Generation and spectroscopic characterization of new 18+δ electron complexes. Relationship between the stability of 18+δ electron organometallic complexes and their ligand reduction potentials

Meyer, Reinhard; Schut, David M.; Keana, Keith; Tyler, David R.

doi:10.1016/0020-1693(95)04561-9

Cited by 37 publications

(18 citation statements)

References 48 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The organometallic species and solvent were the same in all experiments conducted, so differences in chemical dynamics result solely from the different properties of the three coordinating ligands (PR 3 ; R = OMe, Bu, Ph). A low energy π* orbital in the coordinating ligand tends to enhance the stability of 18+δ compounds since the '19th' electron can localize in the anti-bonding orbital rather than occupying a higher energy metal-centered orbital [127][128][129]. Reduction potentials of the lone ligand are correlated with the ligand's ability to stabilize 18+δ compounds by accommodating the extra electron in a vacant molecular orbital [129,164,165].…”

Section: Steric and Electronic Effectsmentioning

confidence: 99%

“…A low energy π* orbital in the coordinating ligand tends to enhance the stability of 18+δ compounds since the '19th' electron can localize in the anti-bonding orbital rather than occupying a higher energy metal-centered orbital [127][128][129]. Reduction potentials of the lone ligand are correlated with the ligand's ability to stabilize 18+δ compounds by accommodating the extra electron in a vacant molecular orbital [129,164,165]. A more positive reduction potential approximately indicates a smaller HOMO/LUMO energy gap and corresponds to more stable 18+δ compounds but decreased reactivity toward electron transfer [129].…”

Section: Steric and Electronic Effectsmentioning

confidence: 99%

“…Reduction potentials of the lone ligand are correlated with the ligand's ability to stabilize 18+δ compounds by accommodating the extra electron in a vacant molecular orbital [129,164,165]. A more positive reduction potential approximately indicates a smaller HOMO/LUMO energy gap and corresponds to more stable 18+δ compounds but decreased reactivity toward electron transfer [129]. In the absence of reduction potentials for the ligands themselves, 7 the reduction potentials (E 0 ) for CpFe(CO)(COMe)PR 3 + will be used to establish the trend for the PR 3 ligands.…”

Section: Steric and Electronic Effectsmentioning

confidence: 99%

“…In addition to electron deficient 17-electron (17e) radicals, 19-electron (19e) species have been identified as potential intermediates in a variety of catalytic and electron transfer reactions [122][123][124]. One of the first 19e complexes, cobaltocene, was synthesized as early as 1953 [125,126], and many stable 19e complexes have subsequently been characterized [127][128][129][130]. While these complexes formally contain 19 valence electrons, the '19th' electron is commonly localized on a ligand, allowing the metal to retain an effective 18-electron count.…”

Section: Introductionmentioning

confidence: 99%

“…For example, the first 19e complex, cobaltocene, was isolated more than fifty years ago [125,126] and a variety of similar complexes have since been identified [127][128][129][130]. The descriptor "19-electron" comes with some qualification-the '19th' or unpaired electron is usually localized on a ligand rather than the transition-metal atom [129,130]. These complexes are thus more accurately given the name 18+δ-electron complexes, where the value of δ reflects the degree of unpaired electron density residing on the metal center.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Investigation of organometallic reaction mechanisms with one and two dimensional vibrational spectroscopy

Cahoon

2008

View full text Add to dashboard Cite

show abstract

Section: Steric and Electronic Effectsmentioning

confidence: 99%

Section: Steric and Electronic Effectsmentioning

confidence: 99%

Section: Steric and Electronic Effectsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Investigation of organometallic reaction mechanisms with one and two dimensional vibrational spectroscopy

Cahoon

2008

View full text Add to dashboard Cite

show abstract

Cobalt: Organometallic ChemistryBased in part on the article Cobalt: Organometallic Chemistry by Ulrich Koelle which appeared in theEncyclopedia of Inorganic Chemistry, First Edition.

Quisenberry

Hanusa

2005

Encyclopedia of Inorganic Chemistry

View full text Add to dashboard Cite

Among the longest known families of organometallic compounds, those of cobalt display great diversity in their structures and oxidation states. The ligands accommodated in organocobalt compounds range from strong σ‐donors such as hydrides and alkyls, to π‐acid ligands such as carbonyls and phosphines. The carbonyl cluster compounds of cobalt are numerous and they play a major role in catalytic reactions of enormous industrial importance such as hydroformylation reactions (conversion of alkenes to aldehydes) and Pauson–Khand cycloaddition (production of cyclic ketones). Cobalt is an electron‐rich late transition metal, a property reflected throughout its organometallic chemistry. Thus, the carbonyl ‘hydride’ HCo(CO) 4 is actually a strong acid and does not have ‘hydridic’ (H − ) properties. Similarly, cobalt does not complex to any group 15 or 16 heterocycles such as pyridine or thiophene. In contrast, boracycles are good ligands for cobalt in a sandwich complex because an electropositive atom such as boron incorporated in a π‐cyclic ring stabilizes the electron‐rich central metal. The cyclopentadienyl ligand is found extensively throughout organocobalt chemistry – not only in cobaltocenes, but also in half‐sandwich complexes of the type (C 5 H 5 )CoL 2 , where L is CO, alkene, alkyne, or phosphine. The (C 5 H 5 )CoL 2 complexes are useful in alkyne dimerization and trimerization. Cobaltocene itself ((C 5 H 5 ) 2 Co) is easily oxidized to the extraordinarily stable 18‐electron cobaltocenium cation, [(C 5 H 5 ) 2 Co] + . Cobalt can be incorporated into carborane cages, which have been found to be efficient extractors of radioactive metal ions such as 90 Sr and 137 Cs in water at low pH. Cobalamins, which consist of a cobalt central atom in a substituted corrin ring, are examples of naturally occurring organometallic compounds, and coenzyme B 12 was the first recognized example of a biological organometallic compound. Methylcobalamins play a role in biology, where they are found in microorganisms and can methylate mercury in the environment.

show abstract

Cobalt: Organometallic ChemistryBased in part on the article Cobalt: Organometallic Chemistry by Ulrich Koelle which appeared in theEncyclopedia of Inorganic Chemistry, First Edition.

Quisenberry

Hanusa

2005

Encyclopedia of Inorganic and Bioinorganic Chemistry

View full text Add to dashboard Cite

show abstract

Generation and spectroscopic characterization of new 18+δ electron complexes. Relationship between the stability of 18+δ electron organometallic complexes and their ligand reduction potentials

Cited by 37 publications

References 48 publications

Investigation of organometallic reaction mechanisms with one and two dimensional vibrational spectroscopy

Investigation of organometallic reaction mechanisms with one and two dimensional vibrational spectroscopy

Cobalt: Organometallic ChemistryBased in part on the article Cobalt: Organometallic Chemistry by Ulrich Koelle which appeared in theEncyclopedia of Inorganic Chemistry, First Edition.

Cobalt: Organometallic ChemistryBased in part on the article Cobalt: Organometallic Chemistry by Ulrich Koelle which appeared in theEncyclopedia of Inorganic Chemistry, First Edition.

Contact Info

Product

Resources

About