Phosphorus-containing cobalt carbonyls III. Monosubstituted derivatives of dicobalt octacarbonyl with phosphines and phosphites

Tris(μ2-carbonyl)octacarbonyl(triphenylphosphite)tetracobalt

In toluene solution, the reaction of [Co2(CO)8] with an equimolar amount of [P(OPh)3] yields first [Co2(CO)7{P(OPh)3}] 1. Following heating of 1, an alternative synthetic access to the tetranuclear cluster [{Co4(μ2-CO)3(CO)8{P(OPh)3}] 2 is provided in a condensation reaction. Compound 2 has been characterized by IR and 31P NMR spectroscopy. The tetranuclear cluster framework has been ascertained by a single-crystal X-ray diffraction study performed at 100 K.

Coordinated “Naked” Pnicogenes and Catalysis

Diphosphorous (P2) side-on coordinated to a dicobalt (Co–Co) moiety was described 45 years ago. This discovery had several links to actual problems of homogeneous molecular catalysis. The new type of organometallic complexes induced several ingenious new ramifications in main-group/transition metal cluster chemistry in the last decades. The present review traces the main lines of these research results and their contacts to actual problems of industrial catalysis.

A "catch-and-release" protocol for alkyne-tagged molecules based on a resin-bound cobalt complex for peptide enrichment in aqueous media

The development of new and mild protocols for the specific enrichment of biomolecules is of significant interest from the perspective of chemical biology. A cobalt-phosphine complex immobilised on a solid-phase resin has been found to selectively bind to a propargyl carbamate tag, that is, "catch", under dilute aqueous conditions (pH 7) at 4 °C. Upon acidic treatment of the resulting resin-bound alkyne-cobalt complex, the Nicholas reaction was induced to "release" the alkyne-tagged molecule from the resin as a free amine. Model studies revealed that selective enrichment of the alkyne-tagged molecule could be achieved with high efficiency at 4 °C. The proof-of-concept was applied to an alkyne-tagged amino acid and dipeptide. Studies using an alkyne-tagged dipeptide proved that this protocol is compatible with various amino acids bearing a range of functionalities in the side-chain. In addition, selective enrichment and detection of an amine derived from the "catch and release" of an alkyne-tagged dipeptide in the presence of various peptides has been accomplished under highly dilute conditions, as determined by mass spectrometry.

A Study of (Binap)(enyne)tetracarbonyldicobalt(0) Complexes

Four (binap)(enyne)tetracarbonyldicobalt(0) complexes have been synthesised and their reactivity monitored by variable temperature (31)P NMR spectroscopy. Formation of (binap)dicarbonylhydridocobalt(-1) 12 occurred at temperatures between 35 and 55 degrees C, depending on the nature of the alkene and alkyne components of the enyne. The structure of 12 was determined by X-ray crystallography, and its presence under Pauson-Khand reaction conditions was verified by NMR spectroscopy.