Synthesis of Ruthenium Half‐Sandwich Complexes by Naphthalene Replacement in [CpRu(C₁₀H₈)]⁺

Abstract

Replacement of the naphthalene ligand in ruthenium complex [CpRu(C 10 H 8 )] + (1) by halide anions readily proceeds at room temperature to give insoluble oligomeric species [CpRuX] n (X = Cl, Br, I). Similar reactions in the presence of mono-or bidentate ligands afford complexes [CpRuL 2 X] where L = CO, P(OMe) 3 , tBuNC; L 2 = dppm, dppe, dppp, bipy, phen, cod, nbd, or 1,4-diphenylbutadiene. Useful catalysts [CpRu(cod)X] were obtained by this method in 70-90 % yields. The structure of [CpRu(cod)I] was determined by Xray diffraction. Reaction of 1 with Brand allyl bromide afforded Ru IV complex [CpRu(η 3 -C 3 H 5 )]Br 2 . Cation 1 also was found to react with azide anion in the presence of bidentate phosphanes to afford [CpRuL 2 N 3 ] (L 2 = dppm, dppe). Reaction of 1 with neutral ligands in the absence of nucleophilic anions proceeded under visible-light irradiation to give cat-[a] A. N. Nesmeyanov Institute of Organoelement Compounds, 481 ionic complexes [CpRuL 3 ] + [L = CO, P(OMe) 3 , P(OEt) 3 , tBuNC] in 80-90 % yields. Complex 1 (2 mol-%) catalyzed cyclotrimerization of dipropargyl Meldrum's acid with various alkynes RCϵCH [R = H, Bu, Hex, Ph, SiMe 3 , (CH 2 ) 4 -CϵCH, (CH 2 ) 3 OH, (CH 2 ) 2 Br, CH 2 OMe, CH 2 OAc, CH 2 NMe-Boc] producing benzene derivatives in 50-85 % yields. According to DFT calculations, the attack of the first ligand (Clor L) is a rate-determining step in the naphthalene replacement in 1. The activation barrier for attack of the Clanion is ca. 10 kcal mol -1 lower in energy than that of the neutral ligands L = CO, MeNC, MeCN, thus providing a rationale for the faster reaction in the presence of halide anions. The barriers for naphthalene replacement in 1 were also found to be ca. 10-15 kcal mol -1 lower in energy than those for the benzene replacement in [CpRu(C 6 H 6 )] + . Scheme 1. Reactions of 1 with neutral 2-electron ligands.

General Route to Cyclobutadiene Rhodium Complexes

“…[5] [8] However,i th as not been used further,p erhaps, because of the limited availability of the rhodiump recursor.H erein we report ag eneral route to cyclobutadiene rhodium compounds based on the arene replacement reactions in the readily available cationic complexes [(C 4 R 4 )Rh(p-xylene)] + . [9] One of the main problems in synthesis of cyclobutadiene complexes is the catalytic oligomerization of startinga lkynes by coordinatively unsaturated metal precursors. In order to avoid such process we chose the 18-electron rhodiumcomplex [(C 2 H 4 ) 2 Rh(p-xylene)] + (1)a saprecursor, which has only two substitutionally labile ethylene ligands.…”

Ruthenium‐Catalyzed Reductive Amidation without an External Hydrogen Source

“…We have proposed a possible mechanism based on the current observations and previous DFT calculations[1a] (Figure ). As mentioned above, under carbon monoxide, complex 15 is expected to generate active species [(C 5 Me 4 CH 2 OMe)Ru(CO) x ] + A . The methoxy group of C 5 Me 4 CH 2 OMe ligand may help to stabilize such species and prevent formation of inactive clusters.…”

“…Among those, the Cp*Ru(cod)Cl (cod = 1,5‐cyclooctadiene) complex has a lower activity, presumably because of the difficult dissociation of the Ru–Cl bond. We assume that all these complexes generate similar catalytic species with a general formula of [(C 5 R 5 )Ru(CO) x ] + . The cyclopentadienyl ligand protects such species against side reactions and precipitation (note that complexes 2 and 7 , which have unsubstituted Cp ligands, are less efficient) .…”

Microwave‐Assisted Synthesis and Transformations of Cationic CpRu(II)(naphthalene) and CpRu(II)(naphthoquinone) Complexes

“…Thus, naphthalene substitution in 2 by arenes, phosphines, acetonitrile, amines takes place under mild conditions and can be accelerated by visible light. [20,22,[25][26][27][28][29][30][31][32] The microwave-mediated substitution of Cp for an arene ligand was extended to the preparation of a number of CpRu(arene) + complexes (Scheme 3).…”