One-pot reactions between 2,6-diformyl-4-methylphenol (DFMP) and 2-aminoethanol (AE) in the presence of cobalt(II) salts [Co(ClO4)2, CoCl2, Co(CH3CO2)2, Co(NO3)2] and sodium azide result in the self-assembly of novel one-dimensional single chain mixed-valence cobalt coordination polymers {[Co2(II)Co2(III) (HL)2(OCH3)2(N3)3]ClO(4).5H2O.CH3OH}n (1), {[Co2(II)Co2(III) (HL)2(OCH3)2(N3)3]Cl.H2O}n (2) in which tetra-cobalt cationic units are bridged by symmetrical 1,3-azides, forming single chains; mixed valence neutral tetranuclear clusters [Co2(II)Co2(III) (HL)2(OCH3)2(N3)4]CH3OH.2H2O (3), [Co2(II)Co2(III)(HL)2(OCH3)2(N3)2(CH3CO2)2].2CH3OH.2H2O (4), and the cationic cluster [Co2(II) Co2(III) (HL)2(OCH3)2(CH3OH)2(N3)2](NO3)2 (5). In all these reactions, H3L, the potentially pentadentate (N2O3), trianionic double Schiff base ligand 2,6-bis[(2-hydroxy-ethylimino)-methyl]-4-methylphenol is formed. The reaction between DFMP and AE in the presence of nickel(ii) salts and sodium azide in methanol-water mixture results in the self-assembly of ferromagnetically coupled hexanuclear complexes [Ni6(H2L)2(HL-1)2(H2O)2(N3)6](ClO4)(2).2CH3OH (6), and [Ni6(H2L)2(HL-1)2(CH3OH)2(N3)6](BF4)2 (7), involving double (H3L) and single (H2L-1) Schiff base ligands, and a neutral tetranuclear complex [Ni4(H2L)2(OCH3)2(CH3CO2)2(N3)2] (8) with only double Schiff-base (H3L). In these complexes, the nature of the anion and the reaction conditions seem to play an important role in directing the formation of tetranuclear, hexanuclear or polymeric clusters. All complexes involve divacant double cubane-type cores containing three to four different types of bridging ligands (phenoxy, azido, methoxy/alkoxy, and acetate). Variable temperature magnetic properties of these spin coupled clusters have been investigated and magneto-structural correlations have been established.

Self-assembly of mixed-valence Co(II/III) and Ni(II) clusters: azide-bridged 1D single chain coordination polymers comprised of tetranuclear units, tetranuclear Co(II/III) complexes, ferromagnetically coupled azide-bridged tetranuclear, and hexanuclear Ni(II) complexes: synthesis, structural, and magnetic properties.

The reaction of a methanolic solution containing M(ClO4)2·nH2O (M = Cu, Ni, Zn or Cd) or CoCl2·6H2O with bis(2-(3,5-dimethyl-1H-pyrazol-1-yl)ethyl)amine (bedmpza) in the presence of NaN3 afforded the complexes [Cu(bedmpza)(μ1,1-N3)]2(ClO4)2 (1), [Ni(bedmpza)(N3)(μ1,1-N3)]2·1.5H2O (2), [Co(bedmpza)(N3)2] (3), [Zn(bedmpza)(N3)]ClO4 (4) and [Cd(bedmpza)(N3)(μ1,1-N3)]2·1.5H2O (5). The five complexes were characterized by spectroscopic techniques and their molecular structures were determined by single crystal X-ray crystallography. The two mononuclear complexes 3 and 4 display distorted TBP and tetrahedral geometry, respectively with the azide ions acting as monodentate ligands. Doubly bridged end-on-azido dinuclear complexes were obtained in the remaining compounds. Compounds 2 and 5 are isomorphic with distorted octahedral geometry, whereas distorted square pyramidal geometry was determined in the Cu(II) complex 1. The magnetic properties for complexes 1 and 2 were investigated by measuring the magnetic susceptibilities at variable temperatures (300–2 K). The Ni(II) complex exhibits moderate ferromagnetic coupling, whereas [Cu(bedmpza)(μ1,1-N3)]2(ClO4)2 (1) which contains two crystallographic independent dinuclear subunits in the unit cell, with different Cu–N(N3)–Cu bond angles, reveals different signs in the magnetic coupling. The complex represents the first example in the literature that has simultaneously two moieties with ferro- (J = 15.4 cm−1) and antiferromagnetic (J = −18.9 cm−1) interactions.

Metal ions directing the geometry and nuclearity of azido-metal(II) complexes derived from bis(2-(3,5-dimethyl-1H-pyrazol-1-yl)ethyl)amine

The reaction of a tridentate Schiff base ligand HL (2-(3-dimethylaminopropylimino)-methyl]-phenol) with Ni(II) acetate or perchlorate salts in the presence of azide as coligand has led to two new Ni(II) complexes of formulas Ni3L2(OAc)(2)(mu(1,1)-N-3)(2)(H2O)(2)]center dot 2H(2)O (1) and Ni2L2(mu(1,1)-N-3) (mu(1,3)-N-3)](n)(2). Single crystal X-ray structures show that complex 1 is a linear trinuclear Ni(II) compound containing a mu(2)-phenwddo, an end-on (EO) azido and a syn-syn acetato bridge between the terminal and the central Ni(II) ions. Complex 2 can be viewed as a one-dimensional (1D) chain in which the triply bridged (di-mu(2)-phenoxido and EO azido) dimeric Ni-2 units are linked to each other in a zigzag pattern by a single end-to-end (EE) azido bridge. Variable-temperature magnetic susceptibility studies indicate the presence of moderate ferromagnetic exchange coupling in complex 1 with J value of 16.51(6) cm(-1). The magnetic behavior of 2 can be fitted in an alternating ferro- and antiferromagnetic model J(FM) = +34.2(2.8) cm(-1) and J(AF) = -21.6(1.1) cm(-1)] corresponding to the triple bridged dinuclear core and EE azido bridge respectively. Density functional theory (DFT) calculations were performed to corroborate the magnetic results of 1 and 2. The contributions of the different bridges toward magnetic interactions in both compounds have also been calculated.

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A Rare Phenoxido/Acetato/Azido Bridged Trinuclear and an Unprecedented Phenoxido/Azido Bridged One-Dimensional Polynuclear Nickel(II) Complexes: Synthesis, Crystal Structure, and Magnetic Properties with Theoretical Investigations on the Exchange Mechanism

Structural characterization of five-coordinate copper(II), nickel(II), and cobalt(II) thiocyanato complexes derived from bis(2-(3,5-dimethyl-1-pyrazolyl)ethyl)amine

Synthesis and characterization of five new thiocyanato- and cyanato-metal(II) complexes with 4-azidopyridine as co-ligand

Azido–NiII complexes of dinuclear, [Ni2(trpn)2(μ1,3-N3)2](ClO4)2 (1), and monodimensional structures cis-[Ni(abap)(μ1,3-N3)]n(ClO4)n (2) and cis-[Ni(Me6trien)(μ1,3-N3)]n(ClO4)n·nH2O (3a) as well as the monomer [Ni(Me6trien)(N3)]ClO4 (3b) {trpn = tris(3-aminopropyl)amine; abap = N-(2-aminoethyl)-N,N-bis(3-aminopropyl)amine; Me6trien = 1,1,4,7,10,10-hexamethyltriethylene tetramine} were synthesized and structurally characterized by spectroscopic techniques, X-ray crystallography, and variable-temperature magnetic measurements. In the complexes 1–3a, the ClO4– groups are counterions and the Ni2+ centers are bridged by the azido ligands in an end-to-end bonding fashion. The coordination geometry around the NiII ions is six-coordinate with a distorted octahedral environment achieved by the four N atoms of the tetradentate amines and two terminal N atoms of the azide groups. Complex 1 consists of dinuclear units with doubly bridged azido groups whereas in 2 and 3a, a polymeric 1D chain is formed in which the adjacent azido groups link the NiII centers in a cis arrangement. In complex 2, the structural parameters of the two adjacent azido bridging ligands are different and an alternating 1D system with two different end-to-end azido bridges is produced. Complex 3a is a uniform 1D system where the strong steric hindrance imposed by the methyl groups of the Me6trien ligand [diagonal N(azide)–Ni–N(amine) bond angles] causes pronounced deviation from the ideal octahedral geometry. Complex 3b exhibits a distorted square pyramidal geometry. The complexes 1–3a show antiferromagnetic coupling. In complex 1, the exchange coupling constant was J = –64(1) cm–1, whereas in the polynuclear species 2 and 3a, the calculated values were J1 = –63.7(2) (α = 0.52) and J = –26.8(1) cm–1, respectively. The magnetic parameters have been correlated to the structural data.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

Elodie Ducasse

Papers

Dinuclear and Polynuclear Bridged Azido–Nickel(II) Complexes: Synthesis, Structure Determination, and Magnetic Properties