Ligand Effects on the Structures of Extended Networks of Dicyanamide-Containing Transition-Metal Ions

Abstract

The structural characterization of a series of complexes of formula [M(dca)2L]n, where dca = dicyanamide, L = 1,10-phenanthroline (phen) [1-4] and 2,9-dimethylphenanthroline (2,9-dmphen) [9-12], and M = Mn (1 and 9), Fe (2 and 10), Co (3 and 11), and Ni (4 and 12), has revealed the effect of the presence of the methyl substituents of L on the resulting network. The structure of [Mn(dca)2(phen)]n (1), which is identical to those of 2-4, together with the investigation of its magnetic properties in the temperature range of 77-300 K were reported elsewhere. The use of the 4,7-dimethylphenanthroline (4,7-dmphen) as the co-ligand yielded a series of compounds of formula [M(dca)2(4,7-dmphen)]n [M = Mn (5), Fe (6), Co (7), and Ni (8)], which are isostructural with 1-4. Compounds containing phen (1-4) and 4,7-dmphen (5-8) are made of two-dimensional grids of metal atoms, each metal atom being linked to three other metal centers through single (three metal atoms involved) and double (two metal atoms involved) dca bridges exhibiting the mu-1,5 coordination mode. The isostructural complexes [M(dca)2(2,9-dmphen)]n (9-12) also have a sheetlike structure, the metal atoms in each layer being linked by two single and one double mu-1,5-dca units, as in 1-8. However, the topology of the network in 9-12 is different from that in 1-8 because of the different arrangement of the two single mu-1,5 dca bridges: cis in 1-8 versus trans in 9-12. The magnetic study of compounds 1-12 in the temperature range of 1.9-290 K has revealed the occurrence of weak ferromagnetic (M = Ni) and antiferromagnetic interactions (M = Mn, Fe, and Co). The different magnetic behavior in 1-12 was analyzed in the light of their structures, and the values of the magnetic interactions were compared to those of related systems.

Dicyanamido–metal(II) complexes. Part 3: Hydrolysis of the dicyanamide into amidocyanamide during its interaction with Cu(II) perchlorate and 2-pyridylcarbonyl-N,N-bis(2-pyridylmethyl)amine

“…The geometrical nature of theses anions precludes the possibility of formation of chelated coordination compounds but instead they can only act as terminal or bridging ligands through the nitrile groups. The ability of these ligands to produce molecule-based materials with novel magnetic or nonlinear optical properties made them important candidates in the ''crystal engineering of coordination polymers" [4][5][6][7][8][9][10]. These ligands can also greatly influence the topology of the resultant polymeric network [5,[11][12][13].…”

An alternating chain consisting of dinuclear Cu(II) ions bridged by end-on bis(μ-dicyanamido-κN1,N5) ligands and hydrogen-bonded pairs of bis(pyrimidin-2-yl)amines, with unusually long Cu⋯Cu distances of 7.20 and 9.99Å: Synthesis, structure and magnetic properties of [Cu(dipm)(μ-dca)(H2O)(ClO4)]2·2EtOH

“…Compounds of transition metals and the ligand dicyanamide (abbreviated as dca = N(CN) 2 ) have also gained much attention in the last decade, because of their interesting coordination, physical and magnetic properties [20][21][22][23][24][25][26][27][28][29][30][31][32]. Due to the fact that the dca anion itself is a very interesting bridging ligand with three potential donor sites, the ligand can vary from monodentate to even pentadentate [20][21][22][23][24][25][26][27][28][29][30][31][32]7,[33][34][35][36].…”

“…Due to the fact that the dca anion itself is a very interesting bridging ligand with three potential donor sites, the ligand can vary from monodentate to even pentadentate [20][21][22][23][24][25][26][27][28][29][30][31][32]7,[33][34][35][36].…”

“…While introducing co-ligands, various new and exciting structures in the field of crystal engineering showing one-, two-and three-dimensional compounds have been obtained [20][21][22][23][24][25][26][27][28][29][30][31][32]7,[33][34][35][36]. With dicyanamide and the dipm ligand already a mononuclear compound has been synthesised with copper(II) triflate as the metal salt, i.e., [Cu(dipm) 2 (dca)(CF 3 SO 3 )](C 2 H 6 O) 1/2 [13].…”

“…As the Cu-Cu distances in all cases are very large, interaction must be via the end-to-end dca bridges. In the literature, also for single end-to-end dca bridged ligands and also for polymeric compounds with end-to-end dca bridges, the interaction is in most cases weak to very weak antiferromagnetic [20][21][22][23][24][25][26][27][28][29][30][31][32]37,48,49]. So it can be concluded that end-to-end bridging dca ligands are indeed poor magnetic intermediates.…”