Chelated alkene-carbene complexes of type 4 are valuable model systems for studying the pivotal steps of important transition-metal-mediated olefin and acetylene reactions like metathesis, cyclopropanation, or annulation. Their reactivity and stability chiefly depend on the ring size (the “tether“ length). Chelated allyl-carbene complexes 5 are less well investigated, although offering a more flexible reactivity pattern, especially towards carbon and heteroatom nucleophiles, which may attack at different sites depending on the particular set of substituents, the central metal fragment, and the nucleophilc. Reactions with enolates, cuprates, acetylides, or phosphanes at distinct sites of the metallacyclic perimeter of 5 provide an easy access to unsaturated organic products like 1,2- or 1,3-dienes, δ-lactones, and highly functionalized cyclopentenones via short-cut rearrangement or cascade pathways. Applications to the synthesis of natural products like pheromones and terpenes are given, and factors governing reactivity and selectivity are discussed.