Vanadium(V/IV) Oxido Complexes: Potential as Bases in Frustrated Lewis Pairs

Frustrated Lewis Pairs (FLP) have found exciting access in catalysis and small molecule activation. Here, we describe the potential of two vanadium(V) oxido complexes with monoanionic bidentate N,O donors, [VOCl(LCF3)2] (1 a), [VOCl(LH)2] (1 b) as bases in FLPs. Upon reaction of 1 a with the Lewis acid B(C6F5)3 the FLP [VOCl(LCF3)2]/B(C6F5)3 (1 a/B(C6F5)3) was observed. Addition of Ph3SiH led to the reduction of VV to VIV under formation of the adduct [V{OB(C6F5)3}(LCF3)2] (2 a) while FLP reactivity was not observed. Dissolving 2 a in CH3CN leads to the VIV oxido complex, [VO(LCF3)2] (3 a). In contrast, when 1 b was reacted with B(C6F5)3, a VIV oxido complex [VO(LH)2] (3 b) was obtained. Upon addition of B(C6F5)3 to 3 b no reaction leading to the expected adduct such as 2 a could be observed. Only few crystals deriving from a disproportion reaction could be identified as an adduct dimer [V{OB(C6F5)3}LH(μ‐O)]2. While FLP reactivity could not be found yet with the described systems, the redox labile nature and versatility of the metal complexes are demonstrated. The discovery of two rare VV/IV oxido‐borane adducts demonstrates the potential of first row transition metal based Frustrated Lewis Pairs (FLP). The electronic properties of the ligands as well as the redox versatility of the metal significantly influence the reactivity with the Lewis acid B(C6F5)3.