Palladium-Assisted Formation of Carbon−Carbon Bonds. 5.¹ Reactions of (o-Styrylaryl)palladium Complexes with Alkynes. Synthesis of Palladium Complexes with Highly Functionalized Indenyl Ligands. Crystal and Molecular Structures of (1-Benzyl-2,3-diphenyl-5,6,7-trimethoxyindenyl)- and (1-Benzyl-3-phenyl-5,6,7-trimethoxyindenyl)palladium(II) Complexes

Abstract

The reactions of [Pd(E-R)Cl(tmeda)] [R = C6H(E-CHCHPh)-6-(OMe)3-2,3,4; tmeda = N,N,N‘,N‘-tetramethylethylenediamine] with Tl(CF3SO3) and CH⋮CH, PhC⋮CPh, or PhC⋮CH selectively give compounds [Pd(η-Ind)(tmeda)]CF3SO3 [Ind = 1-benzyl-5,6,7-trimethoxyindenyl (2), 1-benzyl-2,3-diphenyl-5,6,7-trimethoxyindenyl (3), 1-benzyl-3-phenyl-5,6,7-trimethoxyindenyl (4)]. When a mixture of [Pd(E-R)Cl(bipy)] (bipy = 2,2‘-bipyridine) and [Pd(Z-R)Cl(bipy)] is reacted with Tl(CF3SO3) and MeC⋮CMe, the complex [Pd(η-Ind)(bipy)]CF3SO3 [1-benzyl-2,3-dimethyl-5,6,7-trimethoxyindenyl (5)] is obtained. The structures of 3 and 4 have been determined by X-ray studies at 203 and 173 K, respectively. According to the structural data for 3 and 4, the hapticity of the indenyl ligands is intermediate between η3- and η5-coordination.

Syndiotactic Polypropylene: Discovery, Development, and Industrialization via Bridged Metallocene Catalysts

“…In this context, it is important to be aware of at least two dynamic phenomena regarding the fluxional behavior of metallocene molecules in solution, namely, the phenomena of haptotropy [149][150][151][152][153][154][155][156] and ring slippage. The haptotropy and ring slippage [157][158][159][160]161, and references therein] [162,163], depicted schematically in Fig. 19, could influence the electronic properties of the active site and the steric environment surrounding it, particularly in the cationic state and in the presence of a counter-ion.…”

“…The hapto-flexible aromatic ligands bonded to the transition metal can facilitate the ligand exchange reaction by "temporarily" lowering the hapticity in the transition state and permitting the increase in the formal coordination number without breaking the canonic electronic rules [157][158][159][160]161, and references therein; 162,163]. As a general rule, the hapticity change should be considered to be involved in almost all metallocenes catalyses particularly those comprising at least a fluorenyl and an indenyl, and possibly those with substituted cyclopentadienyl ring system(s).…”

“…4.3 it is clear that the whole notion of a "perfect" molecular symmetry, bilateral or otherwise, in the solution phase should be handled with caution and not t taken very literally. We saw that even with initially "perfect" bilateral symmetric metallocene molecules like 1 (2) and 6 (7), the perfect symmetry may be lost, at least in part, in solution and during different stages of the polymerization due to incessant η 5 , η 3 , and possibly η 1 reversible hapticity change or occasional ring slippage [149][150][151][152][153][154][155][156][157][158][159][160]161, and references therein; 162,163]. Thus, the question to be answered is whether or not the bilateral symmetry embodies the necessary and/or sufficient condition(s) for syndiotactic specificity of a catalyst system.…”

Reactivity of ortho‐Substituted Aryl–Palladium Complexes towards Carbodiimides, Isothiocyanates, Nitriles, and Cyanamides

“…For most reagents the nucleophilic character of the ipso carbon of the aryl ligand in intermediates K is greater than that of the phenolate oxygen and its attack at the carbon atom of the reagent gives a four-membered palladacycle L, which after cleavage of the Pd À C bond and coordination of the oxygen atom affords complexes 2-4, 7-28. However, in a few cases, the phenolate oxygen and the ipso carbon have similar nucleophilic character and protonation/ insertion and addition products (5,6) are obtained.…”

“…[1][2][3] They can insert unsaturated reagents into the CÀPd bond affording new interesting complexes (C and D). [4][5][6][7][8][9][10][11][12][13] Frequently, the product of the insertion reaction decomposes, giving organic compounds in which the R o group plays a crucial role (E and F). [4,6,[12][13][14][15][16][17][18][19] Sometimes, the above processes are steps in the catalytic synthesis of such organic compounds, as has been proved, for example, for indenols, indenones, or isocoumarins.…”