Bonding in cationic MCH2+ (M=K-La, Hf-Rn): a theoretical study on periodic trends

DFT and CCSD(T) calculations have been performed to investigate the bonding situation of 54 cationic methylene complexes, MCH(2)(+) (M=K-La, Hf-Rn). A comparison of the computed results with experimentally and CBS-QB3-derived data demonstrates the reliability of B3LYP/def2-QZVP with regard to the bond dissociation energies. Further, the bonding character of the MCH(2)(+) complexes is revealed by geometrical and molecular-orbital (MO) analysis. The comparison of the periodic trends within the s-, p-, and d-block MCH(2)(+) carbenes shows a pattern different for main-group versus transition-metal complexes. By combining this work with the recently reported trends for the f-block lanthanide carbenes MCH(2)(+), a systematic and comprehensive overview can be obtained.