An Isolable Phosphaethynolatoborane and Its Reactivity

Abstract

The synthesis and characterization of a stable phosphaethynolato-borane, [B]OCP (1, [B] = N,N'-bis(2,6diisopropylphenyl)-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-P2{C[B]}O{CO[B]} (2), which decarbonylates on UV irradiation. By contrast the nickelmediated dimerisation of 1 affords the isomeric diphosphacyclobutene [P(CO[B])]2. 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-borylphosphaalkene [LiOC[B]P(Mes)]2 was observed. The reactivity of this species towards electrophiles is also described.

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

“…The single‐crystal X‐ray structure of 1 (Figure ) revealed a cis ‐ arrangement of the C 6 F 5 and B(C 6 F 5 ) 2 groups and a C=P bond distance (1.701(2) Å) with significant double bond character (typically in the region of 1.69 Å) . This distance is comparable to related boryl‐functionalized phosphaalkyes such as Z ‐(HO)[B]C=PMes (1.699(2) Å), previously reported by our research group. The C−O bond, 1.356(2) Å, is notably longer than that of the [B]OCP precursor (1.269(2) Å) due to the loss of π‐conjugation between the phosphaethynolate and the N , N’ ‐bis(2,6‐diisopropylphenyl)‐2,3‐dihydro‐1 H ‐1,3,2‐diazaboryl moiety.…”

“…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.…”

Facile Access to Uranium and Thorium Phosphaethynolate Complexes Supported by Tren: Experimental and Theoretical Study

“…The C≡P (1.5656(28) Å in 3 ; (1.5489(38)) Å in 4 ) and O—C (1.2278(38) Å in 3 ; 1.2513(43) in 4 ) bond lengths are within expected range for other reported metal salt. [ 29,49,54‐55,60 ] It is worth noting that the Th—O (2.3313(22) Å) bond length is slightly longer than that of the U—O (2.2928(24) Å) due to the larger ion radius of thorium. The U—N amide bond lengths, including U1—N1, U1—N2, U1—N3 bonds, are 2.2422(20), 2.2390(19) and 2.2463(20) Å, respectively, which is not unexpected.…”

A Cyaphide Transfer Reagent

“…To date, only one species with significant covalent character has been structurally authenticated. (22) In situ silylation of the [Na(dioxane)x]PCO with tris(isopropyl)silyl trifluoromethanesulfonate in non-polar aromatic solvents (benzene or toluene) favours silylation at the oxygen atom to afford the kinetic product i Pr3SiOCP (Figure 1), which ultimately rearranges to give the κ-P isomer. (23) Reduction of the former species using Jones' magnesium(I) regent [Mg( Dipp NacNac)]2 (24,25) cleanly affords an equimolar mixture of [Mg( Dipp NacNac)(CP)(dioxane)] ( 1) and [Mg( Dipp NacNac)(OSi i Pr3)(dioxane)] (2)…”