TRIS(2-PYRIDYL) TRIPOD LIGANDS

This review covers the recent literature involving tris(2-pyridyl) tri pod ligands which use nitrogen, phosphorus, arsenic, or carbon as cent ral bridging atoms. In general, tripod ligands are facially coordinati ng, tridentate chelate ligands which have received considerable attent ion in both coordination and organometallic chemistry. Over the past 2 0 years, there have been hundreds of published reports concerning vari ous aspects of metal complexes which contain tripod ligands, with the majority of these reports involving polypyrazolylborate ligands. In li ght of the extensive and also very recent literature coverage of ligan ds which contain pyrazole donors, this review is a timely examination of the literature concerning tripod ligands that use pyridine donors. Further, this review contains the first summary of the chemistry of ca rbon-bridged tris(2-pyridyl) tripod ligands as well as an examination of recent studies involving nitrogen-bridged, phosphorus-bridged and a rsenic-bridged analogues to the carbon-bridged ligands. There is a par ticular focus on tris(2-pyridyl) tripod ligands that coordinate in a f acial manner to a single metal center through the pyridyl nitrogens. ( C) 1998 Elsevier Science S.A. All rights reserved.