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Eight new N-Hoveyda-type complexes were synthesized in yields of 67-92 % through reaction of [RuCl2(NHC)(Ind)(py)] (NHC=1,3-bis(2,4,6-trimethylphenylimidazolin)-2-ylidene (SIMes) or 1,3-bis(2,6-diisopropylphenylimidazolin)-2-ylidene (SIPr), Ind=3-phenylindenylid-1-ene, py=pyridine) with various 1- or 1,2-substituted ferrocene compounds with vinyl and amine or imine substituents. The redox potentials of the respective complexes were determined; in all complexes an iron-centered oxidation reaction occurs at potentials close to E=+0.5 V. The crystal structures of the reduced and of the respective oxidized Hoveyda-type complexes were determined and show that the oxidation of the ferrocene unit has little effect on the ruthenium environment. Two of the eight new complexes were found to be switchable catalysts, in that the reduced form is inactive in the ring-opening metathesis polymerization of cis-cyclooctene (COE), whereas the oxidized complexes produce polyCOE. The other complexes are not switchable catalysts and are either inactive or active in both reduced and oxidized states. [ABSTRACT FROM AUTHOR]

Four 1-(4-R-phenoxy)-2-ethenylbenzenes (R=NMe2, H, Cl, NO2) 4a, 4b, 4c and 4d were reacted with the ruthenium complexes [RuCl2(NHC)(3-phenylindenylidene)(py)] in the presence of a protic resin to result in the formation of the respective Hoveyda-type complexes 5a-d {NHC=SIMes [1,3-bis(2,4,6-trimethylphenylimidazolin)-2-ylidene]} and 6a-d {NHC=SIPr [1,3-bis(2,6-diisopropylphenylimidazolin)-2-ylidene]} in 66-84% yield. The lower steric bulk and the decreased donation of the diaryl ether oxygen atoms in complexes 5 and 6 led to rapidly initiating precatalysts. The Ru(II/III) redox potentials of complexes 6 were determined ( 6a-d: ΔE=0.89-1.08 V). In the crystal structure of 5b two independent molecules were observed in the unit cell, displaying RuO distances of 226.6(4) and 230.5(3) pm. The catalytic performance of complexes 5 and 6 in various ring-closing metathesis (RCM) reactions was studied. Catalyst loadings of between 15-200 ppm are sufficient for the formation of >90% yield of the respective cyclic products. Complex 6b catalyzes the formation of N-protected 2,5-dihydropyrroles with up to TON 64,000 and TOF 256,000 h−1, of the N-protected 1,2,3,6- tetrahydropyridines with up to TON 18,200 and TOF 73,000 h−1 and of the N-protected 2,3,6,7-tetrahydroazepines with up to TON 8,100 and TOF 32,000 h−1 with yields ranging between 77 and 96%. [ABSTRACT FROM AUTHOR]

End-of-life tire granulates were used in olefin metathesis reactions with ethene (ethenolysis); utilizing 0.0074 mmol of a Grubbs type ruthenium complex for 1.0 gram of tire granules leads to the isolation of ca. 0.5 g of organic solubles, which are primarily composed of oligomeric 1,4-cis isoprenes. [ABSTRACT FROM AUTHOR]

Reactions of the Grubbs 3rd generation complexes [RuCl2(NHC)(Ind)(Py)] (N-heterocyclic carbene (NHC)=1,3-bis(2,4,6-trimethylphenylimidazolin)-2-ylidene (SIMes), 1,3-bis(2,6-diisopropylphenylimidazolin)-2-ylidene (SIPr), or 1,3-bis(2,6-diisopropylphenylimidazol)-2-ylidene (IPr); Ind=3-phenylindenylid-1-ene, Py=pyridine) with 2-ethenyl- N-alkylaniline (alkyl=Me, Et) result in the formation of the new N-Grubbs-Hoveyda-type complexes 5 (NHC=SIMes, alkyl=Me), 6 (SIMes, Et), 7 (IPr, Me), 8 (SIPr, Me), and 9 (SIPr, Et) with N-chelating benzylidene ligands in yields of 50-75 %. Compared to their respective, conventional, O-Grubbs-Hoveyda complexes, the new complexes are characterized by fast catalyst activation, which translates into fast and efficient ring-closing metathesis (RCM) reactivity. Catalyst loadings of 15-150 ppm (0.0015-0.015 mol %) are sufficient for the conversion of a wide range of diolefinic substrates into the respective RCM products after 15 min at 50 °C in toluene; compounds 8 and 9 are the most catalytically active complexes. The use of complex 8 in RCM reactions enables the formation of N-protected 2,5-dihydropyrroles with turnover numbers (TONs) of up to 58 000 and turnover frequencies (TOFs) of up to 232 000 h−1; the use of the N-protected 1,2,3,6-tetrahydropyridines proceeds with TONs of up to 37 000 and TOFs of up to 147 000 h−1; and the use of the N-protected 2,3,6,7-tetrahydroazepines proceeds with TONs of up to 19 000 and TOFs of up to 76 000 h−1, with yields for these reactions ranging from 83-92 %. [ABSTRACT FROM AUTHOR]

Abstract: The reaction of amino hexahydro-s-indacene with glyoxal, reduction of the diimine to the diamine and cyclization with HC(OEt)3 yields the new 1,3-bis(1,2,3,5,6,7-hexahydro-s-indacen-4-yl)-4,5-dihydro-1H-imidazol-3-ium chloride 3· HCl with conformationally restricted alkyl groups ortho to the heterocyclic substituent. Reaction of 3· HCl with Ag2O gave the respective silver NHC complex (yield 78%), which was used to synthesize the respective (3)IrCl(cod) (yield 86%), whose reaction with CO gave (3)IrCl(CO)2 6 (yield 98%). The Grubbs II type complex [(3)RuCl2(PCy3)(3-phenyl-indenylid-1-ene)] was synthesized (yield 68%) and converted into [(3)RuCl2(py)(3-phenyl-indenylid-1-ene)] (yield 78%) in pyridine solvent. With this complex the respective Grubbs–Hoveyda species (yield 68%) and two bisNHC complexes [(3)(NHCewg)RuCl2(3-phenyl-indenylid-1-ene)] (yield 87%, 89%) were obtained. The stereoelectronic properties of the new NHC ligand were determined employing IR spectroscopy, cyclic voltammetry and buried-volume analysis based on the crystal structure of complex 6. The activity of the ruthenium complexes in RCM reactions of sterically hindered substrates was tested. [Copyright &y& Elsevier]

Abstract: The utility of [(NHC)(PPh3)RuCl2(CHPh)] for the facile and efficient synthesis of ten complexes of the type [(NHC)(NHCewg)RuCl2(CHR)] with saturated and unsaturated NHC ligands in 85–94% isolated yield via a simple one step synthesis utilizing [AgI(NHCewg)] as NHCewg transfer reagents was demonstrated. [Copyright &y& Elsevier]