title: Coordination chemistry in the solid state: synthesis and interconversion of pyrazolium salts, pyrazole complexes, and pyrazolate MOFs.
abstract: Solid pyrazole reacts with HCl gas to form pyrazolium chloride [H2pz]Cl, which reacts in the solid state, under grinding, with metal chlorides MCl2 (M = Co, Zn, Cu) to form the pyrazolium tetrachlorometallate salts [H2pz]2[MCl4] (M = Co 1, Zn 3, Cu 5). Salt 5 cannot be made in solution, and upon standing at room temperature spontaneously emits HCl to give the coordination compound [CuCl2(Hpz)2] (6). Compounds 1 and 3 do not exhibit this behaviour, but can be ground together with bases such as KOH or K2CO3 to effect the elimination of HCl and afford their respective [MCl2(Hpz)2] compounds (M = Co 2, Zn 4). 2, 4 and 6 can also be synthesised in the solid-state by direct reaction of the appropriate metal chloride with pyrazole, or by reaction of a basic metal salt such as the carbonate or hydroxide with pyrazolium chloride. 4 and 6 {and their nickel analogue [NiCl2(Hpz)2]} can be ground with a further two equivalents of base to make the known polymeric metal pyrazolates [M(pz)2]n (M = Ni 7, Cu 8, Zn 9); the same reaction appears to work for the cobalt analogue 2, but the presumed product [Co(pz)2]n10 then decomposes by oxidation. The imidazolate complexes [M(im)2] (M = Ni, 11; Cu, 12; Zn, 13; Co, 14) were similarly prepared by grinding the appropriate [M(Him)2Cl2] precursor with KOH.
authors.affiliation: School of Chemistry, University of Bristol, Bristol, BS8 1TS, UK.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Adams
authors.forename: Mukhtar A
authors.initials: MA
authors.lastname: Kurawa
authors.forename: A Guy
authors.initials: AG
authors.lastname: Orpen
mesh_terms: D056831:Coordination Complexes / Q000138:chemical synthesis* / Q000737:chemistry; D011720:Pyrazoles / Q000138:chemical synthesis / Q000737:chemistry*; D012492:Salts / Q000138:chemical synthesis / Q000737:chemistry
chemical_list: D056831:Coordination Complexes; D011720:Pyrazoles; D012492:Salts