Coordination compounds of N, N′-olefin functionalized imidazolin-2-ylidenes

Abstract

N-Heterocyclic carbene ligands (NHC) were metalated with Pd(OAc) 2 or [Ni(CH 3CN) 6](BF 4) 2 by in situ deprotonation of imidazolium salts to give the N-olefin functionalized biscarbene complexes [MX 2(NHC) 2] 3– 7 ( 3: M = Pd, X = Br, NHC = 1,3-di(3-butenyl)imidazolin-2-ylidene; 4: M = Pd, X = Br, NHC = 1,3-di(4-pentenyl)imidazolin-2-ylidene; 5: M = Pd, X = I, NHC = 1,3-diallylimidazolin-2-ylidene; 6: M = Ni, X = I, NHC = 1,3-diallylimidazolin-2-ylidene; 7: M = Ni, X = I, NHC = 1-methyl-3-allylimidazolin-2-ylidene). Molecular structure determinations for 4– 7 revealed that square-planar complexes with cis ( 5) or trans ( 4, 6, 7) coordination geometry at the metal center had been obtained. Reaction of nickelocene with imidazolium bromides afforded the η 5-cyclopentadienyl (η 5-Cp) monocarbene nickel complexes [NiBr(η 5-Cp)(NHC)] 8 and 9 ( 8: NHC = 1-methyl-3-allylimidazolin-2-ylidene; 9: NHC = 1,3-diallylimidazolin-2-ylidene). The bromine abstraction in complexes 8 and 9 with silver tetrafluoroborate gave complexes [NiBr(η 5-Cp)(η 3-NHC)] 10 and 11. The X-ray structure analysis of 10 and 11 showed a trigonal-pyramidal coordination geometry at the nickel(II) center and coordination of one N-allyl substituent.