Keywords: Zinc / Lithium / Calcium / Magnesium / N ligands 5-(2-Furanyl)-3-(2-pyridyl)pyrazole (1) and 3-(2-pyridyl)-5-(2-thienyl)pyrazole (2) oligomerize through hydrogen bridges in the solid state to yield tetramers and dimers, respectively. The pyrazole units are very acidic and, therefore, deprotonation of 2 with the organometallic reagents LiN(SiMe 3 ) 2 , PhLi, ZnMe 2 , and ZnEt 2 allows the synthesis of (tetrahydrofuran)lithium 3-(2-pyridyl)-5-(2-thienyl)pyrazolate (3a), bis[methylzinc 3-(2-pyridyl)-5-(2-thienyl)pyrazolate] (4a), and bis[ethylzinc 3-(2-pyridyl)-5-(2-thienyl)pyrazolate] (4b). Recrystallization of 3a in the presence of 1,4-dioxane yields catena- [(1,4-dioxane)lithium 3-(2-pyridyl)-5-(2-thienyl)pyrazolate] (3b). Magnesiation of 2 yields different products depending on the organometallic magnesium rea-

Metalation of 3-phenyl-5-(2-pyridyl)pyrazole (HPz, 1) with alkyllithium and -zinc compounds in tetrahydrofuran (thf) yields dinuclear products [(thf)Li(Pz)] 2 (2) and [MeZn(Pz)] 2 (3), respectively. Magnesiation of 1 with diethylmagnesium in tetrahydrofuran in the presence of 1,4-dioxane leads to cocrystallization of mononuclear [(thf) 2 Mg(Pz) 2 ] (4a) and [(diox) 2 Mg(Pz) 2 ] (4b). Metalation of 1 with KH followed by a metathesis reaction with CaI 2 in tetrahydrofuran leads to the formation of dinuclear [{(thf) 2 Ca}(µ-Pz) 3 Ca(Pz)] (5) with the calcium atoms in different coordination environments. The ligand precursor 1 crystallizes as a dimer with N-H· · ·N bridges between the pyrazole fragments. The pyrazolate anions of the metal complexes 2 to 5 exhibit similar structural parameters regardless of a bridging or terminal coordination mode and the electronegativity of the coordinated metal.

Zincation of 3,5‐bis(pyridine‐2‐yl)pyrazole with Zn[E(SiMe3)2]2 in tetrahydrofuran yields dimeric 3,5‐bis(pyridine‐2‐yl)pyrazolato zinc bis(trimethylsilyl)amide (E = N, 1) and bis(trimethylsilyl)methanide (E = CH, 2). These complexes crystallize in the space groups $\rm P2_1/n$, respectively. The zinc atoms are in distorted tetrahedral environments. In the solid state the 3,5‐bis(pyridine‐2‐yl)pyrazolato anions act as bridging tridentate bases with one pyridyl group not participating in the coordination behavior. In solution, exchange processes, which are fast on the NMR time scale, lead to a single set of resonances for the pyridyl substituents.

Methyl­ation of [1-hy­droxy-3-(pyridin-2-yl)indolizin-2-yl](pyridin-2-yl)methanone was performed via metalation with potassium tert-butano­late in toluene and a subsequent metathesis reaction with methyl iodide yielded the yellow title compound, C20H15N3O2. The substituents at the indolizine unit are twisted [the indolizine ring system makes dihedral angles of 34.67 (7) and 77.49 (5)°, respectively, with the pyridyl and pyridinoyl rings] with single bonds between the central unit and the attached pyridine ring [1.459 (3) Å] and the pyridinoyl group [1.483 (3) Å]. There are no classical hydrogen bonds in the crystal structure.

In a Henry-type reaction nitromethane reacts with N-(2-pyridylmethylidene)-methylamine (1) yielding 1-methylamino-1-(2-pyridyl)-2-nitromethane (2) in nearly quantitative yield. This orange compound decomposes slowly in an inert gas atmosphere and fast in contact with air. Therefore 2 has to be stored at −78 • C as a methanol solution. Reduction of 2 with hydrogen in the presence of a Pd/C catalyst leads to the formation of 1,4-dinitro-2,3-di(2-pyridyl)butane (3) in the rather poor yield of 12 %. The major product is the meso-isomer, meso-3, whereas only traces of (R, R)-and (S, S)-isomers of 3 are formed. A conversion of the nitro groups into amino functionalities succeeds with hydrazine hydrate in the presence of a Pd/C catalyst yielding meso-1,4-diamino-2,3-di(2-pyridyl)butane (4). Recrystallization from an aqueous solution gives 4·2H 2 O. The zinc(II) chloride complex 5 with the metal atoms in distorted tetrahedral environments can be isolated after addition of two equivalents of ZnCl 2 to 4. The molecular structures of trimeric 1, meso-3, (R, R)/(S, S)-3, meso-4, and 5 have been determined and are discussed.