Ring-opening metathesis polymerization (ROMP) is a widespread tool for synthesizing well-defined and highly functionalized polymers.The catalyst is an important factor which affects the ROMP of monomers.It is well-known that the ruthenium-based Grubbs’catalysts have good solubility in non-polar solvents such as CH2Cl2

benzene and toluene

but their solubility in polar solvents such as alcohol

acetone and ionic liquid was very poor

which limited their applications for ROMP in polar solvents.In this paper

an imidazolium saltsupported ruthenium catalyst was synthesized

and its catalytic performance for ROMP of polar or nonpolar cycloolefinic monomers in ionic liquid ［BMIm］BF4 was investigated.A novel pyridyl ligand 2

3-dimethyl-1-2-(4-pyridyloxy)ethyl］ imidazolium hexafluorophosphate (4) was initially designed and synthesized

and its single crystal was obtained.The crystal is monoclinic with the parameters as follow: P21/c

a=1.2469(5) nm

b = 1.6470(7) nm

c=0.7943(3) nm

β=106.691(5)°

V=1.5625(11) nm3.The pyridyl ligand was then used to coordinate with the second generation Grubbs’catalyst to get the first example of the ruthenium catalyst supported by imidazolium saltcontained pyridyl ligand (IL-cat 5).The characterization of the synthesized ligand and the catalyst was carried out by NMR

ICP and elemental analysis.In 1H-NMR spectroscopy

the signal of the benzylidene proton shifts from δH=19.2 in the second generation Grubbs’catalyst to δH=16.3 in the novel catalyst IL-cat 5.In 31P-NMR spectroscopy

the signal of PF-6 in pyridyl ligand was observed at δP=-143.3

while δP=36.6 for PCy3 group was disappeared

which demonstrated the group of PCy3 was replaced by the pyridyl ligand completely.The content of IL-cat 5 in the mixture of prepared catalyst contained excess 4 was 14 wt% tested by ICP method.As expected

the novel catalyst IL-cat 5 is soluable in polar solvents including methanol acetone

and ionic liquid

thus ROMP in pure ionic liquid could be carried out conveniently.The ROMP of three different cycloolefins

i.e.nonpolar cyclooctene (monomer 1)

medium polar 5-hydroxy-1-cyclooctene (monomer 2)

and especially the strong polar monomer 5-norbornene-2-carbonitrile (monomer 3)

was explored in ionic liquid ［BMIm］BF4.The polymerizations of the three monomers catalyzed by catalyst IL-cat 5 processed successfully

and the conversion reached up to 96.0%

73.0%

and 51.7% for monomer 1

monomer 2

and monomer 3 under conventional conditions

respectively.It was worth noting that the value of 51.7% for cyano group (—CN) contained monomer 3 was reasonably high

which is surprisingly much larger than that using the pyridine coordinated second generation Grubbs’catalyst for the same monomer in ［BDMIm］PF6 as reported in published literature.The results strongly confirmed that ROMP could be undertaken readily for all functionalized monomers using ruthenium catalyst coordinated with imidazolium saltcontained pyridyl ligand in ［BMIm］BF4

and fortunately Grubbs’catalyst was actually not poisoned in this imidazolium ionic liquid medium without —CH3 group in 2-position of imidazolyl ring.The molecular weights of polymers were measured by GPC

which were nearly in according with the calculated ones.