Synthesis and crystal structures of mononuclear half-sandwich complexes of Ni and Co containing Klaui's tripodal ligand, [M{κ3-(η5-C5H5)Co[P(=O)(OCH3)2]3}(κ2-NO3)(L)] (M = Ni or Co)

Synthesis of LORM-X-type 1 : 1 mononuclear adducts containing Klaui's tripodal ligands {L-OR = CpCo[P(=O)(OR)(2)](3)} was studied. Addition of NaLOMe to an excess amount of CoCl2 did not afford a mononuclear product but the dinuclear complex [Co(mu-L-OMe)(2)CoCl2] 1, which results from co-ordination of the two P=O oxygen atoms in the initially formed 1 : 2 adduct, Co(L-OMe)(2), to a second molecule of CoCl2. In contrast, similar reaction of nitrate salts M(NO3)(2). 6H(2)O followed by crystallization from acetone produced 1 : 1 mononuclear complexes, [MLOMe(kappa(2)-NO3)(Me2CO] M = Ni 3 or Co 4], with octahedral co-ordination geometry Before crystallization from acetone the dinuclear adduct [Ni(mu-L-OR)(2)(mu-NO3)(2)Ni(NO2)] 2 was isolated from a reaction mixture and subsequent treatment with acetone gave the mononuclear product 3. Thus, for synthesis of LORM-X-type complexes, it is essential to use a potentially kappa(2)-co-ordinating ligand (e.g. NO3) in the presence of a donor (e.g. acetone). The labile acetone ligand in 3 is replaced by P- and N-donors to give the substituted products [NiLOMe(kappa(2)-NO3)(L)] (L = PPh3 5a, 2,5-dimethylpyridine 5b or 3,5-diisopropylpyrazole 5c) and [NiLOMe(kappa(2)-NO3)(py)(3)]NO3 6. Complexes 1, 2b, 2c, 3, 4, 5a-5c, 6, and [NiLOMe(kappa(2)-NO3)(MeOH)] were characterized by X-ray crystallography.