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Joseph G Cordaro

Publications and source records attributed to Joseph G Cordaro.

6 recordsLinked to original sources
PubMed2006

A synthetic cycle for the ruthenium-promoted formation of 1H-phosphindoles from phosphaalkynes.

Beginning with inexpensive and commercially available starting materials, a rational synthesis for the new phosphaalkyne Ph3C-C[triple bond]P (1) is presented. Coordination of 1 to group 8 transition metal centers furnishes the eta1-complexes [MH(dppe)2(Ph3CC[triple bond]P)]OTf, where M = Fe (3) or Ru (4) (dppe = bis-1,2-diphenylphosphinoethane). Treatment of 3 or 4 with a strong acid cyclizes the coordinated phosphaalkyne and is the first example of an electrophilic aromatic substitution reaction in which the electrophile is a low coordinate phosphorus. With the aid of DFT calculations, we were able to gain a more thorough understanding of the energetics and mechanism of this new cyclization reaction. Thermolysis of the iron-3,3-diphenyl-3H-phosphindole adduct (6) in CH3CN results in quantitative formation of the free 3H-phosphindole (7). Alternatively, when ruthenium-3,3-diphenyl-3H-phosphindole adduct (5) is irradiated, a photochemical rearrangement occurs furnishing 2,3-diphenyl-1H-phosphindole (9). Mechanistic work is presented that provides an explanation for this transformation. Compounds 1, 3, 5, and 9 have been characterized by single X-ray diffraction studies. Finally, a synthetic cycle for the conversion of 1 to 1H-phosphindole 9 has been developed that recycles the ruthenium cation [RuH(dppe)2]+.

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PubMed2004

Dissociation of carbanions from acyl iridium compounds: an experimental and computational investigation.

Instead of reductive elimination of aldehyde, or decarbonylation to give a trifluoroalkyl hydride, heating Cp(PMe(3))Ir(H)[C(O)CF(3)] (1) leads to the quantitative formation of Cp(PMe(3))Ir(CO) (2) and CF(3)H. Kinetic experiments, isotope labeling studies, solvent effect studies, and solvent-inclusive DFT calculations support a mechanism that involves initial dissociation of trifluoromethyl anion to give the transient ion-pair intermediate [Cp(PMe(3))Ir(H)(CO)](+)[CF(3)](-). Further evidence for the ability of CF(3)(-) to act as a leaving group came from the investigation of the analogous methyl and chloride derivatives Cp(PMe(3))Ir(Me)[C(O)CF(3)] and Cp(PMe(3))Ir(Cl)[C(O)CF(3)]. Both of these compounds undergo a similar loss of trifluoromethyl anion, generating an iridium carbonyl cation and CF(3)D in CD(3)OD. Three additional acyl hydrides, Cp(PMe(3))Ir(H)[C(O)R(F)] (where R(F) = CF(2)CF(3), CF(2)CF(2)CF(3), or CF(2)(CF(2))(6)CF(3)) undergo R(F)-H elimination to give 2 at a faster rate than CF(3)H elimination from 1. Stereochemical studies using a chiral acyl hydride with a stereocenter at the beta-position reveal that ionization of the carbanion occurs to form a tight ion-pair with high retention of configuration and enantiomeric purity upon proton transfer from iridium.

Journal Article↗
PubMed2004

Elimination of R-H from iridium acyl hydrides without loss of CO: evidence for the intervention of metal cation/carbanion pairs.

Instead of reductive elimination of aldehyde, or decarbonylation to give a trifluoroalkyl hydride, heating Cp*(PMe3)Ir(H)[C(O)CF3] leads to the quantitative formation of Cp*(PMe3)Ir(CO) and CF3H. Kinetic experiments, isotope-labeling studies, solvent effect studies, and DFT calculations support a mechanism which involves dissociation of trifluoromethyl anion to give the transient ion-pair intermediate [Cp*(PMe3)Ir(H)(CO)]+[CF3]-. Further evidence for the ability of CF3 to act as a leaving group came from investigation of the analogous methyl and chloride derivatives Cp*(PMe3)Ir(Me)[C(O)CF3] and Cp*(PMe3)Ir(Cl)[C(O)CF3]. Both of these compounds undergo a similar loss of trifluoromethyl anion, generating an iridium carbonyl cation and CF3D in CD3OD.

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