Pentaphosphaferrocene-mediated synthesis of asymmetric organo-phosphines starting from white phosphorus

Abstract

The synthesis of phosphines is based on white phosphorus, which is usually converted to PCl3, to be afterwards substituted step by step in a non-atomic efficient manner. Herein, we describe an alternative efficient transition metal-mediated process to form asymmetrically substituted phosphines directly from white phosphorus (P4). Thereby, P4 is converted to [Cp*Fe(η5-P5)] (1) (Cp* = η5-C5(CH3)5) in which one of the phosphorus atoms is selectively functionalized to the 1,1-diorgano-substituted complex [Cp*Fe(η4-P5R′R″)] (3). In a subsequent step, the phosphine PR′R″R‴ (R′ ≠ R″ ≠ R‴ = alky, aryl) (4) is released by reacting it with a nucleophile R‴M (M = alkali metal) as racemates. The starting material 1 can be regenerated with P4 and can be reused in multiple reaction cycles without isolation of the intermediates, and only the phosphine is distilled off.

Recent Breakthroughs in P4 Chemistry: Towards Practical, Direct Transformations into P1 Compounds

“…Just six months after Scott and Wolf's report of P 4 hydrostannylation a third major breakthrough was reported by the Scheer group, who are longstanding contributors to the field of fundamental P 4 activation and functionalization chemistry [28] . While the two systems discussed so far exploited relatively underexplored radical methods, this new contribution was instead based upon the much more established concept of transition‐metal‐mediated P 4 activation.…”

Inorganic Ferrocene Analogue [Fe(P4)2]2–

“…But the distance from Fe to the P 4 plane (1.721 Å, avg) accords well with the predicted one (1.739 Å), while the two cyclo -P 4 planes are almost parallel. Unlike in the solid-state, eight P atoms give a singlet at δ = 131.8 ppm in the 31 P NMR spectrum (Figure S16), situated at lower field than in other complexes of iron-containing cyclo -P 4 units …”

“…Unlike in the solid-state, eight P atoms give a singlet at δ = 131.8 ppm in the 31 P NMR spectrum (Figure S16), situated at lower field than in other complexes of iron-containing cyclo-P 4 units. 22 Cluster 2 can be also viewed as a sandwich cluster, where the Fe center is coordinated by a cyclo-P 4 dianion and a norbornadiene-like η 4 -P 7 Zintl anion (Figure 3). The C 2v symmetric [η 4 -P 7 ] 3− unit acts as a formal six-electron donor.…”

Synthesis and electrochemical properties of 3,4,5-tris(chlorophenyl)-1,2-diphosphaferrocenes

“…Since the P atom in phosphaferrocenes retains an electron lone pair, phosphaferrocenes have been used as P-donor ligands [10][11][12] as well as nucleophilic catalysts [13,14]. Recently, the pentaphosphaferrocene Cp*Fe(η 5 -P 5 ) has been used as a mediator in the synthesis of asymmetric phosphines starting from white phosphorus [15]. Moreover, the presence of the lone pair of the P atom opens the route to polynuclear complexes [16][17][18] Scheme 1: Synthesis of bis(chlorophenyl)acetylenes 3.…”