A cationic pi-allylpalladium complex, [(eta(3)-C3H5)Pd (cod)](+)[PF6](-), catalyzes hydrosilylation of 1,6-heptadiyne derivatives to form 1-methylene-2-(silylmethylene) cyclopentanes, HSiMenCl3-n (n = 0-2) being equally applicable to this cyclization-hydrosilylation. Certain 1,6-enynes react faster than 1,6-diynes under same reaction conditions, and 9-oxa-1-dodecene-6,11-diyne undergoes competitive cyclization-hydrosilylation at either diyne or enyne moiety, indicative of an unexpectedly high-reactive ene counterpart.