Spin-orbit coupling and outer-core correlation effects in Ir- and Pt-catalyzed C-H activation

The transition metal-dependent spin-orbit coupling (SOC) and outer-core (5s5p) correlation effects in Ir- and Pt-catalyzed C-H activation processes are studied here using high level ab initio computations. The catalysts involve complexes with oxidation states: Ir(I), Ir(III), Pt(0), and Pt(II). It is demonstrated that for these heavy 5d transition metal-containing systems, the SOC effect and outer-core correlation effect on C-H activation are up to the order of ∼1 kcal/mol, and should be included if chemical accuracy is aimed. The interesting trends in our studied systems are: (1) the SOC effect consistently increases the C-H activation barriers and is apparently larger in higher oxidation states (Pt(II) and Ir(III)) than in low-oxidation states (Pt(0) and Ir(I)); and (2) the magnitude of outer-core (5s5p) correlation effects is larger in less coordinate-saturated system. The effect of basis set on the outer-core correlation correction is significant; larger basis sets tend to increase the C-H activation barriers.