( ( Certain transition-metal ) ( ( stabilized ( carbenes ( ( ( ( function ( as ( ( initiators ( and ( chain ( growth species ) ) ) ) ( in ( ( methathesis polymerization ) ( of ( cyclic olefins ) ) ) ) ) ) ) ( in ( ( aqueous or ) ( water-alcohol solution ) ) ) ) , ) ( one ( of ( ( the ( few cases ) ) ( ( in which ) ( ( an ( organometallic species ) ) ( can ( be ( used ( in ( protic solvents ) ) ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (JJ Certain) (NN transition-metal)) (VP (VBD stabilized) (SBAR (S (NP (NNS carbenes)) (VP (VBP function) (PP (IN as) (NP (NP (NNS initiators) (CC and) (NN chain) (NN growth) (NNS species)) (PP (IN in) (NP (NP (JJ methathesis) (NN polymerization)) (PP (IN of) (NP (JJ cyclic) (NNS olefins))))))) (PP (IN in) (NP (NP (NNS aqueous)) (CC or) (NP (JJ water-alcohol) (NN solution)))) (, ,) (NP (NP (CD one)) (PP (IN of) (NP (NP (DT the) (JJ few) (NNS cases)) (SBAR (WHPP (IN in) (WHNP (WDT which))) (S (NP (DT an) (JJ organometallic) (NN species)) (VP (MD can) (VP (VB be) (VP (VBN used) (PP (IN in) (NP (JJ protic) (NNS solvents))))))))))))))) (. .)))
Certain transition-metal stabilized carbenes function as initiators and chain growth species in methathesis polymerization of cyclic olefins in aqueous  or water-alcohol solution, one of the few cases in which an organometallic species can be used in protic solvents.
(ROOT (S (NP (JJ Aqueous) (NN solution)) (VP (VBZ is) (VP (VBN used) (S (VP (TO to) (VP (VB describe) (NP (NP (DT a) (NN solution)) (SBAR (WHPP (IN in) (WHNP (WDT which))) (S (NP (NN water)) (VP (VBZ is) (NP (DT the) (JJ solvent))))))))))) (. .)))