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

Abstract

Synthesis of LORM–X-type 1∶1 mononuclear adducts containing Kläui’s tripodal ligands {LOR = 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(µ-LOMe)2CoCl2] 1, which results from co-ordination of the two PO oxygen atoms in the initially formed 1∶2 adduct, Co(LOMe)2, to a second molecule of CoCl2. In contrast, similar reaction of nitrate salts M(NO3)2·6H2O followed by crystallization from acetone produced 1∶1 mononuclear complexes, [MLOMe(κ2-NO3)(Me2CO)] M = Ni 3 or Co 4], with octahedral co-ordination geometry. Before crystallization from acetone the dinuclear adduct [Ni(µ-LOR)2(µ-NO3)2Ni(NO3)] 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 κ2-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(κ2-NO3)(L)] (L = PPh3 5a, 2,5-dimethylpyridine 5b or 3,5-diisopropylpyrazole 5c) and [NiLOMe(κ2-NO3)(py)3]NO3 6. Complexes 1, 2b, 2c, 3, 4, 5a–5c, 6, and [NiLOMe(κ2-NO3)(MeOH)] were characterized by X-ray crystallography.