Application of an indenyl molybdenum dicarbonyl complex in the isomerisation of α-pinene oxide to campholenic aldehyde

Abstract

The complex [{(Z 5 -Ind)Mo(CO) 2 (m-Cl)} 2 ] (1) has been tested for the industrially relevant catalytic isomerisation of a-pinene oxide (PinOx) to campholenic aldehyde (CPA) in the liquid phase. PinOx conversion and CPA selectivity are strongly influenced by the solvent employed. Complete conversion of PinOx was achieved within 1 min at 55 1C or 30 min at 35 1C using 1,2-dichloroethane as solvent, giving CPA in 68% yield.Other products included trans-carveol, iso-pinocamphone and trans-pinocarveol. The stability of 1 under the reaction conditions used was investigated by using FT-IR spectroscopy and electrospray ionisation mass spectrometry (ESI-MS) to characterise recovered solids. In the presence of air/moisture 1 undergoes oxidative decarbonylation upon dissolution to give oxomolybdenum species that are proposed to include a tetranuclear oxomolybdenum(V) complex. Conversely, ESI-MS studies of 1 dissolved in dry acetonitrile show mononuclear species of the type [IndMo(CO) 2 (CH 3 CN) n ] + . The crystal structure of the ring-slipped dicarbonyl complex [(Z 3 -Ind)Mo(CO) 2 Cl(CH 3 CN) 2 ] (2) (obtained after dissolution of 1 in acetonitrile) is reported.

Indenyl Compounds with Constrained Hapticity: The Effect of Strong Intramolecular Coordination

“…High values of the envelop fold angle [ Ω = 25.0(5)–26.3(6)°] and Δ(M–C) [0.830(5)–0.871(4) Å], observed for the indenyl ligand, verify the η 3 ‐coordination mode. The indenyl ligand takes a configuration with the C 6 ring above the carbonyl ligands, which is common for hexacoordinate molybdenum compounds without intramolecular coordination , , . The η 3 : κN ‐coordination mode of the functionalized indenyl ligand is unprecedented.…”

“…Due to short intramolecular bridge, the pyridine arm and indenyl are in The indenyl ligand takes configuration with C6-ring above carbonyls that is common for the hexacoordinated molybdenum compounds without intramolecular coordination. [12,13,20] The η 3 :κN-coordination mode of the s functionalized indenyl ligand is unprecedented. Hence, the more conventional η 5 :κN was reported for number of lanthanide [21] and group IV metal compounds.…”

Catalytic isomerisation of α-pinene oxide in the presence of ETS-10 supported ferrocenium ions

“…Recently, we started to explore organometallic complexes for the catalytic isomerisation of a-pinene oxide (PinOx) to campholenic aldehyde (CPA), a reaction that is usually promoted by Lewis acid catalysts. Encouraging results were obtained for the indenyl allyl dicarbonyl derivative (h 5 -Ind)Mo(h 3 -C 3 H 5 )(CO) 2 [32], the dimeric complex [{(h 5 -Ind)Mo(CO) 2 (m-Cl)} 2 ] [33] and methyltrioxorhenium(VII) [34]. CPA is useful as an aroma chemical and as a synthetic intermediate for other aroma chemicals and also for some pharmaceuticals [35,36].…”

Efficient Isomerization of α-Pinene Oxide to Campholenic Aldehyde Promoted by a Mixed-Ring Analogue of Molybdenocene

“…We have determined that molybdenum dicarbonyl, tricarbonyl and tetracarbonyl complexes can effectively promote the isomerization of PinOx to CPA, [21][22][23] and the alcoholysis of epoxides. [23][24][25] All the complexes studied led to 100% selectivity towards 2-ethoxy-2phenylethanol (EPE) in the ethanolysis of styrene oxide (StyOx), with the η 5 -indenyl complex [IndMo(CO) 2 (MeCN) 3 ]BF 4 being particularly active (full conversion after 1 min at 35 °C).…”