Abstract
Metalation of secondary diaminophosphine boranes by alkali metal amides provides a robust and selective access route to a range of metal diaminophosphide boranes M[(R2N)2P(BH3)] (M=Li, Na, K; R=alkyl, aryl) with acyclic or heterocyclic molecular backbones, whereas reduction of a chlorodiaminophosphine borane gave less satisfactory results. The metalated species were characterized in situ by NMR spectroscopy and in two cases isolated as crystalline solids. Single‐crystal XRD studies revealed the presence of salt‐like structures with strongly interacting ions. Synthetic applications of K[(R2N)2P(BH3)] were studied in reactions with a 1,2‐dichlorodisilane and CS2, which afforded either mono‐ or difunctional phosphine boranes with a rare combination of electronegative amino and electropositive functional disilanyl groups on phosphorus, or a phosphinodithioformate. Spectroscopic studies gave a first hint that removal of the borane fragment may be feasible.
Highlights
Coupling of nucleophilic metal diorganophosphides I or diorganophosphide boranes II (Scheme 1) with suitable electrophiles is one of the prime routes for the synthesis of phosphines.[1]
Striving to further establish diaminophosphide boranes as well-defined synthetic tools, we describe here the preparation of reagents with an extended range of amino substituents, including first heterocyclic derivatives, and alkali metal ions, the isolation and crystallographic characterization of sodium and potassium dimethylaminophosphide boranes, and selected reactions with electrophiles which extend the application of the nucleophilic reagents to the synthesis of highly functionalized diaminosilyl phosphines and the activation of a cumulene
Synthesis and spectroscopic characterization of diaminophosphide boranes To deepen our insight into the formation of diaminophosphide boranes, we tested the routes reported for accessing Li[1 a], viz. reductive metalation of the diaminochlorophosphine borane[9] and deprotonation of the secondary diaminophosphine borane,[10] with a larger range of structurally diverse substrates
Summary
Coupling of nucleophilic metal diorganophosphides I or diorganophosphide boranes II (Scheme 1) with suitable electrophiles is one of the prime routes for the synthesis of phosphines.[1]. Whereas the phosphorus atom in primary or silylated phosphines accessible from Ic,d/IIc retains its nucleophilic character, the electronegative substituents in diaminophosphines generated from Ie/IIe impose electrophilic character on the phosphorus atom transferred, which allows for post-functionalization by nucleophiles rather than electrophiles In this respect, diaminophosphide reagents may be considered as tools that allow coupling an electrophilic R2Pfragment with an electrophilic substrate, which makes them synthetic building blocks whose reactivity complements that of primary or silylated phosphides, respectively. Striving to further establish diaminophosphide boranes as well-defined synthetic tools, we describe here the preparation of reagents with an extended range of amino substituents, including first heterocyclic derivatives, and alkali metal ions, the isolation and crystallographic characterization of sodium and potassium dimethylaminophosphide boranes, and selected reactions with electrophiles which extend the application of the nucleophilic reagents to the synthesis of highly functionalized diaminosilyl phosphines and the activation of a cumulene.
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