3‐(Pyridin‐2‐yl)imidazo[1,5‐a]pyridine (Pyridylindolizine) as Ligand in Complexes of Transition and Main‐Group Metals

Abstract

The coordination of the easily prepared 3‐(pyridin‐2‐yl)imidazo[1,5‐a]pyridine (pyridylindolizine, Py‐indz) ligand to several metal moieties was studied, and its electronic properties, similar to those of the classical ligands 2,2′‐bipyridine (bipy) and 1,10‐phenanthroline (phen), are reported. The new complexes were prepared and fully characterized by X‐ray crystallography and other typical spectroscopic methods if possible. Paramagnetic complexes [Ni(S2X)2(Py‐indz)] X = P(OEt)2 (1), COEt (2); [Ni(acac)2(Py‐indz)] (3, acac = acetylacetonate); [Ni(Py‐indz)3](PF6)2 (4); [Mn2Cl4(Py‐indz)2] (6); and [MnCl2(Py‐indz)2] (7) have the magnetic moment expected for a metallic cation with two or five unpaired electrons. Diamagnetic complexes show NMR spectra with similar patterns with small differences depending on the complex. [M{S2P(OEt)2}2 (Py‐indz)] M = Zn (8), Cd (9) have pentacoordinate and hexacoordinate structures, respectively. Octahedral tin complexes [SnL4(Py‐indz)] L4 = I4 (10), Cl3Ph (11), and Cl2nBu2 (12) have different behaviors in solution; whereas complex 10 is practically insoluble, complex 11 displays the expected pattern in its NMR spectrum, and complex 12 shows dynamic behavior. The Py‐indz ligand is also able to stabilize copper(I) and forms [Cu(PPh3)2(Py‐indz)]BF4 (13). The synthesis of the carbonyl complexes [MBr(CO)3(Py‐indz)] M = Mn (14), Re (15) and [Mo(CO)4(Py‐indz)] (16) was followed by IR spectroscopy in solution. [RuCl·p‐cym(Py‐indz)]PF6 (17, p‐cym = p‐cymene) has the familiar half‐sandwich “three‐legged piano‐stool” geometry.