The Stannylphosphide Anion Reagent Sodium Bis(triphenylstannyl) Phosphide: Synthesis, Structural Characterization, and Reactions with Indium, Tin, and Gold Electrophiles

Treatment of P4 with
in situ generated [Na]­[SnPh3] leads to the formation of
the sodium monophosphide [Na]­[P­(SnPh3)2] and
the Zintl salt [Na]3[P7]. The former was isolated
in 46% yield as the crystalline salt [Na­(benzo-15-crown-5)]­[P­(SnPh3)2] and used to prepare the homoleptic phosphine
P­(SnPh3)3, isolated in 67% yield, as well as
the indium derivative (XL)2InP­(SnPh3)2 (XL = S­(CH2)2NMe2), isolated in
84% yield, and the gold complex (Ph3P)­AuP­(SnPh3)2. The compounds [Na­(benzo-15-crown-5)]­[P­(SnPh3)2], P­(SnPh3)3, (XL)2InP­(SnPh3)2, and (Ph3P)­AuP­(SnPh3)2 were characterized using multinuclear NMR spectroscopy
and X-ray crystallography. The bonding in (Ph3P)­AuP­(SnPh3)2 was dissected using natural bond orbital (NBO)
methods, in response to the observation from the X-ray crystal structure
that the dative P:→Au bond is slightly shorter than the shared electron-pair P–Au bond. The bonding in (XL)2InP­(SnPh3)2 was also interrogated using 31P and 13C solid-state NMR and computational methods.
Co-product [Na]3[P7] was isolated in 57% yield
as the stannyl heptaphosphide P7(SnPh3)3, following salt metathesis with ClSnPh3. Additionally,
we report that treatment of P4 with sodium naphthalenide
in dimethoxyethane at 22 °C is a convenient and selective method
for the independent synthesis of Zintl ion [Na]3[P7]. The latter was isolated as the silylated heptaphosphide
P7(SiMe3)3, in 67% yield, or as the
stannyl heptaphosphide P7(SnPh3)3 in 65% yield by salt metathesis with ClSiMe3 or ClSnPh3, respectively.