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We discover MnVI-nanoparticles (NPs) bearing functional groups, high oxidation state, strong electron affinity, unique redox and paramagnetic nature, which opens up a new avenue to catalysis, magnetism and material application. However, its synthesis is challenging and remains unexplored because of associated serious difficulties. A simple benign synthetic strategy is devised to fabricate the high-valent NPs using mild reducing agent bromide, which transformed MnVII to valuable MnVI-species. The EELS-imaging of individual elements, ESI-MS, XPS and other techniques established its composition as Br(Me3SiO)MnVIO2. It revealed significantly improved magnetic moment (SQUID) with isotropic hyperfine splitting of six line spectrum (EPR). The high-oxidation state and incorporated-ligands of the metals present on the active surface of the NPs led to development of a general catalytic process for oxidative heterodifunctionalisation to C-C triple bond towards formation of a new O-C/N-C/S-C and C-C coupling cum cyclisation to biologically important flavones and their aza- and marcapto-analogues, and valuable enaloxy synthons.

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We discover an important property of a small molecule ArCH(OMe)2 which transforms catalytically inactive PtIIBr2 procatalyst in situ to an powerful catalyst PtIV-species for diverse annulation reaction. The powerful catalytic system enables selective activation of C2-H/N-H and C2-H/C4-H of acetoacetanilide and C = O/C≡C of substituted butyne-1,2-dione for C-C/C-N, C-C/C-C and C-O/C-O bond-forming inter- and intramolecular annulation towards direct syntheses of functionalised 2-pyridones, cyclohexenones and 3(2H)-furanones respectively. In contrast to the common ligand, herein highly labile C-OMe bond of ArCH(OMe)2 is expected to react with PtBr2 towards generation of the high-valent active catalyst. Unlike catalyst promoter or initiator, the reaction does not occur with PtBr2 in the absence of ArCH(OMe)2. In situ generation of PtIV-species and -OMe fragment of ArCH(OMe)2 were confirmed from the UV-vis characteristic peaks about 260 nm and trapping of -OMe group respectively. These observations provide new prospects and perspectives in catalysis for innovative catalyst design.

An unprecedented nanofabrication of functionalized Pt-NPs under mild conditions was accomplished through oxidative insertion of PtBr 2 into the O−C bond of ArCH(OMe) 2 . TEM and SEM imaging, EELS, XPS, and ESI−MS analyses found the NPs possessing the molecular formula Br 2 (MeO)Pt IV CH(OMe)Ph and lowdimensional spherical morphology. Ketone and amide functionality-bearing electrophilic cyclopropanes underwent ring-opening cyclization. Size-dependent catalytic activity of the NPs was investigated using stabilizers and newly introduced PhCH(OMe) 2 during the synthesis of 2-pyrrolines. The organometallic-NPs were effective for cyclopropane ring-expansion using propargyl amine to 1-pyrrolines with depropargylation. Interestingly, the diverse catalytic activity of the Pt-NPs was effective for sp 3 C−H activated dual cyclization for the direct synthesis of fused-pyrrolo[3,2c]pyridones. The possible reaction pathway was investigated by 3D-mid-IR-ATR, control experiments, and ESI−MS analyses. The NPs were superior in terms of simple preparation, low catalyst loading, ease of recovery, recycling, diverse catalytic activity, and outstanding ability for the general synthesis of pyrroline analogues.