C O M M U N I C A T I O N S
of the disguised bifunctional Lewis acid [DippNP]22+ into the P-P
bonds of two P4 tetrahedra. The utilization of bifunctional phos-
phenium cations13 represents a rational and potentially versatile
synthetic method for the assembly of large clusters using P4 as a
building block. Due to the cationic charge such cluster may be
amenable to a host of subsequent transformations. Studies directed
at the synthesis of further cationic clusters and the reactivity of 3
and 4 are in progress.
Acknowledgment. We gratefully acknowledge the Alexander
von Humboldt-Foundation (Feodor Lynen Return Fellowship for
J.J.W.), the FCI (Liebig fellowship for J.J.W.), the European
Phosphorus Science Network (PhoSciNet CM0802), and the
International Research Training Group (IRTG 1444). J.J.W. thanks
Prof. F. Ekkehardt Hahn (WWU Mu¨nster) for his generous support
and advice. We thank Dr. Robert Wolf for helpful discussions.
Figure 3. 31P{1H} NMR spectrum of 3[GaCl4] and 4[Ga2Cl7]2 (in C6H5F,
C6D6-capillary, 25 °C; 161.94 MHz); very small amounts of unidentified
side-products are indicated by an asterisk.8b
The reaction of two equiv. of P4 with cation 2 and an excess of
Lewis acid (2, GaCl3 1:4) in C6H5F resulted in the formation of a
pale-yellow solution with small amounts of orange-yellow precipi-
tate (Scheme 1). The 31P{1H} NMR spectrum of the filtrate is
depicted in Figure 3. Beside the resonances of monocation 3, signals
of a new A2MX2 spin system (δA ) -341.8 ppm, δM ) 67.4 ppm,
Supporting Information Available: Full experimental and spec-
troscopic data for compounds 2[Ga2Cl7] and 3[GaCl4]·C6H5F and
selected data for 4[Ga2Cl7]2 (including 31P-31P DQF COSY), and X-ray
crystallographic data for 3[GaCl4] and 4[Ga2Cl7]2 (CCDC numbers
743848, 743849). This material is available free of charge via the
1
1
2
δX ) 142.3 ppm; JAX ) -320.3 Hz, JMX ) -135.2 Hz, JAM
)
21.9 Hz) in a ratio of 2:1:2 indicate the formation of a new species
in approximately 60% yield.8b The resonances for the A2MX2 spin
system are consistent with two C2v-symmetric P5 cages bridged by
two imido groups, suggesting the formation of dication 4 (Figure
3). 4[Ga2Cl7] crystallized as a conglomerate with 3[GaCl4]. The
postulated structure in solution was confirmed by X-ray diffraction
(Figure 4). To our knowledge, dication 4 represents the first
structurally characterized example of two homoatomic P5 cages
fused Via an imido bridge. In the solid state, dication 4 is
centrosymmetric, consistent with the A2MX2 pattern observed in
the 31P{1H} NMR spectrum. The bond lengths and angles in the
P5 cores of dication 4 follow a similar trend as observed for
monocation 3. The N2P2 ring is planar with a short P1-N1 bond
(1.684(2) Å). The pronounced short character of the P-N bonds
in the P2N2 core might account for an increased reactivity. In
solution, dication 4 is not very stable and readily decomposes to
an insoluble orange material at room temperature. The 31P{1H}
NMR spectrum of the reactions mixture after ∼12 h shows
an additional complex set of signals. This indicates the formation
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Figure 4. ORTEP plot of the molecular structure of the cation 4 in
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counteranions omitted for clarity). Selected bond lengths (Å): N1-P1
1.684(2), P1-P2 2.1388(7), P1-P3 2.1380(7), P2-P4 2.2603(8), P2-P5
2.2450(8), P3-P4 2.2598(8), P3-P5 2.2425(8), P4-P5 2.1659(9); [sym-
metry code: (i) -x,-y+1,-z].
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