Structure and Reactivity of C2 Species on Polymetallic Systems

A variety of polymetallic C2 (C2 and C2H) complexes are prepared by structure expansion of parent metal acetylide complexes, Fp*–C≡C–H (1) and Fp*–C≡C–Fp* (2) [Fp* = (η5–C5Me5)Fe(CO)2], and their structure and reactivity have been investigated as models for surface-bound C2 species formed during catalytic CO hydrogenation. The results summarized here involve (1) intramolecular 1,2-H shift of the C2H complexes relevant to the 1-alkyne-to-vinylidene rearrangement within a metal coordination sphere, (2) electronic influence of metal centers on the structure of dinuclear bridging alkynyl complexes, (3) conversion of the C2 moiety into various C2 functional groups, and (4) synthesis of higher nuclearity dicarbide (C2) cluster compounds with novel coordination structure by sequential addition reactions of metal fragments and direct coupling of a preformed low-nuclearity cluster structure.