NewP,N-Chelate Ligands Based on Pyridyl-Substituted Phosphaferrocenes

Abstract

The new pyridyl‐substituted phosphaferrocene ligands 3 and 6 are prepared by addition of lithiated pyridine or α‐picoline to 2‐formyl‐3,4‐dimethylphosphaferrocene (1). The ligands 3 and 6 react with [Cp*RuCl]4 in THF to give the P,N‐chelate complexes [Cp*RuCl·3] (9) and [Cp*RuCl·6] (10) with high diastereoselectivity. Addition of monodentate ligands like CO or PPh3 to the complexes leads by displacement of the Ru‐bound pyridyl group to the respective carbonyl or phosphane complexes with monodentate P‐coordinated phospha‐ferrocene ligands. Reaction of the ligand 6 with [(C3H5)PdCl]2 and NH4PF6 gives the seven‐membered chelate complex [(C3H5)Pd·6]PF6 (13) which was characterized by X‐ray diffraction. The ligands 3 and 6 were tested in the palladium‐catalyzed asymmetric alkylation of 1,3‐diphenylallyl acetate.

Phosphorus Heterocycles: From Laboratory Curiosities to Ligands in Highly Efficient Catalysts

“…In keeping with this, treatment of [{RuCp*Cl} 4 ] (Cp*=C 5 Me 5 ) with the pyridyl‐functionalized phosphaferrocenes 34 and 35 stereoselectively furnished the chelate complexes 36 and 37 with diastereomeric ratios of d.r. >99:1 and 95:5, respectively (Scheme ) 26d. The high diastereoselectivity observed is in sharp contrast to work of Consiglio et al who obtained 1:1 mixtures of diastereomers from the reaction of [{RuCp*Cl} 4 ] with a series of chiral, bidentate P,P‐chelating ligands 35…”

A Comparison of Phosphaferrocene and Phospharuthenocene Ligands in Rh+‐Catalysed Enamide Hydrogenation Reactions: Superior Performance of the Phospharuthenocene

“…www.chemeurj.org 16 were separated by chromatography (40-65 mm SiO 2 ; EtOAc/C 5 H 12 1:10; R f 15 = 0.27, R f 16 = 0.18) [39] and assigned through an X-ray analysis of the slower running diastereomer, which was shown to be the (R Rc S p )-combination 16 on the basis of its distinctly different PÀCH 3 and PÀBH 3 bond lengths ( Figure 3).…”

“…For the heterometallocene systems, the results confirm that a judicious variation of the included metal centre offers potential for improving performance as a ligand significantly, with this prospect being particularly likely if the heteroatom is "soft" enough to interact strongly with the heterometallocene metal centre. One clear conclusion is that the already excellent performance of phosphametallocene ligands in enantioselection, as obtained using the phosphaferrocene class, [13][14][15][16][17][18][19][20][21][22][23][24] should be amenable to significant further optimisation.…”

“…

5492cenes are used as ligands. The results were obtained as part of a program that aims to extend the chemistry of the phosphaferrocene ligand class (which has been shown inter alia [13][14][15][16][17] to give benchmark performance in enantioselective allylic alcohol isomerisation, [18,19] Kinugasa [20] and azomethineimineA C H T U N G T R E N N U N G [3+2] cycloaddition chemistry [21,22] by Fu as well as in allylic substitutions [23] and hydrosilylations [24] by Hayashi/Ogasawara) to include other ligands derived from the wider family of phosphametallocenes. Specifically, our objective was to ascertain whether the phospharuthenocenes developed in this laboratory [25][26][27][28] and also elegantly studied by the Hayashi/Ogasawara group [24,29,30] might provide a more conveniently handled ligand platform than the corresponding phosphaferrocenes.

…”

Synthesis of Chiral, Half‐Sandwich Ruthenium Complexes from Weakly Coordinated Solvent Species

“…In a series of previous papers we have outlined the chemistry of a new type of bidentate ligands that contain a substituted phosphaferrocene moiety as a chiral building block. [1][2][3] The coordination chemistry employing these new ligands, as well as their applicability in asymmetric catalysis, has been studied by us [1,4] and independently by other groups. [5][6][7][8][9][10][11] In a more recent project we have tethered the chiral phosphaferrocene unit to a cyclopentadienyl ring and explored the properties of this anionic ligand system 1 (Scheme 1).…”