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Alkali Metal Directed Assembly of Heterometallic Vv/M (M = Na, K, Cs) Coordination Polymers: Structures, Topological Analysis, and Oxidation Catalytic Properties.

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Title: Alkali Metal Directed Assembly of Heterometallic Vv/M (M = Na, K, Cs) Coordination Polymers: Structures, Topological Analysis, and Oxidation Catalytic Properties.
Authors: Gupta, Samik1, Kirillova, Marina V.1, Guedes da Silva, M. Fátima C.1,2 fatima.guedes@ist.utl.pt, Pombeiro, Armando J. L.1 pombeiro@ist.utl.pt, Kirillov, Alexander M.1 kirillov@ist.utl.pt
Source: Inorganic Chemistry. 8/5/2013, Vol. 52 Issue 15, p8601-8611. 11p.
Subjects: Alkali metal compounds, Molecular self-assembly, Coordination polymers, Chemical structure, Oxidation, Nuclear magnetic resonance spectroscopy, Cyclohexanones
Abstract: The reactions of [VO(acac)2] with bis(salicylaldehyde)-oxaloyldihydrazone (H4L) and an alkali metal carbonate M2CO3 (M = K, Na, Cs), in EtOH/H2O medium upon reflux, resulted in the generation of three new heterometallic VV/M materials, namely the 1D [(VO2)2(µ4-L){Na2(µ-H2O)2(H2O)2}]n (1), 2D [{V(µ-O)2}2(µ4-L){K2(µ-H2O)2(H2O)2}]n (2), and 3D [{V(µ-O)(µ3-O)}2(µ8-L){Cs2(µ-H2O)2(H2O)2}]n (3) coordination polymers. They were isolated as air-stable solids and fully characterized by IR, UV-vis, 1H, and 51V NMR spectroscopy, ESI-MS(±), elemental, thermal, and single-crystal X-ray diffraction analyses, the latter showing that 1-3 are constructed from the resembling [(VO2)2(µ4/8-L)]2- blocks assembled by the differently bound aqua-metal [M2(µ-H2O)2(H2O)2]2+ moieties (M = Na, K, Cs). The main distinctive features of 1-3 arise from the different coordination numbers of Na (5), K (7), and Cs (9) atoms, thus increasing the complexity of the resulting networks from the ladder-like 1D chains in 1 to double 2D layers in 2, and layer-pillared 3D framework in 3. The topological analysis of 2 disclosed a uninodal 4-connected underlying net with a rare kgm [Shubnikov plane net (3.6.3.6)/kagome pattern] topology, while 3 features a trinodal 4,7,8-connected underlying net with an unprecedented topology. Compounds 1-3 also show solubility in water (S25 °C ≈ 4-7 mg mL-1) and were applied as efficient precatalysts for the homogeneous oxidation of cyclohexane by aqueous H2O2, under mild conditions (50 °C) in MeCN/H2O medium and in the presence of an acid promoter. Total yields (based on substrate) of cyclohexanol and cyclohexanone up to 36% and turnover numbers (TONs) up to 5700 were achieved. [ABSTRACT FROM AUTHOR]
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Abstract:The reactions of [VO(acac)2] with bis(salicylaldehyde)-oxaloyldihydrazone (H4L) and an alkali metal carbonate M2CO3 (M = K, Na, Cs), in EtOH/H2O medium upon reflux, resulted in the generation of three new heterometallic VV/M materials, namely the 1D [(VO2)2(µ4-L){Na2(µ-H2O)2(H2O)2}]n (1), 2D [{V(µ-O)2}2(µ4-L){K2(µ-H2O)2(H2O)2}]n (2), and 3D [{V(µ-O)(µ3-O)}2(µ8-L){Cs2(µ-H2O)2(H2O)2}]n (3) coordination polymers. They were isolated as air-stable solids and fully characterized by IR, UV-vis, 1H, and 51V NMR spectroscopy, ESI-MS(±), elemental, thermal, and single-crystal X-ray diffraction analyses, the latter showing that 1-3 are constructed from the resembling [(VO2)2(µ4/8-L)]2- blocks assembled by the differently bound aqua-metal [M2(µ-H2O)2(H2O)2]2+ moieties (M = Na, K, Cs). The main distinctive features of 1-3 arise from the different coordination numbers of Na (5), K (7), and Cs (9) atoms, thus increasing the complexity of the resulting networks from the ladder-like 1D chains in 1 to double 2D layers in 2, and layer-pillared 3D framework in 3. The topological analysis of 2 disclosed a uninodal 4-connected underlying net with a rare kgm [Shubnikov plane net (3.6.3.6)/kagome pattern] topology, while 3 features a trinodal 4,7,8-connected underlying net with an unprecedented topology. Compounds 1-3 also show solubility in water (S25 °C ≈ 4-7 mg mL-1) and were applied as efficient precatalysts for the homogeneous oxidation of cyclohexane by aqueous H2O2, under mild conditions (50 °C) in MeCN/H2O medium and in the presence of an acid promoter. Total yields (based on substrate) of cyclohexanol and cyclohexanone up to 36% and turnover numbers (TONs) up to 5700 were achieved. [ABSTRACT FROM AUTHOR]
ISSN:00201669
DOI:10.1021/ic400743h