Dinuclear and tetranuclear cages of oxodiphenylantimony phosphinates: Synthesis and structures

Article abstract of DOI:10.1021/ic950713w

The novel dimeric compounds [Ph₂Sb(O₂PR₂)O]₂·2CH ₂Cl₂ [R - cycl-C₆H₁₁ (2) and cycl-C₈H₁₅ (3)] have been synthesized by reacting diphenylantimony

Full text of DOI:10.1021/ic950713w

Inorg. Chem. 1996, 35, 3235-3241
3235
Dinuclear and Tetranuclear Cages of Oxodiphenylantimony Phosphinates: Synthesis and
Structures
Musa A. Said,† K. C. Kumara Swamy,*,† Damodara M. Poojary,‡ Abraham Clearfield,‡
M. Veith,§ and V. Huch§
School of Chemistry, University of Hyderabad, Hyderabad, 500046, A.P., India, Department of
Chemistry, Texas A&M University, College Station, Texas 77843-3255, and Anorganische Chemie,
Universita¨t des Saarlandes, 66041 Saarbru¨cken, Germany
ReceiVed June 7, 1995X
The novel dimeric compounds [Ph2Sb(O2PR2)O]2‚2CH2Cl2 [R ) cycl-C6H11 (2) and cycl-C8H15 (3)] have been
synthesized by reacting diphenylantimony trichloride (1) with 3 mol equiv of silver acetate followed by 1 mol
equiv of the phosphinic acid. By the same route under more stringent conditions to exclude moisture, the mixed
phosphinate-acetate [Ph2Sb(O2P(C6H11)2)(O2CMe)]2O (4) was isolated and characterized. Treatment of 2 with
acetic acid/water affords the tetranuclear cage Ph8Sb4O4(OH)2(O2P(C6H11)2)2‚CH3COOH‚CH2Cl2 (5); it is possible
to convert 5 to 2 by heating it with an excess of the phosphinic acid. Compounds 2, 3, and 5 have been characterized
by X-ray structural analysis. All of them possess four membered Sb2O2 rings with hexacoordinated antimony.
In 5 the antimony atoms in the two Sb2O2 rings are connected by oxo bridges on two sides to give an Sb4O6 cage.
These structures are correlated with those of known tin cages.
Introduction
of +4 and +5 can be expected to achieve coordination numbers
of 6 and 7 readily, structural analogies and related chemistry
Recently, we have reported the synthesis and structures of
two oxo-bridged antimony(V) compounds [Ph2SbCl(O2P-
(C6H11)2)]2O (I) and [Ph2Sb(O2CPh)2]2O (II) in which the
can be envisioned for them. Thus we report herein the synthesis
and X-ray structures of three oxoantimony(V) phosphinate
compounds, [Ph2Sb(O2PR2)O]2 [R ) cycl-C6H11 (2), cycl-C8H15
(3)] and Ph8Sb4O4(OH)2(O2P(C6H11)2)2‚CH3COOH‚CH2Cl2 (5);
the structures of these derivatives have been correlated with
those of the analogous tin compounds. The structural inter-
conversion between the dinuclear and the tetranuclear cages 2
and 5 is also described.
Experimental Section
Chemicals were produced from Aldrich/Fluka or from local manu-
facturers; they were purified when required. Diphenylantimony trichlo-
ride was prepared according to a literature procedure.5 Solvents were
purified according to standard procedures.6 Silver salts of phosphinic
acids were prepared by treating the acid with a stoichiometry quantity
of aqueous sodium hydroxide followed by aqueous silver nitrate,
washing the precipitate with methanol, and drying in Vacuo. All
reactions, unless stated otherwise, were performed under dry nitrogen
atmosphere. 1H, 13C, and 31P{1H} NMR spectra were recorded on a
Bruker 200 MHz spectrometer in CDCl3 solutions with shifts referenced
to SiMe4 (δ ) 0) or 85% H3PO4 (δ ) 0) IR spectra were recorded on
a JASCO FT/IR-5300 spectrophotometer. Elemental analyses were
carried out on a Perkin-Elmer 240C CHN analyzer.
CAUTION! Toxicity of the antimony compounds reported here is
unknown, and hence all of them should be handled with care.
Dimeric Oxodiphenylantimony Dicyclohexylphosphinate, [Ph2-
Sb(O2P(C6H11)2)O]2‚2CH2Cl2 (2). Route (A). A mixture of dipheny-
lantimony trichloride (1) (1.01 g, 2.66 mmol) and silver acetate (1.77
g, 0.63 mmol) was heated in dry toluene (50 mL) for 3 h under reflux
and then filtered. The precipitate was washed with 10 mL of dry
toluene, and the washings were added to the filtrate. To this filtrate
dicyclohexylphosphinic acid7 (1.2 g, 2.66 mmol) was added and the
mixture heated overnight under reflux. The 31P NMR spectrum of the
antimony exhibits coordination numbers of 6 and 7, respec-
tively.1 In the course of the reactions leading to I or its
dicyclooctyl phosphinate analogue [Ph2SbCl(O2P(C8H15)2)]2O,
31P NMR analysis showed the formation of other products.
Coupled with this observation, the possibility of replacement
of the carboxylates in II and in the corresponding acetate [Ph2-
Sb(O2CMe)2]2O2 by phosphinates to generate new cages
prompted us to probe these reactions further. Analogous
replacement reactions on the prismane [MeSnO‚O2CMe]6 in tin
chemistry led to the novel “mixed prismane” [MeSnO‚1/2O2-
CMe‚1/2O2P(t-bu)2]63 and “crown” [(MeSn(O)O2P(t-bu)2)(MeSn-
(OH)(OMe)(O2P(t-bu)2)]2[H][O2P(t-bu)2]‚4MeOH‚2H2O.4 As
both tin and antimony in their respective higher oxidation states
† University of Hyderabad.
‡ Texas A&M University.
§ Universita¨t des Saarlandes.
X Abstract published in AdVance ACS Abstracts, April 1, 1996.
(1) Said, M. A.; Kumara Swamy, K. C.; Babu, Kamlesh; Aparna, K.;
Nethaji, M. J. Chem. Soc., Dalton Trans. 1995, 2151.
(2) Sowerby, D. B.; Begley, M. J.; Millington, P. L. J. Chem. Soc., Chem.
Commun. 1984, 896.
(5) Nunn, M.; Sowerby, D. B.; Wosolek, D. M. J. Organomet. Chem.
1983, 251, C45.
(3) Day, R. O.; Chandrasekar, V.; Kumara Swamy, K. C.; Holmes, J.
M.; Burton, S. D.; Holmes, R. R. Inorg. Chem. 1987, 26, 1050.
(4) Kumara Swamy, K. C.; Schmid, C. G.; Day, R. O.; Holmes, R. R. J.
Am. Chem. Soc. 1988, 110, 1067.
(6) Perrin, D. D.; Armarego, W. L. F.; Perrin, D. R. Purification of
Laboratory Chemicals; Pergamon: Oxford, U.K., 1986.
(7) Peppard, D. F.; Mason, G. W.; Andrejasich, C. M. J. Inorg. Nucl.
Chem. 1965, 27, 697.
S0020-1669(95)00713-0 CCC: $12.00 © 1996 American Chemical Society

3236 Inorganic Chemistry, Vol. 35, No. 11, 1996
Said et al.
Table 1. Crystal Data for 2, 3, and 5
2
3
5
empirical formula
fw
C50H68Cl4O6P2Sb2
1212.28
C29H42Cl2O3PSb
662.28
C75H92Cl2O12P2Sb4
1805.43
cryst syst
space group
Z
a/Å
b/Å
triclinic
P1h
1
10.520(12)
11.609(10)
13.35(2)
monoclinic
P21/a
4
12.119(2)
19.739(3)
13.155(2)
monoclinic
P21/n
4
15.111(2)
27.860(5)
18.669(2)
c/Å
R/deg
â/deg
γ/deg
V/Å3
64.65(8)
71.86(9)
68.70(8)
1350(3)
112.21(1)
101.10(1)
2913.4(8)
1.510
7712(1)
1.555
Dc/(g cm-3
)
1.492
cryst size/mm
F(000)
0.2 × 0.2 × 0.4
0.4 × 0.2 × 2
0.3 × 0.2 × 0.1
616
1360
3624
µ(Mo KR)/cm-1
T/°C
13.03
20
12.19
-110
ω - 2θ
50.1 (max)
5615
5349
4372 (I > 3σ(I))
Rigaku AFC5R
Ra ) 0.028 (I > 3σ(I))
Rwa ) 0.037
0.94; -0.68
15.52
23
ω - 2θ
50.1 (max)
14492
scan method
2θ range/deg
total reflcns
unique reflcns
obsd reflcns
diffractom used
final R indices
ω - θ
3.44-34.88
1713
1713
13936
1673 (I > 2σ(I))
Siemens stoe AED2
R1 ) 0.0335 (I > 2σ(I))
WR2 ) 0.0836
0.474; -0.434
4637 (I > 3σ(I))
Rigaku AFC5R
Ra ) 0.061
RWa ) 0.053
1.26; -0.73
largest diff.: peak; hole
2
2
a R ) ∑||Fo| - |Fc||/∑|Fo| and Rw ) {∑w(|Fo| - |Fc| /∑wFo }1/2
.
reaction mixture showed a major peak at 64.3 ppm (>70%) and two
minor peaks at 61.1 and 54.2 ppm. The solvent was completely
removed from the mixture and the residue crystallized from dichlo-
romethane-hexane (1:3). Yield: 1.5 g, 54% (mp 284 °C). IR (major
Compound 4 is moisture sensitive and gives either 2 or 5 upon
hydrolysis; thus crystals of 5 suitable for X-ray were grown while an
attempt was made to crystallized 4 from dichloromethane-hexane
mixture.
bands): 1043 (ν(PdO)) and 962 cm-1
.
1H-NMR (after powdering and
Tetrameric cage Ph8Sb4O4(OH)2(O2P(C6H11)2)2‚HO2CMe‚CH2Cl2
(5). A mixture of dimer 2 (0.50 g, 0.48 mmol), acetic acid (3 mL),
and water (0.2 mL) was heated under reflux for 2 h. Acetic acid was
removed, and the compound was crystallized from dichloromethane-
hexane (1:5). Yield: 0.60 g, 69% (mp 248 °C). IR (major bands
drying in vacuum): δ 0.70-2.20 (br m, 44H, C6H11), 7.20-8.00 (m,
20H, H(Ar)). [If no evacuation is done, a peak at 5.3 ppm for
dichloromethane solvate is observed.] 31P NMR: δ 64.3. Anal. Calcd
for C49H66Cl2O2P2Sb2: C, 52.20; H, 5.86. Found: C, 51.34; H, 5.81.
Route (B). A mixture of 1 (0.39 g, 1.06 mmol) and AgO2P(C6H11)2
(2.65 g, 7.87 mmol) was heated under reflux in dry toluene (60 mL)
for 24 h and filtered. The solvent was removed from the filtrate and
the residue crystallized from dichloromethane-hexane in air to obtain
2. Yield: 0.44 g, 40%. Mp, IR, and 31P NMR of the crystalline product
were identical to that obtained by route A.
only): 1761, 1705 (ν(CdO)) and 1072 (ν(PdO)) cm-1 1H NMR (after
.
evacuation and removal of solvate): δ 0.63-2.15 (br m, 44H + 3H,
C6H11 + CH3), 3.50-3.90 (br, 2H, OH), 6.97-8.00 (m, 40H, H(Ar)).
One solvent molecule (CH2Cl2; δ(1H) 5.2 ppm) per tetrameric cage is
observed if no evacuation is performed. 31P NMR: δ 57.7. Anal. Calcd
for C74H90O12P2Sb4: C, 51.69; H, 5.28. Found: C, 51.45; H, 5.05.
Dimeric Oxodiphenylantimony Dicyclohexylphosphinate, [Ph2-
Sb(O2P(C8H15)2O]2‚2CH2Cl2 (3). The procedure was similar to that
for 2 (routes A or B). Route (A): The following quantites were used:
1, 1.97 g, 5.17 mmol; silver acetate, 2.5 g, 15.50 mmol; dicyclooc-
tylphosphinic acid (mp 118 °C; 31P NMR, 66.7 ppm; procedure for
preparation similar to that for dicyclohexylphosphinic acid7) 2.96 g,
10.33 mmol. The 31P NMR spectrum of the reaction mixture shows a
major peak at 69.6 ppm (>70%) and two minor peaks at 66.1 and
60.5 ppm. The product was crystallized from dichloromethane-hexane.
Yield: 2.3 g, 38.6% (mp 255 °C). IR (major bands): 1039 (ν(PdO))
Conversion of the Tetrameric Cage (5) to the Dimer (2). A
mixture of 5 (0.05 g) and dicyclohexylphosphinic acid (0.02 g) was
heated under reflux in toluene (7 mL) with azeotropic removal of water
for 12 h. The solvent was completely removed and 31P NMR recorded
for the mixture; it showed compound 2 [δ(31P): 64.2 ppm (>85%)].
Two other minor products [δ(31P): 53.8 (<5%), 45.9 (<5%)] and the
excess of the phosphinic acid were also present, at 64.3 (major, >85%,
compound 2), 59.9 (phosphinic acid), 53.8 (<5%), and 45.9 (<5%)
ppm.
X-ray Crystallography. Single crystals of compounds 2 and 3 for
X-ray crystallography were grown from a mixture of dichloromethane
and hexane; compound 5 (for X-ray work) was initially obtained while
an attempt was made to recrystallize 4, and hence the solvent mixture
and 960 cm-1
.
1H NMR (after drying): δ 0.90-2.30 (br m, 60H,
C8H15), 7.08-7.95 (m, 20H, H(Ar)). [A peak for dichloromethane
solvent is observed at 5.3 ppm if the sample is not dried.] 31P NMR
69.6. Anal. Calcd for C56H80O6P2Sb2 (after drying): C, 58.26; H, 6.94.
Found: C, 57.75; H, 7.08. The same compound could be obtained
from route B in 40% yield.
of dichloromethane and hexane contained traces of acetic acid.
A
suitable crystal was mounted on a glass fiber [for 3 and 5] or inside a
Lindemann capillary (for 2). Data were collected on a Siemens Stoe
AED2 or Rigaku AFC5R diffractometer with graphite monochromated
Mo KR radiation. Three control reflections, collected every 150
reflections, showed no significant changes in intensities for 3 and 5;
however, for 2 the intensities dropped very quickly, and hence, data
was collected only up to 2θ of 35 °C. The details pertaining to data
collection and refinement are listed in Table 1. The structures were
solved by conventional methods8,9 and refined by the full-matrix least
squares method.9 An empirical absorption correction was applied, and
the data were corrected for Lorentz and polarization effects. Neutral
atom scattering factors and anamolous-scattering correction terms were
taken from International Tables for X-ray crystallography. The final
positional parameters are listed in Tables 2-4. For compound 2, the
Sb, P, O, and Cl atoms were refined anisotropically, while for 3 all
(µ-Oxo)bis[diphenylantimony dicyclohexylphosphinate acetate],
[Ph2Sb(O2P(C6H11)2)(O2CMe)]2O (4). A mixture of 1 (0.50 g, 1.31
mmol) and silver acetate (0.875 g, 5.25 mmol) was heated in dry toluene
(20 mL) for 3 h under reflux and filtered. To the filtrate, dicyclo-
hexylphosphinic acid (0.30 g, 1.31 mmol) was added and the mixture
heated under reflux for 5 h. Then the solvent was removed and the
residue crystallized from dichloromethane-heptane (1:7) with stringent
precautious against the ingress of moisture. Yield: 0.40 g, 27% (mp
218 °C). IR (major bands only): 1680 (ν(CdO)), 1278, 1091
(ν(PdO)), 1014, and 981 cm-1
.
1H NMR (after drying): δ 0.70-
2.00 (br m, 44H, C6H11), 2.05 (s, 6H, CH3), 7.23-8.15 (m, 20H, H(Ar)).
31P NMR: δ 53.3 Anal. Calcd for C52H70O9P2Sb2: C, 54.60; H, 6.12.
Found: C, 54.10; H, 6.23.

Cages of Oxodiphenylantimony Phosphinates
Inorganic Chemistry, Vol. 35, No. 11, 1996 3237
Table 3. Positional Parameters for 3
Table 2. Positional Parameters for 2
atom
x
y
z
atom
x
y
z
Sb
P
O(1)
O(2)
O(3)
C(1)
C(2)
C(3)
C(4)
C(5)
C(6)
C(7)
C(8)
C(9)
C(10)
C(11)
C(12)
C(13)
C(14)
C(15)
C(16)
C(17)
C(18)
C(19)
C(20)
C(21)
C(22)
C(23)
C(24)
Cl(1)
Cl(2)
C(25)
0.1267 (1)
0.1778 (2)
0.0053 (5)
0.0201 (5)
0.2393 (5)
0.2392 (8)
0.3348 (9)
0.3987 (10)
0.3614 (10)
0.2702 (9)
0.2079 (9)
0.2404 (8)
0.1771 (10)
0.2506 (10)
0.3854 (10)
0.4464 (10)
0.3747 (9)
0.2276 (8)
0.1516 (9)
0.1912 (10)
0.3446 (10)
0.4235 (10)
0.3855 (9)
0.2514 (9)
0.1947 (10)
0.2477 (11)
0.2204 (12)
0.2790 (12)
0.2241 (10)
0.1242 (4)
-0.1131 (4)
0.0332 (11)
-0.1114 (1)
0.1633 (3)
0.0492 (4)
0.2101 (4)
0.0167 (5)
0.4865 (1)
0.4558 (2)
0.3926 (4)
0.4897 (4)
0.4862 (4)
0.3352 (6)
0.2615 (7)
0.1574 (9)
0.1286 (8)
0.1998 (8)
0.3059 (7)
0.6051 (6)
0.7167 (7)
0.7950 (9)
0.7587 (8)
0.6504 (8)
0.5705 (7)
0.3098 (6)
0.2693 (7)
0.1403 (8)
0.1023 (8)
0.1430 (8)
0.2724 (7)
0.5466 (6)
0.5442 (8)
0.6288 (8)
0.7437 (9)
0.7491 (10)
0.6668 (8)
0.0508 (3)
0.0547 (3)
0.1137 (9)
Sb(1)
Cl(1)
Cl(2)
P(1)
O(1)
O(2)
O(3)
C(1)
C(2)
C(3)
C(4)
C(5)
C(6)
C(7)
C(8)
C(9)
C(10)
C(11)
C(12)
C(13)
C(14)
C(15)
C(16)
C(17)
C(18)
C(19)
C(20)
C(21)
C(22)
C(23)
C(24)
C(25)
C(26)
C(27)
C(28)
C(29)
0.03043 (2)
0.7042(1)
0.06823 (1)
0.16138 (6)
0.16243 (8)
0.04775 (4)
0.0884 (1)
0.0229 (1)
-0.0285 (1)
0.1041 (2)
0.0867 (2)
0.1090 (2)
0.1486 (2)
0.1655 (2)
0.1434 (2)
0.1586 (2)
0.1540 (2)
0.2119 (2)
0.2745 (2)
0.2800 (2)
0.2221 (2)
0.0563 (2)
0.0373 (2)
0.0877 (2)
0.0952 (2)
0.1226 (2)
0.0694 (2)
0.0071 (2)
0.0181 (2)
0.0875 (2)
0.0431 (2)
0.0369 (3)
0.0925 (3)
0.1526 (3)
0.2095 (2)
0.2003 (2)
0.1597 (2)
0.1697 (2)
0.05497 (2)
0.2657 (1)
0.3988 (1)
-0.17255 (7)
-0.0647 (2)
-0.0639 (2)
-0.1639 (2)
0.1840 (3)
0.1868 (3)
0.2723 (4)
0.3538 (3)
0.3529 (3)
0.2671 (3)
0.0273 (3)
-0.0164 (3)
-0.0341 (3)
-0.0087 (3)
0.0316 (3)
0.9562 (1)
0.06911 (7)
0.1017 (2)
-0.1011 (2)
0.0464 (2)
0.1872 (3)
0.2990 (3)
0.3995 (3)
0.3900 (4)
0.2797 (4)
0.1780 (3)
-0.0741 (3)
-0.1979 (3)
-0.2668 (3)
-0.2125 (3)
-0.0908 (3)
-0.0212 (3)
0.1988 (3)
0.1749 (3)
0.2257 (3)
0.3605 (3)
0.4257 (3)
0.4876 (3)
0.4133 (3)
0.3028 (3)
-0.0626 (3)
-0.1318 (3)
-0.2629 (4)
-0.3419 (4)
-0.3284 (4)
-0.2437 (5)
-0.1404 (4)
-0.0346 (3)
0.8486 (4)
-0.1512 (7)
-0.0842 (9)
-0.1015 (10)
-0.1828 (9)
-0.2506 (9)
-0.2371 (8)
-0.2767 (7)
-0.3212 (9)
-0.4324 (10)
-0.4956 (9)
-0.4539 (9)
-0.3426 (8)
0.2568 (7)
0.4030 (8)
0.4668 (10)
0.4447 (9)
0.3020 (9)
0.2375 (9)
0.1903 (7)
0.3332 (9)
0.3535 (10)
0.2572 (10)
0.1187 (11)
0.0927 (9)
0.0499 (3)
-0.2086 (3)
-0.3291 (3)
-0.3883 (3)
-0.3510 (3)
-0.2345 (3)
-0.1488 (3)
-0.1487 (3)
-0.1223 (3)
-0.2711 (3)
-0.3719 (3)
-0.4003 (4)
-0.4197 (7)
-0.3472 (4)
-0.3365 (5)
-0.3724 (4)
-0.2969 (3)
0.2669 (4)
0.2217 (4)
0.1543 (4)
0.1016 (11)
nonhydrogen atoms were refined anisotropically. The hydrogen atoms
were included at calculated positions. For 5, Sb and P atoms were
refined anisotropically and the remaining nonhydrogen atoms were
refined isotropically; all of the hydrogen atoms except those bonded
to the solvent molecule were generated on the basis of geometry
considerations. Although the solvent is disordered in 5, the positions
of the carbon and chlorine atoms refined reasonably well, giving
satisfactory bond parameters.
phosphinic acid, two of the acetates may be replaced to give a
mixed acetate-phosphinate; in fact, in the case of dicyclohexy-
lphosphinic acid, when the reaction time after adding the acid
was reduced, we have been able to isolate the mixed acetate-
phosphinate, [Ph2Sb(O2CMe)(O2P(C6H11)2)]2O (4) (31P NMR:
53.1 ppm). Product 4, although isolatable, is moisture sensitive.
If the reaction is allowed to continue for a longer time or if 4
is crystallized in open air, adventitious moisture is sufficient to
hydrolyze this intermediate to 2 (eq 2). Such a feature is
observed for other antimony carboxylates also.1,2
Results and Discussion
The dimeric compounds [Ph2Sb(O2PR2)O]2 (R ) cyclo-C6H11
(2), cycl-C8H15 (3)) have been synthesized by two different
routes (eq 1). The 31P NMR spectra of 2 and 3 show a single
+R2POOH (+H2O)
Ph2SbCl3 + 3AgO2CMe
route A
H2O
[Ph2Sb(O2CMe)(O2P(C6H11)2)]2O
8
-2CH3COOH
(1)
[Ph2Sb(O2PR2)O]2
4
24 h (H2O)
route B
R = cycl-C6H11 (2),
cycl-C8H15 (3)
[Ph2Sb(O2P(C6H11)2O]2
Ph2SbCl3 + 3AgO2PR2
(2)
2
resonance at 64.3 and 69.6 ppm, respectively, and are consistent
with a dimeric structure in solution with a single phosphorus
environment. For both of the compounds route A utilizing silver
acetate affords the best yields of the pure products. In this route
the initially formed acetate Ph2Sb(O2CMe)3 is very moisture-
sensitive and presumably hydrolyzes to give [Ph2Sb(O2-
CMe)2]2O as reported in the literature.2 Upon addition of the
In the second method (route B) for the synthesis of 2, the
chloro compound1 [Ph2SbCl(O2PC6H11)2)]2O [31P NMR: 54.6
ppm] which we have reported before is a minor product; indeed
if the reaction is not allowed to continue for longer than 2 h,
this chloro compound becomes the major product.
Both compounds 2 and 3 are fairly stable in air; however,
when 2 is heated with a mixture of acetic acid and water, the
tetrameric cage Ph8Sb4O4(OH)2(O2P(C6H11)2)2‚CH3COOH (5
without CH2Cl2) is obtained in good yield (eq 3); this compound
(8) (a) Calbrese, J. C. PHASE-Patterson Heavy Atom Solution Extractor.
Ph.D. Thesis, University of WisconsinsMadison, 1972. (b) Beur-
skens, P. T. DIRDIF: Direct Methods for Difference StructuressAn
Automatic Procedure for Phase Extension and Refinement of Differ-
ence Structure Factors; Technical Report 1984/1, Crystallography
Laboratory, Toernooiveld: Nijmegen, Netherlands.
(9) (a) TEXSAN, Texray Structure Analysis Package; Molecular Structure
Corp.: The Woodlans, TX, 1987 (revised). (b) Sheldrick, G. M.
SHELX-86: Program for Crystal Structure Solution; University of
Go¨ttingen: Go¨ttingen, Germany, 1986. (c) Sheldrick, G. M. SHELXL-
93: Program for Crystal Structure Refinement; University of Go¨ttin-
gen: Go¨ttingen, Germany, 1993.
2[Ph2Sb(O2P(C6H11)2)O]2 CH COOH + 2H O8
Ph8Sb4O4(OH)2(O2P(C6H11)2)2‚CH3COOH +
3
2
2(C6H11)2POOH (3)
was initially obtained in an attempt to crystallize the products
from the reaction shown in eq 1 (route A). Compound 5 also

3238 Inorganic Chemistry, Vol. 35, No. 11, 1996
Table 4. Positional Parameters for 5
Said et al.
atom
x
y
z
atom
x
y
z
Sb(1)
Sb(2)
Sb(3)
Sb(4)
Cl(1)
Cl(2)
P(1)
0.32519(9)
0.33668(8)
0.50527(8)
0.48313(8)
0.636(1)
0.599(1)
0.3984(4)
0.3599(4)
0.3395(7)
0.4779(7)
0.3118(8)
0.4243(8)
0.4558(7)
0.3495(8)
0.4804(7)
0.3709(8)
0.5306(7)
0.3448(7)
0.478(1)
0.575(1)
0.181(1)
0.125(1)
0.032(1)
-0.001(1)
0.053(2)
0.145(1)
0.325(1)
0.341(1)
0.336(2)
0.319(2)
0.310(2)
0.309(1)
0.338(1)
0.387(1)
0.389(1)
0.342(2)
0.289(2)
0.290(1)
0.195(1)
0.162(1)
0.071(2)
0.011(2)
0.045(1)
0.137(1)
0.644(1)
0.707(1)
0.801(2)
0.823(2)
0.27922(5)
0.14653(5)
0.15003(5)
0.28194(6)
0.3406(7)
0.2372(7)
0.0460(2)
0.3815(2)
0.0735(4)
0.0753(4)
0.3541(4)
0.3507(4)
0.2925(4)
0.2590(5)
0.1440(5)
0.1593(4)
0.2176(5)
0.2130(5)
0.4651(9)
0.4527(6)
0.2767(7)
0.2928(7)
0.2920(8)
0.2765(8)
0.2604(8)
0.2596(7)
0.3034(7)
0.3490(9)
0.363(1)
0.73455(7)
0.73456(8)
0.64789(8)
0.63807(7)
0.9166(9)
0.884(1)
0.6604(3)
0.6472(3)
0.7039(6)
0.6462(6)
0.6990(6)
0.6129(6)
0.7386(6)
0.6277(6)
0.7549(7)
0.6377(7)
0.6629(6)
0.7654(6)
0.414(1)
0.5203(10)
0.691(1)
0.7380(10)
0.714(1)
0.645(1)
0.599(1)
0.624(1)
0.8454(10)
0.866(1)
0.941(2)
0.986(1)
0.970(1)
0.895(1)
0.841(1)
0.902(1)
0.972(1)
0.981(1)
0.923(1)
0.851(1)
0.692(1)
0.622(1)
0.595(1)
0.642(1)
0.710(1)
0.736(1)
0.6879(10)
0.683(1)
0.710(1)
0.743(1)
C(29)
C(30)
C(31)
C(32)
C(33)
C(34)
C(35)
C(36)
C(37)
C(38)
C(39)
C(40)
C(41)
C(42)
C(43)
C(44)
C(45)
C(46)
C(47)
C(48)
C(49)
C(50)
C(51)
C(52)
C(53)
C(54)
C(55)
C(56)
C(57)
C(58)
C(59)
C(60)
C(61)
C(62)
C(63)
C(64)
C(65)
C(66)
C(67)
C(68)
C(69)
C(70)
C(71)
C(72)
C(73)
C(74)
C(75)
0.763(2)
0.672(1)
0.494(1)
0.412(1)
0.406(2)
0.482(2)
0.564(2)
0.571(1)
0.472(1)
0.393(1)
0.389(1)
0.463(2)
0.543(2)
0.551(1)
0.614(1)
0.634(1)
0.722(2)
0.786(2)
0.765(2)
0.677(1)
0.441(1)
0.369(2)
0.403(2)
0.464(2)
0.539(2)
0.501(2)
0.335(1)
0.243(1)
0.184(2)
0.240(2)
0.334(2)
0.386(1)
0.423(1)
0.363(1)
0.417(1)
0.498(2)
0.554(2)
0.505(2)
0.275(1)
0.205(1)
0.135(2)
0.178(2)
0.249(2)
0.319(2)
0.551(2)
0.541(2)
0.688(2)
0.0795(9)
0.0901(8)
0.1445(7)
0.1481(8)
0.1397(9)
0.1313(9)
0.1292(9)
0.1353(8)
0.2764(7)
0.2854(8)
0.2800(9)
0.2730(8)
0.2630(8)
0.2653(7)
0.3128(6)
0.3540(8)
0.3727(9)
0.3510(9)
0.3110(9)
0.2926(8)
-0.0070(7)
-0.0381(9)
-0.0789(10)
-0.0640(10)
-0.0310(9)
0.0104(10)
0.0321(7)
0.0061(8)
0.0028(9)
-0.0229(10)
0.001(1)
0.0055(9)
0.4323(7)
0.4660(7)
0.5089(8)
0.4956(9)
0.4581(10)
0.4159(9)
0.4053(7)
0.3669(7)
0.3863(9)
0.4042(8)
0.4450(9)
0.4247(9)
0.393(1)
0.740(1)
0.715(1)
0.534(1)
0.486(1)
0.411(1)
0.384(1)
0.427(1)
0.505(1)
0.5230(10)
0.477(1)
0.400(1)
0.373(1)
0.419(1)
0.497(1)
0.6671(10)
0.631(1)
0.649(1)
0.700(1)
0.738(1)
0.719(1)
0.713(1)
0.732(1)
0.783(2)
0.848(1)
0.833(1)
0.782(1)
0.572(1)
0.574(1)
0.495(1)
0.445(1)
0.446(2)
0.522(1)
0.692(1)
0.726(1)
0.762(1)
0.816(1)
0.787(1)
0.747(1)
0.572(1)
0.546(1)
0.481(1)
0.425(1)
0.448(1)
0.513(1)
0.421(2)
0.459(2)
0.937(1)
P(2)
O(1)
O(2)
O(3)
O(4)
O(5)
O(6)
O(7)
O(8)
O(9)
O(10)
O(11)
O(12)
C(1)
C(2)
C(3)
C(4)
C(5)
C(6)
C(7)
C(8)
C(9)
C(10)
C(11)
C(12)
C(13)
C(14)
C(15)
C(16)
C(17)
C(18)
C(19)
C(20)
C(21)
C(22)
C(23)
C(24)
C(25)
C(26)
C(27)
C(28)
0.3309(9)
0.284(1)
0.2690(7)
0.1210(7)
0.1441(7)
0.1274(8)
0.0887(9)
0.0636(9)
0.0807(8)
0.1450(7)
0.1262(8)
0.1229(8)
0.1343(8)
0.1520(8)
0.1560(7)
0.1330(7)
0.1692(8)
0.1578(9)
0.1140(9)
0.440(1)
0.282(1)
shows a single resonance in the 31P NMR spectrum at 57.7 ppm,
showing that the two phosphinates are in an identical chemical
environment (see below for structure). Under similar experi-
mental conditions compound 3 does not hydrolyze to any
significant extent.
What is perhaps more interesting is the observation that we
were able to convert the tetrameric cage 5 back to the dimer 2
by heating the former with an excess of dicyclohexylphosphinic
acid (eq 4). The 31P NMR spectrum of the reaction mixture
Ph8Sb4O4(OH)2(O2P(C6H11)2)2‚CH3COOH +
3(C6H11)2POOH toluene8 2[Ph2Sb(O2P(C6H11)2)O]2 +
4 h
(C6H11)2POOH + CH3COOH + 2H2O (4)
showed compound 2 to be the major product [δ ) 64.3 ppm;
>85%]; two minor products [δ ) 53.8 and 45.9 ppm with total
intensity < 10%)] were also observed. Earlier we have
demonstrated the interconversion between the two carboxylates
[Ph2Sb(O2CMe)2]2O and Ph8Sb4O6(HO2CMe)3.1 Thus it ap-
pears that the Sb-O bonds in these compounds are quite labile;
such a feature is reminiscent of the interconversion observed
in n-butyltin oxocarboxylates/-phosphinates.10
Figure 1. Molecular structure of 2. H atoms and the solvent molecule
not shown.
Structural Aspects
The molecular structures of compounds 2, 3, and 5 are
depicted in Figures 1-3.) Selected bond distances and bond
angles are provided in Tables 5-7. All three compounds
possess four membered Sb-O-Sb-O rings with bridging
phosphinates and hexacoordinated antimony. In 5 the two
(10) Holmes, R. R. Acc. Chem. Res. 1989, 22, 190.

Cages of Oxodiphenylantimony Phosphinates
Inorganic Chemistry, Vol. 35, No. 11, 1996 3239
Table 6. Selected Bond Lengths (Å) and Bond Angles (deg) with
Esds in Parentheses for 3 (Atoms Related by a Center of Symmetry
Given the Suffix A)
Sb(1)-O(1)
Sb(1)-O(2)
Sb(1)-O(2A)
Sb(1)-O(3A)
Sb(1)-C(1)
Sb(1)-C(7)
2.100(2)
1.975(2)
1.977(2)
2.132(2)
2.134(3)
2.137(3)
P(1)-O(1)
1.546(2)
1.542(2)
1.812(3)
1.811(3)
3.0142(5)
P(1)-O(3)
P(1)-C(13)
P(1)-C(21)
Sb(1)‚‚‚Sb(1A)
O(1)-Sb(1)-O(2)
O(1)-Sb(1)-O(2A)
O(1)-Sb(1)-O(3A)
O(1)-Sb(1)-C(1)
O(1)-Sb(1)-C(7)
O(2)-Sb(1)-O(2A)
O(2)-Sb(1)-O(3A)
O(2)-Sb(1)-C(1)
O(2)-Sb(1)-C(7)
85.97(8) O(3A)-Sb(1)-C(1)
85.74(8) O(3A)-Sb(1)-C(7)
168.99(8) C(1)-Sb(1)-C(7)
92.2(1) O(1)-P(1)-O(3)
95.7(1) O(1)-O(1)-C(13)
80.6(1) O(1)-P(1)-C(21)
86.51(8) O(3)-P(1)-C(13)
171.6(1) O(3)-P(1)-C(21)
89.7(1) C(13)-P(1)-C(21)
94.1(1)
92.3(1)
98.7(1)
115.5(1)
104.2(1)
106.4(1)
107.9(1)
110.0(1)
112.9(2)
123.7(1)
O(2A)-Sb(1)-O(3A) 85.10(8) Sb(1)-O(1)-P(1)
O(2A)-Sb(1)-C(1)
O(2A)-Sb(1)-C(7)
91.1(1) Sb(1A)-O(3)-P(1) 123.0(1)
170.1(1) Sb(1)-O(2)-Sb(1A) 99.4(1)
compounds represent new structural types for antimony phos-
phinates.
The Sb-O-Sb-O rings 2 and 3 are nearly planar; however,
the angles at the oxygen atoms are wider [99.1(2)° for 2 and
99.4(1)° for 3] at the expense of those at antimony [80.9(2)°
for 2 and 80.6(1)° for 3] in both of the dinuclear compounds.
It is interesting to note that diminution of the angle at antimony
is found even at pentacoordinated antimony in [Ph3SbO]2 (III)
Figure 2. Molecular structure of 3. H atoms and the solvent molecule
not shown.
(77.4°)11 and the fused ring system in Ph8Sb4O6 (IV) (76°),12
both of which contain the Sb2O2 ring system. The Sb-O
distances within the four membered ring in 2 [mean ) 1.984
Å] are shorter than the Sb-O distances to the bridging
phosphinates but are longer than the Sb-O(oxo) distances in
[Ph2SbCl(O2P(C6H11)2)]2O (I) [1.936(4) and 1.938(4) Å; mean
) 1.937 Å] and [Cl3Sb(O2PMe2)]2O [1.942(2) Å].13 The
transoidal orientation of phosphinates in 2 and 3 as compared
to cisoidal in I is most likely due to a restriction imposed by
the formation of the Sb2O2 ring.
An interesting correlation exists between the compound Ph8-
Sb4O6 (IV) and our compounds 2 and 3. Removal of the two
bonds Sb(2)-O(2) and Sb(1)-O(2) from IV will lead to the
same skeleton as that observed for 2 or 3, with the antimony
atoms Sb(2) and Sb(1)′ (in IV) being replaced by the phosphorus
atoms (in 2 or 3). In fact in the original paper12 the authors
suggest such a canonical structure for IV.
Figure 3. Molecular structure of 5 showing the skeleton. C atoms of
the phenyl, cyclohexyl, acetic acid, and solvent as well as H atoms are
omitted for clarity.
Table 5. Bond Lengths (Å) and Bond Angles (deg) with Esds in
Parentheses for 2 (Atoms Related by a Center of Symmetry Given
the Suffix A)
Sb-O(1)
Sb-O(1A)
Sb-O(2A)
Sb-O(3)
Sb-C(1)
1.986(5)
1.982(5)
2.115(5)
2.112(5)
2.147(8)
P-O(2)
1.530(5)
1.538(5)
1.794(8)
1.805(8)
3.019(4)
P-O(3)
P-C(13)
P-C(19)
Sb-Sb(A)
O(1A)-Sb-O(1)
O(1A)-Sb-O(3)
O(1)-Sb-O(3)
O(1A)-Sb-O(2A)
O(1)-Sb-O(2A)
O(1A)-Sb-C(7)
O(3)-Sb-C(7)
O(3)-Sb-O(2A)
O(1)-Sb-C(7)
O(2A)-Sb-C(7)
O(1)-Sb-C(1)
O(1A)-Sb-C(1)
80.9(2)
O(2A)-Sb-C(1)
C(7)-Sb-C(1)
O(3)-Sb-C(1)
O(2)-P-O(3)
O(2)-P-C(13)
O(2)-P-C(19)
O(3)-P-C(13)
O(3)-P-C(19)
C(13)-P-C(19)
Sb(A)-O(1)-Sb
P-O(2)-Sb(A)
P-O(3)-Sb
92.0(3)
99.4(3)
95.4(3)
116.7(3)
108.6(3)
106.3(3)
106.2(3)
107.0(3)
112.2(4)
99.1(2)
86.6(2)
85.6(2)
84.6(2)
86.3(2)
91.7(3)
93.9(3)
168.9(2)
172.7(2)
93.1(3)
87.9(3)
168.5(2)
In compound 5 charge balance would require the formula
for the unsolvated molecule to be written as Ph8Sb4O4(OH)2-
(O2P(C6H11)2)2. In the actual structure, an acetic acid molecule,
unconnected to the antimony cage even by H bonding, is also
present. On the basis of the bond length data (Table 7) we
propose that the oxygen atoms O(6) and O(7) of the cage are
126.8(3)
125.6(3)
(11) Ferguson, G.; Glidewell, C.; Kaitner, B.; Lloyd, D.; Metcalfe, S. Acta
Crystallogr. 1987, C43, 824.
(12) Bordner, J.; Doak, G. O.; Everett, T. S. J. Am. Chem. Soc. 1986, 108,
4206.
Sb2O2 rings are connected through oxo bridges between the
antimony atoms to form an Sb4O6 cage, and the structure can
be described as a crown.3 The bridging phosphinates in 2, 3,
and 5 are cis to the phenyl groups on antimony. Thus the three
(13) Blo¨sl, S.; Schwarz, W.; Schmidt, A. Z. Naturforsch. 1984, 38B, 143.

3240 Inorganic Chemistry, Vol. 35, No. 11, 1996
Said et al.
Table 7. Selected Interatomic Distances (Å) and Bond Angles
(deg) with Esds in Parentheses for 5
In connection with the Sb4O6 skeleton that we observe in 5,
it is instructive to note that a second alternative structure (A)
Sb(1)-O(5)
Sb(1)-O(6)
Sb(1)-O(3)
Sb(1)-O(10)
Sb(1)-C(1)
Sb(1)-C(7)
Sb(2)-O(8)
Sb(2)-O(7)
Sb(2)-O(1)
Sb(2)-O(10)
Sb(2)-C(13)
Sb(2)-C(19)
Sb(3)-O(8)
Sb(3)-O(7)
Sb(3)-O(2)
Sb(3)-O(9)
2.00(1)
2.17(1)
2.19(1)
1.94(1)
2.17(2)
2.18(2)
2.01(1)
2.13(1)
2.12(1)
1.93(1)
2.10(2)
2.14(2)
2.02(1)
2.11(1)
2.12(1)
1.93(1)
Sb(3)-C(25)
Sb(3)-C(31)
Sb(4)-O(5)
Sb(4)-O(6)
Sb(4)-O(4)
Sb(4)-O(9)
Sb(4)-C(37)
Sb(4)-C(43)
O(1)-P(1)
2.14(2)
2.11(2)
2.02(1)
2.09(1)
2.13(1)
1.95(1)
2.13(2)
2.13(2)
1.52(1)
1.52(1)
1.52(1)
1.53(1)
3.257(2)
3.270(2)
2.79(3)
2.80(2)
P(1)-O(2)
O(3)-P(2)
P(2)-O(4)
Sb(1)-Sb(4)
Sb(2)-Sb(3)
O(11)‚‚‚O(12)a
O(6)‚‚‚O(8)
with an “adamantane” type of skeleton is possible. From the
molecular models at least, there does not appear to be any severe
strain in such a structure. Since such a cage for hexacoordinated
manganese has already been found,14 we believe that the crown
structure observed for 5 is a result of the reaction pathway rather
than any special preference for the observed structure.
O(3)-Sb(1)-O(5)
O(3)-Sb(1)-O(6)
O(3)-Sb(1)-O(10)
O(3)-Sb(1)-C(1)
O(3)-Sb(1)-C(7)
O(5)-Sb(1)-O(6)
O(5)-Sb(1)-O(10)
O(5)-Sb(1)-C(1)
O(5)-Sb(1)-C(7)
O(6)-Sb(1)-O(10)
O(6)-Sb(1)-C(1)
O(6)-Sb(1)-C(7)
O(10)-Sb(1)-C(1)
O(10)-Sb(1)-C(7)
C(1)-Sb(1)-C(7)
O(1)-Sb(2)-O(7)
O(1)-Sb(2)-O(8)
O(1)-Sb(2)-O(10)
O(1)-Sb(2)-C(13)
O(1)-Sb(2)-C(19)
O(7)-Sb(2)-O(8)
O(7)-Sb(2)-O(10)
O(7)-Sb(2)-C(13)
O(7)-Sb(2)-C(19)
O(8)-Sb(2)-O(10)
O(8)-Sb(2)-C(13)
O(8)-Sb(2)-C(19)
O(10)-Sb(2)-C(13)
O(10)-Sb(2)-C(19)
82.3(5) O(7)-Sb(3)-O(9)
89.5(5) O(7)-Sb(3)-C(25)
176.5(4) O(7)-Sb(3)-C(31)
83.7(6) O(8)-Sb(3)-O(9)
88.6(6) O(8)-Sb(3)-C(25)
75.0(4) O(8)-Sb(3)-C(31)
94.2(5) O(9)-Sb(3)-C(25)
158.9(6) O(9)-Sb(3)-C(31)
90.3(5)
89.6(6)
162.9(6)
93.2(5)
164.0(6)
91.6(6)
90.7(6)
101.2(7)
Analogy to Tin Structures
In hexacoordinated systems, five covalent and one coordinate
bond would make antimony(V) electronically equivalent to tin-
(IV) with four covalent and two coordinate bonds. Hence
structural analogies can be expected between Sn(IV) and Sb-
(V) derivatives. Thus compounds 2, 3, and 5 are structurally
equivalent to the “butterfly” (VI)15 and crown (VII) structures
reported for tin.
95.0(6) C(25)-Sb(3)-C(31) 102.8(8)
89.0(5) O(4)-Sb(4)-O(5)
89.1(6) O(4)-Sb(4)-O(6)
170.0(6) O(4)-Sb(4)-O(9)
99.4(6) O(4)-Sb(4)-C(37)
92.3(6) O(4)-Sb(4)-C(43)
100.5(7) O(5)-Sb(4)-O(6)
86.8(5) O(5)-Sb(4)-O(9)
84.6(5) O(5)-Sb(4)-C(37)
175.3(4) O(5)-Sb(4)-C(43)
86.2(6) O(6)-Sb(4)-O(9)
87.1(6) O(6)-Sb(4)-C(37)
74.7(5) O(6)-Sb(4)-C(43)
88.5(5) O(9)-Sb(4)-C(37)
89.7(6) O(9)-Sb(4)-C(43)
85.6(5)
84.3(5)
176.6(5)
83.9(6)
91.2(6)
76.4(5)
92.6(5)
163.3(6)
92.9(6)
92.6(5)
89.7(6)
168.7(6)
97.3(6)
91.7(6)
168.1(6) C(37)-Sb(4)-C(43) 100.2(7)
94.9(5) O(1)-P(1)-O(2)
162.2(6) O(3)-P(2)-O(4)
94.5(6) Sb(2)-O(1)-P(1)
93.1(6) Sb(3)-O(2)-P(1)
97.6(6) Sb(1)-O(3)-P(2)
112.8(7)
113.9(7)
132.2(7)
133.2(7)
130.1(7)
133.3(8)
108.4(5)
99.6(5)
C(13)-Sb(2)-C(19) 100.1(7) Sb(4)-O(4)-P(2)
O(2)-Sb(3)-O(7)
O(2)-Sb(3)-O(8)
O(2)-Sb(3)-O(9)
O(2)-Sb(3)-C(25)
O(2)-Sb(3)-C(31)
O(7)-Sb(3)-O(8)
82.3(5) Sb(1)-O(5)-Sb(4)
86.3(5) Sb(1)-O(6)-Sb(4)
172.5(5) Sb(2)-O(7)-Sb(3)
87.8(6) Sb(2)-O(8)-Sb(3)
86.3(6) Sb(3)-O(9)-Sb(4)
100.9(5)
108.7(5)
143.8(6)
74.9(5) Sb(1)-O(10)-Sb(2) 145.6(6)
a Intermolecular distance.
protonated; it can be readily seen that Sb-O distances to these
oxygen atoms are longer than the other nonphosphinate Sb-O
distances [to O(5), O(8), O(9), and O(10)].
Compared to 2, the Sb2O2 rings in 5 are slightly nonplanar
with a maximum deviation of atoms being e0.1 Å from the
mean plane. What is more interesting in 5, however, is the
dihedral angle between the two Sb2O2 rings [Sb(4)-O(5)-Sb-
(1)-O(6) and Sb(2)-O(7)-Sb(3)-O(8)] which is 30°. This
makes the atoms O(6) and O(8) come closer (2.80 Å);
simultaneously, O(5) and O(7) move farther apart (4.18 Å). The
O(6)-O(8) distance is appropriate for a proton to sit between.
In the X-ray structure of the acetate analogue Ph8Sb4O6(HO2-
CMe)3‚CH2Cl2 (IV) of 5, which has been described briefly in
a communication,2 a proton resides between the atoms corre-
sponding to O(6) and O(8) [O‚‚‚O distance in V: 2.63 Å].
However, in the acetate cage V an acetic acid molecule bridges
the oxygens corresponding to O(5) and O(7) by H bonding;
such a feature is absent in compound 5. The acetate group in
5 exists as acetic acid and is neutral; this conclusion is based
on the intermolecular H bond between the two oxygens
[O(11)‚‚‚O(12′) ) 2.79(3) Å] of the acetic acid.
To summarize, two new structural forms, one with a dinuclear
Sb2O2 skeleton and the other with a tetranuclear Sb4O6 cage
for oxoantimony phosphinates, have been uncovered. It should
be possible to synthesize other structural forms (such as the
adamantane A) with oxo bridges. Indeed in the reactions using
(14) Hagen, K. S.; Westmoreland, T. D.; Scott, M. J.; Armstrong, W. H.
J. Am. Chem. Soc. 1989, 111, 1907.
(15) Holmes, R. R.; Kumara Swamy, K. C.; Schmid, C. G.; Day, R. O. J.
Am. Chem. Soc. 1988,110, 7060.
(16) Kumara Swamy, K. C.; Day, R. O.; Holmes, R. R. Inorg. Chem. 1992,
31, 4184.

Cages of Oxodiphenylantimony Phosphinates
Inorganic Chemistry, Vol. 35, No. 11, 1996 3241
dicyclohexylphosphinic acid we have identified a new com-
pound [δ(31P): 45.9 ppm] in addition to the structurally
characterized derivatives [Ph2SbCl(O2P(C6H11)2)]2O,1 [Ph2Sb-
(O2P(C6H11)2)O]2‚CH2Cl2 (2), and Ph8Sb4O4(OH)2(O2P(C6H11)2)‚
CH3COOH‚CH2Cl2 (5). Efforts are underway to isolate and
characterize this new compound.
gratefully acknowledged for instrumental facilities. K.C.K.
thanks the AvH foundation also for support.
Supporting Information Available: Listings of anisotropic thermal
parameters (Tables S1-S3) and bond lengths and angles (Tables S4-
S6) and an ORTEP diagram of 5 showing all the atoms in the skeleton
(14 pages). Ordering information is given on any current masthead
page.
Acknowledgment. We thank the Council of Scientific and
Industrial Research (New Delhi) for financial support. COSIST
and Special Assistance Programme (UGC, New Delhi) are
IC950713W