The Role of Anionic Ligands on Photoreactivity in Mo(VI) Dioxo Complexes of the Form MoO₂X₂(NN)**

The photoreactivity of d0 metal dioxo complexes in activating C-H bonds has been recently studied.[1-3] We have previously reported that MoO2 Cl2 (bpy-t Bu) is an effective platform for light initiated C-H activation with unique product selectivity for the overall functionalization.[1] Herein we expand on these studies and report the synthesis and photoreactivity of several new Mo(VI) dioxo complexes with the general formula MoO2 (X)2 (NN); where X=F- , Cl- , Br- , CH3- , PhO- , t BuO- and NN=2,2'-bipyridine (bpy) or 4,4'-tert-butyl-2,2'bipyridine (bpy-t Bu). Among these compounds, MoO2 Cl2 (bpy-t Bu) and MoO2 Br2 (bpy-t Bu) are able to participate in bimolecular photoreactivity with several substrates containing C-H bonds of various types such as allyls, benzyls, aldehydes (RCHO) and alkanes. MoO2 (CH3 )2 bpy and MoO2 (PhO)2 bpy do not participate in bimolecular photoreactions and instead they undergo photodecompositions. Computational studies indicate that the nature of the HOMO and LUMO is critical in supporting photoreactivity, with access to an LMCT (bpy→Mo) being necessary for tractable hydrocarbon functionalization.