Taming a Functional Group: Creating Air‐Stable, Chiral Primary Phosphanes

Abstract

Gezähmtes Feuer: Enantiomerenreine primäre Phosphane wurden entwickelt, die sowohl im festen Zustand als auch in Lösung bemerkenswert stabil gegen Luftoxidation sind (siehe Beispiel). Die Stabilität dieser neuen Klasse von Liganden scheint auf der Konjugation des ausgedehnten π‐Elektronensystems zu beruhen, wobei ein zusätzlicher Ring ausreicht.

The Primary Phosphine Renaissance

“…An acetonitrile solution of (R)-5 yielded crystals which were suitable for study by X-ray crystallography and the resulting structure ( Fig. 1.3) represents the first such characterization of an optically-pure primary phosphine [38,39]. The P-C bond length of 1.811(6) Å correlates with the few other crystal structures reported of uncoordinated primary phosphines [1,[6][7][8][9][10][11]40].…”

“…However, their 16% yield of the preceding primary phosphine can be improved to quantitative levels [38,39] by using lithium aluminum hydride in conjunction with chlorotrimethylsilane, and their 5% yield of the phospholanes can now be rationalized at least in part by our isolation of the phenolic compounds (R,R,R ax )-21a and (S,S,R ax )-21b. These phenolic phospholanes should prove to be interesting 'L-X' ligands in their own right; the parent 2-diphenylphosphino derivative has already been shown to be an effective chiral base in the asymmetric aza-Baylis-Hillman transformations of N-sulfonated imines, by virtue of its phenolic residue [67].…”

“…As a result of the irreversibility of phosphine oxidation under these experimental conditions, we have used the potential of maximum slope, E s,max [38,39,41,42], to quantify the position of the waves on the potential axis. The values so obtained (Table 1.1) do suggest a general trend in accord with the observed oxidative stability.…”

New ferrocenylmethylphosphines – Preparation, characterisation and coordination chemistry of PH(CH2Fc)2, P(CH2Fc)3 [Fc=Fe(η5-C5H5)(η5-C5H4)] and their derivatives

“…Not surprisingly, complexes of primary and secondary phosphines have received much less attention, due to the toxicity and high reactivity of the free phosphines (some are even pyrophoric). This lack of attention has prompted the development of primary and secondary phosphines that are more air-stable and hence easier to use [2][3][4][5][6][7][8]. Interest in these phosphines has arisen from the possibility of post-coordination modification of the PH bond, allowing for chemical flexibility in the synthesis of new and intriguing transition metal phosphine complexes [9].…”

Air‐Stable, Highly Fluorescent Primary Phosphanes

“…[1] We have recently demonstrated, however, that they can be stabilized to air oxidation without any need for steric protection, providing sufficient p conjugation is incorporated into the organic R group; thus we were able to prepare the first air-stable chiral 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.…”