An unknown coordination mode of the phosphite unit and a carbon-free heterocycle in two different heterobimetallic alumophosphites

Article abstract of DOI:10.1021/ic701614c

The unique alumophosphite reagent LAI(SH)(μ-O)P(OEt)₂ was prepared and used for the synthesis of the heterobimetallic alumophosphites [{κ²-S,P-LAI(S)(μ-O)P(OEt)₂}₂Zn] and [{κ⁴-S,O,O-LAI(SLi)(μ-O)P(OEt)₂}₂]. The first contains a rare example of two carbon-free five-membered heterocycles (Al-S-Zn-P-O) connected in a spire-fashion through the zinc atom, whereas the second possesses an unknown example of a coordination environment of a phosphite unit M-O-P(μ-OEt)₂M with an uncoordinated lone electron pair on the phosphorus center.

Full text of DOI:10.1021/ic701614c

Inorg. Chem. 2007, 46, 10749−10753
An Unknown Coordination Mode of the Phosphite Unit and a
Carbon-Free Heterocycle in Two Different Heterobimetallic
Alumophosphites
A. Paulina Go´mora-Figueroa, Vojtech Jancik,* Raymundo Cea-Olivares, and Rube´n A. Toscano
Instituto de Qu´ımica, UniVersidad Nacional Auto´noma de Me´xico, Circuito Exterior,
Ciudad UniVersitaria, 04510, Me´xico D.F, Me´xico
Received August 14, 2007
The unique alumophosphite reagent LAl(SH)(
heterobimetallic alumophosphites [{κ2-S,P-LAl(S)(
first contains a rare example of two carbon-free five-membered heterocycles (Al
fashion through the zinc atom, whereas the second possesses an unknown example of a coordination environment
of a phosphite unit M P( -OEt)2M with an uncoordinated lone electron pair on the phosphorus center.
µ
-O)P(OEt)2 was prepared and used for the synthesis of the
-O)P(OEt)2 -O)P(OEt)2 2]. The
2Zn] and [{κ4-S,O,O-LAl(SLi)(
Zn O) connected in a spiro
µ
}
µ
}
−S− −P−
−O− µ
Introduction
(Scheme 2) and the formation of two heterobimetallic
derivatives thereof containing an unknown coordination
mode of the phosphite unit and a carbon-free heterocycle,
respectively.
Recently, we have reported on the preparation of the
unique alumosilicate substrates LAl(EH)(µ-O)Si(OH)(OtBu)2
(E ) O, S; L ) [HC{C(Me)N(Ar)}2]-, Ar ) 2,6-di-iPr2C6H3)
from LAl(SH)2 and (tBuO)2Si(OH)2 and the derivative [LAl-
(SLi)(µ-O)Si(OLi‚thf2)(OtBu)2]2, a molecular heterobimetallic
alumosilicate.1 Thus, we became interested, if a similar
procedure could be used for the preparation of the alumo-
phospite analogue LAl(SH)(µ-O)P(OR)2 (R ) alkyl, aryl).
Such a complex could be used as a precursor for heterobi-
metallic alumophosphites LAl(SM)(µ-O)P(OR)2 (M ) metal,
R ) alkyl, aryl), in which the phosphite unit can be
coordinated to the metal M via the phosphorus (a) or one
(b) or two (c) oxygen atoms (Scheme 1). Despite the fact
that such molecular heterobimetallic alumophosphites are not
known, they can feature unusual or unknown coordination
modes of the PO3 unit. Furthermore, these alumophosphite
species could be used as precursors for alumophosphate
reagents by oxidizing the phosphorus atom similarly to the
synthesis of nucleosides, where the phosphate unit is mostly
constructed via a phosphite intermediate.2 Herein, we report
on the first alumophosphite precursor LAl(SH)(µ-O)P(OEt)2
Experimental Section
General. All of the manipulations described below were
performed under a dried dinitrogen atmosphere using standard
Schlenk and glovebox techniques. The solvents were purchased
from Aldrich and dried prior to use. Diethylphosphite (Strem
Chemicals, 95%) was purified by distillation under reduced pressure
and a nitrogen atmosphere. LAl(SH)2 was prepared according to
the literature procedure.3 The dimethylzinc solution 2.0 M in toluene
was purchased from Aldrich and used as received. [(Me3Si)2NLi‚
OEt2]2 was prepared freshly using a butyllithium solution and
hexamethyldisilazane in diethylether.
LAl(SH)(µ-O)P(OEt)2 (1). (EtO)2P(O)H (0.27 g, 1.95 mmol)
in THF (20 mL) was added dropwise to the solution of LAl(SH)2
(1.00 g, 1.95 mmol) in THF (40 mL) at -78 °C over the period of
35 min. The reaction mixture was allowed to warm up to ambient
temperature and stirred for additional 5 h. All of the volatiles were
removed in vacuum, the crude product was rinsed with cold hexane
(∼5 mL) and dried in a vacuum. 1 was obtained as a white powder.
Yield 1.15 g, 1.87 mmol (96%); Mp 94-96 °C. Elemental analysis
(%) Calcd for C33H52AlN2O3PS (614.8 g‚mol-1): C 64.47, H 8.53,
N 4.56; found: C 64.1, H 8.3, N 4.67. IR (CsI): ν˜ 2572 cm-1
3
(1) prepared from LAl(SH)2 and HP(O)(OEt)2 in THF
* To whom correspondence may be addressed. E-mail: vjancik@
servidor.unam.mx, Fax: (+)(52) 55-561-622-17.
(1) Jancik, V.; Rasco´n-Cruz, F.; Cea-Olivares, R.; Toscano, R. A. Chem.
Commun. 2007, in press.
(2) Kataoka, M.; Hattori, A.; Okino, S.; Hyodo, M.; Asano, M.; Kawai,
R.; Hayakawa, Y. Org. Lett. 2001, 3, 815-818.
(3) Jancik, V.; Peng, Y.; Roesky, H. W.; Li, J.; Neculai, D.; Neculai, A.
M.; Herbst-Irmer, R. J. Am. Chem. Soc. 2003, 125, 1452-1453.
1
(vw, ν SH). H NMR (300 MHz, benzene-d6, 25 °C, TMS): δ )
-0.53 (s, 2H, SH), 0.92 (t, 3JH,H ) 7.0 Hz, 6H, CH2CH3), 1.11 (d,
3JH,H ) 6.0 Hz, 6H, CH(CH3)2), 1.15 (d, 3JH,H ) 6.0 Hz, 6H, CH-
(CH3)2), 1.47 (d, 3JH,H ) 6.0 Hz, 6H, CH(CH3)2), 1.52 (s, 6H, CH3),
1.54 (d, 3JH,H ) 6.0 Hz, 6H, CH(CH3)2), 3.32 (dquart, 2JH,H ) 16.5
3
2
Hz, JH,H ) 7.0 Hz, 2H, CH2CH3), 3.44 (dquart, JH,H ) 16.5 Hz,
10.1021/ic701614c CCC: $37.00
Published on Web 11/07/2007
© 2007 American Chemical Society
Inorganic Chemistry, Vol. 46, No. 25, 2007 10749

Go´mora-Figueroa et al.
Scheme 1. Possible Coordination Modes of LAl(SH)(µ-O)P(OR)2
Scheme 2. Preparation of 1
3
3JH,H ) 7.0 Hz, 2H, CH2CH3), 3.46 (sept, JH,H ) 6.0 Hz, 2H,
3
CH(CH3)2), 3.54 (sept, JH,H ) 6.0 Hz, 2H, CH(CH3)2), 4.86 (s.
1H, CH), 7.08-7.15 ppm (m, 6H, m-, p-, H of Ar); 13C NMR (75.6
MHz benzene-d6, 25 °C, TMS): δ ) 17.0 (CH2CH3), 23.3, 24.5,
24.6, 24.7 (CH(CH3)2), 26.4 (CH3), 28.2, 28.7 (CH(CH3)2), 55.2
(CH2CH3), 97.9 (γ-CH), 124.2, 124.3, 124.7, 144.3, 144.6, 144.8,
(i-, o-, m-, p-C Ar,), 170.9 ppm (CdN); 31P NMR (121.6 MHz,
benzene-d6, 25 °C, 85% H3PO4): δ ) 126.7 ppm. EI-MS: m/z
(%) ) 614 (26) [M+], 556 (57) [M+ - 2CH2CH3], 476 (100)
[M+ - H(O)P(OEt)2].
(CH(CH3)2), 28.0 (CH3), 28.0, 28.5 (CH(CH3)2), 58.7 (CH2CH3),
97.6 (γ-CH), 123.5, 124.9, 127.0, 140.0, 144.3, 146.4, (i-, o-, m-,
p-C Ar), 125.4, 128.2, 129.0, 137.9 (i-, o-, m-, p-C toluene,) 169.8
ppm (CdN); 31P NMR (121.6 MHz, benzene-d6, 25 °C, 85% H3-
PO4): δ ) 106.9 ppm.
[{κ4-S,O,O-LAl(SLi)(µ-O)P(OEt)2}2] (2). A solution of 1 (0.30
g, 0.49 mmol) in THF (15 mL) was cooled to -78 °C and then a
solution of [(Me3Si)2NLi‚OEt2]2 (0.12 g, 0.25 mmol) in THF (10
mL) was added. The reaction mixture was allowed to warm up to
ambient temperature and was stirred for additional 3 h. All of the
volatiles were removed under a vacuum, leaving a white solid as
a product. The crude product was rinsed with cold THF (∼5 mL)
and dried under a vacuum. 2 was obtained as a white powder. Yield
0.25 g, 0.21 mmol (85%); Mp 160 °C (decomp.). Elemental analysis
(%) Calcd for C66H102Al2Li2N4O6P2S2 (1241.5 g‚mol-1): C 63.85,
H 8.28, N 4.51; found: C 63.5, H 8.1, N 4.62. 1H NMR (300 MHz,
THF-d8, 25 °C, TMS): δ ) 0.88 (t, 3JH,H ) 7.2 Hz, 12H, CH2CH3),
1.03 (d, 3JH,H ) 6.0 Hz, 12H, CH(CH3)2), 1.06 (d, 3JH,H ) 6.0 Hz,
X-ray Structure Determination. The crystals were mounted
on a nylon loop and a rapidly placed in a stream of cold nitrogen.
Diffraction data were collected on a Bruker-APEX three-circle
diffractometer using Mo KR radiation (λ ) 0.71073 Å) at 173 K.
The structures were solved by direct methods (SHELXS-974) and
refined against all of the data by full-matrix least-squares on F 2.5
The hydrogen atoms of C-H bonds were placed in idealized
positions, whereas the hydrogen atom from the SH moiety in 1
was localized from the difference electron-density map and refined
isotropically. The disordered toluene molecules as well as the
i
disordered Pr and ethoxy moieties were refined using geometry
and distance restraints (SAME, SADI) together with the restraints
for the Uij values (SIMU, DELU).
3
12H, CH(CH3)2), 1.24 (d, JH,H ) 6.0 Hz, 12H, CH(CH3)2), 1.30
3
(d, JH,H ) 6.0 Hz, 12H, CH(CH3)2), 1.63 (s. 12H, CH3), 3.07
2
3
(dquart, JH,H ) 16.5 Hz, JH,H ) 7.2 Hz, 4H, CH2CH3), 3.22
Results and Discussion
(dquart, 2JH,H ) 16.5 Hz, 3JH,H ) 7.2 Hz, 4H, CH2CH3), 3.64 (sept,
3JH,H ) 6.0 Hz, 4H, CH(CH3)2), 3.69 (sept, JH,H ) 6.0 Hz, 4H,
3
Formation of Complexes 1-3. The choice of the
phosphorus reagent is important because the aluminum
precursor is sensitive toward acids and water.3 Hence, the
use of diesters of phosphoric acid in the reaction, which
would lead directly to the corresponding alumophosphate,
is restricted because of the high acidity of the OH proton
and the presence of traces of alcohols or water in the reagent.
However, the acidity of the hydrogen in the phosphite is
negligible, and the traces of alcohol and water can be
conveniently removed by distillation or under a vacuum.
Moreover, the HOP T HP(O) tautomeric equilibrium sug-
gests the possibility of the isolation of 1. The formation of
1 was confirmed by the shift of the signal in the 31P NMR
spectra from 7.4 ppm (HP(O)(OEt)2) to 126.7 ppm (1).
Although the reaction mechanism is simple, great care has
to be taken while purifying the starting materials to avoid
the formation of the undesired byproducts LAl(OEt)(µ-O)P-
(OEt)2 (31P NMR δ 126.1 ppm) and LAl(SH)(µ-O)P(S)(OEt)2
(31P NMR δ 58.0 ppm), as all three products have similar
solubility and are thus difficult to separate. The first
compound is always present in a bulk of 1, but its amount
can be significantly reduced (from more than 30 to less than
3%) by distillation of the phosphite prior to use and by
CH(CH3)2), 5.06 (s, 2H, CH), 7.02-7.12 ppm (m, 12H, m-, p-, H
of Ar); 13C NMR (75.6 MHz, THF-d8, 25 °C, TMS): δ ) 17.5
(CH2CH3), 24.1, 24.8, 25.1, 25.8 (CH(CH3)2), 26.9 (CH3), 28.6,
28.9 (CH(CH3)2), 56.3 (CH2CH3), 97.8 (γ-CH), 124.1, 124.6, 126.6,
143.3, 145.9, 146.3, (i-, o-, m-, p-C Ar,), 169.0 ppm (CdN); 31P
NMR (121.6 MHz, THF-d8, 25 °C, 85% H3PO4): δ ) 131.7 ppm;
7Li NMR (116.8 MHz, THF-d8, 25 °C, LiCl/D2O 1.8 M): δ )
1.40 ppm.
[{κ2-S,P-LAl(S)(µ-O)P(OEt)2}2Zn]‚3.5 toluene (3). A solution
of 1 (0.26 g, 0.42 mmol) in toluene (15 mL) was cooled to -78
°C and ZnMe2 (2.0 M in toluene, 0.12 mL, 0.24 mmol) was added.
The reaction mixture was allowed to warm up to ambient temper-
ature and was stirred for additional 2 h. The product precipitated
as a white solid. All of the volatiles were removed under vacuum.
The crude product was rinsed with cold toluene (∼5 mL) and dried
under a vacuum. 3 was obtained as a white powder. Yield 0.31 g,
0.24 mmol (57%); Mp 184-186 °C. Elemental analysis (%) Calcd
for C90.5H130Al2N4O6P2S2Zn (1609.5 g‚mol-1): C 67.16, H 8.14,
N 3.48; found: C 67.0, H 8.2, N 3.6. 1H NMR (300 MHz, benzene-
3
d6, 25 °C, TMS): δ ) 0.93 (t, JH,H ) 7.2 Hz, 12H, CH2CH3),
1.05 (d, 3JH,H ) 6.0 Hz, 12H, CH(CH3)2), 1.21 (d, 3JH,H ) 6.0 Hz,
3
12H, CH(CH3)2), 1.49 (d, JH,H ) 6.0 Hz, 12H, CH(CH3)2), 1.51
3
(s. 12H, CH3), 1.70 (d, JH,H ) 6.0 Hz, 12H, CH(CH3)2), 2.10 (s,
10.5H, CH3 from toluene), 2.43 (bs, 4H, CH2CH3), 3.36 (sept. 3JH,H
) 6.0 Hz, 4H, CH(CH3)2), 3.63 (bs, 4H, CH2CH3), 3.86 (bs, 4H,
CH(CH3)2), 4.82 (s. 2H, CH), 6.97-7.15 ppm (m, 29.5H, o-, m-,
p-, H of Ar); 13C NMR (75.6 MHz, benzene-d6, 25 °C, TMS): δ
) 16.5, (CH2CH3), 21.1(CH3 from toluene), 23.4, 23.7, 24.9, 25.0,
(4) Sheldrick, G. M. SHELXS-97, Program for Structure Solution. Acta
Crystallogr. 1990, A46, 467-473.
(5) Sheldrick, G. M. SHELXL-97, Program for Crystal Structure Refine-
ment; Universita¨t Go¨ttingen: Go¨ttingen, Germany, 1997.
10750 Inorganic Chemistry, Vol. 46, No. 25, 2007

Heterobimetallic Alumophosphites
Table 1. Crystallographic Data for 1 - 3
1
2
3‚3.5 toluene
formula
fw
C33H52AlN2O3PS
614.78
C66H102Al2Li2N4O6P2S2
1241.42
C90.50H130Al2N4O6P2S2Zn
1615.38
cryst syst
space group
temp (K)
triclinic
P1h
173(2)
monoclinic
C2/c
173(2)
triclinic
P1h
173(2)
λ (Å)
0.71073
0.71073
0.71073
a (Å)
11.830(3)
12.385(3)
12.462(3)
106.34(3)
94.32(3)
93.73(3)
1740(1)
27.446(5)
16.854(3)
16.243(3)
90
110.82(3)
90
13.004(3)
15.672(4)
24.766(5)
100.03(3)
99.04(3)
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
110.02(3)
4540(2)
V (Å3)
7023(3)
Z
2
4
2
cryst color
colorless
6351/257/475
1.035
0.0521, 0.1309
0.0634, 0.1385
0.547/-0.198
colorless
6191/0/394
1.041
0.0512, 0.1164
0.0751, 0.1271
0.268/-0.206
colorless
16 046/719/1188
1.018
0.0507, 0.1148
0.0731, 0.1253
0.529/-0.258
no. of data/restraints/params
GOF on F 2
R1,a wR2b (I > 2σ(I))
R1,a wR2b (all data)
largest diff. peak/hole (e‚Å-3
)
2
2
2
a R ) ∑||Fo| - |Fc||/∑|Fo|. b wR2 ) [∑w(Fo - Fc )2/∑w(Fo )2]1/2
.
Table 2. Selected Bond Lengths (Angstroms) and Angles (Degrees) for 1 - 3
1a
2
3‚3.5 tolueneb
Al(1)-N(1)
1.891(2)
1.883(2)
2.217(1)
1.723(2)
1.906(2)
1.903(2)
2.124(1)
1.764(2)
1.560(2)
1.650(2)
1.649(2)
96.4(1)
116.0(1)
140.0(1)
103.6(1)
103.7(1)
86.9(1)
1.907(2), 1.905(2)
1.895(2), 1.899(2)
2.160(1), 2.161(1)
1.773(2), 1.768(2)
1.552(2), 1.551(2)
1.607(2), 1.599(2)
1.595(2), 1.595(2)
96.8(1), 96.4(1)
110.5(1), 110.3(1)
125.9(1), 126.4(1)
106.0(1), 106.5(1)
102.0(1), 101.6(1)
98.8(1), 99.7(1)
Al(1)-N(2)
Al(1)-S(1)
Al(1)-O(1)
P(1)-O(1)
1.564(2)
P(1)-O(2)
1.643(2), 1.65(1)
1.611(2), 1.65(1)
99.0(1)
115.6(1)
140.7(1)
94.8(1), 99.1(7)
105.1(1), 91.0(8)
103.2(1), 101(1)
P(1)-O(3)
N(1)-Al(1)-N(2)
S(1)-Al(1)-O(1)
Al(1)-O(1)-P(1)
O(1)-P(1)-O(2)
O(1)-P(1)-O(3)
O(2)-P(1)-O(3)
Other selected bond lengths and angles for 2c
S(1)-Li(1)
2.419(5)
2.343(5)
2.054(5)
2.056(6)
94.5(1)
O(2)-Li(1)-O(3)
O(2)-Li(1)-S(1)
O(2)-Li(1)-S(1A)
O(3)-Li(1)-S(1)
O(3)-Li(1)-S(1A)
S(1)-Li(1)-S(1A)
67.1(2)
S(1)-Li(1A)
107.6(2)
136.4(2)
110.5(2)
121.7(2)
107.5(2)
Li(1)-O(2)
Li(1)-O(3)
Al(1)-S(1)-Li(1)
Al(1)-S(1)-Li(1A)
Li(1)-S(1)-Li(1A)
161.9(1)
72.5(2)
Other selected bond lengths and angles for 3‚3.5 toluene
Zn(1)-S(1)
2.307(1)
2.315(1)
2.429(1)
2.413(1)
128.1(1)
S(1)-Zn(1)-P(1)
S(1)-Zn(1)-P(2)
S(2)-Zn(1)-P(1)
S(2)-Zn(1)-P(2)
P(1)-Zn(1)-P(2)
96.2(1)
Zn(1)-S(2)
112.1(1)
112.1(1)
96.4(1)
Zn(1)-P(1)
Zn(1)-P(2)
S(1)-Zn(1)-S(2)
112.5(1)
a The second number belongs to the bond lengths or angles involving the atoms O(2A) and O(3A) from the second position (ca. 39%) of the PO3 unit.
b The second number belongs to the bond lengths and angles involving the atoms Al(2), P(2), S(2), N(3), N(4), O(4), O(5), and O(6) from the symmetry
3
independent second position of the molecule (Figure 2 for detailed labeling). c The symmetry operation to generate the atoms Li(1A) and S(1A) is /2 - x,
1/2 - y, -z.
adjusting its rate of addition, whereas the second is a result
of the oxidation of 1 by traces of elemental sulfur remaining
from the synthesis of LAl(SH)2. 1 is soluble in common
organic solvents including pentane and hexane. The acidic
proton from the SH moiety can be easily substituted by metal,
and thus the reaction of two equivalents of 1 with
[(Me3Si)2NLi‚OEt2]2 in THF results in the precipitation of a
microcrystalline dimeric species [{κ4-S,O,O-LAl(SLi)(µ-O)P-
(OEt)2}2] (2), whereas the reaction of 2 equiv of 1 with
ZnMe2 in toluene yielded the unique spirocyclic compound
[{κ2-S,P-LAl(S)(µ-O)P(OEt)2}2Zn]‚3.5 toluene (3) (Scheme
3). The amount of the solvating toluene in 3 was determined
by 1H NMR spectroscopy and later unambiguously confirmed
by an X-ray diffraction experiment. The preparation of 2
and 3 can be conveniently monitored using 31P NMR
spectroscopy. The disappearance of the resonance of 1 at
126.7 and presence of the signal at 131.7 (2) or 106.9 ppm
(3), respectively, indicates the end of the reaction. The 31P
NMR chemical shifts of 2 and 3 are significantly different
and suggest different coordination modes of the PO3 unit to
the metal. The substitution of the acidic proton in 2 and 3 is
well evidenced by the disappearance of its resonance in the
Inorganic Chemistry, Vol. 46, No. 25, 2007 10751

Go´mora-Figueroa et al.
Figure 1. Thermal ellipsoid plot of 1 at the 50% level. Carbon-bound
hydrogen atoms are omitted for clarity.
Figure 3. Thermal ellipsoid plot of 3 at the 40% level. All of the hydrogen
atoms and solvating toluene molecules are omitted for clarity.
Scheme 3. Preparation of Heterobimetallic Compounds 2 and 3
Figure 2. Thermal ellipsoid plot of 2 at the 50% level. All of the hydrogen
atoms are omitted for clarity.
1H NMR spectrum at -0.53 ppm as well as the absence of
the S-H vibration band at ν˜ 2572 cm-1 in the IR spectra of
2 and 3. The H NMR shifts for the protons of the S-H
This is most probably caused by the dissociation and
association of the diethoxy phosphite unit from and to the
zinc center. The EI-MS spectrum of 1 contains the molecular
peak at m/z 614 (26%), whereas the spectra of 2 and 3 exhibit
only low-weight fragments.
1
moiety of related compounds are: -0.88 ppm for LAl(SH)2,
-1.00 ppm for [LAl(SH)(SLi‚thf2)]2 and -0.45 ppm for LAl-
(SH)(µ-O)Si(OH)(OtBu)2, and the IR absorption bands for
these compounds can be found at the following wavenum-
bers: ν˜ 2549 cm-1 for LAl(SH)2, 2552 cm-1 for [LAl(SH)-
(SLi‚thf2)]2 and 2560 cm-1 for LAl(SH)(µ-O)Si(OH)(Ot-
Bu)2.3,6 2 is sparingly soluble in THF but readily soluble in
dichloromethane and in chloroform. No reaction was ob-
served between 2 and dichloromethane or chloroform,
respectively. 3 is soluble in hot toluene, THF, dichlo-
X-ray Structural Analyses. The molecular structures of
all three compounds were unambiguously determined by
single-crystal X-ray diffraction studies. Single crystals of 1
were obtained from the saturated hexane solution at
-30 °C, whereas slow cooling of hot saturated solutions of
2 (in THF) and 3 (in toluene) resulted in the growth of X-ray
quality monocrystals (Table 1).
1
romethane, and chloroform. The H NMR spectrum for 3
1 and 3 crystallize in the triclinic space group P1h with
one molecule (1) and 3.5 molecules of toluene (3) in the
asymmetric unit. 2 crystallizes in a monoclinic space group
C2/c with one-half of the molecule in the asymmetric unit.
(Figures 1-3). The crystal structure analysis confirmed the
different coordination modes of the PO3 unit for 2 and 3.
Thus, the PO3 unit is coordinated to the zinc center in 3
through the phosphorus atom, whereas, the lithium atoms in
2 are coordinated to the two oxygen atoms from the ethoxy
revealed a dynamic equilibrium in the solution, resulting in
broad singlet signals for the OCH2CH3 protons (theoretically
should be a doublet of quartets) and for one of the two signals
for the CH(CH3)2 protons (theoretically should be a septet).
These signals remained unresolved even at low temperature.
(6) (a) Jancik, V.; Roesky, H. W. Inorg. Chem. 2005, 44, 5556-5558
and references cited therein. (b) Jancik, V.; Roesky, H. W.; Neculai,
D.; Neculai, A. M.; Herbst-Irmer, R. Angew. Chem. 2004, 116, 6318-
6322; Angew. Chem., Int. Ed. 2004, 43, 6192-6196.
10752 Inorganic Chemistry, Vol. 46, No. 25, 2007

Heterobimetallic Alumophosphites
groups. Surprisingly, the lone electron pair is free and is also
not shielded by the ligand (Figure S1 in the Supporting
Information).
been reported for the salts LAl(SH)(Scat) (cat is cation)
(2.268-2.290 Å).6 The substitution of the SH proton in 2
and 3 led to the elongation of the Al-O bond lengths from
1.723 Å in 1 to 1.764 Å in 2 and finally to 1.768 and 1.773
Å in 3; however, all these bonds are longer than those
reported for LAl(OH)2 (1.711 and 1.695 Å).11 The Al-O
bond length for 1 is comparable to the Al-O(M)bond lengths
in LAl(OH)(µ-O)M(SH)Cp2 (M ) Ti, 1.719 Å; M ) Zr,
1.713 Å).12 Although the Al-S and Al-O bond lengths
follow the same trend in 2 and 3 compared to 1, the P-O
bond lengths depend strongly on the coordination mode of
the PO3 unit. The coordination of the metal to the phosphorus
atom leads to a slight shortening of all three P-O bonds
and a less acute Al-O-P angle, but coordination of the
metal to the OEt oxygen atoms has an effect only on the
P-O bond lengths: AlO-P 1.564 Å (1), av 1.560 Å (2),
1.551 Å (3); P-OEt av 1.638 Å (1), av 1.650 Å (2), av 1.601
Å (3); Al-O-P 140.7° (1), 140.0° (2), av 126.2° (3).
Selected bonds and angles for 1-3 are given in Table 2.
To the best of our knowledge, this is the only known
example of the M-O-P(µy-O)2M (y g 2, M ) metal)
coordination pattern for the phosphite moiety in which the
lone electron pair on the phosphorus atom is not involved
in any interaction. In fact, there is only one record in the
CSD for such a phosphite environment X-O-P(µy-O)2X (y
g 2, X ) any element) in Ar-O-P(µ-O)2P-O-Ar (Ar )
2,6-di-tBu-4-MeC6H2) reported in 1987 by Chasar et al.7 The
lithium atom in 2 is coordinated to two sulfur and two oxygen
atoms; however, in highly irregular shape with the angles
between the atoms ranging from 67.1 (O(2)-Li(1)-O(3))
to 136.4° (O(2)-Li(1)-S(1A)). The central Li2S2 motif is
essentially planar due to the crystallographic symmetry, but
possesses unequal Li-S bond lengths (Li(1)-S(1) 2.419, Li-
(1)-S(1A) 2.343 Å), whereas the Li-O bond lengths are
identical (2.054 and 2.056 Å) and are significantly longer
than the mean value for Li-O(P) bond lengths in the CSD
database (1.955 Å).8 The molecule of 3 is formed by an
unusual chain of four rings connected together in a spiro
fashion through the aluminum and zinc atoms and contains
two carbon-free true heterocycles S-Al-O-P-Zn formed
by as many as five different elements.9 Both S-Al-O-P-
Zn rings are almost perfectly planar (sum of the inner angles
is in both cases is 539.8°; the theoretical value for a five-
membered ring is 540°) and are nearly perpendicular to each
other with an interplanar angle of 85.5°. Because the zinc
atom is shared by both of these rings, it is coordinated to
two phosphorus and two sulfur atoms in a distorted tetra-
hedral fashion (angles between 96.2° and 128.1°). Such a
coordination environment has so far been characterized by
X-ray only in [2-Ph2P-6-Me3Si-C6H3S]2Zn‚CH3CN).10 The
Al-S bond length in 1 (2.217 Å) is comparable to those in
LAl(SH)2 (av 2.220 Å)3 and in LAl(SH)(µ-O)Si(OH)(OtBu)2
(2.222 Å),1 but is longer than that in 2 (2.124 Å) and in 3
(av 2.161 Å); however, longer Al-SH bond lengths have
Conclusions
To sum up, we have prepared an unusual alumophosphite
reagent and used it for the preparation of unprecedented
heterobimetalic alumophosphites. Furthermore, the lithium
salt 2 features a unique coordination mode of the phosphite
unit to two metal atoms via the three oxygen donors, whereas
the lone electron pair on phosphorus is free and is not
shielded by the organic ligand. Thus, 2 can be used not only
as a further reagent but also as a neutral ligand. Reactions
to investigate these possibilities are currently underway in
our laboratory.
Acknowledgment. The authors wish to thank to PAPIIT
for financial support in the form of Grant IN209706. We
thank the Consejo Superior de Investigationes Cient´ıficas of
Spain for the license of the CSD. This article is dedicated to
Prof. Ionel Haiduc on the occasion of his 70th birth
anniversary.
Supporting Information Available: Figures S1 and S2 (PDF)
and the details of the single-crystal X-ray structure determination
of 1-3 (CIF). This material is available free of charge via the
Internet at http://pubs.acs.org. It is also available as CCDC-637667
(1), 637668 (2), 637669 (3) via http://www.ccdc.cam.ac.uk/conts/
retrieving.html (or from the Cambridge Crystallographic Data
Centre, 12 Union Road, Cambridge CB21EZ, UK; fax: (+44)-
1223-336-033; or deposit@ccdc.cam.ac.uk).
(7) Chasar, D. W.; Fackler, J. P., Jr.; Komoroski, R. A.; Kroenke, W. J.;
Mazany, A. M. J. Am. Chem. Soc. 1987, 109, 5690-5693.
(8) The CSD database contains currently 406 records of Li-O-P units.
The analysis of the Li-O(P) bond lengths from these units is shown
in Figure S2 in Supporting Information as an histogram.
(9) The true heterocycle term refers to a heterocycle formed by a maximum
number of different atoms. There are over 600 compounds reported
in the CSD containing such a five-membered heterocycle, where one
of the atoms is carbon. However, to the best of our knowledge, the
CSD database contains only nine compounds with a five-membered
carbon-free true heterocyclic ring. From these nine compounds, only
one contains two of such rings connected in a spiro fashion:
Valderrama, M.; Lahoz, F. J.; Oro, L. A.; Plou, F. J. Inorg. Chim.
Acta 1988, 150, 157-163.
IC701614C
(11) Bai, G.; Peng, Y.; Roesky, H. W.; Li, J.; Schmidt, H.-G.; Noltemeyer,
M. Angew. Chem. 2003, 115, 1164-1167; Angew. Chem. Int. Ed.
2003, 42, 1132-1135.
(12) Jancik, V.; Roesky, H. W. Angew. Chem. 2005, 117, 6170-6172;
Angew. Chem., Int. Ed. 2005, 44, 6016-6018.
(10) Perez-Lourido, P.; Romero, J.; Garcia-Vazquez, J. A.; Sousa, A.;
Maresca, K. P.; Zubieta, J. Inorg. Chem. 1999, 38, 3709-3715.
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