Phosphines with N‐Heterocyclic Boryl‐Substituents: Ligands for Coordination Chemistry and Catalysis

Abstract

Boryl-substituted phosphines NHB-P(R)Ph (R = H, Ph, NHB = N-heterocyclic boryl substituent) react with Fe 2 (CO) 9 to give isolable Fe(CO) 4 complexes, two of which were characterized by single-crystal XRD studies. The electronic and steric properties for a series of the boryl phosphines were further assessed by evaluation of TEPs for in-situ formed complexes [RhCl(NHB-PR 1 R 2 )(CO) 2 ] (R 1 , R 2 = H, Ph, Me, NMe 2 ), and calculations of buried volumes for Fe(CO) 4 complexes. The results imply that the NHB-phosphines exhibit due to their conforma- [a]

Pyridinylidenaminophosphines: Facile Access to Highly Electron‐Rich Phosphines

“…One of the main reasons for their broad range of applications is the intriguing ease with which the steric and electronic properties of phosphines can be rationally tuned using various substituents . Although a huge variety of phosphines with diverse stereoelectronic properties have been synthesized over the last decades, the limit of electron‐donating character accessible to phosphines has been defined by alkylphosphines for more than half a century and modest advancement in this respect has been achieved using electropositive plumbyl, carboranyl, N‐heterocyclic boryl, anionic boratabenzene, or adamantyl substituents.…”

“…Selected bond lengths [] and angles [8]: 7: P-N1 1.6291(10), PÀN3 1.6198(10), PÀN5 1.6333(10), N1ÀC2 1.3175(13), N3ÀC9 1.314(2), N5ÀC16 1.3164(13). 8: PÀN1 1.6094(12), N1ÀC1 1.333(2), C1ÀC2 1.428(2), C2ÀC3 1.363(2), N2ÀC3 1.357(2), N2ÀC4 1.360(2), C4ÀC5 1.357(2), C1ÀC5 1.429(2), P-N1-C1 131.30(10).…”

“…One of the main reasons for their broad range of applications is the intriguing ease with which the steric and electronic properties of phosphines can be rationally tuned using various substituents. [5,6] Although a huge variety of phosphines with diverse stereoelectronic properties have been synthesized over the last decades, [7] the limit of electron-donating character accessible to phosphines has been defined by alkylphosphines for more than half a century and modest advancement in this respect has been achieved using electropositive plumbyl, [8] carboranyl, [9] N-heterocyclic boryl, [10] anionic boratabenzene, [11] or adamantyl [12] substituents.Recently, we discovered that the electron-donating ability of phosphines can be significantly increased, beyond the range of N-heterocyclic carbenes, [13] by attaching up to three strong p-donating imidazoline-2-ylidenamino substituents to the phosphorus atom. [14] The resulting phosphines are promising ligands in catalysis and can activate and transform chemically rather inert species such as CO 2 or SF 6 .…”

“…An alternative method to introduce 6 b into metal complexes is based on the bench-stable phosphonium salts 5 b, thus avoiding the need for isolation of the highly air-sensitive free phosphine 6 b. After removing the volatiles under reduced pressure, complexes 9-11 were obtained as brown (9) and yellow (10,11) solids in quantitative yields. The compounds 9 and 10 are soluble in toluene, THF, CH 2 Cl 2 , or MeCN and can be stored in solution or in the solid state.…”

“…Selected bond lengths [] and angles [8]: 2 b: PÀN1 1.7172(12), N1ÀC1 1.317(2), C1ÀC2 1.446(2), C2ÀC3 1.348(2), C3ÀN2 1.369(2), C4ÀN2 1.362(2), C4ÀC5 1.357(2), C1ÀC5 1.447(2), C1-N1-P 121.03(9). 6 b: PÀN1 1.7015(12), N1ÀC1 1.284(2), C1ÀC2 1.468(2), C2ÀC3 1.360(2), C3ÀC4 1.409(2), C4ÀC5 1.352(2), C5ÀN2 1.367(2), C5ÀN2 1.367(2), P-N1-C1 131.23(10).…”