An Approach to Rigid, Optically Active Chelate Ligands with C₂ Symmetry: Dialkylhexaphosphapentaprismanes

Abstract

Diastereomeric Pd and Pt complexes with a highly rigid chelate cage ligand core have been designed on the basis of alkylated C 2 -symmetric tetra-tert-butylhexaphosphapentaprismanes R 2 P 6 C 4 tBu 4 . The ligands are accessible by substitution of the diiodo derivative I 2 P 6 C 4 tBu 4 with Grignard and organyllithium reagents. Depending on the optical properties of the organyl group, racemic or diastereomeric dialkylhexaphosphapentaprismanes R 2 P 6 C 4 tBu 4 can be treated with suitable Pd II or Pt II precursor complexes to form neutral square-planar cis-[(R 2 P 6 C 4 tBu 4 )PdCl 2 ] and cis-[(R 2 P 6 C 4 tBu 4 )-PtCl 2 ] complexes, respectively. Monoalkylation products RIP 6 C 4 tBu 4 were also observed in the reaction mixtures, but in most cases were inactive as chelate ligands towards Pd II [a]

Optically active P5-deltacyclenes: selective oxidation, ligand properties, and a diastereoselective rearrangement reaction

“…Found C, 47.14%, H, 5.72%, C 25 CrH 37 O 6 P 5 required C, 46.88%, H, 5.83%. Data of 13a NMR: δ H (300 MHz, CDCl 3 ) 1.23 (s, 9H, t Bu), 1.51 (s, 9H, t Bu), 1.56 (s, 9H, t Bu), 1.69(d, 4 J H,P = 1.2 Hz, 9H, t Bu), 8.61 (dddd, 1 J H1,P1 = 466 Hz, 2 J H1,P2 = 37.4 Hz, 3 12 (dt, 1 J P3,P2 = 157 Hz, 2 J P,P = 7.3 Hz, P3), −112.23 (ddd, 1 J P2,P1 = 301 Hz, 1 J P2,P3 = 157 Hz, 2 J P,P = 6.2 Hz, P2), 66.99 (dddd, 2 J P5,P1 = 129 Hz, 2 J P5,P4 = 9.4 Hz, 2 J P,P = 8.9 Hz, 2 J P,P = 8.7 Hz, P5), 151.88 (ddt, 1 J P1,P2 = 301 Hz, 2 J P1,P5 = 129 Hz, 2 J P,P = 5.1 Hz, P1), 367.21 (dd, 2 J P4,P5 = 12.2 Hz, 2 J P,P = 3.2 Hz, P4); no clear separation of 13…”

“…Selenium adds to 5 and rearrangement processes are initiated, leading to one PvSe unit, two P-Se-P bridges and a P-H bond being replaced by a C-H bond. The new CvC double bond has already been identified by 13 C NMR.…”

“…They are represented by only two examples to date, which are available as pairs of optically enriched species, 5′ and 5″ and two diastereomers of bis ((S)-2-methylbutyl)-tetra-tert-butyl-P 6 -pentaprismane 6. 13 Due to a configurationally labile P-H moiety, the enantiomers 5′ and 5″ form pairs of epimers a and b in rapid equilibrium, in contrast (benzene)RuCl 2 complex 7b exists as a single species only for each of its cage enantiomers. 11 Chelate ligand 6 forms C 2 symmetric complexes with suitable metals as for cis-(di(S)-2-methylbutyl-tetra-tert-butyl-P 6 -pentaprismane)PdCl 2 8.…”

“…11 Chelate ligand 6 forms C 2 symmetric complexes with suitable metals as for cis-(di(S)-2-methylbutyl-tetra-tert-butyl-P 6 -pentaprismane)PdCl 2 8. 13 (Scheme 2) (Arene)Ru(II) complexes are enantioselective hydrogen transfer catalysts with chiral β-diamine or β-aminoalcohol co-ligands. 14,15 Chiral Ru(II) complexes of tethered arene phosphine ligands are more reactive, but typically produced smaller enantiomeric excesses.…”

Optically Active P5‐Deltacyclenes: A Unique Cage‐Inversion Reaction and Some Transition‐Metal Complexes of the Rearranged Cage

“…Because of a configurationally labile P–H moiety, each enantiomer of 1 forms a pair of epimers 1a and 1b in rapid equilibrium, but when treated with [(benzene)RuCl 2 ] 2 the mixture of epimers yields a single complex 3b containing only the minority component, in almost quantitative yield, in the cases of each of the cage enantiomers 1 . C 2 ‐symmetric chelate ligand 2 forms C 2 ‐symmetric complexes with suitable metals, such as { cis‐ [di( S )‐2‐methylbutyl‐tetra‐ tert‐ butyl‐P 6 ‐pentaprismane]PdCl 2 } 4 , for example2 (Scheme ).…”