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Reactions of trans-chloro(cyanomethyl)bis(triphenylphosphine)palladium(II), trans-[PdCl(CH2CN)(PPh3)2] (1), with an equimolecular amount of Tl(β-dik) (β-dik=etac, acac, tfac, bzac, and dbm) in dichloromethane afforded the O,O′-chelated β-dik complexes [Pd(CH2CN)(β-dik)(PPh3)] (3). Hydrogen peroxide oxidation and chloride abstraction by AgClO4or AgBF4of 1gave the neutral [PdCl(CH2CN)PPh3]nand the cationic [Pd(CH2CN)(PPh3)2]mXm(X=ClO4or BF4), respectively, from either of which complexes 3were also obtained by the reactions with the β-dik anions. No pure product corresponding to 3was isolated by a similar treatment of 1with Tl(hfac). On the other hand, chloro(cyanomethyl){1,2-bis(diphenylphosphino)ethane}palladium(II), [PdCl(CH2CN)(dppe)] (2), reacted only with Tl(hfac) in refluxing acetone to give the cationic [Pd(CH2CN)(dppe)]2(hfac)2, which was also derived from 2via[Pd(CH2CN)(dppe)]2X2(X=ClO4or BF4).

Oxidative addition reactions of bromopyridines to tetrakis(triphenylphosphine)palladium(0) gave [{PdBr(2-pyridyl)(PPh3)2] (1b), trans-[PdBr(3-pyridyl)(PPh3)2] (2b), and trans-[PdBr(4-pyridyl)(PPh3)2] (3b), which were converted on treatment with triethylpnosphine to trans-[PdBr(2-, 3-, and 4-pyridyl)(PEt3)2] complexes (1d, 2d, 3d, respectively). Titration with perchloric acid in dioxane–water (1:1 by volume) indicated the basicity sequence of these complexes: 2-pyridyl>>4-pyridyl>3-pyridyl. The bromide ligand in 1b–3bcan readily be replaced by Cl−, I−, N3−, NCO−, and NCS−. In each corresponding series the relative thermal stability is in the sequence of 2-pyridyl>4-pyridyl>3-pyridyl. The pyridyl complexes containing triphenylphosphine react with carbon monoxide at ambient temperature and pressure to afford acyl complexes, which produce the corresponding esters by reactions with methanol. They also act as catalysts for cross coupling reactions of bromopyridines.

The dinuclear palladium(II) complexes [(PP)Pd(C1–C3-β-dik(2−)-O,O′)Pd(PP)](ClO4)2containing a β-diketonate dianion as a bridging ligand were prepared by the reactions of the mononuclear complexes [Pd(β-dik(2−)-C1–C3)(PP)] with [Pd(PP)(H2O)2](ClO4)2. In the reactions of [Pd(etac(2−)-C1–C3)(dpe)] with [Pt(PPh3)2(H2O)2](ClO4)2and [Ni(acac)2] in the 1:1 mole ratio, similar dinuclear complexes [(dpe)Pd(C1–C3-etac(2−)-O,O′)Pt(PPh3)2](ClO4)2and [(dpe)Pd(C1–C3-etac(2−)-O,O′)Ni(acac)2] were produced, respectively, while the reactions of [Pd(β-dik(2−)-C1–C3)(PP)] with Ni(ClO4)2·6H2O and Mg(ClO4)2in the 2:1 mole ratio afforded the trinuclear complexes [M{O,O′-β-dik(2−)-C1–C3Pd(PP)}2](ClO4)2(M=Ni(II) and Mg(II)). The trihapto coordination to palladium(II) and O,O′-chelation to another metal atom of the β-diketonate dianion in these complexes were deduced mainly by IR and NMR spectroscopy.

The bis(β-diketonato)platinum(II) complexes react with various nitrogen bases (L) to afford [Pt(β-dik)L2](β-dik), [Pt(β-dik-O)2L2], [PtL4](β-dik)2, and [Pt(β-dik)(β-dik-C)L] depending on the natures of the β-diketonate anions and L. All of these complexes are stable in solution, showing no sign of isomerization and dissociation of L. The platinum(II) complexes containing the O-unidentate β-diketonate ligand are much more stable than the corresponding palladium(II) complexes and [Pt(acac)(piperidine)2](acac) and [Pt(acac-O)2(piperidine)2] constitute a pair of linkage isomers. The complexes containing the 2,4-pentanedionate anion (acac) in the outer sphere readily undergo the H-D exchange of the methine proton of acac and the NH protons of coordinated amines with CDCl3.

Bis(β-diketonato)palladium(II) and -platinum(II) readily react with tertiary phosphines (L) to afford [M(β-dik)(β-dik-O)L], [M(β-dik)L2](β-dik), [ML4](β-dik)2, [M(β-dik-O)2L2], and [M(β-dik)(β-dik-C)L] complexes, which were characterized mainly by infrared and 1H and 13C NMR spectroscopy. Factors influencing the relative stability of each bonding mode of β-diketonate anions were investigated.

Oxidative addition reactions of 2- and 3-chloropyridines and of 2-chloropyrazine to tetrakis(triphenylphosphine)nickel(0) occurred in toluene at ambient temperature to afford dinuclear nickel(II) complexes containing carbon-bonded heterocycles as a ligand. They are quite stable and the bridging chloride was readily substituted by other halides and pseudohalides preserving the dinuclear structure. 8-Chloroquinoline yielded a mononuclear complex as an exception. These novel organonickel(II) complexes were characterized by analytical and molecular weight data together with IR, 1H NMR, and 13C NMR spectra. Di-μ-chloro-bis(2-pyridyl)bis(triphenylphosphine)dinickel(II) was found to be an excellent catalyst for selective cross coupling of 2-chloropyridine with methylmagnesium bromide.

Green-to-blue six-coordinate mixed complexes, Cu(acac)2(en) and Cu(etac)2(diamine)(acac=acetylacetonate anion; etac=ethyl acetoacetate anion; diamine=ethylenediamine, trimethylenediamine, 2,2′-bipyridine or 1,10-phenanthroline) have been isolated by the reactions of the respective parent β-diketonate with the corresponding diamine in dry dichloromethane. On the other hand, the reaction of Cu(acac)2with en in the mole ratio of one-to-two in dichloromethane saturated with water has resulted in purple crystals of Cu(acac)2(en)2·2H2O. This compound has been shown by X-ray analysis to consist of a square-planar copper(II) cation, coordinated by two ethylenediamine molecules, and two planar acetylacetonate anions, the plane of which is not perpendicular to, but slanted against, the CuN4plane. One oxygen atom of the anion participates in the N–H···O hydrogen bonding with an NH2group of the ethylenediamine molecule, while the other occupies the axial position of Cu(en)22+(Cu···O: 2.79(1) Å). Therefore, the compound can be designated by the formula [Cu(en)2]·(acac)2·2H2O. The water hydrogen atoms seem to take part in the hydrogen bonding with the anion oxygen atoms.

Five-coordinate complexes [M(hfac)2L] (M=Pd, Pt; hfac=1,1,1,5,5,5-hexafluoro-2,4-pentanedionate anion) were produced by the reactions of [M(hfac)2] with equimolar amounts of tertiary phosphines, phosphites, and triphenylarsine. They were characterized by 1H, 13C, 19F, and 31P NMR spectra in solution and several complexes containing bulky phosphines as L were isolated, and structures of [Pd(hfac)2{P(o-tolyl)3}] and [Pt(hfac)2{P(cyclohexyl)3}] were determined by X-ray analysis. Both complexes have very distorted square-pyramidal structures, one of the two hfac anions in either of them spanning the apical and basal coordination sites. NMR spectra at various temperatures disclosed the fluxional behaviors of these complexes which retain the solid-state structures at such low temperatures as -60 °C. Two kinds of twist mechanisms were proposed.

Novel palladium(II) complexes [Pd(ß-dik)(?3-etac)] (5), in which anions of a ß-diketone and ethyl 3-oxobutanoate coordinate to the central metal atom by the O,O'-chelation and the ?3carbon bonding, respectively, were prepared by the reactions of a dinuclear complex [PdCl(?3-etac)]2with thallium (I) ß-diketonates in benzene or acetone at room temperature. Reactions of 5with Lewis bases (L) such as triphenylphosphine, diethylamine, propylamine and benzylamine were investigated. In almost all reactions, only the ?3-carbon-bonded ester ligand in 5was converted into a terminal-carbon-bonded one to afford complexes [Pd(ß-dik)(etac-C4)L]. The bonding modes for the ligands in these products as well as in 5were determined by means of IR and 1H and 13C NMR spectroscopy.

Diamagnetic dioxovanadium(V) complexes, VO2(ß-dik)(phen or bpy), were prepared by the direct reactions of VO(ß-dik)2with 1,10-phenanthroline and 2,2'-bipyridine in dichloromethane under aerobic conditions as well as by two other methods. These compounds were concluded to have a cisconfiguration on the basis of the IR and Raman data. These complexes are solvolyzed to afford the di-µ-methoxo-or di-µ-hydroxo-divanadium(V) species, and are reduced by hydrogen bromide to the oxovanadium(IV) species in dichloromethane. In methanol instead of dichloromethane, VO(acac)2reacted with 2,2'-bipyridine to produce a novel mixed-valence divanadium(IV, V) complex, V2O3(acac)3(bpy), which was revealed by the magnetic, spectral, and polarographic data to be a trans adduct of VO(acac)2with VO2(acac)(bpy) viaan oxide ligand.

Bis(acetylacetonato)oxovanadium(IV) reacts with phenol or its para-substituted derivatives in methanol, affording stable adducts with the composition of VO(acac)2(p-XC6H4OH), where X=H, NO2, CHO, COOH, Cl, or CH3. The magnetic and spectral data reveal that these are vanadium(IV) complexes containing the phenol as a neutral ligand. They show an unusually low ?(V=O) frequency of ˜900 cm-1as compared with the value of 1000 cm-1for the parent complex, and are presumed to have a polymeric structure with an infinite chain of V=O…V=O…. The phenol is connected by a hydrogen bond to one oxygen atom of an acetylacetonate ligand. The behavior of the complex in solution is also discussed. The addition of 1,10-phenanthroline or 2,2'-bipyridine to a reaction mixture of VO(acac)2and nitrophenols results in phenolato complexes VO(OC6H5-nXn)(acac)(phen or bpy), where X=NO2and n=1, 2, or 3. Two isomers of VO(OC6H2(NO2)3)(acac)(bpy) are isolated and characterized.

The reactions of [M(ß-dik)2] (M=Pt(II), Pd(II); ß-dik=acetylacetonate (acac), dipivaloylmethanate (dpm), hexafluoroacetylacetonate (hfac) ions) with dppm (dppm=Ph2PCH2PPh2) and mdppm (mdppm=Ph2PCH(Me)PPh2) have been investigated. [M(hfac)2] complexes react with dppm to afford the stable cationic complexes, [M(dppm)2](hfac)2. By contrast, [M(acac)2] complexes react to give the homoleptic bis(diphenylphosphino)methanido complexes, [M(Ph2PCHPPh2)2], through deprotonation of dppm by the displaced acac anions. The analogous complexes, [M(Ph2PC(Me)PPh2)2], are obtained using mdppm, instead of dppm. A complete reaction scheme leading to these products is proposed, based on the IR and 1H, 13C, and 31P NMR spectral data. Some consideration is given to the dependence of these reactions on the metals and the ß-diketonate ligands, employed.

The oxidative addition of 2-(chloromethyl)pyridine to tetrakis(triphenylphosphine)palladium(0) in toluene at 100 °C gave [{PdCl(C5H4N-2-CH2)PPh3}2] (1a), which was characterized by analytical, molecular-weight, and IR data as well as 1H, 31P, and 13C NMR spectroscopy. The chloride ligand was readily replaced by other halides, whereas tertiary phosphines such as diphenylmethyl-, phenyldimethyl-, and triethylphosphines cleaved the bridge after substitution of triphenylphosphine to result in the monomeric trans-[PdCl(C5H4N-2-CH2)(PR3)2] complexes. Reactions of 1awith carbon monoxide and other reagents are also reported. The corresponding 3-picolyl complex [{PdCl(C5H4N-3-CH2)PPh3}n] was also prepared, but could not be well characterized because of lower stability and solubility.

Oxidative-addition reactions of excess 2-(chloromethyl) and 2,6-bis(chloromethyl)pyridines with [RhCl(PPh3)3] in toluene at room temperature afforded (2-pyridylmethyl)- and {2-(6-chloromethyl)pyridylmethyl}rhodium(III) complexes, cis(PP)-[RhCl2{C5H3(6-R)N-2-CH2}(PPh3)2] (R = H, 1-cis; R = CH2Cl, 2-cis), respectively, which isomerized to the corresponding trans(PP) complexes at elevated temperature. In refluxing toluene, the reactions thus resulted in the trans(PP) complexes (R = H, 1-trans; R = CH2Cl, 2-trans) exclusively. A novel dinuclear rhodium(III) complex [Rh2Cl4{C5H3N-2,6-(CH2)2}(PPh3)2], in which the 2,6-dimethylpyridine-α,α′-diyl ligand is C,N-chelated to one rhodium atom and bound to the second one in an η3-pseudo-1-azaallylic fashion, was obtained by reactions of 2,6-bis(chloromethyl)pyridine with [RhCl(PPh3)3] (1 : 2 in mole) and of the 2-ciswith [RhCl(PPh3)3] (1 : 1 in mole), both in refluxing toluene. These were characterized by 1H, 13C, and 31P NMR spectroscopy and mass spectrometry as well as an elemental analysis and a molecular-weight determination.

Reactions of the bis(β-diketonato)palladium(II) complexes with various nitrogen bases (L) afforded [Pd(β-dik)L2](β-dik), [PdL4](β-dik)2, or [Pd(β-dik)(β-dik-C)L] according to the natures of L and β-diketonate anions. Less basic ligands such as 1,1,1,5,5,5-hexafluoro- and 1,1,1-trifluoro-2,4-pentanedionates are readily removed by L to the outer sphere. Tendency of preferring the central-carbon-bonded state of the β-diketonate anion is related with the keto-favoring nature of its conjugate acid. Excess primary amines and pyridines can displace both of the β-diketonate ligands but secondary amines only one. These two types of compounds containing the 2,4-pentanedionate anion in the outer sphere undergo prompt deuteration of methine and amine protons by CDCl3. Tribenzylamine and 2,6-diphenylpyridine react with bis(1,1,1,5,5,5-hexafluoro-2,4-pentanedionato)palladium(II) to afford orthometallated products.

The title complex crystallizes in the monoclinic space group C2/c with a=24.900(6) Å, b=8.272(2) Å, c=30.437(9) Å, and β=97.23(2)°. The structure analysis, which converged at R=0.061 and Rw=0.083 with 3017 reflections for which Fo2>3σ(Fo2), showed that the palladium has a complete square-planar coordination geometry. While one of the tfac ligands is chelating, the other is bound to the metal only through the carbonyl oxygen adjacent to CH3. The O-unidentate tfac ligand lies trans to the CF3CO moiety of chelating tfac and has a planar structure in which the dangling CF3CO group is situated trans to the bonding oxygen atom with respect to the C=C bond. The ab initioMO calculation for the Z,Z-form of the tfac anion indicated that the coordination ability of the acetyl oxygen is higher than that of the trifluoroacetyl oxygen in consistence with the observed structure.

2,6-Bis(chloromethyl)pyridine was oxidatively added to [IrCl(PPh3)3] to give cis(P,P)-[IrCl2(ClCH2-py-CH2-C,N)(PPh3)2] (ClCH2-py-CH2= {2-(6-chloromethyl)pyridyl}methyl) (1a), of which the cycloiridated structure has been established by an X-ray analysis. Complex 1afurther reacts with [RhCl(PPh3)3] to afford an Ir(III)–Rh(III) complex [IrRhCl2(μ-Cl)2(μ-CH2-py-CH2-C,N,C′)(PPh3)3](CH2-py-CH2= 2,6-dimethylpyridine-α,α′-diyl) (3). Upon prolonged heating in toluene, 3liberates one triphenylphosphine ligand and [IrRhCl2(μ-Cl)2(μ-CH2-py-CH2-C,N,C′)(PPh3)2] (4) is formed. X-Ray crystal structure determinations of 3and 4have revealed their dinuclear structures, in which the metals are connected by two Cl atoms and a CH2-py-CH2group acting, in 3, as a κC(for Ir) : κC,κN(for Rh)-bridging ligand, while, in 4, as a κC(for Rh) : κC,κN(for Ir)-bridging ligand. The structure of the corresponding Rh(III)–Rh(III) complex, [Rh2Cl4(μ-CH2-py-CH2)(PPh3)2] (6), which was incorrectly assigned based on its NMR spectral data alone [Bull. Chem. Soc.Jpn., 68, 183 (1995)], has been revised by an X-ray analysis to be analogous to that of 4. Pseudooctahedral geometries at the κC-bonded Rh(III) centers of 4and 6are completed by unusually close Rh···HC(aryl) contacts of 2.79 and 2.75 Å, respectively. Complex 4is static but 3as well as 6are fluxional in haloalkane solvents. Such a solution behavior of 3is discussed in the light of the solid structures of 3and 4.

Oxidative addition reactions of 2-chloropyridine, 2,6-dichloropyridine, 2-chloropyrazine, and 2-chlorobenzothiazole with tetrakis(triphenylphosphine)palladium(0) gave [{PdCl(R)(PPh3)}2] or trans-[PdCl(R)(PPh3)2] depending on the nature of the carbon-bonded heterocycles R. They are all stable and the chloride ligand is readily replaced by other halides and pseudohalides. These novel organopalladium(II) complexes were characterized by the analytical and molecular-weight data together with IR, 1H NMR and 13C NMR spectra, and the 2-pyridyl-bridged dinuclear structure of [{PdBr(C5H4N-C2)(PPh3)}2] was previously revealed by X-ray analysis. Both of the dinuclear and mononuclear 6-chloro-2-pyridylpalladium(II) complexes catalyze the cross coupling reaction between 2,6-dichloropyridine and methylmagnesium bromide to afford 2-methyl-6-chloropyridine selectively. The mononuclear 6-chloro-2-pyridylpalladium(II) complexes react with carbon monoxide to form the acyl complexes.

The reactions of [Pd(hfac)2] with aniline and its derivatives (L) in benzene at room temperature afforded [Pd(hfac)(hfac-C3)L], [Pd(hfac)L2](hfac), and [PdL4](hfac)2depending on the reactants mole ratio. On the other hand, the reactions of various [Pd(β-dik)2] complexes with L in refluxing benzene (in most cases) gave rise to the aniline-bridged dinuclear complexes [Pd(β-dik)(L–H)]2, which in turn reacted with primary amines and pyridine (L′) to produce [PdL′2(L–H)]2(β-dik)2.

A platinum(II)complex containing a 2,4-pentanedionate dianion as a trihapto ligand [Pt(acac(2–)-C1–C3){P(p-ClC6H4)3}2] was prepared by the reaction of [Pt(acac)2] with tris(p-chlorophenyl)phosphine and reacted with pyridinium perchlorate to afford [Pt(acac-C1)(py){P(p-ClC6H4)3}2](ClO4). A similar terminal-carbon-bonded complex of 1,1,1-trifluoro-2,4-pentanedionate monoanion with platinum(II) was also derived from [Pt(tfac(2–)C,O)(AsPh3)2] by the reaction with pyridinium perchlorate. These novel platinum(II) complexes were characterized mainly by IR and NMR spectroscopy.

The reaction of platinum(II) chloride with neat benzonitrile gave bis(benzonitrile)dichloroplatinum(II) as a mixture of cis and trans isomers in variable proportions, depending on the temperature. The geometry of the chromatographically separated isomers was identified on the basis of the dipole-moment and IR data. The 13C NMR spectra in CDCl3also enabled us to discriminate between isomers in both chemical shift and coupling to the 195Pt of the cyanide carbon, the resonance peak of which was utilized to follow the isomerization. The rate constant (kc) for the cis-to-trans isomerization was found to be (3.8±0.3)×10−6s−1in CDCl3at 25 °C, ten times larger than that [kt=(2.9±0.2)×10−7s−1] of the reverse reaction. The equilibrium between cis and trans strongly favored trans in CDCl3at 25 °C, whereas in benzonitrile the cis form was the dominant species at room temperature, while the trans form was dominant at higher temperatures.

A number of palladium(II) and platinum(II) bis-chelates have been prepared which contain one kind of symmetric or unsymmetric ß-diketonate anions, or involve two different ß-diketonate anions. Existence of the cisand transisomers in solution of the binary chelates of unsymmetric ß-diketones was confirmed by 1H and 13C NMR spectroscopy. Geometrical isomerization of the palladium(II) complexes to attain equilibrium in solution is fast, while the platinum(II) complexes are quite inert. The mixed-ligand chelates are stable in solution, showing no sign of disproportionation. The isomeric pairs of bis(1-phenyl-1,3-butanedionato)palladium(II), bis(2,4-hexanedionato)palladium(II), and bis(1,1,1-trifluoro-2,4-pentanedionato)platinum(II) were isolated, and molecular structure of the cisisomer of the first complex was determined by X-ray analysis.

Reactions of bis(trifluoroacetylacetonato)palladium(II), [Pd(tfac)2], with tertiary phosphines followed by pyridine or its derivatives afforded a series of the [Pd(tfac(2–)-C,O)LL']-type complexes which contain a C,O-chelating trifluoroacetylacetonate dianion and a couple of tertiary phosphine and/or heterocyclic nitrogen base ligands (L and L'). Their structures in solution were studied by 1H, 13C, 19F, and 31P NMR spectroscopy and the molecular structure in a crystal of [Pd(tfac(2–)-C,O)(PPh3)(2,6-Me2-py)]·C6H6containing triphenylphosphine and 2,6-dimethylpyridine as L and L' was determined by means of X-ray diffraction.

trans-Dichlorobis(benzonitrile) platinum(II) reacted with twice the molar amount of thallium(I) acetylacetonate and benzoylacetonate in dichloromethane at room temperature to afford mainly N-acetyl ß-ketoamine chelates, trans-[Pt{N(COMe)=C(Ph)CH=COMe(and Ph)}2] (1aand 3a). This N,O-chelate structure of 1awas determined by X-ray analysis. Reactions of cis-[PtCl2(PhCN)2] gave C-acetyl and C-benzoyl ß-ketoamine chelates, cis-[Pt{NH=C(Ph)C(COMe(and Ph))=COMe}2], together with other minor products. Formation of these ß-ketoamine chelates is explained by the nucleophilic reactions of the ß-diketonate carbanions at the coordinated cyanide carbon atom, followed by migration of the acetyl group or the methine proton of the nucleophiles onto the imino nitrogen atom formed during these reactions. In the presence of free ß-diketones, migration of the acyl group was generally suppressed; this led to high yields of C-acyl complexes especially in reactions of cis-[PtCl2(PhCN)2]. In each case, the reaction proceeded with retention of the geometrical configuration around the central metal atom. The structures of other products, including a compound obtained by acid hydrolysis of 1a, were explored and discussed, based on IR and 2H NMR data.

Tris(acetylacetonato)iron(III) Fe(acac)3reacts with an equimolar and double molar amounts of a hydrogen halide in dichloromethane to afford the mixed-ligand iron(III) complexes, FeX(acac)2and FeX2(acac)H2O, respectively, where X is Cl or Br. They are all high-spin iron(III) complexes and exist as monomeric five-coordinate molecules in non-coordinating solvents, but behave as uni-univalent electrolytes in methanol. Further reactions of FeX2(acac)H2O with an excess of hydrogen halides in dichloromethane followed by the addition of twice as many moles of 1,10-phenanthroline produced [FeX2(phen)2]X. The reactions of FeX2(acac)H2O with excesses of pyridine and 2,2'-bipyridine in tetrahydrofuran gave the six-coordinate complexes FeX2(acac)(py)2and FeX2(acac)(bipy), respectively.

The ultraviolet spectrum of Ni(acac)2in dichloromethane shows two maxima, at 265 and at 300 nm. The intensity ratio of these two bands is very sensitive to the water content of the solvent, the high-energy band decreasing and the low-energy band increasing with the water content. It is thus suggested that the trimeric Ni(acac)2might have only one absorption band, at 265 nm, in dichloromethane completely free from donor impurities. The UV spectrum of Ni(acac)2in dichloromethane changes with time due to the hydrolytic reaction. Even in the solvent containing 4.54×10−3mwater, acetylacetone was freed from the complex in the yield of 34.4% after 48 hours’ standing. A minute amount of the residual complex was isolated; its tetrameric structure is suggested on the basis of its UV spectrum in methanol.

The main product in the reaction of bis (acetylacetonato) beryllium with bromine in the mole ratio of one to two was found to be bis(3-bromoacetylacetonato)beryllium. The mass-spectrometric analysis of the product of the same reaction in the mole ratio of one to one revealed the coexistence of mono- and dibrominated chelates, but the quantitative information concerning the product distribution has not been obtained. In this reaction a small amount of white precipitate was produced as a minor product. The same compound was obtained in the reaction of bis-(acetylacetonato) beryllium with hydrogen bromide in dichloromethane containing water, and identified as diaquoacetylacetonatoberyIlium bromide on the bases of the elemental analysis, the anion exchange experiment and the infrared assay.

When the copper(II) chelate of ethyl acetoacetate reacts with bromine in dry dichloromethane, the chelate is broken, forming the a-bromoester and copper(I) or copper(II) bromide depending on the reactants’ mole ratio. However, in the reaction between bromine and the chelate at a mole ratio of 1 : 1 in dichloromethane saturated with water, copper-(I) bromide is not produced primarily; instead copper(II) hydroxide is formed, as is copper-(II) bromide.In the reactions of the copper(II) chelate of acetylacetone or ethyl acetoacetate with dry hydrogen bromide at the mole ratio of 1 : 1 or 1 : 1.5, more than 98% of the total copper precipitated as copper(I) bromide. Even when 2 mol. of hydrogen bromide was employed against 1 mol. of the chelate, more than 90% of the original copper changed to copper(I) bromide, in contrast with the results obtained in a similar reaction with bromine.The entire reaction pattern has been suggested employing a presumed intermediate binuclear complex containing a bromine double brigde.

In the reaction of bis(acetylacetonato)-copper(II) with bromine the chelate ring is broken and 3-bromoacetylacetone and copper-(I) or copper(II) bromide are formed depending on the mole ratio of the reactants.Bis(3-bromoacetylacetonato)copper(II) also reacts with bromine in a similar fashion resulting in 3, 3-dibromoacetylacetone and copper(I) or copper(II) bromide. The possibility of the copper(II) ion functioning as a catalyst in the second step of the bromination of acetylace-tone is suggested.

The reactions of bis(acetylacetonato)nickel(II) with restricted amounts of dry hydrogen bromide have been performed in appropriate mixtures of dichloromethane and petroleum ether at room temperature or lower in order to isolate the intermediary products, Ni3Br(acac)5, Ni3Br2(acac)4, and Ni3Br4(acac)2. The essentially octahedral trinuclear structure of Ni3Br(acac)5was established on the basis of elemental analysis, by molecular-weight and magnetic-moment determinations, and by studying the electronic and IR spectra. Ni3Br2(acac)4and Ni3Br4(acac)2were characterized less satisfactorily because of their lower solubilities. The reactions of these mixed complexes with pyridine have also been examined; a new complex NiBr(acac)(py)3was thus obtained in addition to the known compound, Ni(acac)2(py)2.

When bis (acetylacetonato)cobalt(II) is allowed to react with twice molar quantity of bromine in dichloromethane, cobalt(II) bromide and γ-bromoacetylacetone are produced ultimately. From a deep blue solution of an equimolar reaction mixture at 0°C an intermediary product was isolated and characterized to be dimeric bromo(acetylacetonato)cobalt(II) by means of elemental analysis and molecular weight determination. The structure of this compound was inferred to be tetrahedral from absorption spectra and magnetic data. Acetylacetonate groups were supposed to act as bridging ligands on the basis of IR data in the lower frequency region. Dibromobis(acetylacetonato)dicobalt(II) was also derived from dibromo(acetylacetone)cobalt(II) by the reaction with sodium acetylacetonate in acetylacetone at 0°C.

Dibromo(acetylacetone)cobalt(II), a new complex containing an acetylacetone molecule as the bidentate ligand, was formed by the reaction of tris(acetylacetonato)cobalt(III) with bromine in dichloromethane, and characterized by elemental and thermogravimetric analyses and electronic and infrared spectra. The same compound was also prepared by direct addition of acetylacetone to anhydrous cobalt(II) bromide. The radical nature of the redox step involved in the reaction pathway from the starting cobalt(III) chelate to the product cobalt(II) complex of acetylacetone was demonstrated by polymerization of methyl methacrylate and styrene remarkably enhanced by the reaction system.

The following metal complexes containing ethyl acetoacetate (etacH) or ethyl malonate (etmalH) as a neutral ligand have been prepared: CoCl2L, CoBr2L, ZnCl2L (L=etacH or etmalH), and MnBr2(etmalH). These compounds are all hygroscopic and unstable, releasing the ester ligand below 100°C in vacuoor in donor solvents. The infrared spectra show that the ratio of keto and enol tautomers in etacH complexes is similar to that for the free ligand. The ν(C=O) band attributable to the enol tautomer of etmalH is observed in the complexes, though not in the free ligand. The electronic spectra measured in Nujol suggest that the cobalt(II) complexes are tetrahedral. The structure of MnBr2(etmalH) is not yet certain.

Tris(acetylacetonato)manganese(III) reacts with ethylenediamine (L2) and other primary amines (L) in organic solvents at room temperature producing Mn(acac)2L2. The same Mn(II) complexes were also prepared quantitatively by reactions of Mn(acac)2(H2O)2with amines. Besides the usual hexa-coordinate monomeric complex, allylamine gave a dimeric compound [Mn(acac)2(CH2=CHCH2NH2)]2, which is the first example of the binuclear manganese(II) complex of acetylacetone. The stoichiometry of the redox reaction between Mn(acac)3and ethylenediamine was established and discussed in connection with the initiation mechanism of vinyl polymerization.

The reaction between tris(acetylacetonato)aluminum and bromine in dichloromethane was studied. The main product of this reaction was tris(?-bromoacetylacetonato) aluminum which was soluble in dichloromethane. A small amount of slightly yellow precipitate was also produced as a minor product. The same compound was obtained in the reaction of tris(?-bromoacetylacetonato) aluminum with hydrogen bromide in dichloromethane containing water, and identified as bromoaquobis(?-bromoacetylacetonato) aluminum on the bases of the elemental and water analyses, the ion exchange study, and the infrared spectroscopy.