Transition-metal–carbon bonds. Part 43. Some long-chain and large-ring complexes of nickel, palladium, or platinum with tetramethylene- and hexamethylene-dioxydiphenyl
The dibromo-ethers 1,4-bis(o-bromophenoxy)butane and 1,6-bis(o-bromophenoxy)hexans are dilithiated by n-butyl-lithium (halogen–metal exchange). The dilithio-derivative LiC6H4O[CH2]4OC6H4Li (Li2L) reacts with trans-[NiBr2Y2](Y = PEt2Ph or PEt3) to give yellow [NiLY2] where L acts as a trans-bonded bidentate chelate giving an 11 -membered ring. In contrast, LiC6H4O[CH2]6OC6H4Li (Li2L′) gives a green unidentified product. Corresponding complexes of platinum are not formed : instead binuclear species of the type [Y2XPt(C6H4O[CH2]nOC6H4) PtY2X](X = Br or I) are obtained (Y = PEt2Ph, PMe2But, or AsMe2But). The dibromo-complexes [(ButMe2P)2XPt(C6H4O[CH2]nOC6H4)PtX(PMe2But)2](X = Br) react with Na[BH4] to give the corresponding dihydrides (X = H). Palladium complexes of the type [(Et3P)2XPd(C6H4O[CH2]4OC6H4)PdX(PEt3)2](X = Cl or Br) have also been synthesized. Treatment of trans-[PdBr2(PEt3)2] with Li2L(1 : 1 mol proportion) gives an impure product of the approximate composition [{PdL(PEt3)2}x](x= ?). Hydrogen-1 and 31P n.m.r. data and i.r. data are given.