Structural and spectroscopic analysis of a new family of monomeric diphosphinoboranes

Abstract

A series of monomeric amino- and aryl(diphosphino)boranes has been synthesized and structurally characterized.

Diphosphinoboranes as Intramolecular Frustrated Lewis Pairs: P–B–P Bond Systems for the Activation of Dihydrogen, Carbon Dioxide, and Phenyl Isocyanate

“…From the large family of diphosphinoboranes recently synthesized by our group, 11 we selected compounds 1/1 ′ and 2 for reactivity studies ( Chart 1 ).…”

“…Although the X-ray analysis of 1 indicated that the interactions between P and B atoms lead to a structure with one double and one single PB bond, nuclear magnetic resonance (NMR) analysis, as well as DFT calculations, revealed that this is not the most energetically favorable conformation. 11 Computational studies elucidated that both 1 and lowest-energy 1′ ( Chart 1 ), in which P–B distances are comparable and both phosphorus atoms are pyramidal (see Figures S42 and S45 ), are energetically accessible at the crystallization temperature. 11 Otherwise, in the case of diphosphinoborane 2 , the B atom is substituted by the amino group, and in this case, the N-lone pair and P-lone pairs compete for donation to the empty p-orbital of boron.…”

“… 11 Computational studies elucidated that both 1 and lowest-energy 1′ ( Chart 1 ), in which P–B distances are comparable and both phosphorus atoms are pyramidal (see Figures S42 and S45 ), are energetically accessible at the crystallization temperature. 11 Otherwise, in the case of diphosphinoborane 2 , the B atom is substituted by the amino group, and in this case, the N-lone pair and P-lone pairs compete for donation to the empty p-orbital of boron. As a result of this interaction, due to better orbital matching, a double B=N bond is formed, and in contrast to compound 1 , both P atoms show pyramidal geometries.…”

“…The presence of a single P–B bond, resulting in an accessible P-lone pair and increased nucleophilicity of the P-center, is the key factor for the activation of CO 2 , while the high Lewis acidity of the boron center, leading to the multiple P–B bond character, facilitates heterolytic cleavage of H 2 . 17 , 20 , 30 , 33 Having synthesized a series of the above-described diphosphinoboranes that include systems differing in P–B–P bonding, 11 we decided to test their reactivity toward small molecules.…”

Hydrophosphination of boron–boron multiple bonds

“…due to p-donor or carborane substituents) and phosphorus thus retains its lone pair and tetrahedral geometry, are highly electron rich h 1 ligands for transition metal complexes. [9][10][11] By far the most common route for the construction of P-B bonds is salt elimination [12][13][14][15][16][17][18][19] using an alkali metal phosphide, MPR 2 , and a haloborane (Scheme 1A), although other routes are known, including nucleophilic addition of a boryl anion to a chlorophosphine (B), 20 elimination of silyl halide (C), 10,11,21 and cross-coupling of a B-I species with secondary phosphines using a palladium catalyst (D). 9 Of the different synthetic options for the construction of phosphorus-carbon bonds, hydrophosphination of unsaturated carbon substrates has gained popularity in recent years.…”