Homoatomic cations: From [P5]+ to [P9]+ | Science Advances
Abstract
Recent synthetic approaches to a series of [P
9
]
X
salts (
X
= [F{Al(OR
F
)
3
}
2
], [Al(OR
F
)
4
], and (R
F
= C(CF
3
)
3
); Ga
2
Cl
7
) overcome limitations in classical synthesis methods that proved unsuitable for phosphorus cations. These salts contain the homopolyatomic cation [P
9
]
+
via (I) oxidation of P
4
with NO[F{Al(OR
F
)
3
}
2
], (II) the arene-stabilized Co(I) sandwich complex [Co(arene)
2
][Al(OR
F
)
4
] [arene =
ortho
-difluorobenzene (
o
-DFB) and fluorobenzene (FB)], or (III) the reduction of [P
5
Cl
2
][Ga
2
Cl
7
] with Ga[Ga
2
Cl
7
] as Ga(I) source in the presence of P
4
. Quantum chemical CCSD(T) calculations suggest that [P
9
]
+
formation from [Co(arene)
2
]
+
occurs via the nido-type cluster [(
o
-DFB)CoP
4
]
+
, which resembles the isoelectronic, elusive [P
5
]
+
. Apparently, the nido-cation [P
5
]
+
forms intermediately in all reactions, particularly during the Ga(I)-induced reduction of [P
5
Cl
2
]
+
and the subsequent pick up of P
4
to yield the final salt [P
9
][Ga
2
Cl
7
]. The solid-state structure of [P
9
][Ga
2
Cl
7
] reveals the anticipated
D
2d
-symmetric Zintl-type cage for the [P
9
]
+
cation. Our approaches show great potential to bring other [P
n
]
+
cations from the gas to the condensed phase.