Evaluation Only. Created with Aspose.PDF. Copyright 2002-2021 Aspose Pty Ltd.
organic compounds
Acta Crystallographica Section C
Crystal Structure
Communications
approximately 448 K produced a sudden and violent exotherm
resulting in a massive foaming char. The transesteri®cation
approach proceeded, with dif®culty, to yield (I). An attempt to
substitute a more convenient reagent, i.e. dimethyl methyl-
phosphonate, for the diphenyl methylphosphonate was not
successful.
ISSN 0108-2701
A pentaerythritol-derived spirodi-
phosphonate
The molecule lies on a crystallographic twofold axis, as seen
in Fig. 1. The two CÐCÐC angles which lie across the twofold
axis are unequal, with C3ÐC1ÐC3i being 4.91 (14)ꢀ larger
than C2ÐC1ÐC2i [symmetry code: (i) 1
consistent with the steric difference in this conformation
x, y,
z],
1
2
Hassan Y. Elnagar,a Paul F. Rankena and Frank R.
Fronczekb*
aAlbemarle Technical Center, Albemarle Corporation, PO Box 14799, Baton Rouge,
LA 70898-4799, USA, and bDepartment of Chemistry, Louisiana State University,
Baton Rouge, LA 70803-1804, USA
Correspondence e-mail: fronz@chxray1.chem.lsu.edu
Received 21 February 2000
Accepted 25 April 2000
The title spirodiphosphonate, 3,9-dimethyl-2,4,8,10-tetraoxa-
3ꢀ5,9ꢀ5-diphosphaspiro[5.5]undecane-3,9-dione, C7H14O6P2, a
polymer additive, has crystallographic symmetry 2. At 100 K,
its six-membered rings have chair conformations, with
endocyclic torsion-angle magnitudes in the range 51.87 (8)±
Figure 1
A view of the molecule of (I) with ellipsoids plotted at the 50%
1
probability level [symmetry code: (i) 1 x, y,
z].
2
58.93 (9)ꢀ. The P O distance is 1.4749 (8) A, while the PÐ
Ê
Ê
C(methyl) distance is 1.7691 (12) A.
between opposite ends of the molecule in the twofold direc-
tion. A similar asymmetry exists in two phosphites having
similar spiro ring systems, conformations, and approximate
twofold symmetry (Heinemann et al., 1994; Barren et al.,
1995). The six-membered rings of (I) have the chair confor-
mation, with endocyclic torsion angles having magnitudes
within the range 51.87 (8)±58.93 (9)ꢀ. While boat (Day et al.,
1984) and half-chair (Drew & Rodgers, 1972) conformations
have been observed in 2-dioxaphosphorinane rings, the chair
conformation seen here is more common (Ul-Haque et al.,
1970; Patois et al., 1990; Killean et al., 1971; Browning et al.,
Comment
Many organophosphorus compounds are commercially avail-
able for use as polymer additives. The unique diphosphonate
3,9-dimethyl-2,4,8,10-tetraoxa-3ꢀ5,9ꢀ5-diphosphaspiro[5.5]-
undecane-3,9-dione, (I) (CAS #3001-98-7), has been claimed
to be effective in modifying the stability of resins such as
polyole®ns, polycarbonates and polycarbonate blends
(Granzow, 1981; Hardy et al., 1979; Horn, 1979). We deter-
mined the structure of (I) as part of an effort towards the
design of even more effective organophosphorus additives.
1996; Edmundson et al., 1989). The P O bond has length
O
Ê
1.4749 (8) A, and is in an axial position of the chair. The P
bond is more typically in the equatorial position (Ul-Haque et
al., 1970; Patois et al., 1990; Killean et al., 1971; Browning et al.,
1996; Edmundson et al., 1989). The difference may thus be
attributed to the spiro ring system in (I), which is not present
in the other 2-dioxaphosphorinanes. The PÐC distance in (I),
Ê
1.7691 (12) A, is similar to those in 5-tert-butyl-2-methyl-2-
Ê
oxo-1,3,2-dioxaphosphorinane [1.81 (3) A] (Ul-Haque et al.,
1970) and 2,5,5-trimethyl-1,3,2-dioxaphosphorinan-2-one
Ê
[1.776 (3) and 1.783 (3) A; Patois et al., 1990].
The synthesis of (I) is reported to proceed by the Arbuzov
rearrangement of pentaerythritol dimethyldiphosphite, (II)
(Mukmenev & Kamai, 1963; Friedman, 1964), the transester-
i®cation of pentaerythritol, (III), with diphenyl methyl-
phosphonate (Honig & Weil, 1977), and the reaction of
methylphosphonic dichloride, (V), with pentaerythritol in di-
methyl methylphosphonate, (IV) (Kiefer, 1983). The latter
procedure gave high purity (I) in good yield, and was our
method of choice. The Arbuzov rearrangement of (II) was
found to be uncontrollable; heating the reactants above
Experimental
The title compound was prepared by reaction of methylphosphonic
dichloride with pentaerythritol in dimethyl methylphosphonate
according to the method of Kiefer (1983). Crystals were grown from a
methanol solution.
ꢁ
Acta Cryst. (2000). C56, 905±906
# 2000 International Union of Crystallography
Printed in Great Britain ± all rights reserved 905
Elnagar, Hassan Y.
