The Influence of β-diiminato Ligands on As4 Activation by Cobalt Complexes

Abstract

In a systematic study of the activation of As4, three [LCo(tol)] (L=β-diiminato) complexes have revealed different steric and electronic influences. 2,6-Diisopropylphenyl (Dipp) and 2,6-dimethylphenyl (dmp) flanking groups were used, one of the ligands with H backbone substituents (β-dialdiminate L0) and two with Me substituents (β-diketiminates L3 and L1). In the reaction with As4, different dinuclear products [(LCo)2As4] (LM=L0 (1), L1 (2), L3 (3)) were isolated, with all showing differently shaped [Co2As4] cores in the solid state: octahedral in 1, prismatic in 2, and asterane-like in 3. Thermal treatment of 3 leads to the abstraction of one arsenic atom to yield [(L3Co)2As3] (4). All products were comprehensively characterized by single-crystal X-ray diffraction, FD-MS, and 1H NMR spectroscopy. A rational explanation for the different reactivity is also proposed and DFT calculations shed light on the nature of the highly flexible [Co2As4] cores.