Reaction between [RuCl2(PPh3)(3)] and piperidine (pip) gives the novel [RuCl2(PPh3)(2)(pip)] complex, which quantitatively polymerizes norbornene (NBE) via ring opening metathesis polymerization for less than 1 min at RT, in the presence of 5 muL of ethydiazoacetate. An M-w/M-n value of 1.05 is obtained if amounts of norbomene are added in several batches up to the [NBE]/[Ru] = 5.000. Norbornadiene is polymerized with 48% yield for 5 min at RT. The precursor complex gives only 63% of polynorbornene and 6% of polynorbornadiene for 5 min at 50degreesC. P-31{H-1} NMR analyses indicate that the new complex does not undergo dimerization in solution as it occurs in the case of the precursor complex. It is proposed that the presence of the piperidine is appropriated in enhancing the rate of reaction and controlling the ruthenium metathesis catalysis via a highly active five-coordinated mononuclear Ru(II) complex. (C) 2004 Elsevier B.V. All rights reserved.