Structures and Stability of Ir_n(CO)_m

摘要

The low energy isomers of the Ir_n(CO)_m complexes (n = 1, 2, 3, 4, and 6) were investigated using electronic structure methods at the density functional theory and coupled cluster (CCSD(T) theory levels. The local SVWN5 exchange-correlation functional yielded geometry parameters in good agreement with the available experiment for Ir_n(CO)_m, with calculated bond lengths within 0.01 à . Ir₄(CO)₁₂ is predicted to be the most favored complex for reactions of Ir_n(CO)_m with CO at low temperature, and Ir₆(CO)₁₆ is predicted to be formed above room temperature. Smaller Ir_n(CO)_m clusters will nucleate to form Ir₄(CO)₁₂ spontaneously. Most of the DFT functionals, especially pure GGA functionals, could not predict consistent reaction energies as compared to CCSD(T). The MP2 and ωB97X-D reaction energies provide upper (more negative) and lower (less negative) estimates of the CCSD(T) values. The average value of the reaction energies at the MP2 and ωB97X-D levels qualitatively match the CCSD(T) energies and the average was used to predict the reaction exothermicity for the Ir_n(CO)_m nucleation reactions where CCSD(T) calculations are not feasible.View full textDownload full textKeywordstransition metal carbonyl clusters, electronic structure calculations, coupled cluster theory, density functional theory, cluster nucleation energiesRelated var addthis_config = { ui_cobrand: "Taylor & Francis Online", services_compact: "citeulike,netvibes,twitter,technorati,delicious,linkedin,facebook,stumbleupon,digg,google,more", pubid: "ra-4dff56cd6bb1830b" }; Add to shortlist Link Permalink http://dx.doi.org/10.1080/00268976.2012.703885