Understanding the chemical and reactivity properties of six-coordinate Mo(IV) complexes is key to a better understanding of a wide number of Mo-based enzymatic systems. However, the vast majority of the reported six-coordinate Mo(IV) complexes are supported by neutral, strongly 𝜋-accepting donor ligands such as CO, NO or phosphines, and only a handful of mononuclear six-coordinate Mo(IV) compounds bearing anionic oxygen or sulfur donating ligands have been reported in literature, at the difference of much more common Mo(VI) counterparts. A case in point is the octahedral Mo(IV) bis-acetylacetonate ( Me diket) dichloride complex, [Mo IV ( Me diket)2Cl2] ( Me Mo IV Cl2), early reported but not structurally characterized. It was proposed to display cis coordination of the chloride ligands based on the analysis of IR stretches and suggested to be a coordination polymer type structure owing to its very low solubility. Interestingly, Me Mo IV Cl2 was proposed to act as a pre-catalyst for allylic substitution reactions when combined in-situ with silver salts, such as AgOTf (TfO = trifluoromethylsulfonate) or AgSbF6, (vide infra). Nevertheless, the identity of the catalytically active species as well as the one generated upon addition of the silver salts had never been investigated. This motivated us to further explore the coordination chemistry and reactivity of bis-β-diketonate Mo(IV) complexes. Here, we report the systematic preparation and characterization of a series of Mo(IV) complexes supported by 𝛽-diketonate ligands as well as the investigation of their catalytic activity for allylic substitution reactions. We found that while the parent Mo(IV) complexes were the catalytically most active species, insitu generated higher valent Mo oxo and nitrido complexes could also yield catalytically active species, yet performing at much lower rates. We show that the careful design of catalytic reaction conditions based on this mechanistic analysis enabled efficient and fast catalysis at low catalyst loading. By analogy with the reported synthesis of Me Mo IV Cl2, we explored here the preparation of a series of Mo(IV) dichloride bis-𝛽-diketonate ( R diket, R = Me, t Bu, Ph, CF3) complexes by protonolysis of in-situ generated [MoCl4(CH3CN)2] from [MoCl5] in refluxing acetonitrile (MeCN), with the corresponding 𝛽-diketone ligand. The resulting R Mo IV Cl2 complexes were isolated in pure form in 49%, 47% and 67% yields for R = Me, Ph and t Bu respectively (Scheme 1). Nevertheless, the complexes displayed significant differences in solubility: while for R = Me and Ph, highly insoluble materials were obtained, the use of t Bu groups as terminal substituents on the diketonate ligand enabled significantly improving the solubility of the complex in common solvents such as toluene or tetrahydrofuran (THF), facilitating its purification, isolation and characterization. We did not succeed in isolating the targeted complex for R = CF3 but instead identified products of a disproportionation reaction by single crystal X-ray diffraction (XRD, Fig. ). We hypothesize that the strong electron withdrawing properties of the CF3-substituted diketonate ligand do not allow stabilizing the electron-poor Mo(IV) complex. Exchange of the chloride ligands with -OTf anions was carried out via salt metathesis: addition of two equivalents of solid AgOTf to a solution (R = t Bu) or a suspension (R = Me, Ph) of R Mo IV Cl2 in 1,2-dimethoxyethane resulted in the precipitation of AgCl as a colorless solid and the formation of red-orange solutions. § § Filtration followed by removal of volatiles under reduced pressure afforded the desired bistriflate ( R Mo IV (OTf)2) Scheme 1 Synthesis of Mo(IV) 𝛽-diketonate complexes.