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.
Chan
Zhi-Kai
ZK
Department of Chemistry, Chung-Yuan Christian University, Chung-Li, Taiwan R.O.C.
Wu
Ying-Yann
YY
Chen
Jhy-Der
JD
Yeh
Chen-Yu
CY
Wang
Chih-Chieh
CC
Tsai
Yi-Fang
YF
Wang
Ju-Chun
JC
D000578:Amidines / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism*; D000838:Anions / Q000737:chemistry*; D003300:Copper / Q000737:chemistry*; D018360:Crystallography, X-Ray; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D011743:Pyrimidines / Q000737:chemistry*
D000578:Amidines; D000838:Anions; D008024:Ligands; D011743:Pyrimidines; C077922:formamidine; D003300:Copper; C030986:pyrimidine