The first low-spin nickel complex with two coordinated water molecules, [Ni(o-MeO-dppp)(H2O)(2)](PF6)(2) - Synthesis and structural characterization

A series of nickel complexes of the didentate ligand 1,3-bis[di(o-methoxyph enyl)phosphanyl]propane (o-MeO-dppp) has been synthesized and characterized . The first low-spin nickel complex containing two coordinated water molecu les, [Ni(o-MeO-dppp) (H2O)(2)](PF6)(2) (1), and compounds of the general fo rmula [Ni(o-MeO-dppp)X-2] [X = Cl, Br, I, or trifluoroacetate (TFA)] are re ported. Complex 1 has been characterized by X-ray crystallography. The nick el ion resides in a square-planar coordination environment with two phospho rus donors and two water molecules in a cis configuration (Ni-P distance 2. 19 Angstrom; Ni-O distance 1.97 Angstrom). The structure from those of the complexes [Ni(o-MeO-dppp)X-2]. The halide complexes [Ni(o-MeO-dppp)Cl-2] (2 ) and [Ni(o-MeO-dppp)Br-2] (3) are seemingly mutually isostructural. In the se complexes, the nickel ion also resides in a square-planar geometry, but with a significant tetrahedral distortion. The two different types of mono( o-MeO-dppp)nickel(II) complexes, i.e. [Ni(o-MeO-dppp)(H2O)(2)](PF6)(2) (1) and [Ni(o-MeO-dppp)X-2] [X = Cl (2), Br (3), I, or trifluoroacetate (TFA)] have been analyzed by electronic absorption and NMR spectroscopy. The diffe rences in the crystal structures of 1 and 2 are helpful in rationalizing th e fluxional behavior of these complexes, as has been studied by NMR spectro scopy.