Rare Nuclearities in Ni(II) Cluster Chemistry: An Unprecedented {Ni12} Nanosized Cage from the Use of N-Naphthalidene-2-Amino-5-Chlorobenzoic Acid

The self-assembly reaction between NiI2, benzoic acid (PhCO2H) and the Schiff base chelate, N-naphthalidene-2-amino-5-chlorobenzoic acid (nacbH2), in the presence of the organic base triethylamine (NEt3), has resulted in the isolation and the structural, spectroscopic, and physicochemical characterization of the dodecanuclear [Ni12I2(OH)6(O2CPh)5(nacb)5(H2O)4(MeCN)4]I (1) cluster compound in ~30% yield. Complex 1 has a cage-like conformation, comprising twelve distorted, octahedral NiII ions that are bridged by five μ3-OH−, one μ-OH−, an I− in 55% occupancy, five PhCO2− groups (under the η1:η1:μ, η1:η2:μ3 and η2:η2:μ4 modes), and the naphthoxido and carboxylato O-atoms of five doubly deprotonated nacb2− groups. The overall {Ni12} cluster exhibits a nanosized structure with a diameter of ~2.5 nm and its metallic core can be conveniently described as a series of nine edge- or vertex-sharing {Ni3} triangular subunits. Complex 1 is the highest nuclearity coordination compound bearing the nacbH2 chelate, and a rare example of polynuclear NiII complex containing coordinating I− ions. Direct current (DC) magnetic susceptibility studies revealed the presence of predominant antiferromagnetic exchange interactions between the NiII ions, while photophysical studies of 1 in the solid-state showed a cyan-to-green centered emission at 520 nm, upon maximum excitation at 380 nm. The reported results demonstrate the rich coordination chemistry of the deprotonated nacb2− chelate in the presence of NiII metal ions, and the ability of this ligand to adopt a variety of different bridging modes, thus fostering the formation of high-nuclearity molecules with rare, nanosized dimensions and interesting physical (i.e., magnetic and optical) properties.

Crystal structure of {(R)-N2-[(benzo[h]quinolin-2-yl)meth-yl]-N2'-[(benzo[h]quinolin-2-yl)methyl-idene]-1,1'-binaphthyl-2,2'-di-amine-κ4N,N',N'',N'''}(trifluoromethane-sulfonato-κO)zinc(II)} trifluoromethane-sulfonate di-chloro-methane 1.5-solvate

The zinc(II) atom in the title compound, [Zn(C48H31N4)(CF3SO3)](CF3SO3)·1.5CH2Cl2, adopts a distorted five-coordinate square-pyramidal geometry. It is coordinated by one tri-fluoro-methane-sulfonate ligand and four N atoms of the N2-[(benzo[h]quinolin-2-yl)meth-yl]-N2'-[(benzo[h]quinolin-2-yl)methyl-idene]-1,1'-binaphthyl-2,2'-di-amine ligand. The complex is present as a single-stranded P-helimer monohelical structure incorporating π-π and/or σ-π inter-actions. One of the imine bonds present in the original ligand framework is reduced, leading to variations in bond lengths and torsion angles for each side of the ligand motif. The imine-bond reduction also affects the bond lengths involving the metal atom with the N-donor atoms located on the imine bond. There are two mol-ecules of the complex in the asymmetric unit. One of the mol-ecules exhibits positional disorder within the coordinating tri-fluoro-methane-sulfonate ion making the mol-ecules symmetric-ally non-equivalent.

Terminal NiII-OH/-OH2 complexes in trigonal bipyramidal geometries derived from H2O

The preparation and characterization of two NiII complexes are described, a terminal NiII-OH complex with the tripodal ligand tris[(N)-tertbutylureaylato)-N-ethyl)]aminato ([H3buea]3-) and a terminal Ni II-OH2 complex with the tripodal ligand N,N',N″-[2,2',2″-nitrilotris(ethane-2,1-diyl)]tris(2,4,6-trimethylbenzenesulfonamido) ([MST]3-). For both complexes, the source of the -OH and -OH2 ligand is water. The salts K2[NiIIH3buea(OH)] and NMe4[NiIIMST(OH2)] were characterized using perpendicular-mode X-band electronic paramagnetic resonance, Fourier transform infrared, UV-visible spectroscopies, and its electrochemical properties were evaluated using cyclic voltammetry. The solid state structures of these complexes determined by X-ray diffraction methods reveal that they adopt a distorted trigonal bipyramidal geometry, an unusual structure for 5-coordinate NiII complexes. Moreover, the NiII-OH and NiII-OH2 units form intramolecular hydrogen bonding networks with the [H3buea]3- and [MST]3- ligands. The oxidation chemistry of these complexes was explored by treating the high-spin NiII compounds with one-electron oxidants. Species were formed with S = 1/2 spin ground states that are consistent with formation of monomeric NiIII species. While the formation of NiIII-OH complexes cannot be ruled out, the lack of observable O-H vibrations from the putative Ni-OH units suggest the possibility that other high valent Ni species are formed.

Heterometallic complexes with cube-type [MTi3N4] cores containing Group 10 metals in a variety of oxidation states

The metalloligand [{Ti(η⁵-C₅Me₅)(μ-NH)}₃(μ₃-N)] is capable of stabilizing Group 10 metals in the oxidation states 0,iioriv.