Novel C−C and C−C−P Coupling Reactions Using an Allenylidenerhodium Complex as a Precursor

A Novel Route to Cationic Four-Coordinate Rhodium(I) Complexes with Rh=C Bonds

“…Following the synthesis of the first square-planar structure analysis of a cationic rhodium compound with RhϭCϭCϭCPh 2 as a molecular unit, and an alternative allenylidenerhodium(I) complex trans-[RhCl(ϭCϭCϭ CPh 2 )(PiPr 3 ) 2 ], [1] we have recently shown that rhodium al-preparative route to neutral species with X Ϫ instead of LЈ as ligands coordinated to rhodium(I). lenylidenes of this particular type are useful tools for the generation of metal bound species that are hardly accessible by other preparative routes.…”

“…lenylidenes of this particular type are useful tools for the generation of metal bound species that are hardly accessible by other preparative routes. [2] After having characterized a ؉ OAc, OTos), [3] we became interested to find out whether also four-coordinate cationic allenylidenerhodium(I) com-…”

“…The procedure which we recently used for the synthesis plexes [Rh(L)(ϭCϭCϭCRRЈ)(PiPr 3 ) 2 ] ϩ (L ϭ two-electron of the above-mentioned compounds trans-[Rh(py)(L)-donor ligand) can be obtained. Recent attempts from our (PiPr 3 ) 2 ]X with L ϭ CO, C 2 H 4 and CϭCHR [5] turned out laboratory with the aim to prepare the cation trans-[Rh(ϭ to be not the method of choice for L ϭ CϭCϭCPh 2 .…”

“…Recent attempts from our (PiPr 3 ) 2 ]X with L ϭ CO, C 2 H 4 and CϭCHR [5] turned out laboratory with the aim to prepare the cation trans-[Rh(ϭ to be not the method of choice for L ϭ CϭCϭCPh 2 . TreatCϭCϭCPh 2 ) 2 (PiPr 3 ) 2 ] ϩ unexpectedly led, via a novel CϪC ment of the mixture of [Rh(η 3 -C 3 H 5 )(PiPr 3 ) 2 ] and coupling, to the formation of two isomeric hexapentaene-[pyH]BF 4 with the propargylic alcohol HCϵCCPh 2 OH in rhodium(I) compounds of which the isomer having the acetone at room temperature led, within a short period of polyene coordinated in an unsymmetrical fashion is the time, to the formation of a deep red solution from which a thermodynamically more stable. [4] However, after we found red, moderately air-sensitive solid was obtained after rethat carbonyl-, ethene-and even vinylidenerhodium deriva-moval of the solvent.…”

“…[4] However, after we found red, moderately air-sensitive solid was obtained after rethat carbonyl-, ethene-and even vinylidenerhodium deriva-moval of the solvent. According to the NMR spectra it contives such as trans-[Rh(py)(L)(PiPr 3 ) 2 ] ϩ and trans-sisted mainly of our target, the allenylidene complex trans-[Rh(NH 3 )(L)(PiPr 3 ) 2 ] ϩ (L ϭ CO, C 2 H 4 , CϭCHR) are ac-[Rh(py)(ϭCϭCϭCPh 2 )(PiPr 3 ) 2 ]BF 4 but also contained cessible and, with BF 4 Ϫ or PF 6 Ϫ as counterion, stable un-some impurities. Despite several attempts these could not der ambient conditions, [5] we felt encouraged to prepare be completely separated from the dominating species.…”