Pyrazolate‐Based Oligonuclear Copper and Silver Complexes with N/S Coordination Spheres

Abstract

A series of pyrazole-based potential ligands bearing thioether substituents in 3-and 5-positions of the heterocycle was synthesized [3,5- complex [ (lb)2Cu2](BF4)2 (4) was synthesized. According to an X-ray crystal structure analysis it consists of dinuclear molecules with two bridging pyrazolates, distorted square planar N2S2 coordination spheres for Cu" and an axially bridging tetrafluoroborate. Magnetic susceptibility data reveal an antiferromagnetic exchange ( J = -206 cm-l) that is among the highest found for doubly pyrazolate bridged dicopper(I1) complexes, which is rationalized on the basis of the rather symmetric dinuclear core of 4. The irreversibility of the electrochemical reduction and oxidation processes for the CuII and CuI compounds, respectively, is explained by the inability of the respective coordination framework to adapt to different geometric preferences.

Homo‐ and Heteropolynuclear Platinum Complexes Stabilized by Dimethylpyrazolato and Alkynyl Bridging Ligands: Synthesis, Structures, and Luminescence

“…These kinds of ligands have a proven ability to hold metal atoms in close proximity while permitting a wide range of intermetallic separations, being useful in the synthesis of shape-persistent macrocycles, such as the homonuclear [M I A C H T U N G T R E N N U N G (m-Rpz)] 3 (M = Cu, [36][37][38][39][40][41][42] Ag, [37,38,43,44] Au; [43,[45][46][47][48][49][50] Rpz = pyrazolate or substituted pyrazolate) or [M II 3 A C H T U N G T R E N N U N G (m-Rpz) 6 ] (M II = Pd [51,52] Pt [52,53] ) as the heteronuclear clusters [Pd 2 M 2 A C H T U N G T R E N N U N G (m-Rpz) 6 ] (M = Cu, Ag, Au), [52,54] and [M 2 M' 4 A C H T U N G T R E N N U N G (m-Rpz) 8 ] (M = Pd, Pt; M' = Cu, Ag). [52,55] Apart from the interest arising from their structural diversity, some of these pyrazolate bridging complexes have also been shown to be excellent systems for examining metallophilic interactions [49,[56][57][58][59][60][61][62] and as luminescent materials.…”

Heteropolynuclear Palladium Complexes with Pyrazolate and Its 3‐tert‐Butyl Derivatives: The Effect of Heterometal Ions on the Rate of Isomerization

“…The apparent formation of 3 b in the reaction can be attributed to the isomerization of 3 a to 3 b (vide infra). Although we have reported previously that the reaction of HT-[Pd 2 (m-3-tBupz) 2 2 ] with a Ag I salt gives the HH isomer of [Pd 2 Ag 2 (m-3-tBupz) 6 ] (3 b), [9] it is now clear that the main product of this reaction is the HT isomer 3 a. It is also obvious that the successful isolation of 3 b as a pure product from the reaction of 3-tBupz with the mixture of Pd II and Ag I ions is due to the lower solubility of 3 b than 3 a.…”

“…[13] Pyrazole without any substituent groups (pzH), however, forms a cyclic trinuclear Pd 6 ], under basic conditions and a mononuclear Pd II complex with four neutral pyrazole ligands, [PdA C H T U N G T R E N N U N G (pzH) 4 ]Cl 2 , under acidic conditions. The product formed under basic conditions contrasts with the case of Pt II , which forms a dimer of mononuclear complexes with intermolecular hydrogen bonding,…”

“…[1] Among the various types of structures, pyrazolate and its derivatives are known to favor the formation of cyclic trinuclear complexes such as [M I 3 A C H T U N G T R E N N U N G (m-Rpz) 3 ] (M I = Cu, [2][3][4] Ag, [3,5,6] Au; [5,7] RpzH = pyrazole or substituted pyrazoles) and [M II 3 A C H T U N G T R E N N U N G (m-Rpz) 6 ] (M II = Pd, [8,9] Pt [9,10] ), the structure of the latter being similar to that of palladium(ii) acetate [Pd 3 A C H T U N G T R E N N U N G (m-OAc) 6 ]. [11] The successful partial oxidation of the platinum cyclic trimer [Pt 6 ] have been elucidated. [12] The number of heteropolynuclear pyrazolate complexes is also gradually increasing.…”

“…The heteropolynuclear complexes [Pd 2 M' 2 A C H T U N G T R E N N U N G (m-pz) 6 ] (M' = Ag (1), Au (2); pzH = pyrazole), HT-[Pd 2 M' 2 (m-3-tBupz) 6 ] (M' = Ag (3 a), Au (4 a); 3-tBupzH = 3-tert-butylpyrazole), and HH-[Pd 2 Au 2 (m-3-tBupz) 6 ] (4 b) have been prepared and some of them were structurally characterized. When 3-tertbutylpyrazolate was employed as a bridging ligand, two linkage isomers (head-to-tail (HT) and head-to-head (HH)) arise from the difference in orientation of the substituent groups on the pyrazolate bridges between the two Pd atoms.…”