Activation of Polarized Phosphorus–Phosphorus Bonds by Alkynes: Rational Synthesis of Unsymmetrical 1,2-Bisphosphine Ligands and Their Complexes

Abstract

The reactions of 1,1-diamino-2,2-diphenyl-substituted diphosphines featuring various degrees of P-P bond polarization with different alkynes were investigated. All diphosphines reacted with alkynes carrying one or two electron withdrawing carboxylic ester moieties under cleavage of the P-P bond and stereospecific phosphinyl-phosphination at the triple bond to give unsymmetrical ethane-1,2- bisphosphines. Several of the products were further converted into chelate complexes upon reaction with group-10 metal dihalides. All isolated compounds were characterized by analytical and spectroscopic data, and several of the new ligands and complexes by single-crystal X-ray diffraction studies.

On the Synthesis and Addition Reactions of Chiral N-Heterocyclic Diphosphines

“…The N-heterocyclic diphosphine 7 was synthesized by analogy to 2a, b and 4 [24] via metathesis of 6 with lithium diphenylphosphide. Although the reaction proceeded in almost quantitative yield (by 31 P NMR), we failed to isolate the product by crystallization.…”

“…31 P NMR studies revealed that quantitative conversion of the starting material into a single addition product 16 is observed even at room tempera- ture. The Z-configuration at the double bond has been derived from the observation of a characteristically large [24,44] 3 J PP coupling constant of 94 Hz. The assigned molecular structure was corroborated by conversion of 16 into the chelate complexes 17a, b upon treatment with (cyclooctadiene)palladium dichloride or anhydrous nickel dichloride at room temperature.…”

“…We have recently synthesized N-heterocyclic diphosphines with polarized P-P bonds like 1 and 3 (Scheme 1) which undergo addition reactions with electron-poor alkynes [23,24] and alkenes [25 -27] to give bidentate 1,2-bisphosphines. The attachment of two sterically and electronically distinguishable P-donor moieties to an organic backbone in the diphosphination of terminal alkenes (Scheme 1) is regiospecific, but produces racemic mixtures of enantiomers with R and S configurations at the new stereocenters.…”

Recent Developments in the Chemistry of N-Heterocyclic Phosphines

“…PPh 2 ) and cyclic (e.g. phospholyl) substituents [39,43,44] . In several cases, coupling of the P-chloro-heterocycle with trimethylsilyl phosphines was feasible, although longer reaction times may affect the yields and the reaction is presumably not generally applicable [43] .…”

“…phospholyl) substituents [39,43,44] . In several cases, coupling of the P-chloro-heterocycle with trimethylsilyl phosphines was feasible, although longer reaction times may affect the yields and the reaction is presumably not generally applicable [43] . Coupling of a P-chloro-1,3,2-diazaphospholene with a P-stannyl-phosphine via dehydrostannylation has been reported in one case [45] but this reaction is likewise not generally applicable and its reversion (i.e., cleavage of the P-P bond in a phosphinyl-NHP upon reaction with trimethylstannyl chloride) has likewise been observed [39] .…”