Modular Approach to Tridentate N,O,N′ Ligands Using Pyrazolylborate Chemistry

AbstractTwo anionic tridentate N,O,N′ chelators, [pz(Ph)B(μ‐pz)(μ‐O)B(Ph)pz]− (3−) and [pzPh(Ph)B(μ‐pz)(μ‐O)B(Ph)pzPh]− (4−), as well as the corresponding complexes [Fe(3)(py)Cl], [Fe(3)Cl2] and [Cu(3)Cl], have been synthesised and structurally characterised by X‐ray crystallography (pz: pyrazolyl, pzPh: 3‐phenylpyrazolyl, py: pyridine). Since our synthesis approach takes advantage of the highly modular pyrazolylborate chemistry, inexpensive and relatively resistant N,O,N′ ligands of varying steric demand are readily accessible. The complexes [Fe(3)(py)Cl] and [Fe(3)Cl2] possess a distorted trigonal‐bipyramidal configuration with the pyrazolyl rings occupying equatorial positions and the oxygen donor being located at an apical position. The complex [Cu(3)Cl] crystallises as chloro‐bridged dimers featuring CuII ions with ligand environments that are intermediate between a square‐planar and a trigonal‐bipyramidal geometry.