Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07F—ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM
  • C07F15/00—Compounds containing elements of Groups 8, 9, 10 or 18 of the Periodic Table
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07F—ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM
  • C07F15/00—Compounds containing elements of Groups 8, 9, 10 or 18 of the Periodic Table
  • C07F15/0006—Compounds containing elements of Groups 8, 9, 10 or 18 of the Periodic Table compounds of the platinum group
  • C07F15/0086—Platinum compounds
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07F—ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM
  • C07F15/00—Compounds containing elements of Groups 8, 9, 10 or 18 of the Periodic Table
  • C07F15/0006—Compounds containing elements of Groups 8, 9, 10 or 18 of the Periodic Table compounds of the platinum group
  • C07F15/0033—Iridium compounds

Definitions

• This invention relates to the field of organometallic syntheses and to a process for forming organometallic cyclometallated complexes of transition metals comprising the step of reacting an organozinc complex of a desired organic ligand with a metal complex of an element bearing a leaving group to form the corresponding cyclometallated compound.
• Organometallic cyclometallated complexes of third-row transition metals have become useful materials and have necessitated synthetic methods for preparing them.
• Lamasky et al., Inorg. Chem., 2001, 40, 1704-1711 react a bis-cyclometallated iridium complex with excess amount ligand to form a tris complex.
• this method leads to a mixture of isomers in some cases.
• Tamayo et al., J. Am. Chem. Soc. 2003, 125, 7377-7387 reported an improved method to form a pure meridianal isomer of a tris iridium complex.
• the invention provides a process for forming an organometallic cyclometallated complex comprising the step of reacting, in an aprotic organic solvent, an organozinc complex of a desired organic ligand with a metal complex of an element of atomic number 74 to 79 bearing a leaving group.
• the process forms the corresponding cyclometallated compound.
• the process is versatile and provides high yield and pure isomers of cyclometallated compounds of transition metals. It can be used to prepare complexes of mixed ligands, can be used with a variety of transition metals, and can utilize solvents that cannot be used with lithiated ligands.
• the invention process is summarized above.
• the process is useful for synthesizing organometallic cyclometallated complexes comprising the step of reacting an organozinc complex of a desired organic ligand with a metal complex bearing a leaving group to form the corresponding cyclometallated compound in the presence of a solvent.
• the organozinc complex is represented by Formula 1 or 2: RZnY 1 R,Zn 2 where: Y can be an anion such as chloride, fluoride, bromide, iodide, methoxide, acetate, acetyl acetate, or trifluoromethanesulfonate; and R is a monoanionic ligand that can be coordinated to a metal through a carbon and a heteroatom and that is capable of replacing X in formula 3.
• the carbon may be an sp 2 or sp 3 carbon.
• R can be a material that includes an aromatic ring and a heterocyclic ring that may or may not be aromatic.
• the heterocyclic ring can include a nitrogen for coordinating to a metal.
• the organozinc complex can be prepared by well-known methods.
• an alkyllithium compound, aryllithium compound, or alkyl or aryl Grignard reagent can react with a zinc salt via a transmetallation reaction to form the desired organozinc complex (Negishi et al., J. Org. Chem., 1977, 42, 1821).
• an alkyl halide or aryl halide can react with zinc metal to form the desired organozinc complex via an oxidative zinc insertion reaction (Zhu et al., J. Org. Chem., 1991, 56, 1445).
• the metal complex bearing a leaving group includes a transition element of atomic number 74 to 79, that is, selected from the group of tungsten, rhenium, osmium, iridium platinum, and gold.
• the transition element can be iridium (Ir) or platinum (Pt).
• the metal complex can include from 1 to 6 leaving groups which may be any group capable of being replaced by the R of the zinc complex. The number of leaving groups will depend on the coordination state of the chosen metal (e.g. Pt, which preferably forms square-planar complexes, will accommodate from 1 to 4 leaving groups, while Ir, which forms octahedral complexes, will accommodate from 1 to 6 leaving groups) and on the nature of the leaving groups (e.g.
• the leaving groups can be monodentate or bidentate, and can be neutral or bear a -1 charge.
• the metal complex can include a mixture of leaving groups.
• the metal complex can further include other cyclometallating ligands, provided that sufficient leaving groups remain to allow substitution of at least one more cyclometallating ligand.
• Useful leaving groups with a -1 charge can include chloride, bromide, iodide, fluoride, acetate, acetonylacetate, trifluoromethanesulfonate, and methoxide.
• Useful neutral leaving groups include pyridine, diethyl sulfide, diethyl ether, dimethylsulfoxide, and tetrahydrofuran.
• the metal complex is represented as Formula 3:
• M represents a transition metal of atomic number from 74 to 79; L represents a cyclometallating ligand; m is 0, 1, or 2; X represents a leaving group as described above; and n is fi-om 1 to 6, provided that when n is 2 or more, each X is not necessarily identical.
• n is 4, two leaving groups can be chloride and two can be diethyl sulfide.
• the starting metal complex can be prepared by known methods or can be commercially available.
• a halogen bridged bis- cyclometallated iridium complexes can be readily prepared in high yields by reacting K 3 IrBr 6 or any other type of iridium halide salt with the corresponding cyclometallating ligands according to literature procedure, see Nonoyama, Bull Chem. Soc. Jpn., 1974, 47, 767-768; S.Sprouse et al, J. Am. Chem. Soc. 1984, 106, 6647-6653.
• the amount of the organozinc complex used, relative to the starting intermediate metal complex as per formula 3, can range from 0.5 to 3 equivalents depending upon the degree of desired substitution.
• the exact stoichiometry of the reaction will depend upon the nature of the starting materials and the degree of desired ligand substitution, as shown by the following example reactions. In some cases where desired, an excess amount (>3 equivalents) of organozinc complexes can be used to drive the reaction to completion. Representative examples of substitution reactions are listed below but not limited by them.
• the temperature needed to effect formation of the cyclometallated complex can be adjusted in a broad range, typically from 0°C to room temperature or higher.
• the temperature requirements are dictated by the nature of the substituents described in Formulas 1, 2, and 3, the reaction types shown above, and other factors.
• the reaction should be performed under a dry inert atmosphere (e.g. nitrogen, argon).
• the reaction is conveniently performed in a solvent to lower viscosity of the mixture.
• the solvent is an aprotic organic solvent and may be one that evaporates off during the reaction, or it may remain.
• the solvent can be an ether (e.g. diethyl ether, tetrahydrofuran), an alkyl halide (e.g.
• a polar aprotic solvent e.g. dimethylformamide, dimethylacetamide, dimethylsulfoxide
• a ketone e.g. acetone, methyl ethyl ketone
• a nitrile e.g. acetonitrile
• the solvent is tetrahydrofuran, methylene chloride, or a mixture of the two.
• the solvent should be substantially free of moisture (e.g. Aldrich anhydrous tetrahydrofuran, certified to have less than 0.005% H 2 O).
• the reaction mixture can be heterogeneous at the start and can require stirring.
• Cyclometallated complexes of the type produced by this invention can have a variety of isomeric forms. For example, tris(2-(phenyl)pyridinato,
• N,C 2 )iridium(III) can have two isomeric forms, the facial and the meridianal isomer and bis-(2-(phenyl)pyridinato) N,C )platinum(II) can have the trans or cis isomers.
• trans cis This invention gives good control in the formation of isomers, and frequently produces a single isomer in the case where two or more are possible. It is sometimes desirable to form a different isomer than the one produced in this reaction. Therefore, this invention can be used with methods for interconverting isomers, for example as described by Tamayo et al, above.
• organozinc complex in this case, 2- phenylpyridinato-N,C " -zinc(II)
• organolithium compound which can be prepared by well-known methods and in some cases are commercially available
• Grignard reagent which can be prepared by methods well-known to those skilled in the art
• An additional step which is not required in all cases, is the conversion of an available metal complex bearing a leaving group into a convenient complex (in this case, (ppy) 2 Ir( ⁇ -Br) 2 Ir(ppy) ).
• the organometallic cyclometallated complex can be converted to a different isomer.
• the following schemes show some non-limiting variations on the basic process with different but analogous materials. Steps that are the same as those in another scheme have been omitted for clarity. It will be understood that further substitution is possible.
• Step 3 Preparation of /?ze/--(piq)Ir(ppy)2
• Step 4 Isomerization of 777e7"-(piq) 2 lr(ppy) to/27c-(piq) 2 rr(ppy)
• group means any group or radical other than hydrogen.
• substituent group when reference is made in this application to a compound or group that contains a substitutable hydrogen, it is also intended to encompass not only the unsubstituted form, but also its form further substituted with any substituent group or groups as herein mentioned, so long as the substituent does not destroy properties necessary for the intended utility.
• a substituent group may be halogen or may be bonded to the remainder of the molecule by an atom of carbon, silicon, oxygen, nitrogen, phosphorous, or sulfur.
• the substituent may be, for example, halogen, such as chloro, bromo or fluoro; nitro; hydroxyl; cyano; carboxyl; or groups which may be further substituted, such as alkyl, including straight or branched chain or cyclic alkyl, such as methyl, trifluoromethyl, ethyl, t- butyl, 3-(2,4-di-t-pentylphenoxy) propyl, cyclohexyl, and tetradecyl; alkenyl, such as ethylene, 2-butene; alkoxy, such as methoxy, ethoxy, propoxy, butoxy, 2- methoxyethoxy, sec-butoxy, hexyloxy, 2-ethylhexyloxy, tetradecyloxy, 2-(2,4-di- t-pentylphenoxy)ethoxy, and 2-dodecyloxyethoxy; aryl such as phenyl,
• the substituents may themselves be further substituted one or more times with the described substituent groups.
• the particular substituents used may be selected by those skilled in the art to attain the desired desirable properties for a specific application and can include, for example, hydrophobic groups, solubilizing groups, blocking groups, and releasing or releasable groups.
• the substituents may be joined together to form a ring such as a fused ring unless otherwise provided.
• the above groups and substituents thereof may include those having up to 48 carbon atoms, typically 1 to 36 carbon atoms and usually less than 24 carbon atoms, but greater numbers are possible depending on the particular substituents selected.
• the reaction mixture was transferred into a separating funnel and the organic layer was separated and retained.
• the aqueous phase was extracted with ethyl acetate (EtOAc) (4x100 mL).
• EtOAc ethyl acetate
• the cooling bath was removed and the reaction mixture was warmed to ca 0°C to room temperature.
• the bromide-bridged dimer [Ir(ppy) 2 Br] 2 (0.58 g, 0.5 mmol) was added to the reaction mixture in one portion and the mixture was stirred for 30 min.
• Dichloromethane (10 mL) was added to accelerate the reaction. After stirring for ca. 1 hour at room temperature, the mixture was transferred into a one-necked flask and remaining yellow precipitates were washed into the flask with dichloromethane. The solvent was evaporated and the residue was dissolved in dichloromethane and purified by flash chiOmatography on silica gel with dichloromethane. The product was obtained as isomerically pure 7ze/'-(ppy) 3 lr, 0.51 g, 78%.
• the mixture was poured into water (100 mL) and extracted with dichloromethane (3x100 mL). The combined organic layers were washed with water (2x100 mL) and brine (200 mL) and dried over MgSO 4 . After filtration, the solvents were evaporated and the crude materials were treated with methanol (50 mL) and the product was collected by filtration and washed with methanol (50 mL), yellow orange solids, >98% isomeric purity by HPLC, 1.03 g, 81 %.
• the organometallic cyclometallated complexes synthesized according to this invention may be incorporated in an emissive layer of an OLED device.

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