Ferrocene DPPF

Crespo, O., Canales, F., Gimeno, M.C., Jones, P.G. and Laguna, A. (1999) Synthesis of [Au2(SC6F5)2( l-dppf)] and [Au2(p-SC6F5)(p-dppf)j (dppf = l,l -Bis (diphenylphosphino)ferrocene). Reactivity toward Various Metallic Fragments. Organometallics, 18(16), 3142-3148. 

The structure of [Ir(cod)(dppf)]PF6 shows approximately square-planar geometry at Ir, and the cp rings of the dppf ligand are close to parallel and staggered.592 The systems [Ir(cod)(LL)]C104, where LL = dppf, l-diphenylphosphino-2-(7V,7V-dimethylamino)methyl ferrocene and 1,6-diferrocene-2,5-diazahexane, catalytically trimerize PC=CH to 1,3,5-triphenylbenzene.593 The electrochemistry of [Ir(dppf)2]BPh4 shows two one-electron reductions at —1.560 V and -1.755 V vs. ferrocenium/ ferrocene.753... 

Phosphine ligands based on the ferrocene backbone are very efficient in many palladium-catalyzed reactions, e.g., cross-coupling reactions,248 Heck reaction,249 amination reaction,250 and enantioselective synthesis.251 A particularly interesting example of an unusual coordination mode of the l,l -bis(diphenylphosphino)ferrocene (dppf) ligand has been reported. Dicationic palladium(II) complexes, such as [(dppf)Pd(PPh3)]2+[BF4 ]2, were shown to contain a palladium-iron bond.252,253 Palladium-iron bonds occur also in monocationic methyl and acylpalladium(II) complexes.254 A palladium-iron interaction is favored by bulky alkyl substituents on phosphorus and a lower electron density at palladium. 

Again a distorted tetrahedral coordination of Hg is achieved in the l,l-bis(diphenylphos-phino)ferrocene (dppf) complex with Hgl2. Both Hg—P in the dppf chelate ring and terminal Hg—I bonds (averages 256.5 pm and 277.6 pm, respectively) are clearly longer than in the previous examples all angles around Hg are close to the value for a tetrahedron. Nonlinear optical properties of the material have been studied.241... 

In a related approach from the same laboratory, the perfluorooctylsulfonyl tag was employed in a traceless strategy for the deoxygenation of phenols (Scheme 7.82) [94], These reactions were carried out in a toluene/acetone/water (4 4 1) solvent mixture, utilizing 5 equivalents of formic acid and potassium carbonate/[l,T-bis(diphe-nylphosphino)ferrocene]dichloropalladium(II) [Pd(dppf)Cl2] as the catalytic system. After 20 min of irradiation, the reaction mixture was subjected to fluorous solid-phase extraction (F-S PE) to afford the desired products in high yields. This new traceless fluorous tag has also been employed in the synthesis of pyrimidines and hydantoins. 

Equation 11.5 Internal ablation ofallyltrimethylsilane (DPPF = 1,1 -bIs(di-phenyl phosphino)ferrocene). 

The last example of a dendritic effect discussed in this chapter is the use of core-functionalized dendritic mono- and diphosphine rhodium complexes by Van Leeuwen el al. [45] Carbosilane dendrimers were functionalized in the core with Xantphos, bis(diphenylphosphino)ferrocene (dppf) and triphenylphosphine (Figures 4.22, 4.32 and 4.33). 

Due to the potential problems associated with f3-H elimination, the first examples that were reported involved the intramolecular formation of G-O bonds between tertiary alcohols and aryl bromides using Pd(OAc)2 with 2,2 -bis(di-/>-tolylphosphino)-l,l -binapthyl (tol-BINAP) or bis(diphenylphosphino)ferrocene (dppf) as the ligands (Equation (12)).91 Although the coupling with primary and secondary alcohols was troublesome with this system, the more recent introduction of ligands 23-28 (Figure 3) has ameliorated many of these difficulties (Equation (13)).92... 

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