In this article the recent progress in research of an important class of ⅥB metal-metal triply bonded compounds, R~2M~2(CO)~4 (R=Cp or substituted cyclopentadienyl, indenyl etc.), has been reviewed. The emphasis of the article is placed on chemical reactivities of the functional group M≡M present in this class of compounds. Topics discussed in this article includes synthesis and structures of R~2M~2(CO)~4, the reactions of its metal-metal triple bond with various reagents (such as nucleophiles, carbon-carbon multiple bond compounds, oxygen molecule and metal carbonyls etc.), and some of their applications.

Key words: GROUP VI B ELEMENT