Complexes of Rhodium(I) and Iridium(I) with the Chiral Tridentate Phosphane Pigiphos: Structure and Reactivity Studies

Abstract

The chiral ferrocenyltriphosphane Pigiphos [bis{(S)‐1‐[(R)‐2‐(diphenylphosphanyl)ferrocenyl]ethyl}cyclohexylphosphane] forms four‐coordinate complexes with IrI and RhI. The tridentate ligand assumes different conformations in the derivatives [Rh(CO)(Pigiphos)]OTf (4) and [IrCl(Pigiphos)] (1b), the latter also showing a drastic deviation from the square‐planar geometry. Reactivity studies have focussed on the more reactive 1b. The HCl and O2 adducts have been characterized in solution. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

Enantioselective Addition of Secondary Phosphines to Methacrylonitrile: Catalysis and Mechanism

“…5%: 77.82, 17.8, and 10.9 ppm, mostly obscured by the major conformer). The 31 P{ 1 H} NMR spectrum of [ 3 ][ClO 4 ] 2 is similar to that of [Ni(κ 3 -Pigiphos)(NCCH 3 )][ClO 4 ] 2 (83.42, 18.10, 9.23 ppm), in which the acetonitrile is bonded to nickel via an η 1 -coordination mode through its nitrogen 17a. The dynamic process responsible for the broad 31 P{ 1 H} NMR spectrum at r.t. appears to result from two rapidly exchanging conformations of the ferrocenylethyl backbone of the Pigiphos ligands 17d.…”

“…The 31 P{ 1 H} NMR spectrum of [ 3 ][ClO 4 ] 2 is similar to that of [Ni(κ 3 -Pigiphos)(NCCH 3 )][ClO 4 ] 2 (83.42, 18.10, 9.23 ppm), in which the acetonitrile is bonded to nickel via an η 1 -coordination mode through its nitrogen 17a. The dynamic process responsible for the broad 31 P{ 1 H} NMR spectrum at r.t. appears to result from two rapidly exchanging conformations of the ferrocenylethyl backbone of the Pigiphos ligands 17d. Similar 31 P NMR spectra were observed for Pigiphos complexes of Ni(II), Pd(II), and Ir(I), including [Ni(κ 3 -Pigiphos)Br][BAr f ], [Pd(κ 3 -Pigiphos)Cl][PF 6 ], [Ir(κ 3 -Pigiphos)Cl] .…”

“…The dynamic process responsible for the broad 31 P{ 1 H} NMR spectrum at r.t. appears to result from two rapidly exchanging conformations of the ferrocenylethyl backbone of the Pigiphos ligands 17d. Similar 31 P NMR spectra were observed for Pigiphos complexes of Ni(II), Pd(II), and Ir(I), including [Ni(κ 3 -Pigiphos)Br][BAr f ], [Pd(κ 3 -Pigiphos)Cl][PF 6 ], [Ir(κ 3 -Pigiphos)Cl] . Unfortunately, detailed solution-state NMR characterization of [ 3 ][ClO 4 ] 2 proved to be impossible due to its insolubility and its reactivity with methylene chloride.…”

“…(1-Ad) 2 PH (1-Ad = 1-adamantyl) was synthesized by LiAlH 4 reduction of (1-Ad) 2 P(O)Cl . ( R )-( S )-Pigiphos (only the ( R )-( S )-enantiomer was used throughout), [Ni(κ 3 -Pigiphos)(THF)][ClO 4 ] 2 ([ 1 ][ClO 4 ] 2 ), (C 6 H 5 ) 2 PCH 2 CH(CH 3 )CN, [Pd 2 (μ-Cl) 2 ((κ 2 -( R )-(C 6 H 4 )CHMe(NMe 2 )) 2 ], and [Pd 2 (μ-Cl) 2 ((κ 2 -( R )-(C 10 H 6 )CHMe(NMe 2 )) 2 ] were synthesized according to published procedures. [Ni(H 2 O) 6 ][ClO 4 ] 2 , [Ni(H 2 O) 6 ][BF 4 ] 2 , NiCl 2 , and NiBr 2 were purchased from Aldrich and used as received.…”

“…Our entry into catalytic asymmetric hydrophosphination developed from a longstanding interest in both chiral phosphine synthesis and catalytic asymmetric hydroamination reactions. , Specifically, we reported that the nickel(II)-catalyzed intermolecular reaction of amines and methacrylonitrile affords the 2-cyanopropylamine products in high enantiomeric excesses (up to 96%), when using the tridentate phosphine ligand ( R )-( S )-Pigiphos (( R )-( S )-Pigiphos = bis{( R )-1-[( S )-2-(diphenylphosphino)ferrocenyl]ethyl}cyclohexylphosphine, see Scheme ) 1 …”