Substituent Effects on Reactions of [RhCl(COD)]₂ with Diazoalkanes

Abstract

The reactions of [RhCl­(COD)]2 with a series of diazoalkanes with different substitutents were investigated. The outcomes of the reactions were found to be substituent-dependent via four different pathways. (1) The reactions with diazoindenes produced η5-cyclopentadienyl complexes. (2) The reaction with diazofluorene produced a mixture of olefin and azine compounds. (3) The reactions with monosubstituted diazoalkanes RCHN2 (R = Ph, MeO2C) produced olefins RCHCHR. (4) The reaction with the disubstituted diazoalkane Ph2CN2 produced the azine Ph2CN–NCPh2 only. Computational studies have been carried out to understand the interesting substituent effect by comparing the kinetics and thermodynamics of the reaction pathways. It was found that the reactions with diazocyclopentadiene, diazoindene, and Ph2CN2 are kinetically controlled, while the reactions with RCHN2 and diazofluorene are both thermodynamically and kinetically controlled.

Synthesis of Overloaded Cyclopentadienyl Rhodium(III) Complexes via Cyclotetramerization of tert-Butylacetylene

“…In the absence of X-ray single-crystal data, the exact configuration of the separated enantiomeric complexes remained unknown (in other words, we do not know yet which of the TLC bands contained the R - 2a enantiomer and which contained S - 2a ). Nevertheless, this approach may be useful for the separation and determination of chiral purity of other related planar-chiral rhodium catalysts. , …”

“…Nevertheless, this approach may be useful for the separation and determination of chiral purity of other related planar-chiral rhodium catalysts. 28,29 We explored the catalytic activity of the rhodium(III) complexes 2a,b in several reactions. The reaction of O-pivaloylhydroxamate (5) with alkenes and alkynes was chosen as a classical example of a C−H activation process (Scheme 6).…”

Halide Effects on the Stability of Osmium Indenylidene Complexes: Isolation, Characterization, and Reactivities

“…Methanol, isopropyl alcohol, and acetone were bubbled with N 2 for over 10 min before use. [(η 6 -pcymene)OsCl 2 ] 2, 29 [(η 6 -p-cymene)RuCl 2 ] 2 , 30 CpRuCl(PPh 3 ) 2 , 31 and 3-tert-butyldiazoindene 9 were prepared by following the procedure described in the literature. All other reagents were purchased from commercial suppliers and used without further purification.…”

“…After the volatiles were removed under vacuum, the oily mixture was dissolved with 2 mL of i PrOH and transferred to a vigorously stirred i PrOH solution (3 mL) of NaBPh 4 (274 mg, 0.80 mmol) by cannula to precipitate a white solid, which was collected and washed quickly with i PrOH (3 mL × 2). To remove trace amounts of black impurities, the white solid was extracted with DCM (3 mL × 2) and the extract was filtered and concentrated to about 1 (9). To a stirred DCM (2 mL) solution of 4 (49 mg, 0.05 mmol) was added a DCM solution of 3-tert-butyldiazoindene (0.24 mL, 0.5 M, 0.12 mmol) dropwise.…”

“…The limited progress can be partially attributed to the fact that there have been essentially no reported examples of isolated mononuclear indenylidene complexes from stoichiometric reactions of diazoindenes with transition-metal complexes. Instead, the common products from the reported reactions are η 1 -N-coordinated diazo complexes or complexes derived from further reactions of the expected carbene complexes. − …”