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Title: Tutorial on the Role of Cyclopentadienyl Ligands in the Discovery of Molecular Complexes of the Rare-Earth and Actinide Metals in New Oxidation States

Abstract

A fundamental aspect of any element is the range of oxidation states accessible for useful chemistry. This tutorial describes the recent expansion of the number of oxidation states available to the rare-earth and actinide metals in molecular complexes that has resulted through organometallic chemistry involving the cyclopentadienyl ligand. These discoveries demonstrate that the cyclopentadienyl ligand, which has been a key component in the development of organometallic chemistry since the seminal discovery of ferrocene in the 1950s, continues to contribute to the advancement of science. Lastly, we present background information on the rare-earth and actinide elements, as well as the sequence of events that led to these unexpected developments in the oxidation state chemistry of these metals.

Authors:
 [1]
  1. Univ. of California, Irvine, CA (United States). Dept. of Chemistry
Publication Date:
Research Org.:
Univ. of California, Irvine, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1324845
Alternate Identifier(s):
OSTI ID: 1326633
Grant/Contract Number:
SC0004739; CHE-1565776
Resource Type:
Journal Article: Published Article
Journal Name:
Organometallics
Additional Journal Information:
Journal Volume: 35; Journal Issue: 18; Journal ID: ISSN 0276-7333
Publisher:
American Chemical Society
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Evans, William J. Tutorial on the Role of Cyclopentadienyl Ligands in the Discovery of Molecular Complexes of the Rare-Earth and Actinide Metals in New Oxidation States. United States: N. p., 2016. Web. doi:10.1021/acs.organomet.6b00466.
Evans, William J. Tutorial on the Role of Cyclopentadienyl Ligands in the Discovery of Molecular Complexes of the Rare-Earth and Actinide Metals in New Oxidation States. United States. doi:10.1021/acs.organomet.6b00466.
Evans, William J. Thu . "Tutorial on the Role of Cyclopentadienyl Ligands in the Discovery of Molecular Complexes of the Rare-Earth and Actinide Metals in New Oxidation States". United States. doi:10.1021/acs.organomet.6b00466.
@article{osti_1324845,
title = {Tutorial on the Role of Cyclopentadienyl Ligands in the Discovery of Molecular Complexes of the Rare-Earth and Actinide Metals in New Oxidation States},
author = {Evans, William J.},
abstractNote = {A fundamental aspect of any element is the range of oxidation states accessible for useful chemistry. This tutorial describes the recent expansion of the number of oxidation states available to the rare-earth and actinide metals in molecular complexes that has resulted through organometallic chemistry involving the cyclopentadienyl ligand. These discoveries demonstrate that the cyclopentadienyl ligand, which has been a key component in the development of organometallic chemistry since the seminal discovery of ferrocene in the 1950s, continues to contribute to the advancement of science. Lastly, we present background information on the rare-earth and actinide elements, as well as the sequence of events that led to these unexpected developments in the oxidation state chemistry of these metals.},
doi = {10.1021/acs.organomet.6b00466},
journal = {Organometallics},
number = 18,
volume = 35,
place = {United States},
year = {Thu Sep 15 00:00:00 EDT 2016},
month = {Thu Sep 15 00:00:00 EDT 2016}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1021/acs.organomet.6b00466

Citation Metrics:
Cited by: 22works
Citation information provided by
Web of Science

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  • A fundamental aspect of any element is the range of oxidation states accessible for useful chemistry. This tutorial describes the recent expansion of the number of oxidation states available to the rare-earth and actinide metals in molecular complexes that has resulted through organometallic chemistry involving the cyclopentadienyl ligand. These discoveries demonstrate that the cyclopentadienyl ligand, which has been a key component in the development of organometallic chemistry since the seminal discovery of ferrocene in the 1950s, continues to contribute to the advancement of science. Lastly, we present background information on the rare-earth and actinide elements, as well as the sequencemore » of events that led to these unexpected developments in the oxidation state chemistry of these metals.« less
  • Four chloride-bridged, binuclear bis(cyclopentadienyl) rare-earth-metal complexes have been subjected to detailed mass spectrometric studies adopting exhaustively the B/E-linked scan technique: (Me{sub 2}Si(C{sub 5}H{sub 4}){sub 2}Yb({mu}-Cl)){sub 2} (1), ((Me{sub 3}SiC{sub 5}H{sub 4}){sub 2}Yb({mu}-Cl)){sub 2} (2), (Me{sub 2}Si(C{sub 5}H{sub 4}){sub 2}Y({mu}-Cl)){sub 2} (3), and Me{sub 2}Si(C{sub 5}H{sub 4}){sub 2}Yb({mu}-Cl){sub 2}Y(C{sub 5}H{sub 4}){sub 2}SiMe{sub 2} (5). The strict dominance of binuclear fragments in the spectrum of pure 1 indicates, in excellent accordance with a previous crystallographic X-ray study, the presence of metal-bridging Me{sub 2}Si(C{sub 5}H{sub 4}){sub 2} ligands in the vapor state. The existence of the new complex 5, which could not bemore » separated chemically from admixtures of 1 and 3 (i.e., from sample 4), has been confirmed unambiguously by deducing its individual fragmentation pattern from a systematic B/E-linked scan analysis.« less
  • Chemical preparation and X-ray diffraction determined crystal structures of (CH{sub 3}OCH{sub 2}CH{sub 2}C{sub 5}H{sub 4}){sub 2}LnCl [Ln = La (1), Pr (2), Nd (3), Sm (4), Gd (5), Dy (6), Ho (7), Er (8), Tm (9), Yb (10), Lu (11), Y (12)] are reported. Further characterization by elemental analysis, MS, NMR, and IR spectroscopy was performed for these complexes. From these data, the molecular structures are described.
  • A qualitative treatment of the bonding in Cp{sub 3}M (Cp = {eta}{sup 5}-C{sub 5}H{sub 5}) compounds under C{sub 3{upsilon}} symmetry reveals that the Cp{sub 3}{sup 3{minus}} ligand field contains a high-lying a{sub 2} orbital which is restricted by symmetry to interact only with metals that contain f orbitals. Quantitative investigation of the electronic structure of 5f{sup 3} Cp{sub 3}U via X{alpha}-SW molecular orbital calculations with quasi-relativistic corrections reveals that the Cp ligands donate electron density primarily into the U 6d orbitals while the three principally metal-based valence electrons are housed in the 5f orbitals. Electronic structure calculations of Cl{sub 3}Umore » show that although Cl can be considered isolobal with Cp, it is a poorer donor ligand. Calculations of Cp{sub 3}U bonded to a fourth ligand L (L = H, CO, NO, OH) indicate that the {sigma}-bonding framework is essentially the same for {pi}-neutral (H), {pi}-acidic (CO, NO), or {pi}-basic (OH) ligands: Electron density is donated from the {sigma} orbital of the fourth ligand into a uranium orbital that is primarily 6d{sub z{sup 2}} in character with minor contributions from the 5f{sub z{sup 3}} orbital, the 7p{sub z} orbital, and the 7s orbital. In the {pi}-bonding framework, the U 5f orbitals are responsible for back-donation into the {pi}* orbitals of CO an NO, while acceptance of electron density from the {pi} orbitals of OH involves the U 6d orbitals and, to a lesser extent, the U 5f orbitals. The bonding scheme of Cp{sub 3}UNO suggests that this molecule may prove to be a rather unusual example of a linear NO{sup {minus}} ligand.« less
  • The dependence of the catalytic activity of bicyclic and tricyclic Cu{sup 2+} chelates based on hydrazone imines in a model reaction of liquid-phase oxidation of cyclohexene by molecular oxygen on the donor-acceptor properties of ligands and the number of coordinating atoms of the ligands is studied. Decreasing this number with the retention of the coordination geometry of the chelate center results in the enhancement of the catalytic activity of the Cu{sup 2+} chelate owing to an increase in its stereochemical lability. Introduction of different substituents (C{sub 6}H{sub 5}CO, CH{sub 3}CO, and CF{sub 3}CO) at the {gamma}-position of quasi-aromatic metallocycles resultsmore » in a decrease in the effective rate constants for cyclohexene oxidation in the series C{sub 6}H{sub 5}CO > CH{sub 3}CO > CF{sub 3}CO. Cu{sup 2+} complexes with a tetragonal distortion based on hydrazone imines have unstable structures and isomerize into square-planar chelates during the catalytic oxidation of cyclohexene. {open_quotes}Flattening{close_quotes} of the chelate center results in a decrease in the rate of the catalytic reaction, since the tetrahedrally distorted Cu{sup 2+} complexes are more active than their square-planar isomers. Kinetics of cyclohexene oxidation by molecular oxygen in the presence of stereochemically unstable Cu{sup 2+} chelates is studied, and effective rate constants for oxidation and relaxation times are calculated. The catalytic activity and relaxation times correlate with the {open_quotes}energy gap{close_quotes} of Cu{sup 2+} chelates.« less