| Summary: | Pyridazine-3-aldoxime (pdzoH) has two N atoms that are suitable for chelation to metal atoms, and additional complementary OH (hydrogen bond donor) and N (acceptor) groups. Thus, coordination in trans-planar M(pdzoH)2 complexes is expected to be reinforced by hydrogen bonding.
Three new complexes with the designed trans-planar M(pdzoH)2 structure were prepared: trans-[CoIII(pdzoH)2Cl2]PF6, trans-[NiII(pdzoH)2(H2O)2](NO3)2, and trans-[CuII(pdzoH)2(NO3)2]. These complexes were shown by X-ray analysis to have OHN hydrogen bond distances of 1.83 (2), 2.20 (2), and 1.94 (2) Å respectively. Reaction of pdzoH with K2PdCl4 yields a cis-square planar complex with one intact and one deprotonated oxime ligand, cis-[PdII(pdzoH)(pdzo)]Cl. This Pd complex features an OHO hydrogen bond (OO 2.438 (2) Å).
Substitution reactions of the Co and Ni pdzoH complexes using pyridine were successfully carried out. These reactions yielded cis-[CoIII(pdzo)2(py)2]Cl, and mono- and bis(pyridine) complexes [NiII(pdzoH)(pdzo)(H2O)(py)]NO3 and [NiII(pdzoH)(pdzo)(py)2]NO3. The behavior of the prepared metal complexes in solution was also studied.
Reaction of pdzoH with Pt(II) produces the metal complex cis-[PtII(pdzoH)(pdzo)]Cl. This complex was prepared using an improved preparatory procedure that we developed. X-ray analysis of this cationic complex reveals stacking of the metal centers suggesting metallophilic bonding between the adjacent platinum complexes. Analogous complexes based on pyridine-2-aldoxime (paoH) and pyridine-2-ketoxime (pkoH) were also prepared: cis-[PtII(paoH)(pao)]Cl and cis-[PtII(pkoH)(pkzo)]Cl. All three complexes were found to display thermochromism, solvatochromism and anion sensing capabilities. Additionally, cis-trans isomerism of the prepared platinum complexes was studied.
The synthesis of a β-ketoenamine and its coordination chemistry with Ni(II), was studied via NMR, MS and elemental analysis.
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