Synthesis and Coordination Chemistry of a New N4-Polydentate Class of Pyridyl-Functionalized Scorpionate Ligands: Complexes of Fe", Zn", Ni", V", Pd" and Use for Heterobimetallic Systems.

The new potentially N4-multidentate pyridyl-functionalized scorpionates 4-((tris-2,2,2-(pyrazol-1 -yl)ethoxy)methyl)-pyridine (TpmPy, (1)) and 4- (TpmPyPh (2)) have been synthesized and their coordination behavior toward FeII, NiII, ZnII, CuII, PdII, and VIII centers has been studied. Reaction of (1) with Fe(BF4)2-6H2O yields [Fe(TpmPy)2](BF4)2 (3), that, in the solid state, shows the sandwich structure with trihapto igand coordination via the pyrazolyl arms, and is completely low spin (LS) until 400 K. Reactions of 2 equiv of (1) or (2) with ZnII or NiII chlorides give the corresponding metal complexes with general formula [MCl2(TpmPy*)2] (M = Zn, Ni; TpmPy* = TpmPy, TpmPyPh) (4-7) where the ligand is able to coordinate through either the pyrazolyl rings (in case of [Ni(Tpmpy)2]Cl2 (5)) or the pyridyl-side (for [ZnCl2(TpmPy)2] (4), [ZnCl2(TpmPyPh)2] (6) and [NiCl2(TpmPyPh)2] (7)). The reaction of (1) with VCl3 gives [VOCl2(TpmPy)] (8) that shows the N3-pyrazolyl coordination-mode. Moreover, (1) and (2) react with cis-[PdCl2(CH3CN)2] to give the disubstituted complexes [PdCl2(TpmPy)2] (9) and (PdCl2(TpmPyPh)2] (10), respectively, bearing the scorpionate coordinated via the pyridyl group. Compounds (9) and (10) react with Fe(BF4)2 to give the heterobimetallic Pd/Fe systems [PdCl2(μ-TpmPy)2-Fe](BF4)2 (11) and [PdCl2(μ-TpmPyPh)2Fe2(H2O)6)(BF4)4 (13), respectively. Compound (11) can also be formed from reaction of (3) with cis-[PdCl2(CH3CN)2], while reaction of (3) with Cu(NO3)2·2.5H2O generates (Fe(μ-TpmPy)2-Cu(NO3)2](BF4)2 (12), confirming the multidentate ability of the new chelating ligands. The X-ray diffraction analyses of compounds (1), (3), (4), (5), and (9) are also reported. [ABSTRACT FROM AUTHOR]