The first palladium complex with an indacenediide ligand has been obtained by an unprecedented process involving the reaction of diphenylacetylene with a dipalladated 2,5-distyrylbenzene complex.

The aryl palladium complexes [PdI­(C6H4CH2OH-2)­(N∧N)] (N∧N = bpy = 2,2′-bipyridyl (1a), tbbpy = 4,4′-di-tert-butyl-2,2′-bipyridine (1b), tmeda = N,N,N′,N′-tetramethylethylenediamine (1c)) were synthesized by oxidative addition of 2-iodobenzyl alcohol to one equivalent of “[Pd­(dba)2]” (dba = dibenzylideneacetone) in the presence of the N∧N ligands. By reaction of 1a with three equivalents of XyNC (Xy = 2,6-dimethylphenyl) the insertion complex trans-[PdI­{C­(NXy)­(C6H4CH2OH-2)}­(CNXy)2] (2) was formed. The reaction of 1a with KOtBu resulted in the formation of the chelate complex [Pd­(κ2-C,O-C6H4CH2O-2)­(bpy)] (3), which crystallizes as pairs of molecules bridged by hydrogen bonds to water of crystallization. Complex 3 reacts with XyNC, forming the cyclic imidate N-(2,6-dimethylphenyl)-2-benzofuran-1­(3H)-imine (4). By reaction of 3 with various primary alkyl halides RCH2X, the complexes [PdX­(C6H4CH2OCH2R-2)­(bpy)] (X = I, R = H (5a), X = Br, R = Ph (5b), p-C6H4CH2Br (5c), p-C6H4Br (5d), and p-C6H4I (5e)) were obtained. When the reaction of 3 with p-C6H4(CH2Br)2 was carried out in a 2:1 ratio, the dinuclear arylpalladium complex [{(bpy)­BrPd­(C6H4CH2OCH2-2)}2­(C6H4-1,4)] (6) formed. An halide exchange reaction on 5e, using AgOTf and an excess of NaI, afforded [PdI­{C6H4(CH2OCH2­(C6H4I-4))-2}­(bpy)] (5f), which by oxidative addition to [Pd­(dba)2] in the presence of bpy formed another dinuclear arylpalladium complex, [(bpy)­IPd­(C6H4CH2-2)­O­(CH2C6H4-4)­PdI­(bpy)] (7). All the complexes have been extensively characterized by NMR spectroscopy. The crystal structures of 1a, 3·H2O, and 5e were determined by X-ray diffraction studies.

The dinuclear complexes [C 6 H 2 {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{C 6 H 2 (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 AgClO 4 gave the dipalladated indacenediide complexes [(μ-η,η-C 12 H 2 Bn 2 -1,5-R 4 -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-C 12 H 2 Bn 2 -1,5-Ph 2 -2,6-Me 2 -3,7){Pd(N ∧ N)} 2 ](A) 2 (N ∧ N = tbbpy, A = OTf (5a), ClO 4 (5a′); N ∧ N = tmeda, A = OTf (5b)). The reactions of 2 with the same alkynes afforded the indenyl complexes [Pd(η-C 9 H 2 Bn-1-R 2 -2,3-((E)-CHCHPh)-5-Br-6)(bpy)](A) (R = Ph, A = OTf (6), ClO 4 (6′); R = Me, A = OTf (7)) and [Pd(η-C 9 H 2 Bn-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 [C 6 H 2 {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 [C 6 H 2 {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·7CDCl 3 , s-3b·CH 2 Cl 2 , a-5a′·4CH 2 Cl 2 , 6, and 8 have been determined by X-ray diffraction studies.

The chelate complex [Pd(κ(2)-C,O-C6H4CH2O-2)(bpy)] () reacts with acetonitrile, cyanamides, or carbodiimides, in the presence of AgOTf (1 : 5 : 1 molar ratio) and residual water, to form complexes [Pd{κ(2)-C,N-C6H4{CH2OC([double bond, length as m-dash]NX)Y}-2}(bpy)](OTf), where X = H, Y = Me (), NMe2 (), NEt2 (), X = R, Y = NHR (R = (i)Pr (), Tol ()), as a result of the insertion of the unsaturated reagent into the O-Pd bond of and the protonation of one of the N atoms. In the absence of AgOTf the reaction of with TolN[double bond, length as m-dash]C[double bond, length as m-dash]NTol (Tol = p-Tolyl) results in the formation of the neutral complex [Pd{κ(2)-C,N-C6H4{CH2OC([double bond, length as m-dash]NTol)NTol}-2}(bpy)] (). Complexes and can be interconverted by deprotonation ( + KO(t)Bu) or protonation ( + KOTf + HOTf) reactions. When the reaction of with TolN[double bond, length as m-dash]C[double bond, length as m-dash]NTol in the presence of AgOTf is carried out in a 1 : 1 : 1 stoichiometric ratio, or for a short period of time, a mixture of and a mixed heterometallic Ag2Pd complex is obtained ( = [Ag(N-)2](OTf)). Complex is the major product when the AgOTf is added before the carbodiimide, and the reaction is stopped immediately. can also be obtained by reaction of with 0.5 equiv. of AgOTf. When complex [PdI(C6H4CH2OH-2)(bpy)] () reacts with (i)PrN[double bond, length as m-dash]C[double bond, length as m-dash]N(i)Pr in the presence of TlOTf, instead of AgOTf, a ca. 1 : 1 mixture of and [Pd{κ(2)-O,N-OCH2{C6H4{C([double bond, length as m-dash]NH(i)Pr)N(i)Pr}-2}}(bpy)](OTf) () forms. Complex is the result of the insertion of the carbodiimide into the C-Pd bond. Complexes have been extensively characterized by NMR spectroscopy, and the crystal structures of , , and ·2.5CHCl3·0.5Et2O have been determined by X-ray diffraction studies.