Ngoc Hoa Tran Huy

Electrophilic Terminal-Phosphinidene Complexes: Versatile Phosphorus Analogues of Singlet Carbenes

Electrophilic and nucleophilic terminal-phosphinidene complexes are compared in terms of electronic structures and reactivities. Various precursors of the unstable electrophilic species [R−P−M] (M=Cr, Mo, W(CO)5 and Fe(CO)4) are discussed. The addition reactions of the electrophilic phosphinidene complexes with Lewis bases, insertion reactions into O−H, N−H, and activated C−H bonds, and cycloaddition reactions with double and triple bonds are described, as well as some rearrangements and autocondensations. Various applications to the synthesis of new organophosphorus molecules are discussed and techniques available for demetallation are given.

1,2-dihydrophosphetes as masked 1-phosphabutadienes

Abstract The 1,2-dihydrophosphete ring reacts as a masked 1-phosphabutadiene around 100°C to give the expected [4 + 2] cycloadducts with N-phenylmaleimide, dimethyl acetylenedicarboxylate, and benzaldehyde.

The reaction of electrophilic terminal phosphinidene complexes with benzophenone and fluorenone: The unexpected formation of six- and eight-membered heterocycles

Abstract The phenylphosphinidene-pentacarbonyltungsten complex 2 , as generated from the appropriate 7-phosphanorbornadiene complex 1 , reacts at 60 °C with benzophenone to give a benzo-annellated 1-oxa-2-phosphacyclohex-4-ene 2-oxide as a 1:1 mixture of two isomers 3a,b . The same phosphinidene complex 2 reacts at 120 °C with fluorenone. A deoxygenation of fluorenone takes place leading to the bifluorenylidene 4 and to an eight-membered 1,2,8-oxadiphosphocane 2,8-dioxide 5 . Both compounds 3b and 8 have been fully characterized by X-ray crystal structure analysis. The two reactions are interpreted as resulting from the initial formation of a P ··· O Lewis adduct between the phosphinidene and the ketone.

Reactivity of electrophilic terminal phosphinidene complexes toward phosphorus ylides

Abstract Stabilised phosphorus ylides react with transient terminal phosphinidene complexes [RPW(CO)5] (R=Ph, Me) to give products resulting from a formal insertion of P into a CH bond via an initial nucleophilic attack of the ylidic carbon.

Ortho-Phosphination of azobenzene by terminal phosphinidene complexes

Transient terminal phosphinidene complexes [RP→W(CO)5] (R=Ph or Me) as generated from the appropriate 7-phosphanorbornadiene precursors, insert at 110°C into the ortho-C–H bonds of azobenzene.

Reaction of terminal phosphinidene complexes with aldimines: Synthesis of the first 1,2,3-azadiphosphetidine

Transient terminal phosphinidene complexes [RP-M(CO)5] (M = Mo, W, R = Ph, Me), as generated from the corresponding 7-phosphanorbornadiene complexes, react with N-methyl(benzylidene)amine to afford the diazaphospholane complexes 3,4 (R = Ph) or a mixture of diazaphospholane 9 and 1,2,3-azadiphosphetidine 10 (R = Me), probably by insertion of either one molecule of imine or one molecule of phosphinidene into the weak PN bond of the unstable intermediate azaphosphiridine 11. The new complex 10 has been submitted to an X-ray crystal structure analysis.

Insertion reactions of [Pt(PPh3)2] fragments into the four-membered ring complex [W(CO)5PPhC(OEt)CPhCHPh]. Crystal and molecular structures of [Pt(dppe)PPh(W(CO)5)C(OEt)CPhCHPh] and [Pt(PPh3)2((W(CO)5)PhPC(OEt)CPhCHPh)(η2-PC))]

Abstract Insertion of platinum bis(phosphane) fragments into a 1,2-dihydrophosphete ring lead to complexes derived from a 1-phosphabuta-1,3-diene species.

THE REACTION OF TERMINAL PHOSPHINIDENE COMPLEXES WITH ELECTRON-RICH ALKYNES: A NEW APPROACH TO THE PHOSPHOLE RING

Abstract The reaction of electron-rich alkynes such as ethoxyacetylene or propynyldiethylamine with a transient terminal phosphinidene complex such as [PhP˭W(CO)5] directly yields the corresponding phosphole complexes via a formal [2 + 2 + I] cycloaddition involving two molecules of alkyne and one phosphorus center.

FROM A TERMINAL (CIS-2-BUTENE-1,4-DIYL-1,4-DIPHOSPHINIDENE) COMPLEX TO SOME NEW DIPHOSPHORUS BICYCLES

Abstract The reaction of the transient [cis-2-butene-1,4-diyl-1,4-diphosphinidene]decacarbonylditungsten complex (3) as generated from the appropriate 7-phosphanorbornadiene precursor (2) at 60°C in the presence of CuCl as a catalyst with 3-hexyne, 2,3-dimethylbutadiene and [phenyl(methoxy)carbene]pentacarbonyltungsten yields the products 5, 7 and 8. These products formally result from the [2+2], [4+2] and [1+2] cycloadditions of the reagents with the PP double bond of the [3,6-dihydro-1,2-diphosphinine]decacarbonylditungsten. However, a mechanism involving a monocondensation of the reagent onto one P of the bis-phosphinidene, followed by the insertion of the second P into the monophosphorus heterocycles thus formed is favored.

Conversion of 2-alkylidenephosphiranes into 1,4-diphosphaspiropentanes

The bis-condensation of [MeP-W(CO)5] with 3-methyl-1,2-butadiene yields two stereoisomers of the corresponding 1,4-diphosphaspiropentane, one of which has been characterized by X-ray crystal structure analysis.