Platinum-cobalt bimetallic nanoparticles in hollow carbon nanospheres for hydrogenolysis of 5-hydroxymethylfurfural.

The synthesis of 2,5-dimethylfuran (DMF) from 5-hydroxymethylfurfural (HMF) is a highly attractive route to a renewable fuel. However, achieving high yields in this reaction is a substantial challenge. Here it is described how PtCo bimetallic nanoparticles with diameters of 3.6 ± 0.7 nm can solve this problem. Over PtCo catalysts the conversion of HMF was 100% within 10 min and the yield to DMF reached 98% after 2 h, which substantially exceeds the best results reported in the literature. Moreover, the synthetic method can be generalized to other bimetallic nanoparticles encapsulated in hollow carbon spheres.

Triazolopyridines as ligands: structural diversity in iron(II), cobalt(II), nickel(II) and copper(II) complexes of 3-(2-pyridyl)-[1,2,4]triazolo[4,3-a]- pyridine (L¹°) and spin crossover in [Fe(II)(L¹°)2(NCS)2].

The coordination chemistry of the ligand 3-(2-pyridyl)-[1,2,4]triazolo[4,3-a]pyridine (L¹°) has been investigated and iron(II), cobalt(II), nickel(II) and copper(II) complexes featuring diverse structural motifs have been prepared. In the 2 : 1-type complexes [Co(II)(L¹°)2(MeOH)2](ClO4)2 (20), [Ni(II)(L¹°)2(MeOH)2](ClO4)2 (21), [Cu(II)(L¹°)2(MeOH)2](ClO4)2 (22), [Co(II)(L¹°)2(H2O)2](ClO4)2 (23) and [Cu(II)(L¹°)2(ClO4)2] (24) the metal centres are N4O2 octahedrally coordinated with two N²,N(pyr) bidentate ligands L¹° in the equatorial positions. In the N6 octahedral 4 : 1-type complex [Co(II)(L¹°)4](ClO4)2·H2O (25) both axially coordinating N¹ unidentate and equatorially bound N²,N(pyr) bidentate ligands L¹° are observed. The N6 octahedral 3 : 1-type complex [Fe(II)(L¹°)3](OTf)2·1.5MeCN·0.13H2O·0.87MeO(t)Bu (27) features three N²,N(pyr) bidentate ligands L¹° in the mer configuration. The two closely related N6 octahedral complexes [Fe(II)(L¹°)2(NCS)2] (29) and [Fe(II)(L¹°)2(dca)2] (30) have fundamentally different structures. While complex 29 features two equatorially bound N²,N(pyr) bidentate ligands L¹° and axial NCS⁻ co-ligands, complex 30 is a one-dimensional doubly µ1,5-dicyanamido-bridged polymer with N¹ unidentate ligands L¹° in the axial positions. Temperature-dependent magnetic susceptibility measurements of the iron(II) complexes 28 and 29 have shown the 3 : 1-type complex [Fe(II)(L¹°)3](ClO4)2·H2O (28) to be in the low-spin state over the range 300-2 K and the 2 : 1-type complex 29 to be a spin crossover compound with T(1/2) = 269 K whereas the dicyanamido-bridged complex 30 remains in the high-spin state even down to 113 K, according to X-ray diffraction data. A single end-to-end bridging NCS⁻ co-ligand is found in the N4S square-pyramidal complex [Cu(II)(L¹°)(NCS)2] (31) which shows Curie-Weiss behaviour over the range 300-2 K. A brief review of the coordination chemistry of triazolopyridines is given.