摘要:
The C-Cl bond cis oxidative addition of 12 chloroarenes, including chlorobenzene, chlorotoluenes, chlorofluorobenzenes, and di- and trichlorobenzenes to RhH{xant((PPr2)-Pr-i)(2)} (1; xant((PPr2)-Pr-i)(2) = 9,9-dimethyl-4,5-bis(diisopropylphosphino)xanthene) and the ability of the resulting rhodium(III) species to undergo reductive elimination reactions are reported. Complex 1 reacts with chlorobenzene to give RhHCl(C6H5){xant((PPr2)-Pr-i)(2)} (2), which eliminates benzene to afford RhCl{xant((PPr2)-Pr-i)(2)} (3). On the other hand, in the presence of potassium tert-butoxide ((KOBu)-Bu-t), it undergoes dehydrodechlorination to yield Rh(C6H5){xant((PPr2)-Pr-i)(2)} (4). The reactions of 1 with 3- and 4-chlorotoluenes lead to RhHCl(C6H4-3-Me){xant((PPr2)-Pr-i)(2)} (5) and RhHCl(C6H4-4-Me){xant((PPr2)-Pr-i)(2)} (6), respectively. Treatment of the acetone solutions of both compounds with. KOtBu also results in their dehydrodechlorination to give Rh(C6H4-3-Me){xant((PPr2)-Pr-i)(2)} (7) and Rh(C6H4-4-Me){xant((PPr2)-Pr-i)(2)} (8). Chlorofluorobenzenes undergo both C-Cl oxidative addition and C-H bond activation in a competitive manner. The amount of the C-H activation product increases as fluorine and chlorine are separated. Complex 1 reacts with o-chlorofluorobenzene to afford the C-Cl oxidative addition product RhHCl(C6H4-2-F){xant((PPr2)-Pr-i)(2)} (9). The reaction of 1 with m-chlorofluorobenzene leads to RhHCl(C6H4-3-F){xant((PPr2)-Pr-i)(2)} (10; 91%) and the C-H bond activation product Rh(C6H3-2-Cl-6-F){xant((PPr2)-Pr-i)(2)} (12; 9%), whereas p-chlorofluorobenzene gives a mixture of RhHCl(C6H4-4-F){xant((PPr2)-Pr-i)(2)} (13; 61%) and Rh(C6H3-3-Cl-6-F){xant((PPr2)-Pr-i)(2)} (15; 39%). The addition of (KOBu)-Bu-t to the acetone solutions of 9, 10, and 13 produces the HCl abstraction and the formation of Rh(C6H4-2-F){xant((PPr2)-Pr-i)(2)} (16), Rh(C6H4-3-F){xant((PPr2)-Pr-i)(2)} (17), and Rh(C6H4-4-F){xant((PPr2)-Pr-i)(2)} (18). In contrast to o-chlorofluorobenzene, 1,2-dichlorobenzene reacts with 1 to give RhHCl(C6H4-2-Cl){xant((PPr2)-Pr-i)(2)} (19; 32%), Rh(C(6)H(4)2-Cl){xant((PPr2)-Pr-i)(2)} (20; 51%) and Rh(C6H3-2,3-Cl-2){xant((PPr2)-Pr-i)(2)} (22; 17%).The reactions of 1 with 1,3- and 1,4-dichlorobenzene lead to the respective C-Cl bond oxidative addition products RhHCl(C6H4-3-Cl){xant((PPr2)-Pr-i)(2)} (23) and RhHCl(C6H4-4-Cl){xant((PPr2)-Pr-i)(2)} (24), which afford Rh(C6H4-3-Cl){xant((PPr2)-Pr-i)(2)} (25) and Rh(C6H4-4-Cl){xant((PPr2)-Pr-i)(2)} (26) by dehydrodechlorination with (KOBu)-Bu-t in acetone. Treatment of 1 with 1,2,3-, 1,2,4-, and 1,3,5-trichlorobenzenes leads to RhHCl(C6H3-2,3-Cl-2){xant((PPr2)-Pr-i)(2)} (27), RhHCl(C6H3-3,4-Cl-2){xant((PPr2)-Pr-i)(2)} (28), and RhHCl(C6H3-3,5-Cl-2){xant((PPr2)-Pr-i)(2)} (29). The addition of (KOBu)-Bu-t to acetone solutions of 27-29 affords 22, Rh(C6H3-3,4-Cl-2){xant((PPr2)-Pr-i)(2)} (30) and Rh(C6H3-3,5-Cl-2){xant((PPr2)-Pr-i)(2)} (31).