%0 Journal Article
%A Coletti, Cecilia
%A Gonsalvi, Luca
%A Guerriero, Antonella
%A Marvelli, Lorenza
%A Peruzzini, Maurizio
%A Reginato, Gianna
%A Re, Nazzareno
%D 2012
%T Electron-Poor Rhenium
Allenylidenes and Their Reactivity
toward Phosphines: A Combined Experimental and Theoretical Study
%U https://acs.figshare.com/articles/journal_contribution/Electron_Poor_Rhenium_Allenylidenes_and_Their_Reactivity_toward_Phosphines_A_Combined_Experimental_and_Theoretical_Study/2564482
%R 10.1021/om200083h.s001
%2 https://acs.figshare.com/ndownloader/files/4207570
%K triflate salt
%K rotamer
%K 1.2 equiv
%K Theoretical StudyThe reaction
%K PMe 3
%K allenylidene geometry
%K tripho
%K cationic allenylidene
%K nucleophilic PMe 3
%K PMePh 2.
%K phosphine PMePh 2
%K phosphonioalkynyl
%K phosphonioallenyl
%X The reaction of 1-(phenyl)-1-(p-nitrophenyl)-2-propyn-1-ol
with the Re(I) precursor [(triphos)(CO)2Re(OTf)] in dichloromethane
at 0 °C afforded the cationic allenylidene complex [(triphos)(CO)2Re{CCC(C6H5)(p-C6H4NO2)}]+ (3) as a dark burgundy red triflate salt after solvent
evaporation. The reaction of 3 with 1.2 equiv of the
phosphine PMePh2 at −40 °C led first to the
γ-phosphonioalkynyl complex [(triphos)(CO)2Re{CCCPh(p-C6H4NO2)(PMePh2)}]+ (5) (observed as a pair of distinct
rotamers, 5a,b) and then, on slow
increase of the temperature to 0 °C, to the α-phosphonioallenyl
complex [(triphos)(CO)2Re{C(PMePh2)CCPh(p-C6H4NO2)}]+ (6). On the other hand, the reaction of 3 with the more nucleophilic PMe3 at −60 °C
led to its complete transformation into a compound, suggested to be
the α-phosphonioallenyl derivative [(triphos)(CO)2Re{C(PMe3)CC(C6H5)(p-C6H4NO2)}]+ (7). To study the effect due to the strongly
electron withdrawing p-nitrophenyl substituent on
the allenylidene geometry, electronic structure, and reactivity with
phosphines, we performed theoretical calculations on 3 and other hypothetical p-nitro-substituted allenylidenes
as well as on the products and plausible intermediates of its reaction
with PMe3 and PMePh2. Finally, theoretical methods
were applied to shed light on the nature of the two rotamers observed
for the γ-phosphonioalkynyl complex 5.
%I ACS Publications