In a general formula (1), each of R1 and R2 represents any one of hydrogen, an alkyl group, a halogen group, —CF3, an alkoxy group, and an aryl group. M represents an element that belongs to Group 9 or Group 10. Here, an alkyl group having 1 to 4 carbon atoms is preferable in the alkyl group. A fluoro group is particularly preferable in the halogen group. An alkoxy group having 1 to 4 carbon atoms is preferable in the alkoxy group. A phenyl group is particularly preferable in the aryl group. Iridium is particularly preferable among the elements that belong to Group 9, and platinum is particularly preferable among the elements that belong to Group 10. The general formula (1) is inserted.