B–N Cleavage in (9‐BBN)bis(pyrazolyl)borate Ni^II Complexes

Abstract

Three kinds of NiII complexes, the singly hydroxo‐bridged complex 2, doubly hydroxo‐bridged complexes 3a and 3b, and dinuclear Ni complex 4, were readily prepared from reactions of the salt K[(BBN)BpR] {(BBN)BpR = (9‐BBN)bis(pyrazolyl)borate} and the NiCl2(PPh3)2 precursor via B–N bond cleavage process in dichloromethane or toluene. Complex 2 is a rare example of partial hydrolysis of the coordinated pyrazolylborate ligand, while complexes 3a and 3b demonstrate the unreported new form that complete hydrolyses of the coordinated pyrazolylborate ligand produced. Different mechanisms for the formation of complexes 2–4 are proposed.

Effects on the magnetic interaction caused by molecular recognition in complexes of 1,2-azole-based oxamate and [Cu(bpca)]+ units

“…Focusing on 1H-pyrazole-based ligands, their coordination chemistry is very rich due to the possibility of coordinating to metal atoms in their neutral or deprotonated form since its NH group can be easily deprotonated in the presence of transition metal ions and a base (apparent pK a = 19,8 for 1Hpyrazole in DMSO). The pyrazolate anion acts as a bismonodentate kN:kN′ ligand, forming di-, [22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38] tri-, [22][23][24][37][38][39][40][41][42][43][44][45][46][47] tetra- 22,[48][49][50][51][52][53][54] and polymetallic synthons [55][56][57][58][59][60] or even coordination polymers. [61][62]…”

“…Focusing on 1 H -pyrazole-based ligands, their coordination chemistry is very rich due to the possibility of coordinating to metal atoms in their neutral or deprotonated form since its NH group can be easily deprotonated in the presence of transition metal ions and a base (apparent p K a = 19,8 for 1 H -pyrazole in DMSO). The pyrazolate anion acts as a bis-monodentate kN:kN′ ligand, forming di-, 22–38 tri-, 22–24,37–47 tetra- 22,48–54 and polymetallic synthons 55–60 or even coordination polymers. 61–64 Relatively strong magnetic interactions between paramagnetic centers such as Cu II , Co II , and Fe II can be mediated through this coordination mode.…”