The title compounds ( 1, X=F; 2, X=Cl) were obtained in quantitative yield by refluxing together (NBu 4) 2[Pd 2(μ-Br) 2(C 6X 5) 4] and (NBu 4) 2[Pd 2(μ-Br) 2Br 4]. Treatment of 1 or 2 with AgClO 4 (Pd:Ag= 1:1) gave solutions which behaved as containing ‘Pd(C 6X 5)Br’. 1, 2 and the ‘Pd(C 6X 5)Br’ solutions were checked as precursors of mono-pentahalophenyl derivatives, yielding a variety of complexes [Pd(C 6X 5)Br(L-L)] (L-L=bipy, tmen, dpe, COD), [Pd(C 6X 5)BrL 2] (L= p-TolNH 2, py, PPh 3, AsPh 3, SbPh 3), [Pd 2(μ-Br) 2(C 6X 5) 2L 2] (X=F, L=AsPh 3; X=Cl, L=SbPh 3) and (NBu 4)[Pd(C 6X 5)Br 2L] (X=F, L= py, AsPh 3, SbPh 3; X=Cl, L= p-TolNH 2, py, PPh 3, AsPh 3, SbPh 3). The solutions of ‘Pd(C 6X 5)Br’ proved to be the best general precursors of complexes [Pd(C 6X 5)BrL 2] although complexes with OPPh 3 could not be obtained.