Polynuclear Complexes Containing Ditopic Bispyrazolylmethane Ligands. Influence of Metal Geometry and Supramolecular Interactions

Abstract

The new ligands bis(pyrazol-1-yl)(pyridine-4yl)methane (bpzm4py) (L1) and bis(3,5-dimethylpyrazol-1yl)(pyridine-4-yl)methane (bpz*m4py) (L2) were synthesized and were made to react with different metallic starting materials. In the case of Pd(II), chloride or allyl trinuclear complexes were synthesized, in which the central palladium is bonded to two ligands through the pyridine moiety. Mononuclear [Pd(allyl)L]X complexes were also isolated. On using other M(II) centers (M = Co, Ni, Zn), which could adopt an octahedral geometry, box-like cyclic dimers formed by the self-assembly of two metal centers and two ligands in a head-to-tail disposition were obtained. All metal ions exhibited a distorted octahedral geometry. A complex of Ag(I) with similar cyclic dimers connected through difluorophosphate anions to generate zigzag chains was also crystallized. The silver center was five-coordinate and the chain interactions gave rise to the formation of sheets. In the solid state, different noncovalent interactions were present in the molecular and supramolecular structures, including hydrogen bonds, π−π stacking and anion−π or CH−π interactions. Examples of possible synergy between some of these interactions were found. Where possible, the solution chemistry was analyzed and correlated with the solid state structure. The existence of polynuclear species in solution was evaluated and the effect of some noncovalent interactions on the NMR resonances was observed.

Dinuclear Species versus Zigzag or Helical Polymers in Palladium, Zinc, and Copper Complexes with Ditopic Bis(pyrazolyl)methane Ligands

“…However, in this case the region of the metal centre is flatter, and the NMN/N4(pz) angle (163.92°) is larger than that in the square‐planar complexes; this indicates possible steric hindrance between the bidentate nitrate anion and the biphenyl fragment. Coincidentally, larger values for this angle have been found, for example, in octahedral derivatives 23a. In 12 , with this disposition, the aforementioned anion–π interaction is established with an appropriate distance (Figure 8).…”

Synthesis, structures, and catalytic studies of new copper(II) complexes with arene-linked pyrazolyl methane ligands

“…Ligand design has became a major concept in these investigations to tailor the stability and chemical properties of the complex [12]. Pyrazole and its derivatives are a crucial member of N-heterocyclic ligands, widely used in coordination chemistry due to their multiple nitrogens taking part in coordination with metals [13][14][15]. Pyrazole and its derivatives have high biological activities and widespread applications in pesticides and medicinal preparations [16][17][18][19][20].…”

A Single‐Step Reaction for Silicon and Germanium Nanorods

“…It was found that the final structure depended on the metal geometry and the final products were either discrete species of different nuclearity or polymers. Trinuclear species were formed on employing square‐planar Pd II ions 21. The use of metal centres that were able to give an octahedral geometry, such as Co II , Ni II and Zn II , led, in all cases, to the formation of box‐like cyclic dimers21 (Scheme ).…”

“…Trinuclear species were formed on employing square‐planar Pd II ions 21. The use of metal centres that were able to give an octahedral geometry, such as Co II , Ni II and Zn II , led, in all cases, to the formation of box‐like cyclic dimers21 (Scheme ). Reaction of the ligands with silver(I) ions provided box‐like cyclic dimers and zig‐zag and helical polymers, with factors such as the coordinating ability of the anions and the crystallisation conditions affecting the structure obtained 22,23.…”

“… All‐nitrogen ditopic ligands bis(pyrazol‐1‐yl)(pyridin‐4‐yl)methane (bpzm4py) and bis(3,5‐dimethylpyrazol‐1‐yl)(pyridin‐4‐yl)methane (bpz*m4py), which were described previously,21 and bis(pyrazol‐1‐yl)(pyridin‐3‐yl)methane (bpzm3py, L1 ) and bis(3,5‐dimethylpyrazol‐1‐yl)(pyridin‐3‐yl)methane (bpz*m3py, L2 ) discussed herein. …”