An Organotin Route for the Preparation of 2,6‐Bis(diphenylphosphino)bromo‐benzene and the Related Bis(Phosphine Oxide). Precursors for Novel Ligands

The 2,6‐difluorophenyltrialkylstannanes 2,6‐F 2 C 6 H 3 SnR 3 ( 1 , R=Me; 2 , R=Bu) were prepared from commercial products. With Ph 2 PLi, 1 and 2 underwent nucleophilic substitution to give the 2,6‐bis(diphenylphosphino)phenyltrialkylstannanes 2,6‐(Ph 2 P) 2 C 6 H 3 SnR 3 ( 3 , R=Me; 4 , R=Bu). The reaction of 3 with n ‐BuLi and BrCH 2 CH 2 Br afforded 2,6‐bis(diphenylphosphino)bromobenzene (2,6‐(Ph 2 P) 2 C 6 H 3 Br, 5 ), the oxidation of which gave the related bis(phosphine oxide) 2,6‐[Ph 2 P(O)] 2 C 6 H 3 Br ( 6 ). The reaction of 5 with n ‐BuLi gave rise to the formation of 2,6‐bis(diphenylphosphino)phenyl lithium, 2,6‐(Ph 2 P) 2 C 6 H 3 Li ( 7 ). Attempts to prepare the related bis(phosphine oxide) 2,6‐[Ph 2 P(O)] 2 C 6 H 3 Li ( 8 ) from 6 in a similar way at low temperatures was hampered by decomposition. Compounds 3 , 5 and 7 hold potential for a new anionic tridentate PCP−coordinating ligand, namely, the bis(2,6‐diphenyl)phosphinophenyl ion [2,6‐(Ph 2 P) 2 C 6 H 3 ] − .