LS2 9JT The dibromo-ethers 1,4-bis(o-bromophenoxy)butane and 1,6-bis(o-bromophenoxy) hexana are dilithiated by n-butyl-lithium (halogen-metal exchange). The dilithio-derivative LiC6H40 [CH,I40CsH4Li (Li,L) reacts with trans-[NiBr,Y,J (Y = PEt,Ph or PEt,) to give yellow [NiLY,] where L acts as a trans-bonded bidentate chelate giving an 11 -membered ring. In contrast, LiC6H40[CH2]&C6H4Li (Li,L') gives a green unidentified product. Corresponding complexes of platinum are not formed : instead binuclear species of the type [Y,XPt(C6H40 [CH,],,-OC6H4)PtY,X] (X = Br or I) are obtained ( Y = PEt,Ph. PMe,But. or AsMe2But). The dibromo-complexes [(But-Me,P),XPt(C6H,0[CH2],0C6H4)PtX(PMe,But)2] (X = Br) react with Na[BH,] to give the corresponding dihydrides (X = H). Palladium complexes of the type [(Et,P)2XPd(C6H40[CH2]40C6H4)PdX(PEt,),] (X = CI or Br) have also been synthesized. Treatment of trans-[ PdBr2( PEt3),] with Li,L( 1 : 1 mol proportion) gives an impure product of the approximate composition [(PdL(PEt,),},] ( x = ?). Hydrogen-1 and 31P n.m.r. data and i.r. data are given. SEVERAL transition-metal complexes are now known which have a large chelate ring involving a tram-bonded bidentate ligand. Most of these large rings have two tertiary phosphine donor atoms ; e.g. we have prepared from 12-to 45-membered rings using the flexible diphosphines But2P[CH2].PBut2 (n = 8-10 or 12) with t No reprints available.