JP2014173084A - Conjugated diene polymerization catalyst using yttrium compound and method for producing conjugated diene polymer using the catalyst - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conjugated diene polymerization catalyst using tris (2,4-pentanedionato) yttrium synthesized in a non-aqueous solvent, particularly containing a cis-1,4 structure. It is an object to provide a polymerization catalyst capable of producing a conjugated diene polymer having a high rate.
The present invention is a conjugated diene polymerization catalyst comprising tris (2,4-pentandionato) yttrium (A) synthesized in a nonaqueous solvent.
[Selection figure] None

Description

  The present invention relates to a conjugated diene polymerization catalyst using an yttrium compound and a method for producing a conjugated diene polymer using the catalyst.

  Many proposals have been made on polymerization catalysts for conjugated dienes such as 1,3-butadiene and isoprene, some of which have been industrialized. For example, as a method for producing a conjugated diene polymer having a high cis-1,4 structure, a combination of a compound such as titanium, cobalt, nickel, or neodymium and organic aluminum is often used.

  Polymerization of conjugated dienes using a Group 3 element of the periodic table as a catalyst is known, and various polymerization methods have been proposed so far. For example, Japanese Patent Laid-Open No. 7-268013 (Patent Document 1) discloses a catalyst system comprising a rare earth metal salt, an organometallic compound of Group I to III elements of the periodic table, and a fluorine-containing organoboron compound. .

  JP-A-11-80222 (Patent Document 2) discloses a group IIIB metal compound of a periodic table, an ionic compound of a non-coordinating anion and a cation, and an organic metal of a group I to III element of the periodic table. A polymerization catalyst comprising a compound is disclosed.

  Tris (2,4-pentanedionato) yttrium is a known compound. Hydrate is obtained when synthesized with an aqueous solvent. When synthesized in a non-aqueous solvent, an anhydrous complex can be synthesized. For example, Non-Patent Document 1 discloses an example of synthesis using a toluene solvent.

  It is known to use tris (2,4-pentanedionato) yttrium as a polymerization catalyst. For example, in Non-Patent Document 2, it is used for epoxy ring-opening polymerization. There is no example used for the polymerization of conjugated dienes.

Japanese Patent Laid-Open No. 7-268013 Japanese Patent Laid-Open No. 11-80222 Inorganic Chemistry vol. 32 No. 5 (1993) 497-501 Polymer vol. 43 (2002) 4535-4543

  The present invention provides a conjugated diene polymerization catalyst using tris (2,4-pentanedionato) yttrium synthesized in a non-aqueous solvent, particularly a conjugated diene polymer having a high cis-1,4 structure content. An object of the present invention is to provide a polymerization catalyst capable of producing

  The present invention is to produce a conjugated diene polymer having a high cis-1,4 structure content with high efficiency by using tris (2,4-pentanedionato) yttrium synthesized in a non-aqueous solvent for butadiene polymerization. It is to provide a polymerization catalyst capable of

  The present invention also provides tris (2,4-pentanedionato) yttrium (A) synthesized in a non-aqueous solvent, an ionic compound (B) comprising a non-coordinating anion and a cation, periodic table 2 A conjugated diene polymerization catalyst characterized by comprising an organometallic compound (C) of an element selected from Group 12, Group 12, and Group 13, wherein a conjugated diene compound is polymerized using the catalyst It is a manufacturing method of a conjugated diene polymer.

  By using the yttrium catalyst of the present invention, a polymerization catalyst capable of producing a conjugated diene polymer having a high cis-1,4 structure content can be provided.

  Tris (2,4-pentanedionato) yttrium (A) synthesized with the non-aqueous solvent of the present invention is an ionic compound (B) composed of a non-coordinating anion and a cation, group 2 of the periodic table, 12 By combining with an organometallic compound (C) of an element selected from the group 13 and group 13, it can be used as a catalyst for conjugated diene polymerization.

Tris (2,4-pentanedionato) yttrium (A) synthesized with a non-aqueous solvent that is component (A) of the catalyst system. Tris (2,4-pentanedionato) yttrium is commercially available as a hydrate, but when the hydrate is used, the butadiene polymerization activity is extremely small. When synthesized with a non-aqueous solvent, an anhydride of tris (2,4-pentanedionato) yttrium is obtained, and the peak shift value of ¹ H-NMR is different from that of hydrate. Moreover, when water is added to the anhydride of a complex, it will be confirmed from ¹ H-NMR that a hydrate is formed. When tris (2,4-pentanedionato) yttrium (A) synthesized with this nonaqueous solvent is used, the cis-1,4 structure content is high and the butadiene polymerization activity is large.

  In the ionic compound comprising a non-coordinating anion and a cation as the component (B) of the catalyst system, examples of the non-coordinating anion include tetra (phenyl) borate and tetra (fluorophenyl) borane. , Tetrakis (difluorophenyl) borate, tetrakis (trifluorophenyl) borate, tetrakis (tetrafluorophenyl) borate, tetrakis (pentafluorophenyl) borate, tetrakis (3,5-bistrifluoromethyl) Phenyl) borate, tetrakis (tetrafluoromethylphenyl) borate, tetra (triyl) borate, tetra (xylyl) borate, triphenyl (pentafluorophenyl) borate, tris (pentafluorophenyl) (Phenyl) borate, tridecahydride-7,8- Cal Bowne deca borate - DOO, tetrafluoroborate - DOO, hexafluorophosphate - such DOO and the like.

  On the other hand, examples of the cation include a carbonium cation, an oxonium cation, an ammonium cation, a phosphonium cation, a cycloheptatrienyl cation, and a ferrocenium cation.

  Specific examples of the carbonium cation include tri-substituted carbonium cations such as a triphenyl carbonium cation and a tri-substituted phenyl carbonium cation. Specific examples of the tri-substituted phenylcarbonium cation include tri (methylphenyl) carbonium cation and tri (dimethylphenyl) carbonium cation.

  Specific examples of ammonium cations include trialkylammonium cations, triethylammonium cations, tripropylammonium cations, tri (n-butyl) ammonium cations, tri (isobutyl) ammonium cations, and the like, and N, N-dimethylanilinium. Dialkyls such as cations, N, N-diethylanilinium cations, N, N-dialkylanilinium cations such as N, N-2,4,6-pentamethylanilinium cation, di (isopropyl) ammonium cations and dicyclohexylammonium cations Mention may be made of the ammonium cation.

  Specific examples of phosphonium cations include triphenylphosphonium cation, tetraphenylphosphonium cation, tri (methylphenyl) phosphonium cation, tetra (methylphenyl) phosphonium cation, tri (dimethylphenyl) phosphonium cation, tetra (dimethylphenyl) phosphonium cation, etc. Of arylphosphonium cations.

  As the ionic compound, those arbitrarily selected and combined from the non-coordinating anions and cations exemplified above can be preferably used.

  Among these, as ionic compounds, triphenylcarbonium tetrakis (pentafluorophenyl) borate, triphenylcarbonium tetrakis (fluorophenyl) borate, N, N-dimethylanilinium tetrakis (pentafluorophenyl) borate. And 1,1′-dimethylferrocenium tetrakis (pentafluorophenyl) borate are preferred. An ionic compound may be used independently and may be used in combination of 2 or more type.

  In addition, alumoxane may be used in place of the ionic compound composed of the non-coordinating anion and cation as component (B). The alumoxane is obtained by bringing an organoaluminum compound and a condensing agent into contact with each other, and includes a chain aluminoxane represented by the general formula (—Al (R ′) O—) n or a cyclic aluminoxane. (R ′ is a hydrocarbon group having 1 to 10 carbon atoms, including those partially substituted with a halogen atom and / or an alkoxy group. N is the degree of polymerization and is 5 or more, preferably 10 or more) . Examples of R ′ include a methyl group, an ethyl group, a propyl group, and an isobutyl group, and a methyl group is preferable. Examples of the organoaluminum compound used as an aluminoxane raw material include trialkylaluminums such as trimethylaluminum, triethylaluminum, and triisobutylaluminum, and mixtures thereof.

  Among these, alumoxane using a mixture of trimethylaluminum and tributylaluminum as a raw material can be suitably used.

  Moreover, as a condensing agent, water is typically used, but in addition to this, an arbitrary one in which the trialkylaluminum undergoes a condensation reaction, for example, adsorbed water such as an inorganic substance, a diol, and the like.

  Examples of organometallic compounds of Group 2, 12 and 13 of the periodic table that are the component (C) of the catalyst system include organic magnesium, organic zinc, and organic aluminum. Preferred among these compounds are dialkyl magnesium, alkyl magnesium chloride, alkyl magnesium bromide, dialkyl zinc, trialkyl aluminum, dialkyl aluminum chloride, dialkyl aluminum bromide, alkyl aluminum sesquichloride, alkyl aluminum sesquibromide, alkyl aluminum dichloride, Dialkylaluminum hydride and the like.

  Specific compounds include alkyl magnesium halides such as methyl magnesium chloride, ethyl magnesium chloride, butyl magnesium chloride, hexyl magnesium chloride, octyl magnesium chloride, ethyl magnesium bromide, butyl magnesium bromide, butyl magnesium iodide, and hexyl magnesium iodide. Can be mentioned.

  Furthermore, dialkyl magnesium such as dimethylmagnesium, diethylmagnesium, dibutylmagnesium, dihexylmagnesium, dioctylmagnesium, ethylbutylmagnesium, and ethylhexylmagnesium can be exemplified.

  Furthermore, dialkyl zinc, such as dimethyl zinc, diethyl zinc, diisobutyl zinc, dihexyl zinc, dioctyl zinc, and didecyl zinc, can be mentioned.

  Furthermore, trialkylaluminums such as trimethylaluminum, triethylaluminum, triisobutylaluminum, trihexylaluminum, trioctylaluminum, tridecylaluminum, and the like can be given.

  In addition, dialkylaluminum chlorides such as dimethylaluminum chloride and diethylaluminum chloride, organoaluminum halogen compounds such as ethylaluminum sesquichloride and ethylaluminum dichloride, and hydrogenated organoaluminum compounds such as diethylaluminum hydride, diisobutylaluminum hydride and ethylaluminum sesquihydride. Can be mentioned.

  These organometallic compounds of Groups 2, 12, and 13 of the periodic table can be used alone or in combination of two or more.

  Although the conjugated diene can be polymerized using the above-mentioned catalyst, (1) hydrogen, (2) metal hydride compound, and (3) hydrogenated organometal as the molecular weight regulator of the resulting conjugated diene polymer. A compound selected from compounds can be used.

  Examples of the molecular weight regulator (2) metal hydride compound include lithium hydride, sodium hydride, potassium hydride, magnesium hydride, calcium hydride, borane, aluminum hydride, gallium hydride, silane, germane, Examples thereof include lithium borohydride, sodium borohydride, lithium aluminum hydride, sodium aluminum hydride, and the like.

  (3) Examples of hydrogenated organometallic compounds include alkylboranes such as methylborane, ethylborane, propylborane, butylborane, and phenylborane; dialkylboranes such as dimethylborane, diethylborane, dipropylborane, dibutylborane, and diphenylborane; methyl Alkyl aluminum dihydride such as aluminum dihydride, ethylaluminum dihydride, propylaluminum dihydride, butylaluminum dihydride, phenylaluminum dihydride, dimethylaluminum hydride, diethylaluminum hydride, dipropylaluminum hydride, dibutylaluminum hydride, diphenylaluminum hydride Dialkyl aluminum high dry Silanes such as methylsilane, ethylsilane, propylsilane, butylsilane, phenylsilane, dimethylsilane, diethylsilane, dipropylsilane, dibutylsilane, diphenylsilane, trimethylsilane, triethylsilane, tripropylsilane, tributylsilane, triphenylsilane, Germanium such as methyl germane, ethyl germane, propyl germane, butyl germane, phenyl germane, dimethyl germane, diethyl germane, dipropyl germane, dibutyl germane, diphenyl germane, trimethyl germane, triethyl germane, tripropyl germane, tributyl germane, triphenyl germane And the like.

  Among these, diisobutylaluminum hydride and diethylaluminum hydride are preferable, and diethylaluminum hydride is particularly preferable.

  The order of addition of the catalyst components is not particularly limited, but can be performed, for example, in the following order.

  (1) In an inert organic solvent, the component (C) is added in the presence or absence of the conjugated diene compound monomer to be polymerized, and the components (A) and (B) are added in any order.

  (2) In the inert organic solvent, the component (C) is added in the presence or absence of the conjugated diene compound monomer to be polymerized, the molecular weight regulator is added, and then the components (A) and (B ) Add ingredients in any order.

  (3) After adding the component (A) in the presence or absence of the conjugated diene compound monomer to be polymerized in an inert organic solvent, and adding the component (C) and the molecular weight regulator described above in any order. , (B) component is added.

  (4) After adding the component (B) in the presence or absence of the conjugated diene compound monomer to be polymerized in an inert organic solvent, and adding the component (C) and the molecular weight regulator described above in any order. , (A) component is added.

  (5) After adding component (C) in the presence or absence of a conjugated diene compound monomer to be polymerized in an inert organic solvent, and adding components (A) and (B) in any order Add the above-described molecular weight regulator.

  Moreover, you may age | cure and use each component previously. Especially, it is preferable to age | cure (A) component and (C) component.

  As aging conditions, the component (A) and the component (C) are mixed in an inert solvent in the presence or absence of the conjugated diene compound monomer to be polymerized. The aging temperature is -50 to 80 ° C, preferably -10 to 50 ° C, and the aging time is 0.01 to 24 hours, preferably 0.05 to 5 hours, particularly preferably 0.1 to 1 hour.

  In the present invention, each catalyst component may be supported on an inorganic compound or an organic polymer compound.

  Conjugated diene compound monomers include 1,3-butadiene, isoprene, 1,3-pentadiene, 2-ethyl-1,3-butadiene, 2,3-dimethylbutadiene, 2-methylpentadiene, 4-methylpentadiene, 2 , 4-hexadiene and the like. Among these, a conjugated diene compound monomer mainly composed of 1,3-butadiene is preferable.

  These monomer components may be used singly or in combination of two or more.

  Here, the conjugated diene compound monomer to be polymerized may be the total amount or a part of the monomer. In the case of part of the monomer, the above contact mixture can be mixed with the remaining monomer or the remaining monomer solution. In addition to conjugated dienes, olefins such as ethylene, propylene, allene, 1-butene, 2-butene, 1,2-butadiene, pentene, cyclopentene, hexene, cyclohexene, octene, cyclooctadiene, cyclododecatriene, norbornene, norbornadiene, etc. A compound or the like may be contained.

  The polymerization method is not particularly limited, and bulk polymerization (bulk polymerization) using a conjugated diene compound monomer such as 1,3-butadiene itself as a polymerization solvent, or solution polymerization can be applied. Solvents for solution polymerization include aliphatic hydrocarbons such as butane, pentane, hexane, and heptane, alicyclic hydrocarbons such as cyclopentane and cyclohexane, aromatic hydrocarbons such as benzene, toluene, xylene, and ethylbenzene, Examples thereof include olefinic hydrocarbons such as olefin compounds and cis-2-butene and trans-2-butene.

  Among these, benzene, toluene, cyclohexane, or a mixture of cis-2-butene and trans-2-butene is preferably used.

  The polymerization temperature is preferably in the range of -30 to 150 ° C, particularly preferably in the range of 30 to 100 ° C. The polymerization time is preferably in the range of 1 minute to 12 hours, particularly preferably 5 minutes to 5 hours.

  After performing the polymerization for a predetermined time, the inside of the polymerization tank is released as necessary, and post-treatment such as washing and drying steps is performed.

  The conjugated diene polymer obtained in the present invention preferably includes cis-1,4-polybutadiene having a cis-1,4 structure of 97% or more, more preferably 98% or more. [Η] of the conjugated diene polymer is preferably 0.1 to 10, more preferably 1 to 7, and particularly preferably 1.5 to 5.

Examples according to the present invention will be specifically described below. The polymerization conditions and polymerization results are summarized in Tables 1 and 2. Measuring methods for physical properties and the like are as follows.
1) NMR spectrum: Measured using a JNM / AL400 spectrum meter manufactured by JEOL.
2) Measurement of Y content: Measured by ICP emission spectrometry. For the measurement, Vista MPX type manufactured by Varian Japan was used.
3) Elemental analysis: The CHN coder MT-5 manufactured by Yanaco was used.
4) Microstructure: Performed by infrared absorption spectrum analysis. The microstructure was calculated from the absorption intensity ratio of cis 740 cm-1, trans 967 cm-1, and vinyl 910 cm-1.
5) Intrinsic viscosity ([η]): Measured at 30 ° C. using a toluene solution of the polymer.

(Synthesis Example 1)
To a 300 ml pear-shaped two-necked flask were added 4.20 g (15.8 mmol) of triisopropoxy yttrium manufactured by High Purity Chemical Laboratory and 40 ml of dehydrated toluene, and the mixture was stirred with a magnetic stirrer. Separately, a solution prepared by dissolving 7.89 g (78.8 mmol) of acetylacetone in 70 ml of dehydrated toluene was added dropwise to a toluene solution of triisopropoxy yttrium. The reaction was carried out for 20 hours under toluene reflux, and the toluene was distilled off and dried under reduced pressure. 50 ml of dehydrated hexane was added to the obtained solid, and the mixture was heated to reflux for 1 hour. The solution was cooled to room temperature and the supernatant was removed. The resulting precipitate was dried under reduced pressure to obtain tris (2,4-pentanedionato) yttrium. Yield 3.50 g (9.06 mmol), yield 57%.
As a result of nuclear magnetic resonance spectrum (NMR) of the product, ¹ H-NMR δ (ppm): 1.9 (18H), 5.3 (3H) However, C ₆ D ₆ was used as a measurement solvent.
The Y content of the product was 24%, the C content was 45.4%, and the H content was 5.0%.

Example 1
The inside of the autoclave with an internal volume of 2 L was purged with nitrogen, charged with a solution consisting of 260 ml of toluene and 140 ml of butadiene, the temperature of the solution was adjusted to 30 ° C., and then 5 ml of a toluene solution of triethylaluminum (TEAL) (2 mol / L) was added. The mixture was stirred at 500 rpm for 3 minutes. The temperature was raised to 40 ° C., 1 ml of a toluene solution (20 mmol / L) of tris (2,4-pentanedionato) yttrium and a toluene solution of triphenylcarbenium tetrakispentafluorophenylborate (0.43 mol / L). 1 ml was continuously added to initiate the polymerization. After polymerization for 25 minutes at 40 ° C., 5 ml of an ethanol / heptane (1/1) solution containing an antioxidant was added to stop the polymerization. After releasing the pressure inside the autoclave, the polymerization solution was put into ethanol to recover polybutadiene. The recovered polybutadiene was then vacuum dried at 80 ° C. for 3 hours. The polymerization results are shown in Table 1. The activity was 2554 [gPB / mmol (Y) / h].

(Example 2)
The inside of the autoclave with an internal volume of 2 L was purged with nitrogen, charged with a solution consisting of 260 ml of toluene and 140 ml of butadiene, the temperature of the solution was adjusted to 30 ° C., and then 2 ml of a toluene solution of diisobutylaluminum hydride (DIBAH) (1 mol / L) was added. And stirred for 3 minutes at 500 rpm. The temperature was raised to 40 ° C., 2 ml of a toluene solution of tris (2,4-pentanedionato) yttrium (20 mmol / L) and a toluene solution of triphenylcarbenium tetrakispentafluorophenylborate (0.43 mol / L). 2 ml was added in succession to initiate the polymerization. After polymerization for 25 minutes at 40 ° C., 5 ml of an ethanol / heptane (1/1) solution containing an antioxidant was added to stop the polymerization. After releasing the pressure inside the autoclave, the polymerization solution was put into ethanol to recover polybutadiene. The recovered polybutadiene was then vacuum dried at 80 ° C. for 3 hours. The polymerization results are shown in Table 1. The activity was 350 [gPB / mmol (Y) / h].

(Example 3)
The inside of the autoclave with an internal volume of 2 L was purged with nitrogen, charged with a solution consisting of 260 ml of toluene and 140 ml of butadiene, the temperature of the solution was adjusted to 30 ° C., and a toluene solution of triisobutylaluminum (TIBAL) (1.7 mol / L) 6 .8 ml was added and stirred for 3 minutes at 500 rpm. Next, 2 ml of a toluene solution (20 mmol / L) of tris (2,4-pentanedionato) yttrium was added and stirred for 20 minutes, and then the temperature was raised to 40 ° C. and triphenylcarbenium tetrakispentafluorophenylborate was added. Polymerization was initiated by adding 0.2 ml of a toluene solution (0.43 mol / L). After polymerization for 25 minutes at 40 ° C., 5 ml of an ethanol / heptane (1/1) solution containing an antioxidant was added to stop the polymerization. After releasing the pressure inside the autoclave, the polymerization solution was put into ethanol to recover polybutadiene. The recovered polybutadiene was then vacuum dried at 80 ° C. for 3 hours. The polymerization results are shown in Table 1. The activity was 68 [gPB / mmol (Y) / h].

(Reference Example 1)
The inside of the autoclave with an internal volume of 2 L was purged with nitrogen, charged with a solution consisting of 260 ml of toluene and 140 ml of butadiene, the temperature of the solution was adjusted to 30 ° C., and then 1 ml of a toluene solution of triethylaluminum (TEAL) (2 mol / L) was added. The mixture was stirred at 500 rpm for 3 minutes. Next, 1 ml of a toluene solution (20 mmol / L) of tris (2,2,6,6-tetramethyl-3,5-heptanedionato) yttrium was added and stirred for 4 minutes. Polymerization was initiated by adding 0.1 ml of a toluene solution (0.43 mol / L) of phenylcarbenium tetrakispentafluorophenylborate. After polymerization at 40 ° C. for 30 minutes, 5 ml of an ethanol / heptane (1/1) solution containing an antiaging agent was added to terminate the polymerization. After releasing the pressure inside the autoclave, the polymerization solution was put into ethanol to recover polybutadiene. The recovered polybutadiene was then vacuum dried at 80 ° C. for 3 hours. The polymerization results are shown in Table 1. The activity was 4170 [gPB / mmol (Y) / h].

Example 4
The inside of the autoclave having an internal volume of 1.5 L was purged with nitrogen, and a solution consisting of 375 ml of toluene and 120 ml of butadiene was charged. After the temperature of the solution was adjusted to 30 ° C., 3.25 ml of a toluene solution (2 mol / L) of triethylaluminum (TEAL) was added and stirred for 3 minutes at 500 rpm. Next, the temperature was raised to 40 ° C., 2.5 ml of a toluene solution (0.02 mol / L) of tris (2,4-pentanedionato) yttrium hydrate was added, and immediately triphenylcarbenium tetrakis (pentafluoro). Phenyl) borate in toluene (0.43 mol / L) 0.24 ml was added. After polymerization at 40 ° C. for 50 minutes, 3 ml of an ethanol solution containing an antioxidant was added to stop the polymerization. After releasing the pressure inside the autoclave, ethanol was added to the polymerization solution to recover polybutadiene. The recovered polybutadiene was then vacuum dried at 80 ° C. for 2 hours. The activity was 505 [gPB / mmol (Y) / h]. The microstructure is 99.1% for cis-1,4, 0.3% for trans-1,4, and 0.5% for vinyl-1,2. Intrinsic viscosity [η] = 3.2, molecular weight Mn = 2.66 × 10 ⁵ , Mw = 7.67 × 10 ⁵ , and molecular weight distribution = 2.9.

(Comparative Example 1)
The inside of the autoclave with an internal volume of 2 L was purged with nitrogen, charged with a solution consisting of 260 ml of toluene and 140 ml of butadiene, the temperature of the solution was adjusted to 30 ° C., and then 9 ml of a toluene solution of diethylaluminum hydride (DEAH) (1 mol / L) was added. And stirred for 3 minutes at 500 rpm. Next, 5 ml of a toluene solution (40 mmol / L) of tris (2,4-pentanedionato) yttrium was added and stirred for 4 minutes, and then the temperature was raised to 40 ° C. and toluene of triphenylcarbenium tetrakispentafluorophenylborate. 1 ml of a solution (0.43 mol / L) was added to initiate polymerization. After polymerization at 40 ° C. for 30 minutes, 5 ml of an ethanol / heptane (1/1) solution containing an antiaging agent was added to terminate the polymerization. After releasing the pressure inside the autoclave, the polymerization solution was put into ethanol to recover polybutadiene. The recovered polybutadiene was then vacuum dried at 80 ° C. for 3 hours. The polymerization results are shown in Table 1. The activity was 70 [gPB / mmol (Y) / h].

  As described above, a conjugated diene polymer having a high cis-1,4 structure content can be produced with high activity by using the conjugated diene polymerization catalyst containing the yttrium compound of the present invention.

Claims (3)

A catalyst for conjugated diene polymerization, comprising tris (2,4-pentanedionato) yttrium (A) synthesized with a nonaqueous solvent. Tris (2,4-pentanedionato) yttrium (A) synthesized in a non-aqueous solvent, ionic compound (B) composed of non-coordinating anion and cation, Groups 2, 12, and 13 of the periodic table A conjugated diene polymerization catalyst comprising an organometallic compound (C) of an element selected from: A method for producing a conjugated diene polymer, comprising polymerizing a conjugated diene compound using the conjugated diene polymerization catalyst according to claim 1.