Mono- and DipalladatedDerivatives of 2,5-Distyrylbenzene.Reactivity toward XyNC and Alkynes. Synthesis of Complexes with IndacenediideLigands.

Thedinuclear complexes[C6H2{PdBr(N∧N)}2-1,4-((E)-CHCHPh)2-2,5] (N∧N = tbbpy= 4,4′-di-tert-butyl-2,2′-bipyridine(1a), tmeda = N,N,N′,N′-tetramethylethylenediamine(1b)) have been synthesized by oxidative addition of trans,trans-2,5-distyryl-2,4-dibromobenzene to 2 equiv of“[Pd(dba)2]” (dba = dibenzylideneacetone)in the presence of the N∧N ligands. A similar reactionwith N∧N = bpy = 2,2′-bipyridine affordedthe mononuclear complex [PdBr{C6H2(Br-4){((E)-CHCHPh)2-2,5}(bpy)] (2). The reaction of 1a,bwith PhCCPh,MeCCMe, and PhCCMe in the presence of TlOTf or AgClO4gave the dipalladated indacenediide complexes [(μ-η,η-C12H2Bn2-1,5-R4-2,3,6,7){Pd(N∧N)}2](OTf)2(Bn = benzyl, R =Ph, N∧N = tbbpy (3a), tmeda (3b); R = Me, N∧N = tbbpy (4a), tmeda (4b)) and [(μ-η,η-C12H2Bn2-1,5-Ph2-2,6-Me2-3,7){Pd(N∧N)}2](A)2(N∧N = tbbpy, A = OTf (5a), ClO4(5a′); N∧N = tmeda,A = OTf (5b)). The reactions of 2with thesame alkynes afforded the indenyl complexes [Pd(η-C9H2Bn-1-R2-2,3-((E)-CHCHPh)-5-Br-6)(bpy)](A)(R = Ph, A = OTf (6), ClO4(6′); R = Me, A = OTf (7)) and [Pd(η-C9H2Bn-1-Ph-2-Me-3-((E)-CHCHPh)-5-Br-6)(bpy)]OTf(8). By reaction of either 1aor 1bwith XyNC (Xy = 2,6-dimethylphenyl) the dinuclear complex [C6H2{C(NXy){PdBr(CNXy)2}2-1,4-((E)-CHCHPh)2-2,5] (9) was obtained, while the oxidative addition of trans,trans-2,5-distyryl-2,4-dibromobenzene to [Pd(dba)2] in the presence of 8 equiv of XyNC afforded the dinuclearcomplexes [C6H2{C(NXy){C(NXy)}2{PdBr(CNXy)}}2-1,4-((E)-CHCHPh)2-2,5] (10, 10*) as a mixture ofisomers (1:0.3 ratio) which are in slow exchange in solution, as shownby an EXSY spectrum. The crystal structures of a-3a·7CDCl3, s-3b·CH2Cl2, a-5a′·4CH2Cl2, 6, and 8have been determined by X-raydiffraction studies. [ABSTRACT FROM AUTHOR]