556-05-7)

Conditions	Yield
Stage #1: N,N',N-tris(p-toluenesulfonyl)-1,4,7-triazacyclononane With hydrogenchloride; water at 140℃; for 6h; Stage #2: With sodium hydroxide; formaldehyd; formic acid In water at 0 - 90℃; Further stages.;	75%

methyl bromide (74-83-9) + 1,4,7-triazacyclononane (4730-54-5) → N,N',N''-trimethyl-1,4,7-triazacyclononane (96556-05-7)

Conditions	Yield
With potassium carbonate In acetonitrile for 16h; Reflux;	75%

formaldehyd (50-00-0) + N,N',N-tris(p-toluenesulfonyl)-1,4,7-triazacyclononane (52667-89-7) → N,N',N''-trimethyl-1,4,7-triazacyclononane (96556-05-7)

Conditions	Yield
Stage #1: N,N',N-tris(p-toluenesulfonyl)-1,4,7-triazacyclononane With sulfuric acid In water at 140℃; for 6h; Stage #2: With sodium hydroxide In water Cooling with ice; Stage #3: formaldehyd With formic acid In water at 90℃;	25%

1,4,7-triazacyclononane (4730-54-5) + methyl iodide (74-88-4) → N,N',N''-trimethyl-1,4,7-triazacyclononane (96556-05-7)

Conditions	Yield
With n-butyllithium 1.) Et2O, -78 deg C 2.) r. t., 0.5 h; Yield given. Multistep reaction;
With potassium carbonate In acetonitrile at 20℃; for 16h; Reflux;

formaldehyd (50-00-0) + 1,4,7-triazacyclononane (4730-54-5) → N,N',N''-trimethyl-1,4,7-triazacyclononane (96556-05-7)

Conditions	Yield
With formic acid at 101℃;	0.9 g
With formic acid; hydrogen bromide

formaldehyd (50-00-0) + 1,4,7-trimethylsulfonyl-1,4,7-triazacyclononane → N,N',N''-trimethyl-1,4,7-triazacyclononane (96556-05-7)

Conditions	Yield
Stage #1: 1,4,7-trimethylsulfonyl-1,4,7-triazacyclononane With sulfuric acid; sodium hydroxide In water at 180℃; for 10h; Stage #2: formaldehyd With formic acid In water at 90℃; for 14h;	39 g

formaldehyd (50-00-0) + 1,4,7-triphenylsulfonyl-1,4,7-triazacyclononane → N,N',N''-trimethyl-1,4,7-triazacyclononane (96556-05-7)

Conditions	Yield
Stage #1: 1,4,7-triphenylsulfonyl-1,4,7-triazacyclononane With sulfuric acid In water at 95 - 100℃; for 3h; Stage #2: With sodium hydroxide In water pH=5; Stage #3: formaldehyd With formic acid In water at 80 - 90℃; for 6h; Time;	120 g

perrhenic acid anhydride + N,N',N''-trimethyl-1,4,7-triazacyclononane (96556-05-7) → [ReO3(N,N',N''-trimethyl-1,4,7-triazacyclononane)]ReO4

Conditions	Yield
In tetrahydrofuran N2-atmosphere; stirring equimolar amts. for 15 min (pptn.); decantation, washing (THF), drying (vac.); elem. anal.;	99%

(HNMe2)2Cl2Ti(NPh) (402937-77-3) + N,N',N''-trimethyl-1,4,7-triazacyclononane (96556-05-7) → [Ti(NPh)(1,4,7-trimethyl triazacyclononane)Cl2] (906666-44-2)

Conditions	Yield
In benzene (N2 or Ar); ligand added to a soln. of Ti complex, stirred for 16 h; filtered off, washed (hexanes), dried (vac.); elem. anal.;	99%

chlorobis(cyclooctene)-iridium(I) dimer + hydrogen (1333-74-0) + N,N',N''-trimethyl-1,4,7-triazacyclononane (96556-05-7) → [(1,4,7-trimethyl-1,4,7-triazacyclononane)Ir(H)2(cyclooctene)]Cl (639482-84-1)

Conditions	Yield
In tetrahydrofuran; dichloromethane N2; addn. of triamine to a soln. of Ir complex in THF/CH2Cl2 cooled to -78°C, degassing, cooling to -78°C, addn. of 1 atm of H2, stirring for 1 h, slow warming to room temp., stirring for 1 h; concg. under vac., pptn. by addn. of pentane, washing the ppt. with pentane, vac. drying; elem. anal.;	97%

C6H15N*H(1+)*C32H36B(1-) + N,N',N''-trimethyl-1,4,7-triazacyclononane (96556-05-7) → C32H36B(1-)*C9H21N3*H(1+)

Conditions	Yield
In diethyl ether at 20℃; for 1h; Inert atmosphere;	97%

sodium hexanitro cobaltate(III) + N,N',N''-trimethyl-1,4,7-triazacyclononane (96556-05-7) → cobalt(III)(1,4,7-trimethyl-1,4,7-triazacyclononane)(NO2)3

Conditions	Yield
In methanol; water addn. of organic compound in methanol to a soln. of Co-complex in water, stirring at 60°C for 1 h; cooling to 2°C, filtn.;	96%

bis(dimethylamido)titanium(IV) dichloride (16753-20-1) + N,N',N''-trimethyl-1,4,7-triazacyclononane (96556-05-7) + benzylamine (100-46-9) → Ti(NCH2Ph)(1,4,7-trimethyltriazacyclononane)Cl2 (906666-45-3)

Conditions	Yield
In benzene (N2 or Ar); C6H5CH2NH2 added to a soln. of Ti compd., stirred for 16 h, (C2H4N(CH3))3 added, stirred for 16 h; concd., filtered off, washed (hexanes), dried (vac.); elem. anal.;	96%

iron(III) chloride hexahydrate + N,N',N''-trimethyl-1,4,7-triazacyclononane (96556-05-7) → [(1,4,7-trimethyl-1,4,7-triazacyclononane)trichloroiron(III)] (110827-37-7)

Conditions	Yield
In ethanol (anaerobic conditions); soln. of ligand was added dropwise to soln. of FeCl3; formed ppt. was filtered off, washed with EtOH and Et2O and dried;	95%

zinc(II) nitrate hexahydrate + N,N',N''-trimethyl-1,4,7-triazacyclononane (96556-05-7) → (trimethyltriazacyclononane)triaquozinc(II) nitrate hemihydrate

Conditions	Yield
In ethanol addn. of triamine soln. to soln. of Zn(NO3)2, gently heating and stirring (20 min), stirring (room temp., 3 h); solvent removal (vac.), washing (Et2O), drying; elem. anal.;	95%

bismuth(III) chloride (7787-60-2) + N,N',N''-trimethyl-1,4,7-triazacyclononane (96556-05-7) → BiCl3*C9H21N3 (161584-56-1)

Conditions	Yield
In acetonitrile (argon); addn. of the ligand in MeCN to BiCl3 in MeCN at -78°C, warming to room temp., stirring (50°C, 6 h); removal of solvent, washing (hexane; Et2O), recrystn. (MeCN/CH2Cl2); elem. anal.;	93.1%

Na[tetrakis{3,5-bis(trifluoromethyl)phenyl}borate]·2thf + N,N',N''-trimethyl-1,4,7-triazacyclononane (96556-05-7) → bis(1,4,7-trimethyl-1,4,7-triazacyclononane)sodium tetrakis{3,5-bis(trifluoromethyl)phenyl}borate (1609468-45-2)

Conditions	Yield
In dichloromethane for 4h; Inert atmosphere;	93%

rhenium(I) pentacarbonyl bromide (14220-21-4) + N,N',N''-trimethyl-1,4,7-triazacyclononane (96556-05-7) → {(N,N',N''-trimethyl-1,4,7-triazacyclononane)-tricarbonylrhenium(I)}bromide (115762-96-4)

Conditions	Yield
In N,N-dimethyl-formamide under Ar; 1 mmol of the Re compound in DMF added to 2 mmol of the ligand in DMF; reaction mixt. refluxed for 1 h; addn. of Et2O to the cold soln.; pptd. crystals filtered, washed with Et2O and dried in air; elem. anal.;	92%

potassium hexafluorophosphate (17084-13-8) + manganese(III) triacetate dihydrate (19513-05-4) + N,N',N''-trimethyl-1,4,7-triazacyclononane (96556-05-7) → {(N,N',N''-trimethyl-1,4,7-triazacyclononane)Mn(III)(μ-O)(μ-MeCO2)2Mn(III)(N,N',N''-trimethyl-1,4,7-triazacyclononane)}(PF6)2

Conditions	Yield
With p-TsOH*H2O; NaHCO3; NaOAc In acetonitrile addn. of p-TsOH*H2O to the ligand in MeCN, after dissoln. addn. of NaHCO3, NaOAc, KPF6 and the Mn salt at room temp. with stirring, heating to 333 K for 40 min; filtration, evapn. (vac., 303 K), stirring with water, collection (frit), washing (H2O), drying (vac.); elem. anal.;	92%

vanadium(III) chloride (7718-98-1) + N,N',N''-trimethyl-1,4,7-triazacyclononane (96556-05-7) → trichloro(1,4,7-trimethyl-1,4,7-triazacyclononane)vanadium(III) (112087-96-4)

Conditions	Yield
In acetonitrile heating of a soln. of VCl3 in dry acetonitrile to reflux for 10 min; precipitation on cooling of the soln.; addn. of a CH3CN soln. of the organic compound to the mixture; heating to reflux for 30 min; precipitation;;	92%

titanium(III) chloride (7705-07-9) + N,N',N''-trimethyl-1,4,7-triazacyclononane (96556-05-7) → {N(CH3)CH2CH2N(CH3)CH2CH2N(CH3)CH2CH2}*Ti(3+)*3Cl(1-)={N(CH3)CH2CH2N(CH3)CH2CH2N(CH3)CH2CH2}TiCl3

Conditions	Yield
In acetonitrile Under Ar, dissolving of TiCl3 under reflux, dropwise addn. of triazacyclononane, stirring (30 min, 20°C).; Filtn.;	92%

titanium(III) chloride (7705-07-9) + N,N',N''-trimethyl-1,4,7-triazacyclononane (96556-05-7) → TiCl3(C6H12N3(CH3)3) (143144-83-6)

Conditions	Yield
In acetonitrile Ar-purged soln. of TiCl3 in CH3CN refluxed for 30 min, cooled to room temp., dropwise addn. of ligand in CH3CN, stirred at 20°C for 30 min under Ar, blue pptn.; filtered, washed with dry Et2O, air dried; elem. anal.;	92%

trans,mer-[Ti(t-butylimide)Cl2(pyridine)3] (172481-11-7) + N,N',N''-trimethyl-1,4,7-triazacyclononane (96556-05-7) → [Ti(Cl)2(tert-butylimido)(1,4,7-trimethyltriazacyclononane)] (207612-37-1)

Conditions	Yield
In dichloromethane 2 h at room temp.;	92%

iron(III) chloride + N,N',N''-trimethyl-1,4,7-triazacyclononane (96556-05-7) → [(1,4,7-trimethyl-1,4,7-triazacyclononane)trichloroiron(III)] (110827-37-7)

Conditions	Yield
In diethyl ether for 0.25h;	92%

antimony(III) chloride (10025-91-9) + N,N',N''-trimethyl-1,4,7-triazacyclononane (96556-05-7) → SbCl3*C9H21N3 (185409-27-2)

Conditions	Yield
In acetonitrile (argon); addn. of the ligand in MeCN to SbCl3 in MeCN at -78°C, warming to room temp., stirring (50°C, 6 h); removal of solvent, washing (hexane; Et2O), recrystn. (MeCN/CH2Cl2); elem. anal.;	91.3%

manganese(II) sulfate + dihydrogen peroxide (7722-84-1) + N,N',N''-trimethyl-1,4,7-triazacyclononane (96556-05-7) → [Mn2(μ-O)3(Me3-TACN)2]SO4*4H2O

Conditions	Yield
Stage #1: manganese(II) sulfate; N,N',N''-trimethyl-1,4,7-triazacyclononane In water at 20℃; for 0.5h; Inert atmosphere; Cooling with ice; Stage #2: dihydrogen peroxide With sodium hydroxide In water at 20℃; Inert atmosphere; Cooling with ice; Stage #3: With sulfuric acid In water for 0.5h; pH=5; Inert atmosphere;	91%

bismuth(III) chloride (7787-60-2) + N,N',N''-trimethyl-1,4,7-triazacyclononane (96556-05-7) → BiCl3(C6H12N3(CH3)3) (161584-56-1)

Conditions	Yield
In acetonitrile stirring (50°C, 12 h); solvent removal, washing (hexane, Et2O), recrystallization (acetonitrile, CH2Cl2); elem. anal.;	90.3%

rhodium(III) chloride trihydrate + N,N',N''-trimethyl-1,4,7-triazacyclononane (96556-05-7) → trichloro(N,N',N''-trimethyl-1,4,7-trazacyclononane)rhodium(III) (140175-14-0)

Conditions	Yield
In ethanol N2 or Ar-atmosphere; refluxing (2 h); filtering, washing (EtOH, ether), drying;	90%
In ethanol addn. of RhCl3 soln. to cyclononane soln.; heating, 70°C, 10h; pptn.; filtration; elem. anal.;	66%

sodium hexaflorophosphate + N,N',N''-trimethyl-1,4,7-triazacyclononane (96556-05-7) + mercury dichloride → {Hg(1,4,7-trimethyl-1,4,7-triazacyclononane)Cl}PF6 (135624-47-4)

Conditions	Yield
In water ppt. dissolved again at 40°C, then addn. of NaPF6; ppt. filtered, washed with ethanol and diethyl ether, air-dried, elem. anal.;	90%

indium(III) chloride (10025-82-8) + N,N',N''-trimethyl-1,4,7-triazacyclononane (96556-05-7) → [InCl3(1,4,7-trimethyl-1,4,7-triazacyclononane)] (101652-42-0)

Conditions	Yield
In ethanol; chloroform ethanolic soln. of C6H12N3(CH3)3 added to a chloroformic soln.of InCl3;refluxed for 2 h; filtered; washed (ethanol, ether); dried (air); elem.anal.;	90%

thallium(III) chloride tetrahydrate + N,N',N''-trimethyl-1,4,7-triazacyclononane (96556-05-7) → fac-(N,N',N''-trimethyl-1,4,7-triazacyclononane)thallium(III) chloride (101165-05-3)

Conditions	Yield
In chloroform susp. refluxed for 3 h; filtered; washed (ethanol, ether); dried (air); elem. anal.;	90%

diiodotetracarbonyliron(II) (15616-56-5, 14911-55-8, 14878-30-9) + N,N',N''-trimethyl-1,4,7-triazacyclononane (96556-05-7) → [(N,N',N''-trimethyl-1,4,7-triazacyclononane)FeI(CO)2]I (286389-51-3)

Conditions	Yield
In dichloromethane byproducts: CO; (N2); ligand added to Fe complex soln. in CH2Cl2, reacted for 30 min; pptd. (Et2O), filtered, dried (N2); elem. anal.;	90%

sodium tetraphenyl borate (143-66-8) + N,N',N''-trimethyl-1,4,7-triazacyclononane (96556-05-7) + cobalt(II) bromide → [(1,4,7-trimethyl-1,4,7-triazacyclononane)2Co2(μ-Br)3]BPh4 (190205-14-2)

Conditions	Yield
In chloroform; acetone Ar-atmosphere; addn. of NaBPh4 (in Me2CO) to mixt. of CoBr2 and ligand (in CHCl3), stirring and refluxing for 2.5 h; partial evapn. (crystn.); elem. anal.;	90%

sodium tetraphenyl borate (143-66-8) + N,N',N''-trimethyl-1,4,7-triazacyclononane (96556-05-7) + nickel dibromide → [(1,4,7-trimethyl-1,4,7-triazacyclononane)2Ni2(μ-Br)3]BPh4 (190205-19-7)

Conditions	Yield
In ethanol Ar-atmosphere; refluxing NiBr2 with ligand for 1.5 h, pptn. on NaBPh4 addn.; elem. anal.;	90%

bis[dimethyl(μ-dimethylsulfide)platinum(II)] + N,N',N''-trimethyl-1,4,7-triazacyclononane (96556-05-7) → cis-bis(dimethyl sulfide)dimethylplatinum(II) + [PtMe2(N,N'-1,4,7-trimethyl-1,4,7-triazacyclononane)] (651718-98-8)

Conditions	Yield
In [(2)H6]acetone 2 equiv of azacycle, acetone-d6, 20 h (N2); not sepd., detected by NMR spectra;	A 10% B 90%

nickel(II) perchlorate hexahydrate + N,N',N''-trimethyl-1,4,7-triazacyclononane (96556-05-7) + acetonitrile (75-05-8) → [Ni(1,4,7-trimethyl-1,4,7-triazacyclononane)(BH4)(CH3CN)](BPh4)

Conditions	Yield
With N,N,N,N,-tetramethylethylenediamine for 12h; Reflux;	90%

cobalt(II) chloride hexahydrate + N,N',N''-trimethyl-1,4,7-triazacyclononane (96556-05-7) + lithium chloride → [CoCl3(1,4,7-trimethyl-1,4,7-triazacyclononane)]·3H2O

Conditions	Yield
Stage #1: cobalt(II) chloride hexahydrate; N,N',N''-trimethyl-1,4,7-triazacyclononane In methanol for 0.166667h; Stage #2: lithium chloride In methanol at 20℃; for 2h;	90%

Upstream product

• 4730-54-5 1,4,7-triazacyclononane 
• 74-88-4 methyl iodide 
• 52667-89-7 N,N',N-tris(p-toluenesulfonyl)-1,4,7-triazacyclononane 
• 74-83-9 methyl bromide 
• 50-00-0 formaldehyd 

Downstream Products

• 139168-41-5 {C₉H₂₁N₃Zn(O₂CC₆H₅)2(H₂O)} 
• 108-74-7 1,3,5-trimethyl-1,3,5-triazacyclohexane 
• 289907-25-1 TiCl₂(2,6-(i-Pr)2C₆H₃N)(1,3,5-trimethyl-1,3,5-triazacyclononane) 
• 41203-22-9 1,4,8,11-tetramethyl-1,4,8,11-tetra-azacyclotetradecane 
• 190205-10-8 [(1,4,7-trimethyl-1,4,7-triazacyclononane)2Fe2(μ-Cl)3]BPh4 
• 190205-12-0 [(1,4,7-trimethyl-1,4,7-triazacyclononane)2Co2(μ-Cl)3]BPh4 
• 176388-00-4 [((1,4,7-trimethyl-1,4,7-triazacyclononane)CuBr)2(μ-benzoato)](ClO4) 
• 906666-44-2 [Ti(NPh)(1,4,7-trimethyl triazacyclononane)Cl₂] 
• 870457-33-3 Ti(NNPh₂)Cl₂(trimethyl-1,4,7-triazacyclononane) 
• 505026-06-2 [Ti(NC₆F₅)(1,4,7-trimethyl triazacyclononane)Cl₂] 

Relevant articles and documents

Well-defined iron complexes as efficient catalysts for green atom-transfer radical polymerization of styrene, methyl methacrylate, and butyl acrylate with low catalyst loadings and catalyst recycling

Environmentally friendly iron(II) catalysts for atom-transfer radical polymerization (ATRP) were synthesized by careful selection of the nitrogen substituents of N,N,N-trialkylated-1,4,9-triazacyclononane (R3TACN) ligands. Two types of structures were confirmed by crystallography: [(R3TACN)FeX2] complexes with relatively small R groups have ionic and dinuclear structures including a [(R 3TACN)Fe(μ-X)3Fe(R3TACN)]+ moiety, whereas those with more bulky R groups are neutral and mononuclear. The twelve [(R3TACN)FeX2]n complexes that were synthesized were subjected to bulk ATRP of styrene, methyl methacrylate (MMA), and butyl acrylate (BA). Among the iron complexes examined, [{(cyclopentyl) 3TACN}FeBr2] (4b) was the best catalyst for the well-controlled ATRP of all three monomers. This species allowed easy catalyst separation and recycling, a lowering of the catalyst concentration needed for the reaction, and the absence of additional reducing reagents. The lowest catalyst loading was accomplished in the ATRP of MMA with 4b (59ppm of Fe based on the charged monomer). Catalyst recycling in ATRP with low catalyst loadings was also successful. The ATRP of styrene with 4b (117ppm Fe atom) was followed by precipitation from methanol to give polystyrene that contained residual iron below the calculated detection limit (0.28ppm). Mechanisms that involve equilibria between the multinuclear and mononuclear species were also examined. It's easy being green: Structurally well-defined [(R3TACN)FeX 2] complexes realized green atom-transfer radical polymerization by judicious choice of the R group on the N,N,N-trialkylated-1,4,9- triazacyclononane (R3TACN) ligands (see scheme). [{(Cyclopentyl) 3TACN}FeBr2] was the best catalyst for controlled polymerization of all three monomers.

A method for preparing nitrogen heterocyclic

The invention discloses a preparation method of azacyclo. The preparation method comprises the following steps of: (1) reacting diethylenetriamine or triethylene tetramine with methylsulfonyl chloride to generate methanesulfonamide; (2) during two-phase reaction, cyclizing compound catalytic cyclization on methanesulfonamide and a compound having the structure shown in a chemical formula (a) under the composite catalysis of benzyl triethylanmine compound and 15-crown-5 at 90 DEG C under a backflow condition; and (3) removing methylsulfonyl from methanesulfonamide azacyclo and performing methylation treatment, wherein X represents bromine, iodine or sulphonate. The preparation method has the advantages that raw materials are low in cost, atom economy is high, and operation is easy and safe. The preparation method is suitable for industrial production.

Method of producing polymer using iron complex as catalyst

The object of the present invention is to provide a method of producing a polymer wherein radical-polymerizable monomers can be polymerized in a quantitative manner in a relatively short time, and a polymer or a block copolymer having at its termini a functional group that can be chemically converted while the polymer or the block copolymer has a high molecular weight can be produced. Furthermore, the object of the present invention is to provide a method of producing a polymer wherein the polymer is re-precipitated in a general solvent by an easy method, and the used iron complexes are recovered in the solvent, thereby recycling the iron complexes.