Heterocubane Phosphoraniminato Complexes of Cadmium

Phosphoraniminato complexes of cadmium
[CdX(NPEt3)]4 {X = Cl
(1), Br (2), I (3),
[CdI(NPMe3)]4 (4)}
are
formed by the reaction of cadmium dihalides with silylated
phosphoranimines Me3SiNPR3 (R = Me, Et)
in the
presence of a fluoride source, e.g. NaF, at elevated temperatures. High
yields can be achieved when R = Et and
X is a heavy halogen. The exocyclic bromo function in complex
2 can be replaced by reaction with
organolithium
reagents to give organocadmium compounds
[CdMe(NPEt3)]4 (5) and
[Cd(C2SiMe3)(NPEt3)]4
(6) in excellent
yields. Complexes 1−6 consist of a
[Cd4N4] heterocubane core in which the
cadmium atoms are linked by μ3-N
bridges of the phosphoraniminato ligand with the cubane angles being
close to 90°. The crystal structure of an
unsymmetrical cubane
[Cd4I4(OSiMe3)(NPEt3)3]
(7) is reported, in which one of the phosphoraniminato
moieties
has been replaced by a silyloxy function. All complexes are
colorless oxygen- and moisture-sensitive crystalline
materials, the heterocubane structure of which has been shown by
crystal structure determinations and is consistent
with spectroscopic findings, including IR, NMR, and mass
spectra.