Peculiarities of the reaction of (SPY-5-34)-dichloro-(κ2(C,O-2-formylbenzylidene)(1,3-bis(2,4,6-trimethylphenyl)-4,5-dihydroimidazol-2-ylidene) ruthenium with potassium hydridotris(pyrazolyl)borate

The reaction of (SPY-5-34)-dichloro-(kappa(2)(C, O)-2-formylbenzylidene) (H(2)IMes) ruthenium (H2IMeS=1,3-bis(2,4,6-trimethylphenyl)-4, 5-dihydroimidazol-2-ylidene) with potassium hydridotris(pyrazolyl)borate (KTp) in dichloromethane yielded an unusual ruthenium complex chloro(kappa(3)(N,N,N)-chlorotris(pyrazolyl)borate)(kappa(2)(C,C)-1-(2,4,6-trimethylphenyl)-3-(4,6-dimethylphenyl-2-methylidene)-4,5-dihydroimidazol-2-ylidene)ruthenium (2). In 2, a chlorotris(pyrazolyl)borate ligand, which had been created during this reaction, binds in kappa(3)(N,N,N)-mode to the central ruthenium atom. Additionally, a double C-H activation of a methyl group of the H(2)IMes resulted in the formation of a chelating N-heterocyclic biscarbene ligand and liberation of the former 2-formylbenzylidene as 2-methylbenzaldehyde. Formally, a double hydrogen transfer from a methyl group of the H(2)IMes to the initial carbene carbon occurred. 2 was characterized by NMR spectroscopy, elemental analysis and single crystal X-ray structure determination. The reaction of KTp with (SPY-5-34)-dichloro(kappa(2)(C, O)-2-ethoxycarbonylbenzylidene)(H(2)IMes)ruthenium, on the other hand, gave the expected product chloro(K 3 (N,N, N)-hydridotris(pyrazolyl)borate)(H(2)IMes)(2-etiloxycarbonylbenzylidene) ruthenium (6). Compound 6 was characterized by NMR spectroscopy, elemental analysis and single crystal X-ray structure determination. Investigations of the relative activities of these complexes in model ring opening metathesis polymerizations showed a pronounced thermal latency. Polymerizations proceeded at temperatures above 100 degrees C in case of 6 and 130 degrees C in case of 2. (c) 2006 Elsevier B.V. All rights reserved.