Molecular Electronic Structures of Transition Metal Complexes I
J.P. Dahl: Carl Johan Ballhausen (1926–2010).- J.R. Winkler and H.B. Gray: Electronic Structures of Oxo-Metal Ions.- C.D. Flint: Early Days in Kemisk Laboratorium IV and Later Studies.- J.H. Palmer: Transition Metal Corrole Coordination Ch
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Electronic Structures of Oxo-Metal Ions Jay R. Winkler and Harry B. Gray
Abstract The dianionic oxo ligand occupies a very special place in coordination chemistry, owing to its ability to donate p electrons to stabilize high oxidation states of metals. The ligand field theory of multiple bonding in oxo-metal ions, which was formulated in Copenhagen 50 years ago, predicts that there must be an “oxo wall” between Fe–Ru–Os and Co–Rh–Ir in the periodic table. In this tribute to Carl Ballhausen, we review this early work as well as new developments in the field. In particular, we discuss the electronic structures of beyond-the-wall (groups 9 and 10) complexes containing metals multiply bonded to O- and N-donor ligands. Keywords Ferryl Ligand field theory Oxo wall Vanadyl
Contents 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 The B&G Bonding Scheme . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1 The Vanadyl Ion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2 The Chromyl and Molybdenyl Ions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3 The Oxo-Metal Triple Bond . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.4 Lower Bond Orders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 The Oxo Wall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Beyond the Oxo Wall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Concluding Remarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
J.R. Winkler and H.B. Gray (*) Beckman Institute, California Institute of Technology, Pasadena, CA 91125, USA e-mail: [email protected]; [email protected]
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J.R. Winkler and H.B. Gray
1 Introduction Transition metal ions in aqueous solutions typically are coordinated by multiple water molecules. Binding to a Lewis acidic metal center increases the Brønsted acidity of the water ligand such that, depending on the pH of the medium, one or two protons can be lost producing, respectively, hydroxo and oxo ligands. In some cases, the acidity of a coordinated water is so great that the oxo ligand ca
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