TY - JOUR
T1 - The elusive [Ni(H2O)2(15-crown-5)]2+ cation and related co-crystals of nickel(II) hydrates and 15-crown-5
AU - Siegler, Maxime A.
AU - Parkin, Sean
AU - Selegue, John P.
AU - Brock, Carolyn Pratt
PY - 2008
Y1 - 2008
N2 - Initial attempts to make [Ni(H2O)2(15-crown-5)](NO3) 2, i.e. to insert the Ni2+ ion into the 15-crown-5 macrocycle, gave the mono- (two polymorphs) and dihydrate of a co-crystal of [Ni(H2O)6](NO3)2 and 15-crown-5 (1,4,7,10,13-pentaoxacyclopentadecane = 15C5). Synthetic routes designed to restrict the water available to the Ni2+ cation gave three additional compounds, [Ni(H2O)6](NO3)2-trans-[Ni(H 2O)4(MeOH)2](NO3) 2·2(15C5), cis-[Ni(H2O)4(NO 3)2]-trans-[Ni(H2O)4(NO 3)2]·2(15C5) and [Ni(H2O) 2(MeCN)(NO3)2]·15C5·MeCN. All five compounds contain Ni2+ ions with two trans aqua ligands. In all six structures these aqua ligands make hydrogen bonds to the 15C5 molecules to form stacks in which the Ni complexes and 15C5 molecules alternate. The structures are surprisingly complicated: all are co-crystals, some are also solvates, and most have Z′ > 1. The target compound was finally prepared by heating pale green crystals of [Ni(H2O) 6](NO3)2·15C5·2H2O to over 350 K and then cooling the resulting mixture of yellow crystals and solution to room temperature. Formation of the target compound seems to be favored at higher temperatures by a positive △rxn S o and an increased rate of ligand exchange.
AB - Initial attempts to make [Ni(H2O)2(15-crown-5)](NO3) 2, i.e. to insert the Ni2+ ion into the 15-crown-5 macrocycle, gave the mono- (two polymorphs) and dihydrate of a co-crystal of [Ni(H2O)6](NO3)2 and 15-crown-5 (1,4,7,10,13-pentaoxacyclopentadecane = 15C5). Synthetic routes designed to restrict the water available to the Ni2+ cation gave three additional compounds, [Ni(H2O)6](NO3)2-trans-[Ni(H 2O)4(MeOH)2](NO3) 2·2(15C5), cis-[Ni(H2O)4(NO 3)2]-trans-[Ni(H2O)4(NO 3)2]·2(15C5) and [Ni(H2O) 2(MeCN)(NO3)2]·15C5·MeCN. All five compounds contain Ni2+ ions with two trans aqua ligands. In all six structures these aqua ligands make hydrogen bonds to the 15C5 molecules to form stacks in which the Ni complexes and 15C5 molecules alternate. The structures are surprisingly complicated: all are co-crystals, some are also solvates, and most have Z′ > 1. The target compound was finally prepared by heating pale green crystals of [Ni(H2O) 6](NO3)2·15C5·2H2O to over 350 K and then cooling the resulting mixture of yellow crystals and solution to room temperature. Formation of the target compound seems to be favored at higher temperatures by a positive △rxn S o and an increased rate of ligand exchange.
KW - Crown ligand
KW - Hydrogen bonding
KW - Ligand exchange
KW - Macrocycles
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U2 - 10.1107/S0108768108034058
DO - 10.1107/S0108768108034058
M3 - Article
C2 - 19029702
AN - SCOPUS:56849105638
SN - 0108-7681
VL - 64
SP - 725
EP - 737
JO - Acta Crystallographica Section B: Structural Science
JF - Acta Crystallographica Section B: Structural Science
IS - 6
ER -