The term agostic is reserved to describe two-electron, three-center bonding interactions between carbon, hydrogen, and a metal. Two-electron three-center bonding is clearly implicated in the complexation of H, e.g., in W(CO)(PCy)H, which is closely related to the agostic complex shown in the figure. Silane binds to metal centers often via agostic-like, three-centered Si┄H−M interactions.  Because these interactions do not include carbon, however, they are not classified as agostic.