Fumiyuki Ozawa

Catalytic double carbonylation of organohalogen compounds promoted by palladium complexes

Abstract Various organohalogem compounds can be catalytically converted into α-keto amides on reaction with carbon monoxide and amines. Tertiary phosphine-coordinated palladium compounds are particularly suitable as the double carbonylation catalyst.

Palladium(0) complexes coordinated with substituted olefins and tertiary phosphine ligands

Abstract New palladium(0) complexes with a variety of coordinated olefins [Pd(olefin)(PMePh2)2] (II) (olefin = styrene, ethyl methacrylate, methyl methacrylate, methyl acrylate, methacrylonitrile, and dimethyl maleate), were prepared by the reactions of [PdEt2(PMePh2)2] (I) with corresponding olefins in toluene. These complexes were characterized by means of elemental analysis, IR and 1H NMR spectroscopy and the chemical reactions. The dissociation of the coordinated olefin from complex II in solution was confirmed by spectroscopic studies of [Pd(mma)(PMePh2)2] (mma = methyl methacrylate). From the variable temperature NMR study, kinetic parameters for the dissociation process were determined as Ea = 7 kcal/mol, and ΔS‡ (293 K) = -30 cal/deg · mol. Some new hydrido complexes, [Pd(H)ClL2] (IV) (L = PMePh2, PEtPh2 and PEt2Ph), were prepared by the reactions of [Pd(olefin)L2] with dry HCl.

Mechanism of reaction of trans- diarylbis(diethylphenylphosphine)palladium(II) complexes with aryl iodides to give biaryls

Abstract The mechanism of reaction of trans -PdAr 2 L 2 (Ar = m -tolyl or phenyl, L = Pet 2 Ph) with aryl iodides affording biaryls has been studied. The rate of reaction is independent of the concentration of aryl iodide but is significantly accelerated by the presence of trans -PdAr(I)L 2 . Cross-over experiments on the reaction of diarylpalladium complexes with monoarylpalladium iodides reveals the occurrence of two types of intermolecular processes between the diaryl and monoaryl complexes. The first process results in a scrambling of aryl groups between the diaryl and monoaryl complexes without formation of biaryls, while the second yields the reductive elimination products, biaryls.

Trans-cis isomerization of dimethylbis(diethylphenylphosphine)palladium(II) catalyzed by methylmagnesium compounds☆

Abstract Dimethylbis(diethylphenylphosphine)palladium(II) complex was found to undergo a facile trans - cis isomerization reaction in tetrahydrofuran containing methylmagnesium compounds such as Me 2 Mg and MeMgBr. Kinetic and isotopic studies on the isomerization process suggest the occurrence of methylmagnesium-catalyzed isomerization through an intermolecular methyl exchange process between methylpalladium and methylmagnesium compounds involving a partial dissociation of phosphine ligand.

Synthesis, characterization, and carbonylation reactions of methylpalladium amide, carbamate, and alkyl carbonate complexes

Abstract A series of trans- and cis-methylpalladium carbamate complexes PdMe(OCONRR′)L2 (L = tertiary phosphine; R, R′= H, alkyl, and phenyl) was prepared by the reaction of dimethylpalladium complexes with primary or secondary amine and carbon dioxide. When diphenylamine was used, methylpalladium amide complexes trans-PdMe(NPh2)L2 (L = PMe3 and PEt2Ph) were isolated instead of carbamates. The carbamate and amide complexes thus prepared were characterized by IR and NMR spectroscopy and elemental analysis. The carbamate complex trans-PdMe(OCONEt2)(PMe3)2 released one of the PMe3 ligands on recrystallization to form a dimeric compound Pd2Me2 (μ-OCONEt2)2(PMe3)2, whose structure was determined by X-ray diffraction study. The carbamate complexes reacted with carbon monoxide under pressure to give corresponding α-keto amide (MeCOCONRR′) and amide (MeCONRR′). Reactions of dimethylpalladium complexes with alcohols and carbon dioxide gave methylpalladium alkyl carbonate complexes trans-PdMe(OCOOR)L2 (R = Me, sBu; L = PMe3, PPh3). Treatment of alkyl carbonate complexes with carbon monoxide afforded the corresponding alkyl acetate as the sole carbonylation product.

Protonation and alkylation of benzoyl(carbamoyl)-palladium(II) and -platinum(II) complexes to give cationic benzoyl complexes with O-protonated and O-alkylated carbamoyl ligands. Characterization of an intermediate in the reaction of trans-[Pd(COPh)(CO)(PMe3)2]BH4 with pyrrolidine to give trans-Pd(COPh)(CON(CH2)3CH2)(PMe3)2

trans-[Pd(COPh)(CO)(PMe3)2BF4 (1) reacts with pyrrolidine to afford a cationic benzoylpalladium(II) complex with an O-protonated carbamoyl ligand trans-[Pd(COPh){C(OH)(N(CH2)3CH2)}(PMe3)2] BF4 (2b), which has been characterized by means of NMR spectroscopy. Complex 2b reacts further with pyrrolidine to give trans-Pd(COPh)(CON(CH2)3CH2)(PMe3)2 (3) together with the pyrrolidinium salt CH2(CH2)3NH2BF4. The conversion of 2b to 3 is a reversible process, and treatment of 3 with the pyrrolidinium salt regenerates 2b. Thermodynamic and kinetic parameters for the protonation-deprotonation equilibration between 2b and 3 have been determined by means of NMR spectroscopy. Treatment of trans-Pd(COPh)(CON(CH2)4CH2)(PMe3)2 with Et3OBF4 affords trans-[Pd(COPh){C(OEt)(N(CH2)4CH2)}(PMe3)2]BF4 (4). Ethylation of benzoyl(carbamoyl)platinum complexes trans- and cis-Pt(COPh)(CONMe2)(PPh3)2 with Et3OBF4 also gives corresponding O-ethylated carbamoyl complexes trans- and cis-[Pt(COPh){C(OEt)(NMe2)}(PPh3)2]BF4 (5 and 6, respectively).

The preparation and reductive elimination behavior of trans-Pd(COPh)(CONMe2)(PMe3)2: a model intermediate in the catalytic double carbonylation of aryl halides with amines to give α-keto amides

Abstract The cationic benzoylcarbonylpalladium(II) complex, trans-[Pd(COPh)(CO)(PMe3)2]+BF4− (1), reacts with Me2NH under CO to give trans-Pd(COPh)(CONMe2)(PMe3)2 (3). Complex 3 is stable in neat solvent, whereas rapid decomposition of 3 to give PhCOCONMe2 takes place in the presence of Me2NH2BF4 and Me2NH under CO.

Reactions of acyl(carbonyl)ruthenium(II) and acyl(carbonyl)iron(II) complexes with amines. Preparation of novel propionyl(carbamoyl)ruthenium(II) complexes

Abstract Treatment of Ru(COEt)Cl(CO)(PPh 3 ) 2 ( 1 ) with secondary amines (R 2 NH) under pressure of CO and / or ethylene gives propionyl-carbamoyl complexes Ru(COEt)(CONR 2 )(CO)(PPH 3 ) 2 (NR 2 = NEt 2 ( 4a ), N(CH 2 ) 4 CH 2 ( 4b ), NMe, ( 4c )) together with the ammonium salt R 2 NH 2 Cl. Complexes 4a–c have been isolated as pale yellow crystals and characterized by means of NMR and IR spectroscopy and elemental analysis. Reactions of Fe(COMe)I(CO) 2 (PMe 3 ) 2 and [Fe(COMe)(CO) 3 (PMe 3 ) 2 ]BF 4 with nucleophiles (HNEt 2 , LiNMe 2 , EtOH (in conjunction with Et 3 N) and NaOMe) give the corresponding acetamides and acetic acid esters. The carbonyl(propionyl)ruthenium complex 1 in solution under CO pressure was found to undergo nucleophilic attack of secondary amines on the coordinated CO ligand to give isolable acyl(carbamoyl)ruthenium complexes 4 in a parallel behavior with the previously reported acyl(carbonyl) palladium complexes [4g,h]. However, the isolated acyl(carbamoyl)ruthenium complexes differ in their behavior from the palladium analogs in their inactivity to release α-keto amide. The exact reason for the different behavior is not clear. A possible explanation for the reluctance of reductive elimination from the acyl(carbamoyl)ruthenium complex is that the acyl and the carbamoyl ligands are situated at unfavorable sites for a concerted reductive elimination to occur. In a theoretical treatment of reductive elimination of two organic groups from a five-coordinated nickel complex, it has been discussed that (i) the organic ligands both situated at equatorial positions in a trigonal-bipyramidal complex are symmetrically forbidden to undergo the reductive elimination process, and (ii) kinetic barriers for pseudorotation to bring the concerned organic ligands to axial and equatorial sites are very high [13]. A similar argument might be advanced in the present case but we would rather defer from advancing the discussion further until more bis-acyl type complexes are prepared and their behavior examined.

Reactions of benzoyl(carbonyl)transition metal complexes with LiNMe2: on the feasibility of a reaction route to α-keto amide through an acyl(carbamoyl)cobalt intermediate

Abstract CO-coordinated benzoyltransition metal complexes, PhCOCo(CO) 3 L (L ue5fb PPh 3 , PCy 3 , and PMe 3 ), PhCOMn(CO) 5 , have been prepared and their reactions with LiNMe 2 examined. The reactions give α-keto amide (PhCO-CONMe 2 ) after treating the systems with Br 2 or organic halides.