ROOM-TEMPERATURE HYDRODEBROMINATION OF 4,4'-DIBROMOBIPHENYL CATALYZEDBY 1,1'-BIS(DIPHENYLPHOSPHINO) FERROCENE COMPLEXES OF PALLADIUM

Hydrodebromination of 4,4'-dibromobiphenyl to 4-bromobiphenyl and biph enyl was studied by using a variety of metal complexes of Ru(IT), Ni(I I), Pd(II), Pt(II) and Cu(I) under different ligand environments. Pall adium complexes are most effective in giving biphenyl whereas other co mplexes give 4-bromobiphenyl. 1,1'-Bis(diphenylphosphino)ferrocene (dp pf) is the best phosphine ligand whereas NaBH4 and N,N,N',N'-tetrameth ylethylenediamine are the best reductant and base, respectively. The u se of catalytic PdCl2(CH3CN)(2) and PdCl2(dppf) gives 4-bromobiphenyl (86%) and biphenyl (100%) respectively. PdCl2(dppf) is effective even at a low concentration of 3.5 mol.% and at room temperature (r.t.) wit h a short reaction time (10 min) and performs better than Pd on charco al (5%). It also leads to a complete breakdown of 4-monobromobiphenyl and decabromobiphenyl giving 100% of biphenyl in 4 min and 40 h, respe ctively. (C) 1998 Elsevier Science B.V. All rights reserved.