Formation of Indanone from an Iridanaphthalene Complex

Abstract

The first example of evolution of an iridanaphthalene into an indanone through an intermediate indenyl is reported, serving as a good example of starting material to obtain indanones. Two new iridanaphthalenes are obtained by intramolecular C−H activation of a phenyl ring of a carbene ligand in [IrCp*{C(OMe)CHCPh 2 }(L)]PF 6 (L = PPh 2 Me, PMe 3 ) complexes. It is demonstrated that these iridanaphthalene complexes can undergo a thermal reaction to give indenyl complexes and 3-phenylindanone.M etallacyclic aromatic compounds incorporating transition metals are a subject of great interest, since they display a behavior that includes properties from both aromatic organic and organometallic compounds. Although many metallabenzenes of osmium, iridium, platinum, and ruthenium are known, to the best of our knowledge only two metallanaphthalenes have been reported, one with osmium 1 and another with iridium. 2 The importance of this type of metal-organic functionality is emphasized by the fact that metal cyclopentadienyls can be formed from transitory metallabenzenes. 3 Analogously, an osmanaphthalene has been proposed as intermediate leading to an indenyl complex. 4 Recently, we have reported that the new (methoxy)-alkenylcarbeneiridium complex [IrCp*Cl{C(OMe)CH CPh 2 }(PPh 2 Me)]PF 6 (1a) reacts with amines to undergo the unexpected cleavage of the O−CH 3 bond instead of the usual aminolysis. 5 This peculiar behavior has prompted us to further explore the reactivity of these types of compounds. Here, we report that treatment of [IrCp*Cl{C(OMe)CHCPh 2 }-(L)]PF 6 (L = PPh 2 Me (1a), PMe 3 (1b)) with AgPF 6 gives high yields of the iridanaphthalene complexes [IrCp*{C(OMe)-CHC(o-C 6 H 4 )(Ph)}(L)]PF 6 (L = PPh 2 Me (2a), PMe 3 (2b)) through an intramolecular C−H activation of one of the phenyl rings of the carbene ligand (eq 1).The structures of both iridanaphthalene complexes have been confirmed by single-crystal X-ray diffraction (see the Supporting Information). Figure 1 shows the complex cation 2a. The iridium atom becomes part of a metallanaphthalene moiety and the metal coordination sphere is completed with a pentamethylcyclopentadienyl (Cp*) and a phosphane ligand.The NMR spectra support the solid-state structures of 2a,b (see the Supporting Information).Remarkably, the iridanaphthalene moiety is not stable and refluxing 2 in 1,2-dichloroethane or toluene for 24 h gives 3-phenylindanone (4) (eq 2). The same transformation occurs also at longer reaction times in dichloromethane at 35°C (eq 2).

A Metallaanthracene and Derived Metallaanthraquinone

“…the protonated metallabenzofuran, II). [10] As yet the chemical reactivity of these metallanaphthalenes has scarcely been explored. [6] Them etalla-analogues of the simple linear polycyclic aromatic hydrocarbons (Scheme 1) are fused-ring metallabenzenes that fall under category (A).…”

“…Compounds of class (B) in which one end of the fused ring is bound to the metal have been referred to as "tethered" metallabenzenes. [8,10] Only one related tricyclic metallaaromatic hydrocarbon has been reported and that is the lithium salt of ar uthenaphenanthrene oxide.T his compound, which was detected in solution spectroscopically at low temperatures,decomposes above 0 8 8C. Currently,t he only isolated examples of this type are metallanaphthalenes.T wo of the three possible isomers of these compounds (a-c, that is, metal at positions a-c in Scheme 1) have been reported.…”

A Metallaanthracene and Derived Metallaanthraquinone

“…A small set of closely related iridanaphthalenes of isomer a have been prepared by insertion of alkenes into a benzannelated iridacyclopentadiene . In addition, metallanaphthalenes of isomer b have been prepared through oxidation of a fused‐ring iridacyclohexadiene, by rearrangement of an osmium vinyl carbyne complex, and by intramolecular C−H activation of a phenyl substituted alkenylcarbeneiridium complex . As yet the chemical reactivity of these metallanaphthalenes has scarcely been explored .…”

“…[7] In addition, metallanaphthalenes of isomer b have been prepared through oxidation of af usedring iridacyclohexadiene, [8] by rearrangement of an osmium vinyl carbyne complex, [9] and by intramolecular CÀHa ctivation of ap henyl substituted alkenylcarbeneiridium complex. [10] As yet the chemical reactivity of these metallanaphthalenes has scarcely been explored. [8,10] Only one related tricyclic metallaaromatic hydrocarbon has been reported and that is the lithium salt of ar uthenaphenanthrene oxide.T his compound, which was detected in solution spectroscopically at low temperatures,decomposes above 0 8 8C.…”

Reactions of Metal–Carbon Bonds within Six‐Membered Metallaaromatic Rings

“…In addition, we have shown that heating a solid sample of ruthenabenzene 4 at 150 °C gave a free cyclopentadienyl derivative 51 . In 2013, Bolaño and co‐workers reported the formation of an indanone starting from an α‐OMe substituted iridanaphthalene . It was proposed that the transformation involves the initial carbene migratory insertion to form the 16e intermediate AD .…”