Tat'yana A. Peganova

Synthesis of η5-1,2,3,4,5-pentamethylcyclopentadienyl-platinum complexes☆

Reaction of K2PtCl4 with pentamethylcyclopentadiene gave the exo-H isomer (1b, 25%) as well as the endo-H isomer (1a, 75%) of [Pt(η4-C5Me5H)Cl2]. The mixture reacted with AgBF4 in acetone at −78°C to give the mixed endo-H, exo-H isomeric dication solvate complexes [Pt(η4-C5Me5H)(acetone)x]2+(BF4−)2 (2a,b), which decompose at room temperature to give [Pt(η4-C5Me5H)(η5-C5Me5)]+BF4− (3). The same reaction of 1a,b in the presence of dienes (pentamethylcyclopentadiene, cyclopentadiene, 1,3-cyclohexadiene, and 1,5-cyclooctadiene) occurs with spontaneous deprotonation to give the monocationic complexes, 3, [Pt(η4-C5Me5H)(η5-C5Me5)]+BF4− (4a,b), [Pt(η4-C6H8)(η5-C5Me 5)]+BF4− (5), and [Pt(η4-C8H12)(η5-C5Me5)]+BF4− (6 ), respectively, in high yield. The products from the reaction depend on the ability of the coordinated diene to undergo deprotonation in an intermediate, in the order, η4-1,3-cyclohexadiene ∼η4-1,5-cyclooctadiene < η4-endo-pentamethylcyclopentadiene < η4-exo-pentamethylcy- clopentadiene < η4-cyclopentadiene. The solvent complexes [M(η5-C5Me5)(acetone)3]2+(BF4−)2 (M  Rh, Ir) react with C5Me5H to give decamethyl-rhodocenium and -iridocenium salts.

Redox-induced activation of CH bonds in 1,2,3,4,5-pentamethylcyclopentadiene platinum complexes

The electrochemical behaviour of the platinum complexes [Pt(η4C5Me5H)(η5C5H5)] +BF4− (1+) and [Pt(η4-diene)(η5C5Me5)]+BF4− (diene = C5Me5H (2+) or 1,3-cyclohexadiene; (3+) 1,5-cyclooctadiene(4+)) has been studied by cyclic voltammetry. The complexes 1+−4+ are capable of both oxidation and reduction. The bulk electrolysis of 2+ at the potential of its reduction gives a mixture of twe neutral isomeric complexes 5a and 5b. These are assigned structures with η3-allylic and of σ, π-bonding methylene cyclopentenyl Me3C5H(CH2) ligand. This is the proposed result from methyl CH bond breakage in pentamethylcyclopentadiene ligand of an intermediate 19-electron complex [Pt(η4C5Me5H) (η5C5Me5)]. (2.). The same mixture of isomers 5a and 5b forms in interaction of 2+ and tBuOK in tetrahydrofuran. The preparative electrochemical oxidation of 2+ proceeds with CH bond scission at the pentamethylcyclopentadiene sp3-hydridized carbon in an intermediate 17-electron dication radical [Pt(η4C5Me5H)(η5C5Me5)].2+ (2.2+) to give decamethylplatinacene dication [Pt(η5C5Me5)2]2+(BF4−)2 (72+). The one-electron reduction of 72+ regenerates 2+.

Transfer Hydrogenation of Ketones Catalyzed by Surface-Active Ruthenium and Rhodium Complexes in Water

An improved, high-yield, one-pot synthetic procedure for water-soluble ligands functionalized with trialkyl ammonium side groups H2 N(CH2 )2 NHSO2 -p-C6 H4 CH2 [NMe2 (Cn H2n+1 )](+) ([HL(n) ](+) ; n=8, 16) was developed. The corresponding new surface-active complexes [(p-cymene)RuCl(L(n) )] and [Cp*RhCl(L(n) )] (Cp*=η(5) -C5 Me5 ) were prepared and characterized. For n=16 micelles are formed in water at concentrations as low as 0.6 mM, as demonstrated by surface-tension measurements. The complexes were used for catalytic transfer hydrogenation of ketones with formate in water. Highly active catalyst systems were obtained in the case of complexes bearing C16 tails due to their ability to be adsorbed at the water/substrate interface. The scope of these catalyst systems in aqueous solutions was extended from partially water soluble aryl alkyl ketones (acetophenone, butyrophenone) to hydrophobic dialkyl ketones (2-dodecanone).

Synthesis and reduction of trifluoromethyl-substituted arenecyclopentadienylruthenium sandwiches [Ru(η5-C5Me4CF3)(η6-C6R6)]+ (R=H, Me) and [Ru(η5-C5Me5)(η6-C6H5CF3)]+

Abstract Dimer [Ru 2 ( η 5 -C 5 Me 4 CF 3 ) 2 Cl 2 ( μ -Cl) 2 ] ( 1 ) has been prepared by reaction of RuCl 3 ·(H 2 O) 3 with 1,2,3,4-tetramethyl-5-(trifluoromethyl)cyclopentadiene in ethanol under reflux. Cationic arenecyclopentadienyl complexes [Ru( η 5 -C 5 Me 4 CF 3 )( η 6 -arene)] + PF 6 − ( 2 + , arene=C 6 H 6 ; 3 + , arene=C 6 Me 6 ) and [Ru( η 5 -C 5 Me 5 )( η 6 -C 6 H 5 CF 3 )] + BF 4 − ( 4 + ) were obtained by refluxing [Ru 2 ( η 5 -C 5 Me 4 CF 3 ) 2 Cl 2 ( μ -Cl) 2 ] ( 1 ) or [Ru 2 ( η 5 -C 5 Me 5 ) 2 Cl 2 ( μ -Cl) 2 ] with corresponding arenes in alcohol. The redox properties of 2 + – 4 + were studied by cyclic voltammetry (CV). All three complexes 2 + – 4 + are reduced irreversibly in one-electron process. The values of reduction peak potentials for 2 + – 3 + are less negative than those found for η 5 -C 5 Me 5 analogues. The reduction of 2 + and 3 + with sodium amalgam in tetrahydrofuran led to the formation of dimers [Ru 2 ( η 5 -C 5 Me 4 CF 3 ) 2 ( μ – η 5 : η 5 -C 6 H 6 C 6 H 6 )] ( 5 ) and [Ru 2 ( η 5 -C 5 Me 4 CF 3 ) 2 ( μ – η 5 : η 5 -C 6 Me 6 C 6 Me 6 )] ( 6 ) respectively. The reduction of 4 + gave a non-identifiable mixture of neutral products.

X-ray structures of decamethylplatinocene dication in the crystal of [Pt(η5-C5Me5)2]2+(PF6−)2 and decamethyliridocenium cation in the crystal of [Ir(η5-C5Me5)2]+(BPh4−) · CH2Cl2

Abstract The molecular crystal structures of the [Ir( η 5 -C 5 Me 5 ) 2 ] + cation in the complex of [Ir( η 5 -C 5 Me 5 ) 2 ] + (BPh 4 ) − · CH 2 Cl 2 ( 1 ), (space group P l¯, Z = 2), and dication [Pt( η 5 -C 5 Me 5 )] 2+ in the complex of [Pt( η 5 -C 5 Me 5 ) 2 ] 2+ (PF 6 ) 2 − ( 2 ), (space group I 4¯2 d , Z = 8) were proved by an X-ray investigation at 153 K ( R = 0.0661 and 0.0528 for 1 and 2 respectively). X-ray analysis revealed that in both structures the cations and anions are ordered, cation [Ir( η 5 -C 5 Me 5 ) 2 ] + has the staggered conformation, whereas the dication [Pt( η 5 -C 5 Me 5 )] 2+ has the ideal eclipsed one. The distances from the metal to the C 5 Me 5 ring in 1 (1.817(6) A and 1.821 (6) A are close to those in the neutral complex Os( η 5 -C 5 Me 5 ) 2 ( 3 ) (1.810(7) A). The similar distance in the dication [Pt( η 5 -C 5 Me 5 ) 2 ] 2+ in 2 (1.84(1) A) is slightly elongated in comparison with 1 and 3 .

Synthesis of Diaminophosphonium Salts [Ph2(ArNH)2P]+Br- (Ar = o-MeC6H4, p-MeC6H4, p-PriC6H4, p-EtO2CC6H4, p-MeOC6H4)

The behavior of different anilines H2NC6H4R (R = o-Me, p-Me, o-, m- and p− i Pr, p-OMe, p-CO2Et) and 2,6-Me2C6H3NH2 towards trihalophosphoranes was studied. 2,6-Me2C6H3NH2 failed to form the diaminophosphonium salt [Ph2PNH(2,6-Me2C6H3)2]Br, and the aminophosphine oxide Ph2(2,6-Me2C6H3NH)PO was the only isolated product. Both o- and p-toluidine gave the corresponding diaminophosphonium salts; however in the case of o-toluidine, the yield was low and a mixture with the respective aminophosphine oxide was observed. Anilines containing methoxy and ethoxycarbonyl groups in para-position form the diaminophosphonium salts in reasonable yields.

Bis(η5-pentamethylcyclopentadienyl)-and(η5cyclopentadienyl) (η5-pentamethylcyclopentadienyl)-platinium dications: Pt(IV) metallocenes

Abstract Reaction of [Pt2(η5-C5Me5)2(η-Br)3]3+(Br−)3 with C5R5H (R = H,Me) in the presence of AgBF4 gives the first platinocenium dications, [Pt(η5-C5Me5)(η5-C5R5)]2+(BF4− )2. On electrochemical reduction, [pt(η5-C5Me5)2]2+ yields [Pt(η4-C5Me5H)(η2-C5Me5)]+ BF4−. kw]Cyclopentadienyl; Metallocenes; Platinum; Electrochemistry

NOVEL OLEFIN NICKEL(0) COMPLEXES OF THE METHYL-DERIVATIVES OF METHYLENECYCLOPROPANE AND CYCLOPROPENE

The interaction of phosphine nickel complexes Ni(PPh3)3 and Ni(PPh3)2(η2-C2H4) with methyl derivatives of methylenecyclopropane and cyclopropene has been studied. The novel olefin complexes: (η2-2,2-dimethyl-1-methylenecyclopropane)bis(triphenylphosphine)nickel, (η2-1,3,3-trimethylcyclopropene)bis(triphenylphosphine)nickel and (η2-tetramethylcyclopropene)bis(triphenylphosphine)nickel have been prepared. The structure of the compounds obtained is discussed on the basis of the 1H and 31P{1H} NMR spectra. Comparative studies of the reactivities of the resulting complexes in the substitution reactions of η2-olefin ligands are described.

Palladium(II) aminoiminophosphoranate complexes as cross-coupling catalysts

The Tsuji-Trost reaction between diethyl malonate and allyl acetate catalyzed by palladium(II) NPN-aminoiminophosphoranate complexes yields mono- and diallylation products in the ratios depending on the complex used. The Suzuki-Miyaura cross-coupling of 4-bromoacetophenone with phenylboronic acid catalyzed by these palladium complexes proceeds with 66–99.5% conversions.

Synthesis of platinum complexes with η4-C5Me4(CF3)H ligand. X-ray structure of [Pt(η4-C5Me4H2)Cl2] and [Pt{η4-C5Me4(CF3)H}(η5-C5H5)]PF6

Abstract Reaction of isomeric mixture of 1,2,3,4-tetramethyl-5-(trifluoromethyl)cyclopentadiene with Zeises salt dimer gave the only isomer [Pt{η 4 -C 5 Me 4 (CF 3 )H}Cl 2 ] ( 1 ) bearing CF 3 group exo to sp 3 carbon atom in a high yield. An attempt to prepare 1 by reaction of K 2 PtCl 4 with C 5 Me 4 (CF 3 )H using hydrochloric solution of tin dichloride as a catalyst unexpectedly resulted in a formation of [Pt(η 4 -C 5 Me 4 H 2 )Cl 2 ] ( 2 ). The X-ray structure of compound 2 is presented. Reactions of 1 with AgBF 4 in the presence of three different cyclopentadienes C 5 R 1 4 (R 2 )H (R 1 =R 2 =H; R 1 =R 2 =Me; R 1 =Me, R 2 =CF 3 ) were studied. Crystal structure of complex [Pt{η 4 -C 5 Me 4 (CF 3 )H}(η 5 -C 5 H 5 )]PF 6 ( 3 ) resulted from the reaction with cyclopentadiene was determined. When C 5 Me 4 (CF 3 )H is used the reaction yields [Pt{η 4 -C 5 Me 4 (CF 3 )H}{η 5 -C 5 Me 4 (CF 3 )}]BF 4 ( 4 ) unstable in solutions. Reaction with pentamethylcyclopentadiene led to complex [Pt(η 4 -C 5 Me 5 H)(η 5 -C 5 Me 5 )]BF 4 ( 5 ) and no complexes with CF 3 containing ligands were obtained.