Masafumi Hirano

Condensation reactions of benzaldehyde catalysed by gold alkoxides

Condensation reactions between active methylene compounds, CH2(X)(Y), such as alkyl cyanoacetate or acetophenone and benzaldehyde proceed smoothly in the presence of Catal.ytic amounts of gold alkoxides, Au(OR)L (L=PPh3: R=CH2CF3 (la), CH(CF3)2 (lb); L=PCy3: R=CH2CF3 (1c), CH(CF3)2 (1d) or AuMe2(OR)L (L=PPh3: R=CH2CF3 (2a), CH(CF3)2 (2b). Gold(I) complexes show higher catalytic activity than gold(III). In the catalytic system, the catalysts exist as the C-bonded gold enolate complexes Au(I)(CH(X)(Y))(L) or Au(III)Me2(CH(X)(Y))(L), which can be isolated independently from the reactions of gold alkoxides with the corresponding active methylene compounds. The catalytic activity of the gold alkoxides is generally higher than that of isolated C-bonded gold enolates. The reaction rate increases with increase in the concentrations of catalyst and benzaldehyde, but is independent of the concentration of alkyl cyanoacetate. A reaction mechanism involving two catalytic pathways has been proposed.

Michael reactions promoted by η1-O-enolatoruthenium(II) complexes derived from Ru(cod)(cot), diphosphine, and dimethyl malonate

Abstract The Michael reaction of 1,3-dicarbonyls with α,β-unsaturated esters and nitriles has been carried out very efficiently, under mild and neutral conditions, in the presence of a catalytic amount of trans -hydrido( η 1 - O -enolato) ruthenium(II) complex ( 2 ), which is prepared from the reaction of Ru(cod)(cot) ( 1 ) (cod = cycloocta-1,5-diene; cot = cycloocta-1,3,5-triene) with dimethyl malonate in the presence of 1,2-bis(diphenylphosphino)ethane (dpe).

CSi bond cleavage of trihalomethyltrimethylsilane by alkoxo- and aryloxogold or -copper complexes

Abstract The CSi bond cleavage of trihalomethyltrimethylsilane Me 3 SiCX 3 (X=F, Cl) proceeds smoothly by alkoxo- and aryloxogold(I or III) or -copper(I) complexes Au(OR)L (OR=OCH(CF 3 ) 2 , OPh), L=PCy 3 , PPh 3 , PMe 2 Ph, PMe 3 ), cis -AuMe 2 (OPh)L (L=PMePh 2 , PEt 3 , PMe 2 Ph, PMe 3 ), Cu(OR)(PPh 3 ) 3 (OR=OCH(CF 3 ) 2 , OPh) to give trihalomethylgold or -copper complexes Au(CX 3 )L, cis -AuMe 2 (CF 3 )L, or Cu(CF 3 )L 3 with liberation of the corresponding silyl ether Me 3 SiOR.

C–S, C–H, and N–H bond cleavage of heterocycles by a zero-valent iron complex, Fe(N2)(depe)2 [depe=1,2-bis(diethylphosphino)ethane]

Abstract Treatment of Fe(N2)(depe)2 [depe=1,2-bis(diethylphosphino)ethane] (1) with benzo[b]thiophene at room temperature results in the regioselective C–S and C–H bond cleavages giving Fe(SC 6 H 4 CHC H)(depe)2 (2a) and trans-FeH( CCHC 6 H 4 S )(depe)2 (3a) in 72 and 19% yields, respectively. Complex 1 also reacts with thiophene, 2- and 3-acetylthiophenes and 2- and 3-methylthiophenes to give both C–S and C–H bond oxidative addition products: Fe(SCHCHCHC H)(depe)2 (2b) and trans-FeH( CCHCHCHS )(depe)2 (3b), Fe[SC(COMe)CHCHC H](depe)2 (2c) and trans-FeH[ CCHCHC(COMe)S ](depe)2 (3c), Fe[SC(Me)CHCHC H](depe)2 (2d) and trans-FeH[ CCHCHC(Me)S ](depe)2 (3d), and Fe[SCHC(Me)CHC H](depe)2 (2e) and trans-FeH[ CCHC(Me)CHS ](depe)2 (3e), respectively. On the other hand, only C–H bond cleavage takes place in the reactions of 1 with furans such as furan, benzo[b]furan, and 2,3-dihydrofuran to give trans-FeH( CCHCHCHO )(depe)2 (4a), FeH( CCHC 6 H 4 O )(depe)2 (4b) and trans-FeH( CCHOCH 2 C H2)(depe)2 (4c) and N–H bond is exclusively cleaved by the reaction of 1 with pyrroles such as pyrrole, indole and 2-acetylpyrrole to give trans-FeH( NCHCHCHC H)(depe)2 (5a), trans- and cis-FeH( NCHCHC 6H4)(depe)2 (5b) and FeH[ NC(COMe)CHCHC H](η2-depe)(η1-depe) (6). Treatment of 2a with MeI results in the Fe–S bond cleavage of the thiaferracycle giving trans-FeI[(E)-CHCHC6H4-2-SMe](depe)2 (7) whose structure is unequivocally characterized by X-ray analysis. In contrast, hydrogenolysis of 2a with H2 (50 atm) leads to the cleavage of the Fe–C bond of the thiaferracycle to yield cis- and trans-FeH(SC6H4-2-Et)(depe)2 (8).

Catalytic synthesis of thiobutyrolactones via CO insertion into the C–S bond of thietanes in the presence of a heterodinuclear organoplatinum–cobalt complex

Heterodinuclear organoplatinum-cobalt complex having a 1,2-bis(diphenylphosphino)ethane ligand (dppe)MePt-Co(CO)4 catalyzes CO insertion into the C-S bond of thietanes in THF at 100 degrees C under 1.0 MPa of CO for 2 h to give gamma-thiobutyrolactone in quantitative yield.

Synthesis of hydridoplatinum–molybdenum (or tungsten) heterodinuclear complexes by β-hydrogen elimination of (dppe)EtPt–MCp(CO)3. Selective hydride transfer from Pt to Mo (or W)

Abstract Hydridoplatinum–molybdenum (or tungsten) heterodinuclear complexes (dppe)HPt–MCp(CO)3 [M=Mo (1), W ( 2 ); dppe=1,2-bis(diphenylphosphino)ethane] have been prepared by selective β-hydrogen elimination of corresponding ethylplatinum–molybdenum (or tungsten) complexes (dppe)EtPt–MCp(CO)3 [M=Mo (3), W (4)]. The β-hydrogen elimination process is significantly facilitated by electron-withdrawing transition metal ligand at platinum such as Co(CO)4 (5). Acetylenes having electron withdrawing groups induce selective hydride transfer reaction in these heterodunucelar complex 1–2 to give hydridomolybdenum (or tungsten) and zero-valent (acetylene)platinum complexes.

C–O and C–S bond activation of allyl esters, ethers, and sulfides by low valent ruthenium complexes

Abstract Allyl carboxylates or ethers react with Ru(cod)(cot) (1) [cod: 1,5-cyclooctadiene, cot: 1,3,5-cyclooctatriene] in the presence of monodentate tertiary phosphines such as PMe3, PEt3, PMe2Ph or PMePh2 to give a series of neutral (η3-allyl)ruthenium(II) complexes Ru(η3-C3H5)(OCOCF3)(PR3)3 [PR3=PEt3 (2a), PMe3 (2b), PMe2Ph (2c), PMePh2 (2d)], Ru(η3-C3H5)(OCOR′)(PMe3)3 [R′=Me (2e), Ph (2f)], Ru(η3-syn-C3H4R)(OCOCF3)(PMe3)3 [R=Me (2g), Ph (2h)] and Ru(OAr)(η3-C3H5)(PMe3)3 [Ar=Ph (3a), C6H4-o-Me (3b), C6H4-o-Et (3c), C6H4-o-OMe (3d)], whereas similar reactions of these allyl ethers, sulfides and carboxylates in the presence of the bidentate depe ligand [depe=1,2-bis(diethylphosphino)ethane] afford the cationic (η3-allyl)ruthenium(II) complexes, [Ru(η3-C3H5)(depe)2]+[RY]− [RY=PhS (4a), MeS (4b), PhO (4c), CF3COO (4d), CH3COO (4e)]. Protonolysis of all (η3-allyl)ruthenium(II) and (η3-crotyl)ruthenium(II) complexes with HCl liberate propylene and trans-2-butene, respectively. Complex 2a reacts with benzaldehyde to give 1-phenyl-3-butene-1-ol. Reaction of 2b with CO forces the bonding mode of allyl moiety in 2a from η3 to η1.

Synthesis, structure and reactivity of an (η6-naphthalene)iron(0) complex having a 1,2-bis(dicyclohexylphosphino)ethane ligand

Abstract A zerovalent iron complex having an η 6 -naphthalene ligand, Fe( η 6 -C 10 H 8 )(dcype) ( 3 ) [dcype=1,2-bis(dicyclohexylphosphino)ethane] has been prepared by the reduction of high spin 14 electron dichloroiron(II) complex, FeCl 2 (dcype) ( 1 ) with sodium-naphthalene. In refluxing benzene solution of 3 , the coordinated naphthalene can be replaced by benzene giving Fe( η 6 -C 6 H 6 )(dcype) ( 4 ). Exposure of 3 to CO results in the formation of Fe(CO) 3 (dcype) ( 5 ). Protonation of 3 with HBF 4 yields cationic complex, [FeH( η 6 -C 10 H 8 )(dcype)][BF 4 ] ( 6 ), which can be deprotonated by lithium diisopropylamide.

SYNTHESIS OF ORGANO(SILOXO)PLATINUM AND -PALLADIUM COMPLEXES AND PREPARATION OF SUPPORTED NANOCLUSTERS BY FACILE LIGAND REDUCTION

Abstract A series of organosiloxo complexes of platinum and palladium, MR(OSiPh3)(L2) (M=Pt, Pd; R=Me, Et, Ph; L2=cod, dppe), has been prepared and characterized. The square planar geometries of PtPh(OSiPh3)(cod) and PtEt(OSiPh3)(cod) are confirmed by X-ray structure analysis. In the reactions with hydrogen at 0°C and 1 atm, the siloxo complexes of Pt and Pd are reduced readily to give agglomerates of nanoclusters with complete hydrogenation of the ligands. The reduction activities of the siloxo and alkoxo complexes are higher than those of the corresponding alkyl complex PtMe2(cod). This high activity in reduction is applied to the preparation of supported Pt or Pd nanoclusters on silica, and the siloxo complexes adsorbed on silica are reacted with hydrogen at mild conditions. The resulting Pt/SiO2 gives a smaller mean diameter than that prepared from H2PtCl6/SiO2.

Successive OH and sp3 CH bond activation of ortho-substituted phenols by a ruthenium(0) complex

Abstract Successive OH and sp3 CH bond activation of ortho-substituted phenols has been achieved by the reactions of Ru(1,5-cyclooctadiene)(1,3,5-cyclooctatriene) (1) with 2,6-xylenol and 2-allylphenol in the presence of PMe3 giving oxaruthenacycle complexes such as cis- Ru[OC 6 H 3 ( 2-C H2)(6-Me)](PMe3)4 (4) or Ru[OC 6 H 4 (2-η 3 -C 3H4)](PMe3)3 (5), respectively. They are formed by the initial protonation of Ru(1-2-η2:5-6-η2-cycloocta-1,5-diene)(1-4-η4-cycloocta-1,3,5-triene)(PMe3) by phenols giving cationic (η5-cyclooctadienyl)ruthenium(II) complexes [Ru(η5-C8H11)(PMe3)3]+[OAr]−·(HOAr)n [Ar=C6H3Me2-2,6 (2a), C6H4(2-CH2CHCH2) (2b), C6H4{2-(E)-CHCHMe} (2c), Ph (2d); C6H4Me-2 (2e); C6H4(2-CHMe2) (2f), and C6H4(2-CMe3) (2g)] followed by sp3 CH bond cleavage reaction. The molecular structure of 2c reveals that the cyclooctadienyl group coordinates to the ruthenium center by an η5-fashion, where one equivalent of (E)-2-propenylphenol is associated with aryloxo anion. Further treatment of 2a and 2c with PMe3 results in the formation of oxaruthenacycle complexes to give 4 and 5, respectively. These facts clearly demonstrate that this sp3 CH bond cleavage reaction occurs at a divalent ruthenium center. On the other hand, reactions of 2d–g afford (hydrido)(aryloxo)ruthenium(II) complexes, cis-Ru(H)(OAr)(PMe3)4 [Ar=Ph (6a), C6H4Me-2 (6b), C6H4(2-CHMe2) (6c), C6H4(2-CMe3) (6d)].