Single and Multiple Insertion of Arylallene into the Rh−H Bond To Give (π-Allyl)rhodium Complexes

The reaction of RhH(PPh 3 ) 4 at room temperature with excess phenylallene, (4-methylphenyl)allene, (4-methoxyphenyl)allene, (4- tert -butylphenyl)allene, (4-chlorophenyl)allene, and (4-fluorophenyl)allene results in the insertion of four arylallene molecules into the Rh−H bond to afford Rh{η 3 -CH 2 C[CH(Ar)]C( CHAr)CH 2 C( CHAr)CH 2 CH 2 CH CHAr)}(PPh 3 ) 2 ( 1, Ar = C 6 H 5; 2, Ar = C 6 H 4 Me- p; 3, Ar = C 6 H 4 OMe- p; 4, Ar = C 6 H 4 - t -Bu- p; 5, Ar = C 6 H 4 Cl- p; 6, Ar = C 6 H 4 F- p ), respectively. NMR ( 1 H, 13 C, and 31 P) spectroscopy was used to characterize the (π-allyl)rhodium(I) complexes. Reaction of (4-methoxyphenyl)allene with RhD(PPh 3 - d 15 ) 4 gives 3 - d 31, Rh{η 3 -CH 2 C[CH(Ar)]C( CHAr)CH 2 C( CHAr)CH 2 CH 2 CD=CHAr)}(PPh 3 - d 15 ) 2 (Ar = C 6 H 4 OMe- p ), whose vinylene hydrogen is deuterated selectively. Complexes 1 and 3 do not react further with arylallene at room temperature. Reaction of arylallenes with an equimolar amount of RhH(CO)(PPh 3 ) 3 leads to the insertion of a molecule into the Rh−H bond to give the (π-allyl)rhodium complexes Rh(η 3 -CH 2 CHCHC 6 H 4 X- p )(CO)(PPh 3 ) 2 ( 9, X = Me; 10, X = OMe; 11, X = F; 12, X = Cl), while excess phenylallene reacts with the hydridorhodium complex to give a mixture of 1, Rh(η 3 -CH 2 CHCHPh)(CO)(PPh 3 ) 2, and unreacted RhH(CO)(PPh 3 ) 3 . A crystallographic study of 9 and 1 H NMR data for the complexes indicate that the aryl substituent has a syn orientation. The π-allyl complexes react with monosubstituted acetylenes to give trans -Rh(C⋮CZ)(CO)(PPh 3 ) 2 ( 13, Z = Ph; 14, Z = C 6 H 4 Me- p; 15, Z = SiMe 3 ) accompanied by the generation of 1-arylpropene.