Zhi-Kai Chan

Adjusting the frameworks of polymeric silver(I) complexes with 2-aminopyrimidyl ligands by changing the counterions

The complexes [Ag2(L)2(SO4)]∞, (L = 2-aminopyrimidine) 1, [Ag(L)1.5(ClO4)]∞, 2, and [Ag(L)(OAc)·2H2O]∞, 3, were prepared by layering the aqueous solution of the corresponding Ag(I) salt with L in ethanol, while [Ag(L′)(NO3)]∞, 4, and [Ag(L′)(ClO4)·H2O]∞, 5, were prepared by refluxing AgNO3 and AgClO4, respectively, with 2-amino-4,6-dimethylpyrimidine (L′) in H2O. Reaction of Ag2SO4 with L′ in methanol afforded the complex [Ag4(L′)2(SO4)2(H2O)4]∞, 6. In complex 1, the L ligands are coordinated to the Ag(I) metal centers in new tridentate fashions, forming 2-D pleated molecular sheets which are interlinked by the SO42− anions to form a 3-D layer structure. Complex 2 forms a pleated molecular sheet consisting of twenty four-membered metallocycles, involving six Ag ions which are bridged by six L ligands through the pyrimidyl nitrogen atoms. Complex 3 forms linear chains with sinusoidal geometry, which are interlinked through extensive Ag⋯Ag interactions (Ag⋯Ag = 3.102 A) to form 2-D wavy rectangular grids. Complex 4 forms single-strained helical coordination polymers, which are interlinked through a series of Ag⋯O interactions (2.667 and 2.699 A) to form 2-D chair like grids. The silver atoms of 5 are bound to the nitrogen atoms of two symmetry-related L′ ligands in a distinctly non-linear geometry, forming zigzag chains. The structure of 6 consists of clusters of the formula [Ag8(L′)4(SO4)4(H2O)8], which are interlinked through L′ ligands to form 2-D sheets. The μ1-O, μ2-O′- bonding mode of the SO42− anion in complex 6 is unique for Ag(I) complexes. Their thermal properties have been investigated by using differential scanning calorimetry (DSC) and thermogravimetric analyses (TGA)

Roles of I⋯I and Ag⋯I interactions on the self-assembly of Ag(I) complexes containing 2-amino-5-iodopyrimidine; formation of the unique Ag⋯I⋯I⋯Ag interaction

A series of silver(I) complexes [Ag(L)(NO3)]4, (L = 2-amino-5-iodopyrimidine), 1, [Ag(L)(PF6)]∞, 2, and [Ag(L)(ClO4)]∞, 3, have been prepared by the reactions of AgX (X = NO3−, PF6− and ClO4−, respectively) with L. All the complexes have been structurally characterized by X-ray crystallography, confirming that complex 1 forms sixteen–membered metallocycles interlinked by I⋯I and Ag⋯O interactions to create a porous structure. Complexes 2 and 3 form helical chains, with different periods of 22.584 and 11.465 A, respectively. In addition to the Ag⋯O interaction and hydrogen bonds, the unique discrete Ag⋯I⋯I⋯Ag and linear ⋯(Ag⋯I⋯I⋯Ag)n⋯ interactions with short I⋯I and Ag⋯I contacts were found in complexes 2 and 3, respectively, to support their supramolecular structures.

Linear and cyclic tetranuclear copper(I) complexes containing anions of N, N'-bis(pyrimidine-2-yl)formamidine

The reaction of Kpmf (pmf = anion of N,N[prime or minute]-bis(pyrimidyl-2-yl)formamidine, Hpmf) with CuSCN afforded the complexes K[Cu4(pmF)3(SCN)2], 1, and Cu(4)(pmf)4, 2. Reaction of 1 with [(n-Bu)4N]PF6 in THF gave the complex [(n-Bu)4N][Cu4(pmf)3(SCN)2], 3. Their structures were characterized by X-ray crystallography. Complexes 1 and 3 are the first linear tetranuclear complexes containing only Cu(I) atoms, while complex 2 is cyclic. The four Cu(I) atoms of complexes 1 and 3 are helically bridged by three tetradentate pmf- ligands. The [Cu4(pmf)3(SCN)2]- anions of 1 show weak interactions with adjacent [K(THF)5]+ cations through the sulfur atoms, forming infinite chains which are subjected to a series of intermolecular pi-pi interactions. In complex 2, the pmf- ligands are coordinated to the copper atoms in bidentate fashion through the two central amine nitrogen atoms, leaving the pyrimidine nitrogen atoms uncoordinated. Unexpected fluxional behaviors were observed for complexes 1 and 3 in solution. By the DNMR analysis, the free energy of activation (DeltaGc(not equal)) for the exchange is 12.8 kcal mol(-1) at 278 K (T(c)), and the rate constant of exchange (K(c)) is 470 s(-1) for 1. The DeltaGc(not equal) and Kc are 12.6 kcal mol(-1) at 273 K and 433 s(-1), respectively, for 3.

Structural characterization of copper complexes containing N,N′-di(6-methyl-2-pyridyl)formamidine

Abstract The reactions of N,N′-di(6-methyl-2-pyridyl)formamidine (HDMepyF) with copper halide produced complexes of the types CuCl2(HDMepyF) (1), Cu2X4(HDMepyF)2 (X=Cl, 2; X=Br, 3), Cu4I4(HDMepyF)2 (4), and [Cu2(HDMepyF)2](PF6)2 (5). All complexes were characterized by X-ray crystallography. The structure of 1 is tetrahedral with the Cu(II) center chelated by one HDMepyF ligand and coordinated by two chloride ligands. Complexes 2 and 3 are dinuclear complexes, in which the two Cu(II) centers are bridged by two halide atoms. Each Cu(II) metal center are also coordinated by one terminal halide atom and chelated by one HDMepyF ligand, forming a distorted square-pyramidal geometry. Complex 4 is tetranuclear with the four copper atoms forming a parallelogram and each Cu atom being in a three-coordination environment. One iodo atom and one HDMepyF ligand bridge two adjacent copper atoms. In complexes 1–4, the neutral HDMepyF ligands coordinate to the metal centers through one amine nitrogen atom and one adjacent pyridine nitrogen atom. In dinuclear complex 5, the HDMepyF ligands coordinate to the Cu(I) ions in a tridentate fashion, forming a chelating and a bridging bonding modes. The molecules of 5 are chiral due to the ligand constraints and each Cu atom forms a trigonal-planar geometry. All the HDMepyF ligands in complexes 1–5 adopt the s-cis, s-trans conformation.