organic compounds
Acta Crystallographica Section C
Crystal Structure
Communications
ISSN 0108-2701
Bis(diethoxyselenophosphinoyl)
triselenide and bis(diisopropoxy-
selenophosphinoyl) diselenide
Virginie B e reau and James A. Ibers*
Northwestern University, Department of Chemistry, 2145 Sheridan Road, Evanston,
IL 60208-3113, USA
Figure 1
The molecular structure of (I). Displacement ellipsoids are drawn at the
50% probability level and H atoms are drawn as spheres of an arbitrary
radius.
Received 24 November 1999
Accepted 31 January 2000
Within the Se bridge of (I), the SeÐSe bond distances are
3
The title compounds, bis(diethoxyselenophosphinoyl) triselen-
ide, [P(OEt) Se]Se [P(OEt) Se], and bis(diisopropoxy-
equivalent with Se1ÐSe2 = 2.3448 (6) and Se1ÐSe3 =
Ê
2
3
2
2
.3439 (6) A. In the Se bridge of (II), the SeÐSe bond
2
i
selenophosphinoyl) diselenide, [P(O Pr) Se]Se [P(O Pr) Se],
i
2
2
2
Ê
distance is Se2ÐSe2 = 2.3951 (6) A. These distances are
normal for SeÐSe single bonds (Tattershall et al., 1997). The
two P atoms have tetrahedral environments in both (I) and
comprise an Se chain or an Se chain bridging two (RO) PSe
3
2
2
groups.
(II), being bonded to two Se atoms and two O atoms. The PÐ
Se bond distances involving Se atoms of the Se and Se chains
Comment
3
2
As part of our investigation of selenometalate complexes, we
have recently reported the preparation, structure and spec-
Ê
Ê
are 2.2412 (11) and 2.2378 (10) A for (I), and 2.2223 (8) A for
II); these correspond to single bonds. Those PÐSe bonds
(
involving terminal Se atoms, at 2.0652 (9) and 2.0721 (9) A for
troscopy of [Mo (ꢀ -S)(ꢀ -S ) (Se P(OEt) ) ]Br (B e reau &
Ê
3
3
2
2 3
2
2 3
+
+
Ibers, 2000). Although the H (Jùrgensen, 1962) and K salts
Kudchadker et al., 1968) of the Se P(OEt) ligand have been
Ê
I), and 2.0733 (7) A for (II), correspond to double bonds. The
(
PÐO bond distances range from 1.569 (2) to 1.581 (2) A for
(
Ê
2
2
known for some time, metal complexes of the ligand are rare;
only three compounds containing [Se P(OEt) ] have been
structurally characterized (Liu et al., 1998, 1999; B e reau &
Ê
I) and are 1.567 (2) and 1.567 (2) A for (II).
There appears to be no literature on the metal coordination
chemistry of compounds (I) and (II). Yet, given the extensive
literature on chalcogen ligands, we believe that (I) and (II)
could act as potential ligands, exhibiting an Se,Se-chelation
mode through the two terminal Se atoms to form an eight-
(
2
2
Ibers, 2000). As an extension of these studies we reacted
K[Se P(OEt) ] with VCl in ethanol. Triselenide (I) was
2
2
3
obtained as a by-product. This synthesis is very different from
the literature preparation (Kudchadker et al., 1968), which
involves re¯uxing a stoichiometric mixture of P Se and
2
5
ethanol in cyclohexane for 4 h. Diselenide (II) was obtained
according to this same procedure from P Se , 2-propanol and
n-heptane.
2
5
Figs. 1 and 2 show the molecular structures of (I) and (II),
respectively. Compound (II) has a crystallographically
imposed center of symmetry, but it possesses non-crystal-
lographic symmetry very close to 2/m. The least-squares plane
i
i
i
through atoms Se1, Se1 , Se2, Se2 , P1 and P1 [symmetry code:
i) 1 � x, 1 � y, � z] has the equation in crystal coordinates of
2.830x + 5.713y + 5.419z = 1.441. The coef®cients do not
have rational ratios and hence the molecular symmetry does
not correspond to undetected crystallographic symmetry.
(
�
Figure 2
The molecular structure of (II). Displacement ellipsoids are drawn at the
50% probability level and H atoms are drawn as spheres of an arbitrary
radius [symmetry code: (i) 1 � x, 1 � y, � z].
5
84 # 2000 International Union of Crystallography ꢀ Printed in Great Britain ± all rights reserved
Acta Cryst. (2000). C56, 584±586