Exemplary metal carbene compounds include the compounds of the formula (V): ##STR4## wherein M is tungsten and molybdenum, R5 is a C1-10 alkoxy group or a C6-10 aryl group, and R6 is a C1-10 alkyl group, a C3-10 cycloalkyl group, a C6-10 aryl group or a hydrogen atom; the compounds obtained by reacting tungsten hexachloride or molybdenum pentachloride with monosubstituted acetylene represented by