The Organic Chemistry of the Transition Elements. Part I. Tricarbonylchromium Derivatives of Aromatic Compounds. by B. Nichollasn D M. C. Whiting.
[19593 Organic Chemistry of the Tramition Elements. Part
r.
View Online
551
Downloaded by University of Washington on 01 February 2011 Published on 01 January 1959 on http://pubs.rsc.org | doi:10.1039/JR9590000551
113. The Organic Chemistry of the Transition Elements. Part I.
Tricarbonylchromium Derivatives of Aromatic Compounds.
By B. NICHOLLS M. C. WHITING. and
Many aromatic compounds, ArH, displace carbon monoxide from chromium hexacarbonyl with the formation of complexes Cr(CO),(ArH) (I). These are stable and may carry any of several functional groups. The effects of the metallic residue upon typical properties of these groups and of the aromatic system as a whole are outlined, and methods for the regeneration of the aromatic components are described.
TRICARBONYLBENZENECHROMIUM (I) was first obtained by Fischer and Ofele in 27% yield from chromium hexacarbonyl and dibenzenechromium in benzene in a sealed system at 220". We had independently discovered a simpler and more general method for preparing compounds of this type which involves heating chromium hexacarbonyl under reflux in an excess of the aromatic compound or with a molar quantity in an inert solvent.
Shortly after our preliminary communication,2 Natta and his co-workers also described the direct preparation of several of these compounds, but used a pressurised system (with intermittent release of carbon monoxide) and higher temperatures (200-235"). The work of Fischer and his school shows that equilibria are involved in these reactions-an excess of carbon monoxide converts the dibenzenechromium complex into the hexacarbonyl-and therefore it is advantageous in principle, as well as much easier in practice, to employ an open system, the free escape of carbon monoxide then driving the reaction to completion. In early experiments decalin was employed as solvent, but because the commercial product contains tetralin as an impurity, and perhaps because of hydrogen-transfer processes,
r.
View Online
551
Downloaded by University of Washington on 01 February 2011 Published on 01 January 1959 on http://pubs.rsc.org | doi:10.1039/JR9590000551
113. The Organic Chemistry of the Transition Elements. Part I.
Tricarbonylchromium Derivatives of Aromatic Compounds.
By B. NICHOLLS M. C. WHITING. and
Many aromatic compounds, ArH, displace carbon monoxide from chromium hexacarbonyl with the formation of complexes Cr(CO),(ArH) (I). These are stable and may carry any of several functional groups. The effects of the metallic residue upon typical properties of these groups and of the aromatic system as a whole are outlined, and methods for the regeneration of the aromatic components are described.
TRICARBONYLBENZENECHROMIUM (I) was first obtained by Fischer and Ofele in 27% yield from chromium hexacarbonyl and dibenzenechromium in benzene in a sealed system at 220". We had independently discovered a simpler and more general method for preparing compounds of this type which involves heating chromium hexacarbonyl under reflux in an excess of the aromatic compound or with a molar quantity in an inert solvent.
Shortly after our preliminary communication,2 Natta and his co-workers also described the direct preparation of several of these compounds, but used a pressurised system (with intermittent release of carbon monoxide) and higher temperatures (200-235"). The work of Fischer and his school shows that equilibria are involved in these reactions-an excess of carbon monoxide converts the dibenzenechromium complex into the hexacarbonyl-and therefore it is advantageous in principle, as well as much easier in practice, to employ an open system, the free escape of carbon monoxide then driving the reaction to completion. In early experiments decalin was employed as solvent, but because the commercial product contains tetralin as an impurity, and perhaps because of hydrogen-transfer processes,