Dioxomolybdenum(VI) complexes of hydrazone phenolate ligands - syntheses and activities in catalytic oxidation reactions

Insight into the synthesis, structure affirmation and catalytic efficiency of divalent and trivalent metal chelates of mandelic acid hydrazone derivative

The current work reports the synthesis of Cr(iii), Mn(ii), Co(ii), Ni(ii) and Cu(ii) chelates of the Schiff base ligand named hydroxy-phenyl-acetic acid (2-hydroxy-naphthalen-1-ylmethylene)-hydrazide with multi-chelation centre toward metal ions. The spectral tools, 1H-NMR, FTIR, mass, UV-vis spectra, and the analytical elemental and thermal analysis, in addition to magnetic moment and conductivity measurements all combined have been applied to conclude the structure and geometry of the synthesized metal complexes. The formed metal chelates have been assured to be formed with the molar compositions of 1 L : 1 M for PANH-Cr, PANH-Mn, PANH-Co, PANH-Ni and 2 L : 1 M for PANH-Cu. All the complexes have been confirmed to be non-electrolytic except the PANH-Mn and PANH-Ni which are 1 : 1 electrolytes. FTIR spectral analysis assured the ligand to act as mono basic bi or tridentate ligand leading to the formation of octahedral complexes with all metals except Cu(ii) complex which assured to has square planar structure. Except PANH-Cr, all the synthesized metal chelates exhibited phenoxazinone synthase like efficacy with varying activity with dramatically high activity for PANH-Mn complex with TOF number of 169.89 h-1.

Single-Site Carbon-Supported Metal-Oxo Complexes in Heterogeneous Catalysis: Structure, Reactivity, and Mechanism

When early transition metal complexes are molecularly grafted onto catalyst supports, well-defined, surface-bound species are created, which are highly active and selective single-site heterogeneous catalysts (SSHCs) for diverse chemical transformations. In this minireview, we analyze and summarize a less conventional type of SSHC in which molybdenum dioxo species are grafted onto unusual carbon-unsaturated scaffolds, such as activated carbon, reduced graphene oxide, and carbon nanohorns. The choice of earth-abundant, low-toxicity, versatile metal constituents, and various carbon supports illustrates "catalyst by design" principles and yields insights into new catalytic systems of both academic and technological interest. Here, we summarize experimental and computational investigations of the bonding, electronic structure, reaction scope, and mechanistic pathways of these unusual catalysts.