Abstract
ABSTRACT
We report a method for converting white phosphorus (P
4
) directly into tetra‐ and pentaphosphanes using
N
‐heterocyclic carbene (NHC) copper(I) complexes. The insertion of P
4
into the metal‐element bonds of the NHC complexes (6Dipp)Cu(Nu) [Nu = O
t
Bu and N(
i
Pr)
2
] affords [(6Dipp)Cu(
κ
2
‐P
4
O
t
Bu)] (
1
) and [(6Dipp)Cu{
κ
2
‐P
4
N(
i
Pr)
2
}] (
3
), which exhibit rotation of the [P
4
Nu]
−
ligand around the copper center in solution. This fluxional process is suppressed at low temperature, as shown by variable‐temperature
31
P{
1
H} NMR spectroscopy. Treatment of
1
with W(CO)
5
(thf) resulted in the formation of the bimetallic complex [(6Dipp)Cu(μ,
κ
2
:
κ
1
‐P
4
O
t
Bu){W(CO)
5
}] (
2
) which does not show fluxional behavior. Reactions of
1
and
3
with p‐block element halides release metal‐free asymmetrically substituted bicyclo[1.1.0]tetraphosphabutane ‘butterfly’ compounds. The polyphosphanes P
4
(PMes
2
)(O
t
Bu) (
4a
), P
4
[P{N(
i
Pr)
2
}
2
](O
t
Bu) (
4b
), P
4
[P{N(
i
Pr)
2
}
2
]{N(
i
Pr)
2
} (
4c
), and P
4
(BPh
2
){N(
i
Pr)
2
} (
5
) were isolated as stable compounds. Treatment of
4c
with the NHC IMes induces further phosphorus–phosphorus bond cleavage and rearrangement to give NHC‐phosphinidene adduct [
cyclo
‐P
3
{N(
i
Pr)
2
}(P{N(
i
Pr)
2
}
2
)(P═IMes)] (
6
). Compound
4c
also reacts with W(CO)
5
(thf) and CuBr·SMe
2
to give coordination complexes [W(CO)
5
{
κ
1
‐P
4
(P{N(
i
Pr)
2
}
2
)(N{
i
Pr}
2
)}] (
7
) and [Cu(Br){
κ
2
‐P
4
(P{N(
i
Pr)
2
}
2
)(N{
i
Pr}
2
)}] (
8
), respectively, demonstrating the ability of
4c
to serve as a mono‐ and bidentate ligand for transition metals. All compounds were characterized crystallographically and spectroscopically.