Mono- and Dipalladated Derivatives of 2,5-Distyrylbenzene. Reactivity toward XyNC and Alkynes. Synthesis of Complexes with Indacenediide Ligands

The
dinuclear 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 reaction
with N∧N = bpy = 2,2′-bipyridine afforded
the mononuclear complex [PdBr­{C6H2(Br-4)­{((E)-CHCHPh)2-2,5}­(bpy)] (2). The reaction of 1a,b with PhCCPh,
MeCCMe, and PhCCMe in the presence of TlOTf or AgClO4 gave 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 2 with the
same 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 1a or 1b with 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 dinuclear
complexes [C6H2{C­(NXy)­{C­(NXy)}2{PdBr­(CNXy)}}2-1,4-((E)-CHCHPh)2-2,5] (10, 10*) as a mixture of
isomers (1:0.3 ratio) which are in slow exchange in solution, as shown
by an EXSY spectrum. The crystal structures of a-3a·7CDCl3, s-3b·CH2Cl2, a-5a′·4CH2Cl2, 6, and 8 have been determined by X-ray
diffraction studies.

双核金属配合物[C₆H₂{PdBr(N∧N)}₂-1,4-((E)-CH=CHPh)₂-2,5]（其中N∧N = tbbpy = 4,4'-二叔丁基-2,2'-联吡啶(1a)，tmeda = N,N,N',N'-四甲基乙二胺(1b)）通过反,反-2,5-二苯乙烯基-2,4-二溴苯与2当量的“[Pd(dba)₂]”（dba = 二亚苄基丙酮(dibenzylideneacetone)）在N∧N配体存在下发生氧化加成反应合成得到。当使用N∧N = bpy = 2,2'-联吡啶进行类似反应时，得到单核金属配合物[PdBr{C₆H₂(Br-4){((E)-CH=CHPh)₂-2,5}(bpy)] (2)。1a、1b与PhC≡CPh、MeC≡CMe和PhC≡CMe在三氟甲磺酸铊(TlOTf)或高氯酸银(AgClO₄)存在下反应，得到双钯配位的茚二阴离子配合物[(μ-η,η-C₁₂H₂Bn₂-1,5-R₄-2,3,6,7){Pd(N∧N)}₂](OTf)₂（其中Bn = 苄基，R = Ph，N∧N = tbbpy(3a)、tmeda(3b)；R = Me，N∧N = tbbpy(4a)、tmeda(4b)）以及[(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)）。2与上述相同炔烃反应，得到茚基配合物[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)）以及[Pd(η-C₉H₂Bn-1-Ph-2-Me-3-((E)-CH=CHPh)-5-Br-6)(bpy)]OTf (8)。将1a或1b与XyNC（Xy = 2,6-二甲基苯基）反应，得到双核金属配合物[C₆H₂{C(=NXy){PdBr(CNXy)₂}}₂-1,4-((E)-CH=CHPh)₂-2,5] (9)；而反,反-2,5-二苯乙烯基-2,4-二溴苯与[Pd(dba)₂]在8当量XyNC存在下发生氧化加成反应，得到比例为1:0.3的异构体混合物双核配合物[C₆H₂{C(=NXy){C(=NXy)}₂{PdBr(CNXy)}}₂-1,4-((E)-CH=CHPh)₂-2,5] (10、10*)，EXSY谱显示该异构体混合物在溶液中存在缓慢交换过程。通过X射线衍射分析，确定了a-3a·7CDCl₃、s-3b·CH₂Cl₂、a-5a'·4CH₂Cl₂、6和8的晶体结构。