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- Title
Tetranuclear Nickel and Cobalt Complexes with an Incomplete Double-Cubane Structure - Homo- and Heterometallic Complexes and Their 1D Coordination Polymers.
- Authors
Nakajima, Takayuki; Seto, Keiko; Scheurer, Andreas; Kure, Bunsho; Kajiwara, Takashi; Tanase, Tomoaki; Mikuriya, Masahiro; Sakiyama, Hiroshi
- Abstract
The reactions of M(OAc)2 ·4H2O (M = Ni, Co) with three unsymmetrical amine-diol ligands RN(CH2CH2OH)(CH2CH2CH2OH) (H2 L n: n = 1, R = benzyl; n = 2, R = 4-methylbenzyl; n = 3, R = 2-naphthalenylmethyl) in the presence of NEt3 or pyridine in MeOH or BnOH gave the tetranuclear complexes [M4(H L n)2(OAc)6(MeOH)2] {M = Ni, n = 1 ( 1a), 2 ( 1b), 3 ( 1c); M = Co, n = 1 ( 4a), 2 ( 4b), 3 ( 4c)} and [M4(H L n)2(OAc)6(BnOH)2] {M = Ni, n = 1 ( 2a), 2 ( 2b), 3 ( 2c); M = Co, n = 1 ( 5a), 2 ( 5b), 3 ( 5c)}. When p-xylene-α,α′-diol was used instead of monoalcohols, the tetranuclear {M4O6} units were linked by p-xylene-α,α′-diol to form the 1D coordination polymers [M4(H L n)2(OAc)6( p-HOCH2C6H4CH2OH)] m {M = Ni, n = 1 ( 3a), 2 ( 3b); M = Co, n = 1 ( 6a), 2 ( 6b)}. The structures of 1- 6 were determined by X-ray crystallography and consist of centrosymmetrical tetranuclear {M4O6} face-shared defective double-cubane cores supported by two monodeprotonated (H L n)- ligands. The mixed-metal tetranuclear complexes [Ni2.2Co1.8(H L1)2(OAc)6(MeOH)2] ( 7) and [Mn1.7Ni2.3(H L1)2(OAc)5(OMe)2] ( 8) were also synthesized by using equimolar amounts of Ni2+ and M2+ (M = Co, Mn) ions. X-ray crystallographic and fluorescent analyses revealed that 7 is isomorphous with 1a and 4a and contains nonstoichiometric amounts of disordered Ni2+ and Co2+ ions in an average ratio of 2.2:1.8 with different occupancies for the two crystallographically independent metal centers. In contrast, 8 consists of a C2-symmetrical face-shared defective double-cubane {MII3MnIIIO6} core with a Ni/Mn ratio of 2.3:1.7; the amounts of Ni2+ and Mn2+ ions vary depending on the metal sites, and one of the C2 axial positions is exclusively occupied by Mn3+ ions. Detailed magnetostructural analyses on the nickel ( 1a, 2a, 3a) and cobalt ( 4a) complexes with appropriate spin-Hamiltonian models showed that both ferro- and antiferromagnetic spin exchange interactions were involved within the tetranuclear units, and their extent depends on the combination of the metal ions and the ligand systems in a delicate fashion.
- Subjects
NICKEL compounds; COBALT compounds; CUBANES; COORDINATION polymers; LIGANDS (Chemistry)
- Publication
European Journal of Inorganic Chemistry, 2014, Vol 2014, Issue 29, p5021
- ISSN
1434-1948
- Publication type
Article
- DOI
10.1002/ejic.201402536