We investigated 10 organometallic reactions from the WCCR10 All DLPNO-CCSD(T 0 ) and pair-selected multi-level DLPNO-CCSD(T 0 ) calculations were performed with the above mentioned development version of SERENITY. In the first step, the canonical Hartree-Fock orbitals were calculated. The resulting orbitals of the reactant structures are then localized with the IBO approach. All subsequent structures are then aligned to previous structures before being localized with the IBO approach. The frozen-core approximation is applied except for proton transfer reactions from the BH9 set where the influence of core orbitals is investigated. The DLPNO-CCSD(T 0 ) calculations were performed for LOOSEPNO, NORMALPNO, and TIGHTPNO DLPNO thresholds, whereas the pair-selected multi-level DLPNO-CCSD(T 0 ) calculations were only performed for the target accuracies of NORMALPNO and TIGHTPNO using LOOSEPNO SC-MP2 to approximate pair energies for the multi-level prescreening. For the latter, several pair selection thresholds and their combinations were tested. All thresholds are given in E h in the following. For the WCCR10 set, the thresholds τ ∆ CutPNO , and τ ∆ CutPairs , and τ ∆ CutTriples described in Sec. 2.3 were tested separately for the target accuracy of NOR-MALPNO. In his case, e.g., for τ ∆ CutPNO = 1 • 10 -3 , all orbital pairs which are not fulfilling Eq. ( )