A Convenient, Safe, and Atom‐Economical Route to a Large Portfolio of Grubbs‐Type Catalysts for Olefin Metathesis via Four‐Coordinate Ruthenium Alkylidynes

p-Tolyl(trimethylsilyl)diazomethane is a readily accessible and easy-to-handle net carbyne donor reagent. It reacts with [(p-cymene)RuCl₂]₂ in MeCN to give the phosphine-free chloride-bridged dinuclear complex [(MeCN)₂RuCl₂( = C(p-tolyl)(SiMe₃))]₂ (2) carrying a silyl group on each of the carbene ligands. Treatment of 2 with either PCy₃ or an N-heterocyclic carbene (NHC) causes elimination of TMSCl with formation of the corresponding four-coordinate ruthenium alkylidynes. The non-bonding electron lone pair of significant d_z2 character at their Ru center is prone to protonation; in this way, the alkylidyne unit is converted into a carbene ligand under very mild conditions. The sequence of alkylidyne formation/protonation opens a novel entry into all relevant "generations" of Grubbs and Grubbs-Hoveyda type catalysts, which is distinguished by a superior ligand- and atom economy, a good safety profile, and high overall yields. Moreover, the method is inherently flexible and arguably suitable for parallel screening and reaction optimization purposes.