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

Abstract

The 2,6‐difluorophenyltrialkylstannanes 2,6‐F2C6H3SnR3 (1, R=Me; 2, R=Bu) were prepared from commercial products. With Ph2PLi, 1 and 2 underwent nucleophilic substitution to give the 2,6‐bis(diphenylphosphino)phenyltrialkylstannanes 2,6‐(Ph2P)2C6H3SnR3 (3, R=Me; 4, R=Bu). The reaction of 3 with n‐BuLi and BrCH2CH2Br afforded 2,6‐bis(diphenylphosphino)bromobenzene (2,6‐(Ph2P)2C6H3Br, 5), the oxidation of which gave the related bis(phosphine oxide) 2,6‐[Ph2P(O)]2C6H3Br (6). The reaction of 5 with n‐BuLi gave rise to the formation of 2,6‐bis(diphenylphosphino)phenyl lithium, 2,6‐(Ph2P)2C6H3Li (7). Attempts to prepare the related bis(phosphine oxide) 2,6‐[Ph2P(O)]2C6H3Li (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‐(Ph2P)2C6H3]−.