Which transition-metal groups commonly form Fischer carbene complexes?

Fischer carbene complexes are commonly formed by transition metals in groups 6–8 of the periodic table.1

These complexes are characterized by a metal-carbon double bond where the carbene carbon is electron-poor, a property attributed to the significant electronegativity of these middle to late d-block metals. This electronic structure contrasts with Schrock carbenes, which typically involve metals from the early part of the d-block and feature an electron-rich carbene carbon.1