Low Coordinate Metals

We are very interested in “three-coordinate complexes,” in which the metal has only three bonds (a typical number of bonds to the metal is six). These complexes are a springboard into new chemistry for several reasons. First, low coordinate complexes have not been studied as extensively as higher coordinate systems (109 3-coordinate structures versus >11000 6-coordinate structures for Ni!)

Pictured above are two examples of three coordinate transition metal complexes of iron (left) and nickel (right). Low-coordinate complexes are electronically unsaturated: whereas most complexes prefer an 18-electron configuration, the complexes shown above have only 12-14 valence electrons. This leads to unusual reactions, and the third ligand may be varied for electronic and steric control of the reactions. Finally, the potential for low coordination numbers in enzyme active sites and on surfaces suggests that we can gain insights into potential mechanisms of these catalysts using our compounds.

Relevant Publications

Sean F. McWilliams, Emma Brennan-Wydra, K. Cory MacLeod, Patrick L. Holland
Density Functional Calculations for Prediction of 57Fe Mössbauer Isomer Shifts and Quadrupole Splittings in β-Diketiminate Complexes
ACS Omega  20172, 2594-2606.  
Patrick L. Holland
Reaction: Opportunities for Sustainable Catalysts
Chem  20172, 443-444.  
Daniël L. J. Broere, Ilija Čorić, Anna Brosnahan, Patrick L. Holland
Quantitation of the THF Content in Fe[N(SiMe3)2]2·xTHF
Inorg. Chem.  201756, 3140–3143.  
Daniel E. DeRosha, Brandon Q. Mercado, Gudrun Lukat-Rodgers, Kenton R. Rodgers, Patrick L. Holland
Enhancement of C-H Oxidizing Ability in Co-O2 Complexes through an Isolated Heterobimetallic Oxo Intermediate
Angew. Chem. Int. Ed.  201756, 3211–3215.  
Sarina M. Bellows, William W. Brennessel, Patrick L. Holland
Effects of Ligand Halogenation on the Electron Localization, Geometry and Spin State of Low-Coordinate β-Diketiminate Iron Complexes
Eur. J. Inorg. Chem.  2016, 3344-3355.  
Malik H. Al-Afyouni, Elizaveta Suturina, Shubhrodeep Pathak, Mihail Atanasov, Eckhard Bill, Daniel E. DeRosha, William W. Brennessel, Frank Neese, Patrick L. Holland
Spin Isomers and Ligand Isomerization in a Three-Coordinate Cobalt(I) Carbonyl Complex
J. Am. Chem. Soc.  2015137, 10689-10699.  
Chi Chen, Sarina M. Bellows, Patrick L. Holland
Tuning steric and electronic effects in transition-metal β-diketiminate complexes
Dalton Trans.  201544, 16654-16670.  Open Access
Simon J. Bonyhady, Jonathan M. Goldberg, Nicole Wedgwood, Thomas R. Dugan, Andrew G. Eklund, William W. Brennessel, Patrick L. Holland
Cobalt(II) Complex of a Diazoalkane Radical Anion
Inorg. Chem.  201554, 5148-5150.  
Richard A. Lewis, K. Cory MacLeod, Brandon Q. Mercado, Patrick L. Holland
Geometric and redox flexibility of pyridine as a redox-active ligand that can reversibly accept one or two electrons
Chem. Commun.  201450 , 11114-11117.  
Roman M. Davydov, Matthew P. McLaughlin, Eckhard Bill, Brian M. Hoffman, Patrick L. Holland
Generation of High-Spin Iron(I) in a Protein Environment Using Cryoreduction
Inorg. Chem.  201352, 7323-7325.  
P. Chandrasekaran, Karen P. Chiang, Dennis Nordlund, Uwe Bergmann, Patrick L. Holland, Serena DeBeer
On the Sensitivity of X-ray Core Spectroscopy to Changes in Metal Ligation: A Systematic Study of Low-Coordinate High-Spin Ferrous Complexes
Inorg. Chem.  201352, 6286-6298.  
Thomas R. Dugan, Eckhard Bill, K. Cory MacLeod, Gemma J. Christian, Ryan E. Cowley, William W. Brennessel, Shengfa Ye, Frank Neese, Patrick L. Holland
Reversible C-C Bond Formation Between Redox-Active Pyridine Ligands in Iron Complexes
J. Am. Chem. Soc.  2012134, 20352-20364.  
Karen P. Chiang, Christopher C. Scarborough, Masaki Horitani, Nicholas S. Lees, Keying Ding, Thomas R. Dugan, William W. Brennessel, Eckhard Bill, Brian M. Hoffman, Patrick L. Holland
Characterization of the Fe-H Bond in a Three-Coordinate Terminal Hydride Complex of Iron(I)
Angew. Chem. Int. Ed.  201251, 3658-3662.  
Ryan E. Cowley, Gemma J. Christian, William W. Brennessel, Frank Neese, Patrick L. Holland
A Reduced β-Diketiminatoiron Complex with End-on and Side-on Nitriles: Strong Backbonding or Ligand Non-Innocence?
Eur. J. Inorg. Chem.   2012, 479-483.  
Thomas R. Dugan, Xianru Sun, Elena V. Rybak-Akimova, Olayinka Olatunji-Ojo, Thomas R. Cundari, Patrick L. Holland
A Masked Two-Coordinate Cobalt(I) Complex That Activates C-F Bonds
J. Am. Chem. Soc.   2011133, 12418-12421.  
Patrick L. Holland
All square with high-spin iron(II)
Nature Chem.  20113, 507-508.  
Patrick L. Holland
Two-Coordinate Transition Metal Centers With Metal-Metal Bonds
Angew. Chem. Int. Ed.  201150, 6213-6214.  
Sara S. Rocks, William W. Brennessel, Timothy E. Machonkin, Patrick L. Holland
Solution and Structural Characterization of Iron(II) Complexes with Ortho-Halogenated Phenolates: Insights into Potential Substrate Binding Modes in Hydroquinone Dioxygenases
Inorg. Chem.   201049, 10914-10929.  
Daniel J. Mindiola, Patrick L. Holland, Timothy H. Warren
Complexes of Bulky Beta-Diketiminate Ligands: Introduction
Inorg. Synth.  201035, 1-4.  
Matthew S. Varonka, Timothy H. Warren, Thomas R. Dugan, Ryan E. Cowley, Patrick L. Holland
Beta-Diketiminate Precursors HLMe,Me3 and TlLMe,Me3
Inorg. Synth.  201035, 4-8.  
Debashis Adhikari, Ba L. Tran, Francisco J. Zuno-Cruz, Gloria Sanchez Cabrera, Daniel J. Mindiola, Karen P. Chiang, Ryan E. Cowley, Thomas R. Dugan, Patrick L. Holland
Beta-Diketiminate Precursors LMe,iPr2H, [LMe,iPr2Li]x, and [LtBu,iPr2K]x
Inorg. Synth.  201035, 8-13.  
Bryan D. Stubbert, Patrick L. Holland, Debashis Adhikari, Daniel J. Mindiola
Iron 2,4-Bis-(2,6-diisopropylphenylimido)pentyl Chloride Dimer
Inorg. Synth.  201035, 38-41.  
Karen P. Chiang, Patrick L. Holland, Debashis Adhikari, Daniel J. Mindiola
Iron 2,2,6-6-Tetramethyl-3,5-bis-(2,6-diisopropylphenylimido)heptyl Chloride
Inorg. Synth.  201035, 41-43.  
Keying Ding, Patrick L. Holland, Debashis Adhikari, Daniel J. Mindiola
Cobalt 2,2,6-6-Tetramethyl-3,5-bis-(2,6-diisopropylphenylimido)heptyl Chloride
Inorg. Synth.  201035, 43-45.  
Marie M. Melzer, Elzbieta Kogut, Matthew S. Varonka, Stefan Wiese, Timothy H. Warren, Sara S. Rocks, Patrick L. Holland
Beta-Diketiminate Supported Nickel(II) and Nickel(I) Complexes of LMe,Me3
Inorg. Synth.  201035, 45-48.  
Thomas R. Dugan, Patrick L. Holland, Stefan Wiese, Timothy H. Warren
Nickel 2,4-Bis-(2,6-diisopropylphenylimido)pentyl Chloride Dimer
Inorg. Synth.  201035, 48-50.  
Yosra M. Badiei, Timothy H. Warren, Karen P. Chiang, Patrick L. Holland
Bis[Copper 2,4-Bis-(2,4,6-trimethylphenylimido)pentyl] Toluene
Inorg. Synth.  201035, 50-53.  
Patrick L. Holland, Marie M. Melzer, Timothy H. Warren
Copper 2,4-Bis-(2,6-diisopropylphenylimido)pentyl Chloride
Inorg. Synth.  201035, 54-55.  
Timothy E. Machonkin, Patrick L. Holland, Kristine N. Smith, Justin S. Liberman, Adriana Dinescu, Thomas R. Cundari, Sara S. Rocks
Determination of the Active Site of Sphingomonas chlorophenolica 2,6-dichloro-p-hydroquinone dioxygenase (PcpA)
J. Biol. Inorg. Chem.   201015, 291-301.  
Keying Ding, Thomas R. Dugan, William W. Brennessel, Eckhard Bill, and Patrick L. Holland
Synthesis, Properties, and Reactivity of Diketiminate-Supported Cobalt Fluoride Complexes
Organometallics  200928, 6650-6656.  
Karen P. Chiang, Pamela M. Barrett, Feizhi Ding, Jeremy M. Smith, Savariraj Kingsley, William W. Brennessel, Meghan M. Clark, Rene J. Lachicotte, Patrick L. Holland
Ligand Dependence of Binding to Three-Coordinate Fe(II) Complexes
Inorg. Chem.  200948, 5106-5116.  
Sara S. Rocks, William W. Brennessel, Timothy E. Machonkin, Patrick L. Holland
Solid-State and Proton NMR Characterization of an Iron(II) Complex of a Tridentate, Facially Coordinating N,N,O Donor Ligand
Inorg. Chim. Acta   2009362, 1387-1390.  
Sebastian Stoian, Jeremy M. Smith, Patrick L. Holland, Eckard Münck, Emile L. Bominaar
Mössbauer, EPR, and theoretical study of a high-spin, four-coordinate Fe(II) diketiminate complex
Inorg. Chem.  200847, 8687-8695.  
Patrick L. Holland
Electronic Structure and Reactivity of Three-Coordinate Iron Complexes
Acc. Chem. Res.  200841, 905-914.  
Ryan E. Cowley, Jerome Elhaik, Nathan A. Eckert, William W. Brennessel, Eckhard Bill, Patrick L. Holland
A bridging hexazene (RNNNNNNR) ligand from reductive coupling of azides
J. Am. Chem. Soc.  2008130, 6074-6075.  Highlight in Chemical & Engineering News
Javier Vela, Liwei Zhu, Christine J. Flaschenriem, William W. Brennessel, Rene J. Lachicotte, and Patrick L. Holland
Macrocyclic Binucleating β-Diketiminate Ligands and their Lithium, Aluminum, and Zinc Complexes
Organometallics  200726, 3416-3423.  
Javier Vela, Jordi Cirera, Jeremy M. Smith, Rene J. Lachicotte, Christine J. Flaschenriem, Santiago Alvarez, and Patrick L. Holland
Quantitative Geometric Descriptions of the Belt Iron Atoms of the Iron-Molybdenum Cofactor of Nitrogenase and Synthetic Iron(II) Model Complexes
Inorg. Chem.  200746, 60-71.  
Travis J. Hebden, William W. Brennessel, Christine J. Flaschenriem, and Patrick L. Holland
A dinucleating ligand related to the β-diketiminates
Dalton Trans.   2006, 3855-3857.  
Javier Vela, Sridhar Vaddadi, Savariraj Kingsley, Christine J. Flaschenriem, Rene J. Lachicotte, Thomas R. Cundari, Patrick L. Holland
Bidentate Coordination of Pyrazolate in Low-Coordinate Iron(II) and Nickel(II) Complexes
Angew. Chem., Int. Ed. Engl.   200645, 1607-1611.  
Nathan A. Eckert, Adriana Dinescu, Thomas R. Cundari, Patrick L. Holland
A T-Shaped Three-Coordinate Nickel(I) Carbonyl Complex and the Geometric Preferences of Three-Coordinate d9 Complexes
Inorg. Chem.  200544, 7702-7704.  
Nathan A. Eckert, Sebastian Stoian, Jeremy M. Smith, Emile L. Bominaar, Eckard Münck, Patrick L. Holland
Synthesis, Structure, and Spectroscopy of an Oxodiiron(II) Complex
J. Am. Chem. Soc.   2005127, 9344-9345.  
Sebastian Stoian, Ying Yu, Jeremy M. Smith, Patrick L. Holland, Emile L. Bominaar, Eckard Münck
Mössbauer, EPR and Crystallographic Characterization of a High-Spin Fe(I) Diketiminate Complex with Orbital Degeneracy
Inorg. Chem.   200544, 4915-4922.  
Javier Vela, Jeremy M. Smith, Ying Yu, Nicole A. Ketterer, Christine J. Flaschenriem, Rene J. Lachicotte, Patrick L. Holland
Synthesis and Reactivity of Low-Coordinate Iron(II) Fluoride Complexes and Their Use in the Catalytic Hydrodefluorination of Fluorocarbons
J. Am. Chem. Soc.   2005127, 7857-7870.  
Elizabeth A. Gregory, Rene J. Lachicotte, Patrick L. Holland
A Cationic Three-Coordinate Iron(II) Complex and the Reaction of Diketiminate with Ethyl Diazoacetate
Organometallics  200524, 1803-1805.  
Javier Vela, Sridhar Vaddadi, Thomas R. Cundari, Jeremy M. Smith, Elizabeth A. Gregory, Rene J. Lachicotte, Christine J. Flaschenriem, Patrick L. Holland
Reversible Beta-Hydrogen Elimination of Three-Coordinate Iron(II) Alkyl Complexes: Mechanistic and Thermodynamic Studies
Organometallics   200423, 5226-5239.  Correction
Nathan A. Eckert, Jeremy M. Smith, Rene J. Lachicotte, Patrick L. Holland
Low-coordinate Fe(II) Amido Complexes of β-Diketiminates: Synthesis, Structure and Reactivity
Inorg. Chem.  200443, 3306-3321.  
Nathan A. Eckert, Emily M. Bones, Rene J. Lachicotte, Patrick L. Holland
Nickel Complexes of a Bulky β-Diketiminate Ligand
Inorg. Chem.  200342, 1720-1725.  
Patrick L. Holland, Thomas R. Cundari, Lanyn L. Perez, Nathan A. Eckert, Rene J. Lachicotte
Electronically Unsaturated Three-Coordinate Chloride and Methyl Complexes of Iron, Cobalt, and Nickel
J. Am. Chem. Soc.   2002124, 14416-14424.  
Hanspeter Andres, Emile M. Bominaar, Jeremy M. Smith, Nathan A. Eckert, Patrick L. Holland, Eckard Münck
Planar Three-Coordinate High-Spin Fe(II) Complexes with Large Orbital Angular Momentum: Mössbauer, Electron Paramagnetic Resonance, and Electronic Structure Studies
J. Am. Chem. Soc.   2002124, 3012-3025.  Correction
Jeremy M. Smith, Rene J. Lachicotte, Patrick L. Holland
Tuning Metal Coordination Number by Ancillary Ligand Steric Effects: Synthesis of a Three-Coordinate Iron(II) Complex
Chem. Commun.   2001, 1542-1543.