posted on 1996-04-24, 00:00authored byGilles Alcaraz, Antoine Baceiredo, Martin Nieger, Wolfgang W. Schoeller, Guy Bertrand
The structure of
P,P-bis(diisopropylamino)-4-phenyl-1,3,2λ5-diazaphosphete,
1a, has been determined by a single-crystal X-ray diffraction study
(C19H33N4P, monoclinic system,
space group P21, a = 9.482(1)
Å, b = 11.374(3)
Å, c = 9.668(2) Å, β = 97.16(1)°,
Z = 2). According to quantum chemical calculations at
an RHF level of
optimization utilizing the 6-31g(d,p) basis set, 1a has
a zwitterionic structure with the negative charge
delocalized
on the NCN allylic fragment and the positive charge localized at the
phosphorus. Heterocycle 1a reacts with
water and benzaldehyde affording N-phosphoranylbenzamidine
3 (95% yield) and the expected aza-Wittig
adduct
4 (85% yield), respectively. Addition of 1 equiv of
methyl trifluoromethanesulfonate and of 2 equiv of
BH3·THF
to 1a affords cyclic phosphonium salt 5 (94%
yield) and the bis(borane) adduct 6a (90% yield),
respectively.
Dimethyl acetylenedicarboxylate slowly reacts with 1a
giving rise to 1,3,4λ5-diazaphosphinine, 9, in
70% yield.
The X-ray crystal structures of products 2,
3, and 6a are reported (2:
C26H38N5P, monoclinic system,
space
group C2/c, a = 16.337(8) Å,
b = 19.810(2) Å, c = 8.800(2) Å,
β = 117.68(2)°, Z = 4. 3:
C19H35N4OP,
orthorhombic system, space group
P212121, a
= 9.090(1) Å, b = 12.955(2) Å, c
= 17.860(3) Å, Z = 4.
6a:
C19H39B2N4P,
orthorhombic system, space group
P212121, a
= 10.340(1) Å, b = 13.247(1) Å, c
= 16.996(1) Å,
Z = 4).