Syntheses and single-crystal X-ray diffraction studies of the
bis(tert-butylamino)cylodiphosphazane
cis-[(tBuNP)2(tBuNH)2], 1a, and its lithium
and magnesium salts are described. The pristine molecule has
crystallographic C
2
symmetry, both N−H groups being disposed in an endo fashion, and
crystallizes in the monoclinic space group
P2/c with unit cell dimensions (193 K)
a = 9.600(4) Å, b = 5.904(4) Å,
c = 18.97(1) Å, β = 101.09(3)°,
and
Z = 2. Treatment of 1a with
nBuLi or (nBu)2Mg in
refluxing THF yielded the heterocubic
cis-[(tBuNP)2(tBuNLi·THF)2], 2a, and the seco-heterocubic
{[(tBuNP)2(tBuN)2]Mg·(THF)2},
3a, respectively. The crystal data
(223
K) for the dilithio compound are monoclinic, space group
P21
/c, a = 10.691(1) Å,
b = 15.827(2) Å, c =
19.424(4) Å, β = 105.617(7)°, and Z = 4, and those
for the magnesium derivative (213 K) are monoclinic, space
group
P21
/n, a =
10.6272(4) Å, b = 17.6643(7) Å, c
= 16.3625(6) Å, β = 90.46(3)°, and Z =
4. The lithium and
magnesium complexes are shown to be isostructural with isoelectronic
cyclodisilazane species, and the development
of a parallel coordination chemistry for both ligands is
proposed.
