2417-93-8Relevant articles and documents
Directional properties of fluorenylidene moieties in unsymmetrically substituted N-heterocyclic carbenes. Unexpected CH activation of a methylfluorenyl group with palladium. Use in palladium catalysed Suzuki-Miyaura cross coupling of aryl chlorides
Teci, Matthieu,Brenner, Eric,Matt, Dominique,Gourlaouen, Christophe,Toupet, Loic
, p. 12251 - 12262 (2014/08/05)
Benzimidazolium salts having their two nitrogen atoms substituted by different 9-alkylfluorenyl groups (4a-e and 4g, alkyl1/alkyl 2 = Me/Et, Me/Pr, Me/n-Bu, Me/i-Pr, Me/Bn, Me/CH2SMe have been synthesised in high yields in two or three steps from N,N′-bis(9H- fluoren-9-ylidene)benzene-1,2-diamine (1). The imidazolium salts 4a-e were converted readily into the corresponding PEPPSI-type palladium complexes (PEPPSI = pyridine-enhanced precatalyst preparation stabilisation and initiation), while reaction of the methylthioether-substituted salt 4g with PdCl 2/K2CO3/pyridine afforded the palladacycle 5g resulting from metallation of the methyl group attached to the fluorenylidene moiety. NMR and X-ray diffraction studies revealed that the carbene ligands in 5a-5e behave as clamp-like ligands, the resulting metal confinement arising from a combination of the orientational properties of the fluorenylidene moieties that push the alkyl groups towards the metal centre and attractive anagostic interactions involving CH2(fluorenyl) groups. Complexes 5a-e were assessed in Suzuki-Miyaura cross-coupling reactions. Like their symmetrical analogues they displayed high activity in the coupling of phenyl boronic acid with p-tolylchloride but their performance remained slightly inferior to that of the related, symmetrical Et/Et complex 5h.
Method for producing alkyl-bridged ligand systems and transition metal compounds
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, (2008/06/13)
The invention relates to a method for producing highly substituted alkyl-bridged ligand systems on the basis of indene derivatives and transition metal compounds. Said alkyl-bridged ligand systems can be obtained in high yields using this method.
On the Lewis Acidity Of Nickel(0), IX. - Alkyllithium Complexes Of Nickel(0)
Poerschke, Klaus-Richard,Jonas, Klaus,Wilke, Guenther
, p. 1913 - 1920 (2007/10/02)
Tris(ethene)nickel(0) reacts with stoichiometric amounts of alkyllithium compounds LiR (R = C2H5, n-C3H7, n-C4H9) in ether/PMDTA as solvent at low temperature to afford the yellow crystalline complexes (PMDTA)2(LiR)2Ni(C2H4)2 (R = n-C3H7, n-C4H9, 5, 6) and (PMDTA)(LiR)Ni(C2H4)2 (R = C2H5, n-C3H7, n-C4H9, 3a, 7a, 8a).Ionic complexes of the type +-, which are known already for R = C2H5 (3b), are obtained in ether/TMEDA for R = n-C3H7 (7b) and n-C4H9 (8b) as suspensions but cannot be isolated without decomposition. (Et2O)2(C4H8O2)(Li2C4H8)(Ni(C2H4) (4) is obtained from Ni(C2H4)3 and 1,4-dilithiobutane in ether/dioxane. - With the exception of 4 all complexes undergo an alkyl/alkene exchange reaction with ethene in solution (ether, THF, toluene) at 0 deg C.NMR studies of the partially deuterated (PMDTA)(LiC2D5)Ni(C2H4)2 (-3a) show that the H/D distribution becomes statistical at this temperature.In the presence of ethene, 5-8 yield 3a or 3b with liberation of propene or 1-butene.The alkyllithium complexes of nickel(0) can be regarded as model compounds for the starting and product complexes of nickel(0) postulated to explain the "Nickel Effect" reaction of aluminium trialkyls and ethene.