Palladium carbene complexes, CX₂=PdX₂, are prepared along with the insertion products, CX₃–PdX, in reactions of laser-ablated Pd atoms with tetrahalomethanes and identified from matrix infrared spectra and density functional frequency calculations. The carbon–metal bonds of the CCl₂=PdCl₂ and CClF=PdCl₂ complexes are essentially double bonds with effective bond orders of 1.9, near those for the Pt and Ni analogues, as calculated by CASPT2 methods. On the other hand, only insertion complexes are generated from mono-, di-, and trihalomethane precursors. While the carbenes have staggered allene-type structures, many insertion complexes containing C–Cl bonds reveal distinct bridged structures, which indicate effective coordination of Cl to the metal center.

Nickel carbene complexes, CX₂ = NiX₂, are prepared along with the insertion products, CX₃ – NiX, in reactions of laser-ablated Ni atoms with tetrahalomethanes. These reaction products are identified from matrix infrared spectra and density functional frequency calculations. In agreement with the previously studied Pt cases, the carbon – nickel bonds of the Ni carbene complexes are essentially double bonds with CASPT2-computed effective bond orders of 1.8 – 1.9. On the other hand, only insertion complexes are generated from dihalomethane and trihalomethane precursors. The nickel carbenes have staggered structures, and several insertion complexes containing C – Cl bonds reveal distinct bridged structures similar to those observed in the corresponding Fe products, which indicate effective coordination of Cl to the metal center. The unique F-bridged CH₂F – NiCl structure is also observed.