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.
Highlights
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
The classical way to synthesise phosphines is via salt metathesis or hydrophosphination starting from PCl3 or PH3, respectively (Fig. 1)[12,13,17]
The targeted variation of the organic substituents is synthetically very challenging. Both PCl3 and PH3 are synthesised from P4 either by reaction with chlorine gas or by hydrolysis in basic or acidic aqueous media[18]
Summary
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. 1 can be isolated from the reaction solution in 69% yield (Supplementary Fig. 66), indicating that this process could be carried on for many more cycles. The polyphosphorus compound [Cp*Fe(η5-P5)] (1) can be used as a recyclable platform for the targeted synthesis of symmetric or asymmetric phosphines, via a sequence of nucleophilic-electrophilic-nucleophilic reactions, directly from white phosphorus, avoiding the use of intermediate products
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