title: Synthesis and activity of ruthenium alkylidene complexes coordinated with phosphine and N-heterocyclic carbene ligands.
abstract: This paper reports the synthesis and characterization of a variety of ruthenium complexes coordinated with phosphine and N-heterocyclic carbene (NHC) ligands. These complexes include several alkylidene derivatives of the general formula (NHC)(PR(3))(Cl)(2)Ru=CHR', which are highly active olefin metathesis catalysts. Although these catalysts can be prepared adequately by the reaction of bis(phosphine) ruthenium alkylidene precursors with free NHCs, we have developed an alternative route that employs NHC-alcohol or -chloroform adducts as "protected" forms of the NHC ligands. This route is advantageous because NHC adducts are easier to handle than their free carbene counterparts. We also demonstrate that sterically bulky bis(NHC) complexes can be made by reaction of the pyridine-coordinated precursor (NHC)(py)(2)(Cl)(2)Ru=CHPh with free NHCs or NHC adducts. Two crystal structures are presented, one of the mixed bis(NHC) derivative (H(2)IMes)(IMes)(Cl)(2)Ru=CHPh, and the other of (PCy(3))(Cl)(CO)Ru[eta(2)-(CH(2)-C(6)H(2)Me(2))(N(2)C(3)H(4))(C(6)H(2)Me(3))], the product of ortho methyl C-H bond activation. Other side reactions encountered during the synthesis of new ruthenium alkylidene complexes include the formation of hydrido-carbonyl-chloride derivatives in the presence of primary alcohols and the deprotonation of ruthenium vinylcarbene ligands by KOBu(t). We also evaluate the olefin metathesis activity of NHC-coordinated complexes in representative RCM and ROMP reactions.
authors.affiliation: Arnold and Mabel Beckman Laboratory of Chemical Synthesis, Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA.
authors.forename: Tina M
authors.initials: TM
authors.lastname: Trnka
authors.forename: John P
authors.initials: JP
authors.lastname: Morgan
authors.forename: Melanie S
authors.initials: MS
authors.lastname: Sanford
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Wilhelm
authors.forename: Matthias
authors.initials: M
authors.lastname: Scholl
authors.forename: Tae-Lim
authors.initials: TL
authors.lastname: Choi
authors.forename: Sheng
authors.initials: S
authors.lastname: Ding
authors.forename: Michael W
authors.initials: MW
authors.lastname: Day
authors.forename: Robert H
authors.initials: RH
authors.lastname: Grubbs
mesh_terms: D000475:Alkenes / Q000138:chemical synthesis / Q000737:chemistry*; D018360:Crystallography, X-Ray; D006571:Heterocyclic Compounds / Q000737:chemistry*; D006838:Hydrocarbons; D007093:Imidazoles / Q000737:chemistry; D008024:Ligands; D008697:Methane / Q000031:analogs & derivatives* / Q000737:chemistry; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D010720:Phosphines / Q000737:chemistry*; D012428:Ruthenium / Q000737:chemistry*; D014230:Triazoles / Q000737:chemistry
chemical_list: D000475:Alkenes; D006571:Heterocyclic Compounds; D006838:Hydrocarbons; D007093:Imidazoles; D008024:Ligands; D009942:Organometallic Compounds; D010720:Phosphines; D014230:Triazoles; C030011:carbene; D012428:Ruthenium; D008697:Methane