The synthesis, and spectroscopic and magnetic characterisation of four isomorphous cluster compounds of general formula [{MX( L)( EtOH)},] [L = 3,5-dimethyl-1 -oxymethylpyrazolate(l -); X = CI or Br; M = Co" or Ni"] is described. The compounds are formed upon reaction of 1 -(hydroxymethyl)-3,5-dimethylpyrazole (HL) with the metal(ii) halides in ethanol in the presence of one equivalent of KOH. The deprotonated ligand co-ordinates as a bidentate ligand through its pyrazole N2 nitrogen and the oxy-part. The oxygen atom bridges between three metal ions, thereby forming a M,O, cubane-type cluster. In the case of M = Ni the metal ions are ferromagnetically coupled, whereas in the case of M = Co antiferromagnetic coupling occurs. The presence of the cubane-type structure was confirmed by the crystal structure determination of [{NiCI( L) (EtOH)};].The complex crystallizes in space group P2Jn with a =12.936(6), b = 18.1 52(5), c = 20.79(1) A, = I 06.23", and Z = 4. Standard least-squares refinement gave R = 0.039 (R' = 0.047). The Ni atom has a Ni0,NCI chromophore in a distorted octahedral geometry. Important averaged distances are: Ni-N = 2.06, Ni-CI = 2.35, Ni-O( EtOH) = 2.08, Ni-0 = 2.08 and, Ni Ni = 3.1 8 A. Intramolecular hydrogen bonds between CI (bound to one Ni) and EtOH (bound to another Ni) with average 0 CI contacts of 3.01 A stabilize the cluster.The co-ordination chemistry of pyrazoles and other nitrogencontaining heterocyclic compounds has received much attention in the last decade.'-4 Only recently, new chelating-type ligands based on pyrazole have been r e p~r t e d ,~~' using a new synthetic method., A route has now been opened to new interesting coordination compounds. A starting material in the synthesis of 3,5-dimethylpyrazole chelates is 1 -( hydroxymethyl)-3,5-dimethylpyrazole (HL). In addition to its properties as a starting compound, HL has some features which make its co-ordination chemistry worth studying, since it contains both a nitrogen and an oxygen atom in the proper orientation to chelate. The similarity with aminoalcohols suggests that after deprotonation of the oxygen, which results in the formation of the anion L ( = 3,5-dimethyl-N-oxymethylpyrazolate), metal clusters may be formed on co-ordination.' or imidazoles l 2 are known, as well as cubane-type clusters with a M 4 0 4 core ( M = Co, Ni, or Cu).' '-" Cluster compounds with chelating pyrazole ligands have not yet been studied. This paper describes the first results obtained with this ligand. Using nickel and cobalt halides as the initial choice, cubane-type clusters are formed, as evidenced by spectroscopic and magnetic measurements and a single-crystal X-ray structure determination of the compound [{ NiCI(L)(EtOH)},] (1).
Cluster compounds with transition metals and pyrazolesExperimental Stcrrting Mutericrls.-Commercially available solvents and metal salts were used. The ligand HL was synthesized by the t Supplemenrary dutu uvuiluhlu (No. SUP 56158, 7 pp.): H-atom coordinates, thermal parameters, remaining bond distances and angle...