Synthesis and Crystal Structures of P-Iron-Substituted Phosphinoborane Monomers

Abstract

A family of P-iron-substituted phosphinoboranes, Cp(CO) 2 Fe{P(Ar)BMes 2 } (Ar = Ph, Mes, Tipp, Mes*), have been prepared from the reaction of Cp(CO) 2 FeCl and (Li)(Ar)PBMes 2 . All the complexes have been characterized successfully by 1 H, 11 B, and 31 P NMR; IR spectroscopy; and Xray crystallography. In the IR spectra, all the complexes display similar carbonyl stretching frequencies that are remarkably higher than those of closely related phosphide complexes. These observations indicate that a repulsive interaction between the filled d orbital on the iron and the lone pair on the phosphorus is less severe in the studied iron-phosphinoboranes, which is most likely because of the P→B π interaction that occurs in them. The 31 P{ 1 H} NMR chemical shifts of the phosphinoborane phosphorus move upfield with the increasing steric bulk of the Ar groups in the order Ph (−51.4 ppm) < Mes (−68.8 ppm) < Tipp (−84.9 ppm). However, the phosphorus bearing the most sterically demanding Mes* group appears at an unexpectedly downfield value of −44.9 ppm, which is probably reflective of its structural peculiarities. The 1 H NMR spectrum of each complex displays two sets of signals, assignable to inequivalent Mes groups on the boron atom, as a consequence of a hindered rotation around the P−B bond. This high rotational barrier most likely results from the significant double-bond character in the P−B bond. The X-ray diffraction studies have confirmed the iron-phosphinoboranes considered herein to be monomeric species. Each molecule consists of a nearly planar phosphinoborane fragment with a short P−B bond. The Fe−P bond is notably elongated as the Ar group becomes larger, demonstrating its somewhat vulnerable nature with respect to steric congestion. In contrast, the variation in the P−B bond distance is relatively small throughout the series of iron-phosphinoboranes, suggesting that the PB double-bond character is balanced by steric and electronic effects of the substituents around the phosphorus.

Monomeric phosphinoboranes

“…It has been applied to the synthesis of the bulky phosphinoboranes 23a-c [18,54], 25 [26] and 26a-d [55] whose properties and reactivity have been extensively studied (see Section 4.3) as well as the borylphosphines 27 [56], 28 [57], 30 [58] and 31a-c and 32 [59] which have been used as ligands (see Section 4.4).…”

Simulations Suggest Possible Triply Bonded Phosphorus≡E13 Molecules (E13 = B, Al, Ga, In, and Tl)

“…Therefore, the R-E13 moiety and the R-P component have two and four valence electrons, respectively. The computational results show that the ground states of these two units are a singlet for R-E13 ([R-E13] 1 ) and a triplet for R-P ([R-P] 3 ). Therefore, model [I] in Figure 1 is considered as [R…”

“…Simulations Suggest Possible Triply Bonded Phosphorus≡E13 Molecules (E13 = B, Al, Ga, In, and Tl) http://dx.doi.org/10.5772/intechopen.77055 R 0 E13 ☰ PR 0 compound at the singlet ground state constitutes a combination of two triplet units, [R 0 -E13] 3 and [R 0 -P] 3 . Therefore, using the information in Figure 1, the bonding nature of the E13 ☰ P triple bond in R 0 E13 ☰ PR 0 can be regarded as RE13 PR.…”

“…Even though phosphorus and nitrogen belong to the same group in the periodic table, molecular nitrogen is a triply bonded diatomic molecule, but elemental white phosphorus is a tetrahedral compound wherein each atom is connected by three single bonds to the other atoms in the molecule. Phosphorus is usually connected to other elements by a single chemical bond, which has been verified by lot of experimental evidences [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. Also, molecules that feature a phosphorus double bond have been the subject of many experimental and theoretical studies of structure and reactivity [15][16][17][18][19][20][21][22][23][24][25][26][27].…”

Boron, aluminium, gallium, indium and thallium

“…185 A related diborene derived from reduction Annual Reports A Review of (NHC)B(aryl)Cl 2 coordinated to a silver centre in a side on Z 2 manner reminiscent of the olefin Z 2 coordination mode. 186 Group 13-15 hetero-alkenes (R 2 PBR 2 ) have been synthesised 187 including one example where a side on Z 2 coordination mode was observed for R 2 PB(C 6 F 5 ) 2 towards Pt(PPh 3 ) 2 (R = Cy, tBu). 188 Alkyl and aryl boranes (including frustrated Lewis pair (FLP) reactivity)…”