Contrasting coordination behavior of Group 12 perchlorate salts with an acyclic N₃O₂donor ligand by X-ray crystallography and¹H NMR

Abstract

An unbranched N3O2 ligand 2,6-bis[((2-pyridinylmethyl)oxy)methyl]pyridine (L1) was used to prepare new mononuclear heteroleptic Group 12 perchlorate complexes characterized by IR, (1)H NMR and X-ray crystallography. Racemic complexes with pentadentate L1 and one to four oxygens from either water or perchlorate bound to a metal ion were structurally characterized. Octahedral [Zn(L1)(OH2)](ClO4)2 (1) and pentagonal bipyramidal [Cd(L1)(OH2)(OClO3)]ClO4 (2) structures were found with lighter congeners. The polymorphic forms of [Hg(L1)(ClO4)2] characterized (3 in P1[combining macron] and 4 in P21/c) had a mix of monodentate, anisobidentate and bidentate perchlorates, providing the first examples of a tricapped trigonal prismatic Hg(ii) coordination geometry, as well as additional examples of a rare square antiprismatic Hg(ii) coordination geometry. Solution state (1)H NMR characterization of the Group 12 complexes in CD3CN indicated intramolecular reorganization remained rapid under conditions where intermolecular M-L1 exchange was slow on the chemical shift time scale for Zn(ii) and on the J(M(1)H) time scale for Cd(ii) and Hg(ii). Solution studies with more than one equivalent of ligand also suggested that a complex with a 1 : 2 ratio of M : L1 contributed significantly to solution equilibria with Hg(ii) but not the other metal ions. The behavior of related linear pentadentate ligands with Group 12 perchlorate salts is discussed.

Metal Substitution and Solvomorphism in Alkylthiolate-Bridged Zn3 and HgZn2 Metal Clusters

“…Because the H a protons of related multidentate pyridyl ligands have typically demonstrated much greater sensitivity to subtle differences in the environment when bound to group 12 metal ions, coincidental stereoisomer chemical shifts for the remaining protons are reasonable (Figure 17c). 30,43−45 Significantly, at −40 °C, the two chemical shift environments for H a were better resolved, and a second chemical shift environment was partially resolved for H h with roughly one-third the intensity of the main H h resonance (Figure S7). At an elevated temperature, the resonances for H a and all aliphatic protons collapsed to broad singlets, consistent with a thermally-induced bond cleavage process permitting interconversion of the stereoisomers.…”

Synthesis, Solid State, Solution and ESI‐MS Studies of Zinc(II) Cluster Complexes with a Branched Mixed Donor Thiolate Ligand

“…Significantly, while ligands favoring formation of mononuclear complexes commonly produce group 12 metal ion complexes with comparable composition under similar conditions, the small clusters isolated from bridging thiolate ligands can vary considerably in composition , . Efforts to prepare a Zn(II) complex of LH with trimethylamine as base consistently led to the isolation of the unusual spirobicylic complex [Zn((Zn L ) 2 (µ‐OH)) 2 ](ClO 4 ) 4 · CH 3 CN · 7H 2 O ( 1 ) rather than a carbonate complex.…”