Base induced isomerisation of a phosphaethynolato-borane: mechanistic insights into boryl migration and decarbonylation to afford a triplet phosphinidene

Abstract

We report on the (tert-butyl)isocyanide-catalysed isomersation of a phosphaethynolato-borane, [B]OCPto its linkage isomer, a phosphaketenyl-borane, [B]PCO. Mechanistic insight into this unusual isomerisation was gained through a series of stoichiometric reactions of [B]OCP with isocyanides and theoretical calculations at the Density Functional Theory (DFT) level. [B]PCO decarbonylates under photolytic conditions to afford a novel boryl-substituted diphosphene, [B]P]P[B]. This reaction proceeds via a transient triplet phosphinidene which we have been able to observe spectroscopically by Electron Paramagnetic Resonance (EPR) spectroscopy. † Electronic supplementary information (ESI) available: Full experimental (including spectra and X-ray data) and computational details. CCDC 1963000-1963006. For ESI and crystallographic data in CIF or other electronic format see

Linkage Isomerism Leading to Contrasting Carboboration Chemistry: Access to Three Constitutional Isomers of a Borylated Phosphaalkene

“…All reactions and product manipulations were carried out under an inert atmosphere of argon or dinitrogen using standard Schlenk‐line or glovebox techniques (MBraun UNIlab glovebox maintained at <0.1 ppm H 2 O and <0.1 ppm O 2 ). [B]OCP, [B]PCO and tris(pentafluorophenyl)borane were synthesized according to previously reported synthetic procedures . Hexane (hex; Sigma Aldrich, HPLC grade), and toluene (Sigma Aldrich, HPLC grade) were purified using an MBraun SPS‐800 solvent system.…”

“…In the case of tris(pentafluorophenyl)borane, related reactions are only possible using more reactive substrates, such as allenyl ketones and isocyanates . It is these latter studies, as well as related work exploring the hydroboration of phosphaalkynes, that prompted us to explore the reactivity of BCF towards two isomeric forms of a boryl‐phosphaethynolate, [B]OCP and [B]PCO (where [B]= N , N’ ‐bis(2,6‐diisopropylphenyl)‐2,3‐dihydro‐1 H ‐1,3,2‐diazaboryl) . Interestingly, these reactions give rise to three different borylated phosphaalkenes with the same molecular formula.…”

Phosphorus and Arsenic Atom Transfer to Isocyanides to Form π‐Backbonding Cyanophosphide and Cyanoarsenide Titanium Complexes

“…[8] Moreover,B ertrand observed that irradiation of (L)PÀPCO in the presence of AdNC affords disubstituted (L)P À PCN À Ad (Ad = 1-adamantyl), [9] whereas Goicoechea described how t BuNC catalyzes linkage isomerization between (L)B À OCP and (L)B À PCO,e ventually affording (L)BÀPCNÀ t Bu upon decarbonylation. [10] Given the persisting EÀPl inkages,t he above isocyanide conversions are best construed as phosphinidene transfer reactions.H owever, Na(OCP) itself could engage in Pa tom transfer reactivity, which has gained momentum in main group [11] and transition metal [12] chemistry.A ne nticing possibility along these lines would be to generate amonosubstituted cyanophosphide:By virtue of steric accessibility,s uch an RÀNCP À unit could engage in more unrestrained bonding interactions than disubstituted analogues prepared via phosphinidene transfer. Moreover,r educed forms of monosubstituted cyanophosphide remain unknown, posing the question whether these fragments are too reactive to engage in redox activity.Given the isoelectronic relationship between P À and S, we pursued the conversion of an isocyanidet ot he phosphorus analogue of an organic isothiocyanate,R ÀNCP À , via Pa tom transfer from Na(OCP), and extended this methodology to As to form the heavier cyanoarsenide congener,R À NCAs À ,u sing ad ivalent Ti center as the reductant.…”

1,3,4-Azadiphospholides as building blocks for scorpionate and bidentate ligands in multinuclear complexes

“…[23][24][25][26] Due to its ambident nucleophilic character, it binds to soft centers [27][28][29][30][31][32] via the phosphorus atom (M-PvCvO) and hard centers via the oxygen atom (M-O-CuP). [33][34][35][36][37][38][39] Furthermore, phosphaketenes ([M]-PvCvO) with [M] = main group element or transition metal fragment show a tendency to lose carbon monoxide which allows to prepare mono-and polynuclear metal phosphides. 23,33,[40][41][42][43][44][45][46][47] There are very few examples which show a bridging OCP-unit between two metal centers.…”