Diastereoselective Formation of Complexed Methylenediphosphiranes

Abstract

Stable syn-substituted methylenediphosphirane complexes are obtained from the reaction of transient, electrophilic phosphinidenes [R-PdW(CO) 5 ] (R ) Me, Ph), thermally generated from the corresponding benzophosphepines, with 1-phosphaallene. A DFT analysis at the B3PW91/6-31G(d) level of theory reveals that the high diastereoselectivity of this reaction results from the preferred negative activation energy for syn cyclization of the P,P-ylide intermediates.

Valence isomerization of cyclohepta-1,3,5-triene and its heteroelement analogues

“…Also for the phosphepine system [ 108 ], benzannulation leads to interesting targets. Namely, the thermal lability of the transition-metal-complexed 3 H -benzophosphepine 33 was explored by Lammertsma et al for the synthesis of a variety of organophosphorus compounds by means of [1 + 2] cycloadditions of the in situ generated singlet phosphinidene 35 with olefins or acetylenes ( Scheme 7 ) [ 5 – 9 ]. This approach has even lead to the detection of the transient phosphinidene species by employing electrospray ionization tandem mass spectrometry (ESIMS/MS); its gas-phase reactivity perfectly matches the well-established solution-phase chemistry [ 109 ].…”

“…This interest extended to the heterocyclic analogues 3 – 8 , bearing one oxygen, sulfur or nitrogen atom, after the discovery of their biological importance ( Scheme 1 ) [ 3 – 4 ]. The phosphane analogues 9 and 10 received far less attention, with their applicability as a phosphinidene (R–P) precursor being the most notable use [ 5 – 9 ].…”

Valence Isomerization of Phosphepines

“…Benzannulating the bow of 11a has a similar effect to that on the parent 3a . In fact, anti 3-phenyl-3 H -3-benzophosphepine 12a (ML n = W(CO) 5 ) is a known phosphinidene precursor (mp 115 °C) , that generates [Ph−PW(CO) 5 ] with a half-life time of 203 min at 75 °C in the presence of a trapping agent . The effect of benzannulation raises the barrier by over 12 kcal·mol −1 ( anti 29.0; syn 23.8) for the endergonic ring closure to the corresponding P-norcaradiene 12b ( anti 19.1; syn 14.5 kcal·mol −1 , Table ).…”

“…To date, the parent metal-complexed phosphepines, such as phenyl-substituted 11a , remain unknown, but the 3 H -3-benzophosphepine complexes 12a are available and do serve as precursor to generate singlet phosphinidenes by cheletropic elimination from their valence isomers 12b (ML n = W(CO) 5 , Mo(CO) 5 , Cr(CO) 5 , Mn(CO) 2 Cp). , Metal-complexed ( 13a ) and metal-free phosphepines ( 15a , 16a ) containing a dimethylamino substituent are also promising but yet unknown precursors, except for 14a . It is therefore of interest to obtain a better understanding of the stability of the phosphepine moiety for designing new singlet phosphinidene precursors.…”

Phosphines and related C–P bonded compounds

“…385 Stable syn-substituted methylenediphosphirane complexes have been obtained from the reaction of transient electrophilic phosphinidene complexes [RP ¼ W(CO) 5 ] (R ¼ Me or Ph), thermally generated from complexed benzophosphepines, with 1-phosphaallene. 386 Related to the phosphinidene area is a study of the reactions of the triply bonded molecule P 2 with stable carbenes, giving bis(phosphinidene) complexes of the type R 2 C-P-P'CR 2 , involving a phosphorus-phosphorus single bond. 387 Similar complexes may also arise in the reactions of singlet and triplet methylene with P 4 .…”