The bonding nature of metallocene acetylene complexes Cp 2 M(η 2 -H 3 SiC 2 SiH 3 ) 1M and Cp 2 M(η 2 -HC 2 H) 1M 0 (M = Ti, Zr, Hf) was studied by density functional theory method. It is found that this acetylene complex has indeed a metallacyclopropene moiety with two in-plane M-C σ-bonds and one out-of-plane π-bond interacting with the metal center, resulting in the formation of a delocalized three-center and two-electron (3c-2e) system. Along with its delocalized out-of-plane bonding, this complex has been characterized as aromatic on the basis of the computed stabilizing energy and negative nucleus-independent chemical shifts (NICS). The aromatic stabilization increases from Ti to Zr and Hf, and this is because of the increased charge separation between the Cp 2 M fragment and the H 3 SiC 2 SiH 3 (also HC 2 H) unit. The decrease of the M-C bond length from Zr to Hf is attributed to the increased s character of both M and C hybridization of the M-C σ-bonds.

Cp*2Ti(OTf) (2) was prepared by oxidation of the known(alkyne)titanocene complex Cp*2Ti(η2‐Me3SiC2SiMe3) with Fe(OTf)3. This reaction is highly selective; formation of Cp*2Ti(OTf)2 by using an excess of the oxidizing agent was not observed. Complex 2 was treated with water to give Cp*2Ti(OH)(OTf) (5) and hydrogen gas. This reaction was monitored by GC and volumetric analysis. Complexes 2 and 5 were characterized by X‐ray crystallography and investigated by DFT analysis.

The complex [(PNHP)Fe(H)(CO)(HBH)] (PNHP = HN(CHCHPi-Pr)) serves as a catalyst precursor for the selective dehydrocoupling of methylamine borane at room temperature, tentatively via an off-metal polymerisation pathway.

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In organometallic chemistry numerous complexes are known to cleave activated and nonactivated C–F bonds of organic compounds. These reactions are either stoichiometric or catalytic and offer different possibilities for a wide range of synthetic and catalytic applications. This review attempts to summarize a selection of most important developments made since 1997 for C–F bond cleavages by lanthanide and group 4 transition-metal complexes.