The reactions of [MCl(cod)]2 (M = Rh, Ir) with different NHC·HX (X = Cl, I), K2CO3 in technical grade acetone under air provide simple access to various [(NHC)MX(cod)] complexes; a facile one-pot synthesis of [(NHC)MCl(CO)2] (M = Rh, Ir) is also reported.

A strategy towards photochromic SI-ROMP homopolymers based on spiropyran and spirooxazine in mesopores is presented and photochromism is systematically investigated using UV-VIS spectroscopy and NMR.

Four 1-(4-R-phenoxy)-2-ethenylbenzenes (R = NMe 2 , H, Cl, NO 2 ) 4a, 4b, 4c and 4d were reacted with the ruthenium complexes [RuCl 2 A C H T U N G T R E N N U N G (NHC)(3phenylindenylidene)(py)] in the presence of a protic resin to result in the formation of the respective Hoveyda-type complexes 5a-d {NHC = SIMes [1,3bis(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 RuA C H T U N G T R E N N U N G (II/III) redox potentials of complexes 6 were determined (6a-d: DE = 0.89-1.08 V). In the crystal structure of 5b two independent molecules were observed in the unit cell, displaying Ru À 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 2,5dihydropyrroles with up to TON 64,000 and TOF 256,000 h À1 , of the N-protected 1,2,3,6-tetrahydropyridines with up to TON 18,200 and TOF 73,000 h À1 and of the N-protected 2,3,6,7-tetrahydroazepines with up to TON 8,100 and TOF 32,000 h À1 with yields ranging between 77 and 96%.

Abstract1,3,5‐Tricycloalkylbenzene (cycloalkyl = C5H9, C6H11) was converted into the respective anilines (by means of nitration and reduction) and then into the corresponding diimines (with glyoxal), the cyclization of which with (HCHO)n/ZnCl2 provided the respective 1,3‐bis(2,4,6‐tricyclopentylphenyl)imidazolium salt in modest yields. An analogous reaction sequence that employed acenaphthene‐1,2‐dione instead of glyoxal yielded the two azolium salts in good yields, which were converted into the respective N‐heterocyclic carbene (NHC) complexes [(NHC)AgCl], [(NHC)AuCl], [(NHC)RhCl(cod)] (cod = cyclooctadiene), and [(NHC)RhCl(CO)2].

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.