Iridium(III)–vinylidene chemistry: Conversion of an iridacyclopentadiene-chlorido complex and terminal alkynes to iridacyclopentadiene–vinyl complexes

• Published in: Inorganica Chimica Acta Vol. 361; no. 11; pp. 3033 - 3041
• Main Authors: O’Connor, Joseph M., Wenzel, Anna G., Hiibner, Kristin
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 27-07-2008
• Subjects: 2-Propyn-1-ol; Allenol; Allenylidene complex; Allenylidene ligand; Cycloaromatization; Enolallenyl ligand; Iridacyclopentadiene; Iridium complexes; Iridium(III)–vinylidene; Iridium–vinyl complexes; Metallacycle; Metallacyclopentadiene; Oxygen-18 labeling; Propargyl alcohol; Trimethyl 1,3-dihydro-3-oxo-4,5,6-isobenzofurantricarboxylate; Allenylidene complex; Allenol; Propargyl alcohol; Allenylidene ligand; Metallacyclopentadiene; Iridium–vinyl complexes; 2-Propyn-1-ol; Iridium complexes; Oxygen-18 labeling; Iridacyclopentadiene; Enolallenyl ligand; Metallacycle; Iridium(III)–vinylidene; Cycloaromatization; Trimethyl 1,3-dihydro-3-oxo-4,5,6-isobenzofurantricarboxylate
• ISSN: 0020-1693; 1873-3255
• DOI: 10.1016/j.ica.2007.12.019

Under anhydrous conditions, reaction of [κ
2(
C
1,
C
4)-CR
CRCR
CR](PPh
3)
2Ir(Cl) and 2-propyn-1-ol generates a [2
+
2
+
2] cycloaromatization product. Under aqueous conditions the same reactants form iridium–vinyl complexes bearing the general structure [κ
2(
C
1,
C
4)-CR
CRCR
CR](PPh
3)
2Ir(CO)(κ
1-vinyl). In these, the CO ligand is derived from a terminal alkyne carbon and an oxygen atom from water.
The reactions of [κ
2(
C
1,
C
4)-CR
CRCR
CR](PPh
3)
2Ir(Cl) (
9, R
=
CO
2Me) with propargyl alcohol derivatives (2-propyn-1-ol, 2-methyl-3-butyn-2-ol, 1-ethynylcyclopentanol, and 1-ethynylcyclooctanol), in the presence of water leads to the formation of iridium(III)–vinyl complexes bearing the general structure [κ
2(
C
1,
C
4)-CR
CRCR
CR](PPh
3)
2Ir(CO)(κ
1-vinyl) where vinyl
=
–CH
CH
2, -(
E)-CH
CHMe, –CH
C(CH
2)
4, or –CH
C(CH
2)
7. In these, the CO ligand was derived from the terminal carbon of the starting alkyne and the oxygen atom from water. Under anhydrous conditions,
9 undergoes reaction with 2-propyn-1-ol to give trimethyl 1,3-dihydro-3-oxo-4,5,6-isobenzofurantricarboxylate, the result of a cycloaromatization/transesterification involving the buta-1,3-dien-1,4-diyl ligand in
9 and 2-propyn-1-ol.