Predicting the Air Stability of Phosphines

Abstract

DFT calculations form the basis of a model capable of predicting the air stability of phosphines. The sensitivity of 18 primary phosphines is accounted for; the model also predicts the trend of increasing stability from phenylphosphine to triphenylphosphine. There is evidence that the radical cation SOMO energy for each corresponding phosphine may be key to its air stability/sensitivity.

The Primary Phosphine Renaissance

“…In principle this effect could be between the phosphorus lone pair and the aromatic system, or simply within the aromatic system itself, or both. In considering this, we take into account the following: (1) conjugation of the phosphino group and aromatic rings has been a most contentious issue in the literature [15,[46][47][48][49]; (2) both 1-naphthyl and 2-naphthyl substitution lead to a similar stabilization, whereas a conjugative effect to the lone pair might be expected to show a difference; (3) there appears to be no simple relationship between the basicity of the phosphine (as defined in terms of its effect on transition metal-bound carbonyls) and its airstability, which would again imply that the phosphorus 'lone pair' is not involved in the factors imparting the air-stability; (4) a higher oxidation potential of the phosphine seems to correlate with greater air-stability; (5) PES studies [46][47][48] have To understand this issue in more detail we have undertaken molecular modeling studies of many relevant primary phosphines [50]. The geometry optimizations of each of the phosphines were performed in the gas phase at the DFT level of theory using the B3LYP functional with a 6-31G * basis set, as employed in the Spartan '06 Essential edition from Wavefunction, Inc.…”

Zirconium-Catalyzed Alkene Hydrophosphination and Dehydrocoupling with an Air-Stable, Fluorescent Primary Phosphine

“…Primary phosphines can be difficult to handle due to toxicity and facile oxidation that renders many simple derivatives pyrophoric. A vigorous effort to understand and expend the family of airstable primary phosphines emerged in recent years to avail greater use of these molecules [12][13][14][15]. Among this class of primary phosphines are 8-[(4-phosphino)phenyl]-4,4-dimethyl-1,3,5,7-tetramethyl-2,6-diethyl-4-bora-3a,4a-diaza-s-indacene (2) [12,[15][16][17][18] and (2′-methoxy-[1,1′-binaphthalen]-2-yl)phosphine (3) [19,20] (Figure 1).…”

Air‐Stable, Highly Fluorescent Primary Phosphanes

“…[2] Since then, we have been developing a working model based on DFT, which indicates that, contrary to popular belief, many primary phosphanes will be air-stable if the molecule contains a high degree of conjugation (see below). [3] As such, the model predicted that the incorporation of the phosphino group onto a boron dipyrromethene (Bodipy [4] ) skeleton would also produce air-stable primary phosphanes. These phosphanes should provide a highly versatile gateway into a vast range of fluorescent phosphane derivatives, which are currently sorely underrepresented, despite the importance of phosphanes in catalytic and biomedical applications.…”

“…[3] For 4 b, the phosphino group is not incorporated in any orbital above HOMO-3 ( Figure S7 in the Supporting Information). The two methyl groups on the boron of 4 b are involved in the HOMO-1, but in contrast to the diphenyl substitution on 4 a, the dimethyl substitution has a much lower impact on the quantum yield of 4 b (see above, Table 1), which has a value almost eight times that of 4 a.…”

“…Zubieta, Valliant et al have shown that fluorescent, tripodal, quinoline-derived complexes of rhenium and technetium have tremendous potential as radiopharmaceutical imaging agents. [8] With this in mind, we treated 4 b with two equivalents of vinyldiphenylphosphane, using [Pt(nbd) 3 A sample of 6 b was analyzed by X-ray crystallography, and the molecular structure is depicted in Figure 3. This structure shows that the tripodal phosphane adopts a mer configuration about the rhenium center, with the central phosphorus atom trans to a carbonyl ligand and the terminal phosphorus atoms of the ligand 5 b trans to each other.…”