An Isolable Phosphaethynolatoborane and Its Reactivity

Abstract

The synthesis and characterization of a stable phosphaethynolatoborane, [B]OCP (1, [B]=N,N'-bis(2,6-diisopropylphenyl)-2,3-dihydro-1H-1,3,2-diazaboryl), is described. The increased triple bond character of the P-C bond in 1 relative to the free ion (PCO ) is probed in a series of reactivity studies. Compound 1 readily dimerises in donor solvents to afford a cyclic five-membered 6π-aromatic compound, cyclo-P {C[B]}O{CO[B]} (2), which decarbonylates on UV irradiation. By contrast the nickel-mediated dimerisation of 1 affords the isomeric diphosphacyclobutene [P(CO[B])] . When 1 is reacted with organolithium reagents such as MesLi (Mes=2,4,6-trimethylphenyl), the boryl moiety shifts and the formation of the lithoxy-boryl-phosphaalkene [LiOC[B]P(Mes)] was observed. The reactivity of this species towards electrophiles is also described.

The Chemistry of the 2‐Phosphaethynolate Anion

“…This allows for subsequent coordination of the formal PC triple bond to other metal centres,a sd emonstrated by the formation of an adduct between (amid) 3 Th(OCP) and aN i-(COD) fragment (where COD = 1,5-cyclooctadiene); [34] or perhaps more remarkably,inthe cleavage of the O À Cbond to afford the cyaphide ligand (C P À )asshown by Meyer and coworkers (see below). [37] Ar elated phosphaethynolatoborane has been postulated as an intermediate in the formation of the phosphorus-containing analogue of cyanuric acid P 3 C 3 (OH) 3 (see below). [18] Forthe main-group elements,phosphaketenyl compounds (such as the phosphanyl phosphaketene E pictured in Figure 2) are also quite numerous and have been shown to readily decarbonylate affording phosphandiyls,t he majority of which oligomerise on formation (see below).…”

“…Calculations of the nuclear independent chemical shift (NICS) indicate that the central P 2 Cr ing is best described as a2 p-electron aromatic ring. [37] This involves the formation of ap hosphaethynolato compound by making use of ab ulky boryl substituent. [37] This involves the formation of ap hosphaethynolato compound by making use of ab ulky boryl substituent.…”

Crystalline BP‐Doped Phenanthryne via Photolysis of The Elusive Boraphosphaketene

“…It is noteworthy that this is the first structurally characterized example of a boraphosphaketene compound, which has been observed but not isolated. [11,12] The carbene-boron (C1 À B1) bond distance [1.637(2) ] and the C1-B1-P1 angle of 2 [115.39 (11)8] are similar to those in compound 1 [ carbene C À B 1.640(4) , carbene C-B-Br 114.8(2)8].…”

“…Molecular structure of 2 (thermal ellipsoids at 50 % probability; H atoms were omitted for clarity). Selected experimental [calculated] bond lengths [] and angles[8]: B1-C1 1.637(2), B1-P1 2.0830(18), P1-C35 1.6404(19), C35-O1 1.171(2), B1-C23 1.632(3), B1-C34 1.625(3); C1-B1-P1 115.39(11), B1-P1-C35 95.65(8), P1-C35-O1 174.51(17).Scheme 1. Synthesis of boraphosphaketene (2).Scheme 2.…”

“…Molecular structures of 3 (thermal ellipsoids at 50 % probability; H atoms were omitted for clarity). Selected experimental bond lengths [] and angles[8]: B1-C1 1.596(3), B1-P1 1.811(3), P1-C34 1.806(2), B1-C23 1.550(3); C1-B1-P1 117.99(16), B1-P1-C34 100.76(11), P1-B1-C23 121.46(18), C23-B1-P1-C34 À16.8(2).…”