Synthesis and x-ray structures of dilithium complexes of the phosphonate anions [PhP(E)(NtBu)2]2- (E = O, S, Se, Te) and dimethylaluminum derivatives of [PhP(E)(NtBu)(NhtBu)]- (E = S, Se)

Article abstract of DOI:10.1021/ic020471h

The dilithium salts of the phosphonate dianions [PhP(E)(N^tBu)₂]^2- (E = O, S, Se) are generated by the lithiation of [PhP(E)(NH^tBu)₂] with n-butyllithium. The formation of the corresponding telluride (E = Te) is achieved by oxidation of {Li₂[PhP(N^tBu)₂]} with tellurium. X-ray structural determinations revealed dimeric structures {Li(THF)₂[PhP(E)-(N^tBu)₂]}₂ in which the monomeric units are linked by Li-E bonds. In the case of E = Se or Te, but not for E = S, transannular Li-E interactions are also observed, resulting in a six-rung ladder. By contrast, for E = O, this synthetic approach yields the Li₂O-templated tetramer {(THF)Li₂[PhP(O)(N^t Bu)₂]}₄·Li₂O in THF or the tetramer {(Et₂O)_0.5Li₂[PhP(O) (N^tBu)₂]}₄ in diethyl ether. The reaction of trimethylaluminum with PhP(E)(NH^tBu)₂ produces the complexes Me₂Al[PhP(E)(N^tBu)(NH^tBu)] (E = S, Se), which were shown by X-ray crystallography to be N,E- chelated monomers.

Full text of DOI:10.1021/ic020471h

Inorg. Chem. 2002, 41, 6808−6815
Synthesis and X-ray Structures of Dilithium Complexes of the
t
Phosphonate Anions [PhP(E)(N Bu)2]2- (E ) O, S, Se, Te) and
t
t
Dimethylaluminum Derivatives of [PhP(E)(N Bu)(NH Bu)]- (E ) S, Se)
Glen G. Briand, Tristram Chivers,* Mark Krahn, and Masood Parvez
Department of Chemistry, UniVersity of Calgary, Calgary, Alberta, Canada T2N 1N4
Received July 22, 2002
t
The dilithium salts of the phosphonate dianions [PhP(E)(NBu)2]2- (E ) O, S, Se) are generated by the lithiation
t
of [PhP(E)(NHBu)2] with n-butyllithium. The formation of the corresponding telluride (E ) Te) is achieved by oxidation
t
of {Li2[PhP(NBu)2]} with tellurium. X-ray structural determinations revealed dimeric structures {Li(THF)2[PhP(E)-
t
(NBu)2]}2 in which the monomeric units are linked by Li−E bonds. In the case of E ) Se or Te, but not for E )
S, transannular Li−E interactions are also observed, resulting in a six-rung ladder. By contrast, for E ) O, this
t
synthetic approach yields the Li2O-templated tetramer {(THF)Li2[PhP(O)(NBu)2]}4‚Li2O in THF or the tetramer
t
t
{(Et2O)0.5Li2[PhP(O)(NBu)2]}4 in diethyl ether. The reaction of trimethylaluminum with PhP(E)(NHBu)2 produces
t
t
the complexes Me2Al[PhP(E)(NBu)(NHBu)] (E ) S, Se), which were shown by X-ray crystallography to be N,E-
chelated monomers.
Introduction
Polydentate anions involving a combination of hard (N)
and soft (S or Se) donor sites attached to a P(V) center
display versatile coordination behavior. For example, the
dianions [tBuN(E)P(µ-NtBu)2P(E)NtBu]2- (E ) S, Se), which
are formally dimers of the metaphosphates [EP(NtBu)2]-,
adopt a different bonding mode toward Li+ than that
observed for Na+ or K+.8 Bis(N,E)-chelation is observed for
Li+, whereas the large alkali-metal cations Na+ and K+
coordinate in an N,N′ and E,E′ bonding mode. In addition
to these structural variations, the P-E bonds within these
anions are more labile than the P-N bonds. This can result
in unexpected transformations, e.g., the formation of [(THF)-
LiP(NtBu)3]2 from the reaction of [P(S)(NHtBu)3] with
alkyllithium reagents9 and the generation of the P(III)/P(V)
monoanion [tBuN(Se)P(µ-NtBu)2PNHtBu]- 8b from [(tBuNH)-
(Se)P(µ-NtBu)2P(Se)(NHtBu)] and LinBu in boiling THF.
As a further contribution to the chemistry of polydentate
phosphorus(V)-centered anionic ligands, we have investi-
gated the reactions of chalcogenidobis(amido)phosphonates,
[PhP(E)(NHtBu)2] (1a, E ) O; 1b, E ) S; 1c, E ) Se),
Investigations of polyimido analogues of common main-
group oxo anions have led to interesting multidentate ligands
that, as their alkali-metal derivatives, form novel cluster
structures.1 Recent studies of polyimido-phosphorus systems
have uncovered a family of anions: [P(NR)2]-,2 [R2P(NR′)2]-,3
[P(NR)3]-,4 [P(NR)4]3-,5 and [HP(NR′)3]2-, that are iso-
6
electronic to the corresponding oxo-anions of phosphorus.
Examples of all of the foregoing anions have been structur-
ally characterized as their alkali-metal (usually lithium)
derivatives. In addition, the in situ formation of the phen-
ylphosphonate analogue Li2[PhP(NiPr)3] has been inferred
on the basis of derivative chemistry.7
* To whom correspondence should be addressed. Telephone: (403) 220-
5741. Fax: (403) 289-9488. E-mail: chivers@ucalgary.ca.
(1) For recent reviews see: (a) Brask, J. K.; Chivers, T. Angew. Chem.,
Int. Ed. Engl. 2001, 40, 3960 and references cited; (b) Aspinall, G.
M.; Copsey, M. C.; Leedham, A. P.; Russell, C. A. Coord. Chem.
ReV. 2002, 227, 217.
(2) Detsch, R.; Niecke, E.; Nieger, M.; Schoeller, W. W. Chem. Ber. 1992,
125, 1119.
(3) Steiner, A.; Stalke, D. Inorg. Chem. 1993, 32, 1977.
(4) Niecke, E.; Frost, M.; Nieger, M.; von der Go¨nna, V.; Ruban, A.;
Schoeller, W. W. Angew. Chem., Int. Ed. Engl. 1994, 33, 2111.
(5) Raithby, P. R.; Russell, C. A.; Steiner, A.; Wright, D. S. Angew. Chem.,
Int. Ed. Engl. 1997, 36, 649.
(6) Burke, L. T.; Hevia-Freire, E.; Holland, R.; Jeffery, J. C.; Leedham,
A. P.; Russell, C. A.; Steiner, A.; Zagorski, A. Chem. Commun. 2000,
1769.
(7) Bailey, P. J.; Grant, K. J.; Parsons, S. Organometallics 1998, 17, 551.
(8) (a) Chivers, T.; Krahn, M.; Parvez, M. Chem. Commun. 2000, 463.
(b) Chivers, T.; Krahn, M.; Parvez, M.; Schatte, G. Inorg. Chem. 2001,
40, 2547. (c) Briand, G. G.; Chivers, T.; Krahn, M. Coord. Chem.
ReV., in press.
(9) Chivers, T.; Krahn, M.; Parvez, M.; Schatte, G. Chem. Commun. 2001,
1922.
6808 Inorganic Chemistry, Vol. 41, No. 25, 2002
10.1021/ic020471h CCC: $22.00 © 2002 American Chemical Society
Published on Web 11/15/2002

Synthesis and X-ray Structures of Dilithium Complexes
mL under vacuum. The product 1a was obtained as a white
crystalline solid (4.651 g, 17.33 mmol, 78%) after 24 h at -15 °C.
1H NMR (C6D6, δ): 7.1-8.1 (m, 5 H, C6H5), 2.18 [d, 2 H, NH,
2J(1H-31P) ) 7.4 Hz], 1.24 [d, 18 H, NtBu,4J(1H-31P) ) 0.5 Hz].
31P{1H} NMR (C6D6, δ): 11.6 (s); (solid state): 14.8 (s). IR (cm-1):
3396 (N-H), 3227 (N-H). MS [EI, m/z (rel int)]: 268 (4) (M+).
Mp 182-185 °C. Anal. Calcd for C14H25N2OP: C, 62.66; H, 9.39;
N, 10.44. Found: C, 62.07; H, 9.99; N, 10.33.
with both alkyllithium and alkylaluminum reagents. Since
1d (E ) Te) could not be prepared (vide infra), the oxidation
of {Li2[PhP(NtBu)2]} with elemental tellurium was also
studied. Herein we report the synthesis and X-ray structures
of the dimers {Li(THF)2[PhP(E)(NtBu)2]}2 (2b, E ) S; 2c,
E ) Se; 2d, E ) Te), the Li2O-templated tetramer {(THF)-
Li2[PhP(O)(NtBu)2]}4‚Li2O (2a‚Li2O), and the tetramer
{(Et2O)0.5Li2[PhP(O)(NtBu)2]}4 (2a′), all of which contain
tetrahedral dianions [PhP(E)(NtBu)]2- (3a-d). The synthesis
and structures of the dimethylaluminum complexes {Me2-
Al[PhP(E)(NtBu)(NHtBu)]} (4b, E ) S; 4c, E ) Se), which
involve the monoanions [PhP(E)(NHtBu)(NtBu)]- (5b, E )
S; 5c, E ) Se), are also reported.
Synthesis of [PhP(S)(NHtBu)2] (1b). Hexane (40 mL) was added
to a mixture of sulfur (1.323 g, 41.26 mmol) and PhP(NHtBu)2
(10.412 g, 41.26 mmol) at 0 °C. A white precipitate formed
immediately. The hexane was decanted from the product to give
1
1b as a white crystalline solid (11.065 g, 38.90 mmol, 94%). H
NMR (C6D6, δ): 7.1-8.2 (m, 5 H, C6H5), 2.12 [d, 2 H, NH, 2J(1H-
4
31P) ) 4.6 Hz], 1.25 [d, 18 H, NtBu, J(1H-31P) ) 0.7 Hz]. 31P-
{1H} NMR (C6D6, δ): 50.9 (s). IR (cm-1): 3383 (N-H), 3339
(N-H). MS [EI, m/z (rel int)]: 284 (30) (M+). Mp 99-101 °C.
Anal. Calcd for C14H25N2SP: C, 59.13; H, 8.86; N, 9.85. Found:
C, 58.00; H, 8.12; N, 9.47.
Synthesis of [PhP(Se)(NHtBu)2] (1c). Hexane (45 mL) was
added to a mixture of selenium (3.195 g, 40.46 mmol) and PhP-
(NHtBu)2 (10.210 g, 40.46 mmol) at 0 °C. The reaction mixture
was refluxed in hexane at 65 °C for 18 h. While still hot, the
solution was decanted from a small amount of unreacted Se and
concentrated to 20 mL. Storage at -15 °C for 24 h yielded gray
1
crystals of 1c (10.947 g, 33.05 mmol, 82%). H NMR (C6D6, δ):
Experimental Section
7.1-8.2 (m, 5 H, C6H5), 2.20 [d, 2 H, NH, 2J(1H-31P) ) 4.1 Hz],
1.24 (s, 18 H, NtBu). 31P{1H} NMR (C6D6, δ): 46.7 [s, J(31P-
1
Reagents and General Procedures. Solvents were dried and
distilled prior to use: toluene, tetrahydrofuran, diethyl ether,
pentane, and n-hexane (Na/benzophenone). n-Butyllithium (2.5 M
solution in hexanes, Aldrich), trimethylaluminum (2.0 M solution
in hexanes, Aldrich), tert-butyl hydroperoxide (5.0-6.0 M, Aldrich),
sulfur (99.5%, Aldrich), selenium (99.5%, Aldrich), and tellurium
(99.5%, Matheson) were used as received. The compounds [PhP-
77Se) ) 787 Hz]. 77Se NMR (C6D6, δ): -154.5 [d, 1J(31P-77Se) )
785 Hz]. IR (cm-1): 3377 (N-H), 3323 (N-H). MS [EI, m/z (rel
int)]: 331 (19) (M+). Mp 95-98 °C. Anal. Calcd for C14H25N2-
SeP: C, 51.07; H, 7.04; N, 8.51. Found: C, 51.03; H, 7.20; N,
8.35.
Synthesis of {(THF)Li2[PhP(O)(NtBu)2}4‚Li2O (2a‚Li2O).
n-Butyllithium (1.50 mL, 3.75 mmol) was added dropwise to a
stirred solution of PhP(O)(NHtBu)2 (0.502 g, 1.87 mmol) in THF
(25 mL) at 23 °C. After 18 h, the volume of the reaction mixture
was reduced to 5 mL and layered with pentane (2 mL). Colorless
X-ray quality crystals of 2a(THF)4‚Li2O (0.194 g, 0.135 mmol,
29%) formed after 3 days at 23 °C.1H NMR (THF-d8, δ): 7.2-8.1
(m, 5 H, C6H5), 3.58 (m, THF), 1.76 (m, THF), 1.14 (s, 18 H,
11
(NHtBu)2]10 and {Li2[PhP(NtBu)2]}2 were prepared by literature
procedures. The reactions and handling of air- and moisture-
sensitive reagents were performed under an atmosphere of argon
gas by using Schlenk techniques or a glovebox.
Instrumentation. With the exception of 2d, solution NMR data
were recorded at 23 °C. 1H NMR spectra were collected on a Bruker
AM-200 spectrometer and chemical shifts are reported relative to
Me4Si in CDCl3. 31P and Li NMR spectra were obtained on a
7
7
NtBu). 31P{1H} NMR (THF-d8, δ): 23.8 (s). Li NMR (C6D6, δ):
Bruker AMX 300 spectrometer; chemical shifts are reported relative
to 85% H3PO4 and 1 M LiCl in D2O, respectively. 77Se NMR and
125Te NMR were obtained on a Bruker DRX 400 spectrometer;
chemical shifts are reported relative to Ph2Se2 (+463 ppm relative
to Me2Se) and neat Me2Te, respectively. For the thermally unstable
complex 2d all solution NMR data were recorded on a Bruker DRX
400 spectrometer at -63 °C. Solid-state NMR spectra were
collected on a Bruker AMX 300 spectrometer. Infrared spectra were
recorded as Nujol mulls on KBr plates on a Nicolet Nexus 470
FTIR in the range 4000-350 cm-1. Mass spectra were obtained
with a VG micromass spectrometer VG7070 (70 eV). Elemental
analyses were provided by the Analytical Services Laboratory,
Department of Chemistry, University of Calgary.
-0.20 (sh), -0.87 (br). Anal. Calcd for C72H124N8O9P4Li10: C,
60.09; H, 8.68; N, 7.79. Found: C, 59.88; H, 8.33; N, 8.08.
Synthesis of {(Et2O)0.5Li2[PhP(O)(NtBu)2]}4 (2a′). n-Butyl-
lithium (2.433 mL, 6.083 mmol) was added dropwise to a stirred
solution of PhP(O)(NHtBu)2 (0.816 g, 3.041 mmol) in diethyl ether
(25 mL) at 23 °C. After 3 h, the solvent was removed in vacuo
and the white product was redissolved in a minimal amount of
pentane (6 mL). Colorless X-ray quality crystals of 2a(Et2O)2 (0.620
g, 1.954 mmol, 64%) formed after 24 h at 23 °C.1H NMR (C6D6,
δ): 7.2-8.2 (m, 5 H, C6H5), 3.27 (q, Et2O), 1.10-1.90 (br m, 18
H, NtBu), 1.12 (t, Et2O). 31P NMR (solid state, δ): 25.6, 22.5, 13.2,
7
6.5. Li NMR (solid state, δ): 2.48, 2.23, 1.71, 1.45, 1.15. Anal.
Calcd for C64H112N8O6P4Li8: C, 60.57; H, 8.90; N, 8.83. Found:
C, 58.34; H, 9.11; N, 9.34.
Synthesis of [PhP(O)(NHtBu)2] (1a). A 5.0-6.0 M solution of
tBuOOH in decane (4.4 mL, 22.00-26.40 mmol) was added
dropwise to a stirred solution of PhP(NHtBu)2 (5.609 g, 22.22
mmol) in toluene (45 mL) at 0 °C. A white precipitate formed
immediately. After 2 h, the volume of solvent was reduced to 15
Synthesis of {(THF)2Li2[PhP(S)(NtBu)2]}2 (2b). n-Butyllithium
(2.81 mL, 7.03 mmol) was added dropwise to a stirred solution of
PhP(S)(NHtBu)2 (1.000 g, 3.516 mmol) in THF (25 mL) at 23 °C.
After 3 h, the volume of solvent was reduced to 8 mL under vacuum
and hexane (5 mL) was added. Colorless X-ray quality crystals of
2b (1.056 g, 2.397 mmol, 68%) formed after 24 h at 23 °C.1H
NMR (THF-d8, δ): 7.1-8.3 (m, 5 H, C6H5), 3.61 (m, THF), 1.76
(10) Lane, A. P.; Morton-Blake, D. A.; Payne, D. S. J. Chem. Soc. A 1967,
1492. No NMR data for 1a-c were reported in this article.
(11) Eichhorn, B.; No¨th, H.; Seifert, T. Eur. J. Inorg. Chem. 1999, 2355.
Inorganic Chemistry, Vol. 41, No. 25, 2002 6809

Briand et al.
Table 1. Crystallographic Data for 2a‚Li2O, 2a′, 2b, 2c, 2d, and 4c
2a‚Li2O
2a′
2b
2c
2d
4c
c
formula
fw
space group
a, Å
b, Å
c, Å
R, deg
â, deg
γ, deg
V, Å3
Z
C77H136Li10N8O9P4
1511.22
P1
C64H112Li8N8O6P4
1269.02
P21/a
16.9725(3)
20.8445(3)
21.5041(4)
C22H39Li2N2O2PS
440.46
P21/c
9.70790(10)
28.8250(4)
10.3105(2)
C22H39Li2N2O2PSe
487.36
P1
C22H39Li2N2O2PTe
536.00
P1
C16H30AlN2PSe
387.33
Cc
15.9353(4)
14.6635(4)
8.8872(2)
15.8348(2)
15.9927(2)
20.2186(3)
102.2300(10)
111.6290(10)
99.7310(10)
4476.27(10)
2
9.41300(10)
10.2438(2)
15.1293(2)
89.0090(10)
73.1940(10)
66.3900(10)
1271.54(3)
2
9.2017(2)
10.1328(2)
15.8982(4)
94.6527(7)
104.7860(8)
110.9496(9)
1313.89(5)
2
94.6600(6)
115.3140(6)
101.7208(12)
7582.6(2)
4
2608.15(7)
4
2033.35(9)
4
T, K
λ, Å
173(2)
0.71069
1.121
0.14
1632
170(2)
0.71069
1.112
0.15
2736
0.053
0.15
173(2)
0.71069
1.122
0.204
952
173(2)
0.71069
1.273
1.558
512
170(2)
0.71073
1.355
1.21
548
170(2)
0.71069
1.265
1.97
808
0.030
0.080
d
calcd, g cm-3
µ, mm-1
F(000)
Ra
0.066
0.196
0.051
0.137
0.037
0.098
0.049
0.150
b
Rw
a R ) Σ||Fo| - |Fc||/Σ|Fo|. b Rw ) [Σw(|Fo| - |Fc|)2/ΣwFo ]1/2
.
c Contains one molecule of pentane.
2
(m, THF), 1.06 (s, 18 H, NtBu). 31P{1H} NMR (THF-d8, δ): 39.5
(s). 7Li NMR (THF-d8, δ): 2.14 [s]. Anal. Calcd for C22H39N2O2-
PSLi2: C, 59.99; H, 8.92; N, 6.36. Found: C, 59.35; H, 8.98; N,
6.69.
Synthesis of {Me2Al[PhP(Se)(NtBu)(NHtBu]} (4c). Pale yellow
X-ray quality crystals of 4c (0.36 g, 0.93 mmol, 62%) were obtained
from the reaction of trimethylaluminum (0.75 mL, 1.51 mmol) and
PhP(Se)(NHtBu)2 (0.50 g, 1.51 mmol) in toluene (25 mL) by the
1
Synthesis of {(THF)2Li2[PhP(Se)(NtBu)2]}2 (2c). n-Butyllithium
(2.42 mL, 6.05 mmol) was added dropwise to a stirred solution of
PhP(Se)(NHtBu)2 (1.000 g, 3.018 mmol) in THF (25 mL) at 23
°C. After 3 h, the volume of solvent was reduced to 8 mL under
vacuum. Pale yellow X-ray quality crystals of 2c (1.243 g, 2.550
mmol, 85%) formed after 24 h at 23 °C.1H NMR (THF-d8, δ):
7.1-8.3 (m, 5 H, C6H5), 3.61 (m, THF), 1.76 (m, THF), 1.08 [d,
procedure described above for 4b. H NMR (C6D6, δ): 7.0-8.1
(m, 5 H, C6H5), 2.35 [d, 1 H, NH, 2J(1H-31P) ) 3.2 Hz], 1.28 [d,
9 H, NtBu,4J(1H-31P) ) 0.51 Hz], 1.08 [d, 9 H, NtBu,4J(1H-31P)
) 0.86 Hz], 0.10 (s, 3 H, Me), 0.07 (s, 3 H, Me). 31P{1H} NMR
(C6D6, δ): 29.1 [s, 1J(31P-77Se) ) 499 Hz]. 77Se NMR (C6D6, δ):
1
-102.4 (d, J(31P-77Se) ) 497 Hz]. Anal. Calcd for C16H30N2-
PSeAl: C, 49.61; H, 7.81; N, 7.23. Found: C, 47.54; H, 7.58; N,
6.77.
4
18 H, NtBu, J(1H-31P) ) 0.68 Hz]. 31P{1H} NMR (THF-d8, δ):
1
27.6 [s, J(31P-77Se) ) 514 Hz]. 77Se NMR (THF-d8, δ): -45.7
X-ray Analyses. Crystals of 2a‚Li2O‚C5H12, 2a′, 2b, 2c, 2d, and
4c were coated with Paratone oil and mounted on a glass fiber. All
measurements were made on a Nonius Kappa CCD FR540C
diffractometer. Crystallographic data are summarized in Table 1.
Structures were solved by direct methods (SIR-92)12a and refined
by full-matrix least-squares methods on F2 with SHELXL-97.12b
Unless otherwise stated the non-hydrogen atoms were refined
anisotropically; hydrogen atoms were included at geometrically
idealized positions but not refined.
2a‚Li2O‚C5H12: The C atoms of a molecule of pentane solvate
were allowed isotropic displacement parameters as they were
disordered and showed large vibrational parameters.
2a′: The non-hydrogen atoms were refined anisotropically except
for the smaller fractions of the disordered atoms, which were
allowed isotropic displacement parameters.
[d,1J(31P-77Se) ) 513 Hz]. 7Li NMR (THF-d8, δ): 1.92 [s]. Anal.
Calcd for C22H39N2O2PSeLi2: C, 54.22; H, 8.07; N, 5.75. Found:
C, 54.02; H, 8.35; N, 6.12.
Synthesis of {(THF)2Li2[PhP(Te)(NtBu)2]}2 (2d). A mixture
of {Li2[PhP(NtBu)2]}2 (0.250 g, 0.946 mmol) and Te powder (0.121
g, 0.946 mmol) in THF (6 mL) was heated to 70 °C for 3 h. After
cooling to 23 °C, the mixture was centrifuged and the supernatant
was decanted to remove unreacted tellurium. The solvent was
removed under vacuum and the product was dissolved in diethyl
ether (6 mL). After filtration, the solution was concentrated (ca. 2
mL) to give yellow needles of 2d (0.069 g, 0.14 mmol, 14%) after
1
4 days at 23 °C. H NMR (THF-d8, 235 K, δ): 7.0-8.3 (m, 5 H,
4
C6H5), 3.62 (m, THF), 1.77 (m, THF), 1.12 [d, J(1H-31P) ) 1
Hz, 18 H, NtBu]. 31P{1H} NMR (THF-d8, 235K, δ): -14.4 [s,
1J(31P-125Te ) 1209 Hz)]. 125Te NMR (THF-d8, 235K, δ): -333
[d, 1J(125Te-31P ) 1212 Hz). Anal. Calcd for C22H39Li2N2O2PTe:
C, 49.30; H, 7.33; N, 5.23. Found: C, 49.57; H, 7.92; N, 5.45.
2b: One of the THF ligands had three disordered C atoms, which
were included in the refinements with partial site occupancy factors.
2c: The C atoms of one THF ligand were disordered over two
sites with partial occupancy factors.
Synthesis of {Me2Al[PhP(S)(NtBu)(NHtBu]} (4b). Trimethyl-
aluminum (0.88 mL, 1.76 mmol) was added dropwise to a solution
of PhP(S)(NHtBu)2 (0.50 g, 1.76 mmol) in toluene (25 mL) at 23
°C. The reaction mixture was refluxed at 130 °C for 18 h to give
an orange solution. The solvent was removed in vacuo and the oily
product was redissolved in a minimal amount of pentane (5 mL).
Pale yellow X-ray quality crystals of 4b (0.46 g, 1.35 mmol, 77%)
formed after 24 h at -15 °C.1H NMR (C6D6, δ): 7.1-8.0 (m, 5
Results and Discussion
Preparation of Lithium Imido/Chalcogenido Phospho-
nates. The preparation of bis(tert-butylamido)phenylphos-
phine chalcogenides, [PhP(E)(NHtBu)2] (1a, E ) O; 1b, S;
1c, Se), was first reported by Lane et al. in 1967.10 The
reaction of [PhP(NHtBu)2] with tert-butyl hydroperoxide,
2
H, C6H5), 2.38 [d, 1 H, NH, J(1H-31P) ) 6.0 Hz], 1.28 (s, 9 H,
NtBu), 1.08 [d, 9 H, NtBu,4J(1H-31P) ) 0.86 Hz], -0.01 (s, 3 H,
Me), -0.03 (s, 3 H, Me). 31P{1H} NMR (C6D6, δ): 38.4 (s). Anal.
Calcd for C16H30N2PSAl: C, 56.45; H, 8.88; N, 8.23. Found: C,
54.61; H, 8.88; N, 8.78.
(12) (a) SIR-92. Altomare, A.; Cascarano, M.; Giacovazzo, C.; Guagliardi,
A. J. Appl. Crystallogr. 1993, 26, 343. (b) Sheldrick, G. M. SHELXL-
97, Program for the Solution of Crystal Structures; University of
Go¨ttingen: Go¨ttingen, Germany, 1997.
6810 Inorganic Chemistry, Vol. 41, No. 25, 2002

Synthesis and X-ray Structures of Dilithium Complexes
elemental sulfur, or selenium produces 1a-c, respectively,
in good yields. The 1H NMR spectra for all three compounds
exhibit the expected resonances for phenyl protons at δ 7.1-
4
8.1, NtBu groups at δ 1.24-1.25 with J(31P-1H) ) 0.0-
0.7 Hz, and the NH protons in the range δ 2.12-2.18 with
2J(31P-1H) ) 4.1-7.4 Hz. The 31P NMR spectra reveal
singlets at δ 11.6 (1a), 50.9 (1b), and 46.7 (1c). The 77Se
NMR spectrum of 1c consists of a doublet centered at δ
-154.5 [1J(77Se-31P) ) 785 Hz] [cf. -153 ppm and 765
Hz for Ph2P(Se)N(SiMe3)2].13
Dilithiation of 1a-c with n-butyllithium occurs readily
in THF at room temperature (eq 1). The products are obtained
9
in good yields and, unlike the lithiation of SP(NHtBu)3 or
n
[(tBuNH)(Se)P(µ-NtBu)2P(Se)(NHtBu)]8b by BuLi, no in-
dication of P-S or P-Se bond cleavage was observed.
THF
Figure 1. X-ray structure of {(THF)Li2[PhP(O)(NtBu)2}4‚Li2O (2a‚Li2O)
(x/2)[PhP(E)(NHtBu)2] + xnBuLi
8 (1/2)
-2nBuH
showing the numbering scheme (30% probability ellipsoids). Only the
t
{[Li(THF)]2[PhP(E)(NtBu)2]}x
R-carbons of the Bu groups, the ipso-carbons of the phenyl groups, and
the oxygen atoms of THF molecules are shown.
(1)
2a, E ) O, x ) 4
2b, E ) S, x ) 2
2c, E ) Se, x ) 2
by one molecule of THF. The remaining four lithium cations
and a molecule of Li2O comprise the inner pseudo-octahedral
µ6-OLi64+ core. The four phosphonate dianions display two
different coordinaton modes. In each of the two modes, the
phosphonate ligands coordinate five different lithium cations
through the two imido nitrogen atoms and the single oxygen
atom. The phosphonate ligands centered at P11 and P31 are
(N,N′)-chelated to one lithium ion, while the phosphonate
ligands centered at P21 and P41 are (N,O)-chelated to one
lithium ion; further coordination occurs through both the
oxygen and nitrogen atoms to four other lithium ions. As a
result there is a pair of three-coordinate and a pair of four-
coordinate oxygen atoms in the peripheral 16-membered
P4N4O4Li4 ring. The four nitrogens in this ring are four-
coordinate, whereas the remaining four nitrogen atoms are
five-coordinate. Altogether, each phosphonate dianion co-
ordinates three lithium ions of the central Li6O core and two
lithium ions that link the phosphonate dianion with two
adjacent dianions.
The oxygen-scavenging properties of alkali-metal com-
plexes, especially those that contain lithium, are reasonably
well understood.15 Several examples exist in which trace
amounts of moisture, introduced either purposely or un-
intentionally, have resulted in a similar µ6-OLi6 core.16 The
cluster 2a‚Li2O is unique in exhibiting both three- and four-
coordinate Li+ ions in the OLi6 core. As expected, the Li-O
distances involving three-coordinate Li+ ions are significantly
shorter than those involving four-coordinate ions, 1.852(4)-
1.985(4) Å vs 2.099(4)-2.166(4) Å. The geometry around
The analogous phosphine telluride [PhP(Te)(NHtBu)2] 1d
cannot be obtained by oxidation of [PhP(NHtBu)2] with
elemental tellurium, even in boiling toluene. However, we
have recently described a new approach to the synthesis of
metalated amidophosphine tellurides that involves carrying
out the metalation step prior to oxidation with elemental
tellurium.14 As a further example, we find that the reaction
of Li2[PhP(NtBu)2]11 with elemental tellurium in THF at 70
°C produces the dilithium salt 2d (eq 2).
2Li2[PhP(NtBu)2] + 2Te THF8
{[Li(THF)]2[PhP(Te)(NtBu)2]}2
(2)
2d
X-ray Structures and NMR Characterization of {(THF)-
Li2[PhP(O)(NtBu)2}4‚Li2O (2a‚Li2O) and {(Et2O)0.5Li2-
[PhP(O)(NtBu)2]}4 (2a′). Two different products were
isolated from the lithiation of PhP(O)(NHtBu)2 with LinBu,
depending on the solvent. In THF, the complex {(THF)-
Li2[PhP(O)(NtBu)2}4‚Li2O (2a‚Li2O), in which a tetramer
encapsulates a molecule of Li2O, is formed. By contrast, in
diethyl ether a tetramer {(Et2O)0.5Li2[PhP(O)(NtBu)2]}4 (2a′)
without the Li2O template is obtained. The molecular
geometry and atomic numbering schemes for these two
complexes are shown in Figures 1 and 2; pertinent structural
parameters are summarized in Tables 2 and 3, respectively.
The X-ray structural analysis of 2a‚Li2O reveals a 27-atom
P4N8O5Li10 cluster including a central oxide coordinated in
an octahedral fashion to six lithium cations. The four
phosphonate dianions are on the periphery of the cluster with
their phenyl substituents pointing away from the center. Four
of the lithium cations are also on the outer surface linking
the phosphonate units, and each of these Li+ ions is solvated
(15) Wheatley, A. E. H. Chem. Soc. ReV. 2001, 30, 265.
(16) (a) Gais, H.-J.; Vollhardt, J.; Guenther, H.; Moskau, D.; Lindner, H.
J.; Braun, S. J. Am. Chem. Soc. 1988, 110, 978. (b) Ball, S. C.; Cragg-
Hine, I.; Davidson, M. G.; Davies, R. P.; Lopez-Solera, M. I.; Raithby,
P. R.; Reed, D.; Snaith, R.; Vogl, E. M. J. Chem. Soc., Chem. Commun.
1995, 2147. (c) Clegg, W.; Horsburgh, L.; Dennison, P. R.; Mackenzie,
F. M.; Mulvey, R. E. Chem. Commun. 1996, 1065. (d) Driess, M.;
Pritzkow, H.; Martin, S.; Rell, S.; Fenske, D.; Baum, G. Angew. Chem.,
Int. Ed. Engl. 1996, 35, 986. (e) Chivers, T.; Downard, A.; Yap, G.
P. A. J. Chem. Soc., Dalton Trans. 1998, 2603. (f) Jones, C.; Junk, P.
C.; Leary, S. G.; Smithies, N. A. J. Chem. Soc., Dalton Trans. 2000,
3186.
(13) Chivers, T.; Parvez, M.; Seay, M. A. Inorg. Chem. 1994, 33, 2147.
(14) Briand, G. G.; Chivers, T.; Parvez, M. Angew. Chem., Int. Ed. Engl.
2002, 41, 3468.
Inorganic Chemistry, Vol. 41, No. 25, 2002 6811

Briand et al.
Figure 2. X-ray structure of {(Et2O)1/2Li2[PhP(O)(NtBu)2]}4 (2a′) showing the numbering scheme (30% probability ellipsoids). Only the R-carbons of the
tBu groups, the ipso-carbons of the phenyl groups, and the oxygen atoms of Et2O molecules are shown.
Table 2. Selected Bond Lengths (Å) and Bond Angles (deg) for
{(THF)Li2[PhP(O)(NtBu)2}4‚Li2O (2a‚Li2O)
Table 3. Selected Bond Lengths (Å) and Bond Angles (deg) for
{(Et2O)1/2Li2[PhP(O)(NtBu)2]}4 (2a′)
Li(11)-O(11)
Li(11)-N(21)
Li(12)-O(5)
Li(12)-O(11)
Li(12)-N(22)
P(11)-O(11)
P(11)-N(11)
P(11)-N(12)
N(11)-Li(41)
N(11)-Li(52)
N(12)-Li(41)
N(12)-Li(42)
Li(21)-O(21)
Li(21)-N(31)
Li(21)-N(32)
Li(22)-O(5)
Li(22)-O(21)
Li(22)-N(31)
P(21)-O(21)
O(41)-Li(52)
N(41)-Li(52)
1.890(4)
1.989(4)
1.852(4)
1.924(4)
2.036(4)
1.5371(15)
1.6190(18)
1.6219(17)
2.122(4)
2.189(4)
2.026(4)
2.099(4)
1.899(4)
2.040(5)
2.090(4)
1.906(4)
1.985(4)
2.080(4)
1.5500(15)
2.151(4)
2.081(4)
P(21)-N(21)
P(21)-N(22)
O(21)-Li(51)
N(22)-Li(51)
Li(31)-O(31)
Li(31)-N(42)
Li(32)-O(5)
Li(32)-O(31)
Li(32)-N(41)
P(31)-O(31)
P(31)-N(31)
P(31)-N(32)
N(32)-Li(51)
Li(41)-O(41)
Li(42)-O(5)
Li(42)-O(41)
P(41)-O(41)
P(41)-N(42)
P(41)-N(41)
O(5)-Li(51)
O(5)-Li(52)
1.6087(18)
1.6123(17)
2.166(4)
2.094(4)
1.881(4)
1.989(4)
1.856(4)
1.935(4)
2.055(4)
1.5343(16)
1.6181(19)
1.6240(19)
2.200(4)
1.904(4)
1.904(4)
Li(1)-O(1)
Li(1)-O(2)
Li(1)-N(7)
Li(1)-N(8)
Li(2)-N(3)
Li(2)-O(1)
Li(2)-N(1)
Li(2)-O(2)
Li(3)-O(3)
Li(3)-O(2)
Li(3)-N(7)
Li(4)-O(2)
Li(4)-N(4)
Li(4)-N(8)
Li(4)-O(3)
Li(5)-O(4)
Li(5)-O(3)
Li(5)-N(6)
Li(5)-N(8)
1.848(5)
2.011(5)
2.087(5)
2.319(5)
1.983(5)
2.066(5)
2.361(6)
2.450(6)
1.967(5)
1.975(5)
2.045(5)
1.944(5)
2.114(5)
2.125(5)
2.143(5)
1.924(5)
1.968(5)
2.074(5)
2.255(5)
Li(6)-N(5)
Li(6)-N(4)
Li(6)-O(3)
Li(7)-O(4)
Li(7)-N(6)
Li(8)-N(2)
Li(8)-N(1)
P(1)-O(1)
P(1)-N(2)
P(1)-N(1)
P(2)-O(2)
P(2)-N(3)
P(2)-N(4)
P(3)-O(3)
P(3)-N(5)
P(3)-N(6)
P(4)-O(4)
P(4)-N(7)
P(4)-N(8)
1.956(5)
1.977(5)
1.995(5)
1.835(5)
2.068(6)
1.953(6)
1.964(6)
1.5388(18)
1.600(2)
1.617(2)
1.5680(17)
1.574(2)
1.625(2)
1.5821(17)
1.582(2)
1.613(2)
1.5421(18)
1.610(2)
1.637(2)
1.984(4)
1.5515(15)
1.6102(18)
1.6177(18)
2.099(4)
O(1)-P(1)-N(2)
O(1)-P(1)-N(1)
N(2)-P(1)-N(1)
O(2)-P(2)-N(3)
O(2)-P(2)-N(4)
N(3)-P(2)-N(4)
116.48(12)
111.67(11)
99.84(12)
107.98(10)
102.65(10)
122.80(12)
O(3)-P(3)-N(5)
O(3)-P(3)-N(6)
N(5)-P(3)-N(6)
O(4)-P(4)-N(7)
O(4)-P(4)-N(8)
N(7)-P(4)-N(8)
102.75(10)
105.26(11)
126.39(12)
115.81(11)
110.14(11)
101.70(11)
2.136(4)
Li(12)-O(5)-Li(32) 152.33(19) Li(32)-O(5)-Li(51)
88.80(17)
Li(12)-O(5)-Li(42)
Li(32)-O(5)-Li(42)
Li(12)-O(5)-Li(22)
Li(32)-O(5)-Li(22)
98.18(17) Li(42)-O(5)-Li(51) 170.89(17)
98.62(18) Li(22)-O(5)-Li(51)
98.91(18) Li(12)-O(5)-Li(52)
98.24(17) Li(42)-O(5)-Li(52)
69.76(16)
77.40(16)
69.53(15)
Li(42)-O(5)-Li(22) 103.73(17) Li(22)-O(5)-Li(52) 171.00(17)
Li(12)-O(5)-Li(51) 77.05(16) Li(51)-O(5)-Li(52) 117.60(15)
phosphonates at P1 and P4 coordinate two lithium ions via
(N,N′) and (N,O) chelation. Coordination to three additional
lithium ions occurs through both the oxygen and nitrogen
atoms.
the central oxide is a very distorted octahedron with LiOLi
bond angles in the range 69.5(2)° - 117.6(2)°.
Complex 2a′, which was formed in diethyl ether under
identical conditions to those used for the isolation of 2a‚
Li2O, is also tetrameric but, in the absence of encapsulated
Li2O, the symmetry of the cluster is low (Figure 2). It is a
24-atom P4N8O4Li8 cluster in which only two lithium ions
are solvated by a molecule of diethyl ether. Like 2a‚Li2O,
the lithium and oxygen atoms in 2a′ reside in the inner part
of the cluster, while the phenyl substituents are on the
periphery. The predominant features are the numerous four-
membered rings, including a central Li2O2 ring. There are
also two six-membered (Li2O2PN) rings. As in 2a‚Li2O, there
are two modes of coordination for the phosphonate dianions
in which each dianion coordinates to a total of five unique
lithium ions. The phosphonates at P2 and P3 coordinate two
lithium ions in a bis(N,O) coordination mode, while the
In the cluster 2a′ there are three- and four-coordinate
lithium ions, three- and five-coordinate oxygen atoms, and
three-, four-, and five-coordinate nitrogen centers. Conse-
quently, there is a broader range of Li-N and Li-O
distances in 2a′ compared to those in 2a‚Li2O [the ranges
for Li-N and Li-O distances are 1.953(6)-2.319(5) Å and
1.835(5)-2.450(6) Å compared with 1.989(4)-2.200(4) Å
and 1.881(4)-2.166(4) Å, respectively].
Both clusters were characterized by multinuclear NMR
studies. For 2a‚Li2O the NMR data indicate a higher
1
symmetry in solution than in the solid state. Thus the H
NMR spectrum in THF-d8 at 23 °C reveals a single NtBu
environment, while the 31P NMR spectrum exhibits a singlet
7
at δ 23.8. The Li NMR spectrum consists of a broad
resonance at δ -0.87 with a shoulder at δ -0.20. The
6812 Inorganic Chemistry, Vol. 41, No. 25, 2002

Synthesis and X-ray Structures of Dilithium Complexes
Scheme 1
Figure 3. X-ray structure of {(THF)2Li2[PhP(S)(NtBu)2]}2 (2b) showing
the numbering scheme (30% probability ellipsoids). Only the R-carbons of
the tBu groups, the ipso-carbons of the phenyl groups, and the oxygen atoms
of THF molecules are shown. Symmetry transformations used to generate
equivalent atoms: -x + 1, -y, -z.
solution NMR data for 2a′ are not very informative. Both
1
the H and 31P NMR spectra in THF-d8 at 23 °C exhibit a
multitude of resonances, suggesting that dissociation to give
a mixture of oligomers occurs.17 However, the solid-state
31P NMR spectrum shows four distinct resonances at δ 25.6,
22.5, 13.2, and 6.5, consistent with the X-ray structure. In
7
the solid-state Li NMR spectrum only five resonances are
observed, rather than the eight expected from the X-ray
structure, likely as a result of overlap of resonances for Li+
ions in similar environments.
The mechanism of formation of the Li2O-encapsulated
cluster merits further discussion. In three separate experi-
ments crystals of the product of the reaction of 1a with 2
Figure 4. X-ray structure of {(THF)2Li2[PhP(Se)(NtBu)2]}2 (2c) showing
the numbering scheme (30% probability ellipsoids). Only the R-carbons of
the tBu groups, the ipso-carbons of the phenyl groups, and the oxygen atoms
of THF molecules are shown. Symmetry transformations used to generate
equivalent atoms: -x, -y, -z.
n
equiv of BuLi could not be obtained from THF solution
until a minimum of 3 days had elapsed. In all three cases
the crystals were shown by determination of unit cell
parameters to be 2a‚Li2O. Junk et al. report that the deliberate
addition of water was necessary to grow crystals of [(C5H3-
NMeN(H)Li)6(Et2O)2‚Li2O].16f Similarly, Li4[nBuC(NtBu)2]4‚
Li2O is formed when a stoichiometric amount of water is
added to a THF solution of Li[nBuC(NtBu)2].16e In the current
work the reaction of Li2[PhP(O)(NtBu)2] with a stoichio-
metric amount of water was monitored by 31P NMR, which
revealed the presence of Li[PhP(O)(NHtBu)(NtBu)] [δ 31P
(C6D6) ) 7.6 (s)] as an intermediate. An authentic sample
of this monolithiated complex of 5a was prepared by the
reaction of 1a with 1 equiv of nBuLi. Thus we suggest that,
by analogy with the formation of Li4[nBuC(NtBu)2]4‚Li2O,16e
the cluster 2a‚Li2O is generated by the two-step process
shown in Scheme 1. The net reaction requires only traces of
water, which may be present in THF solvent or the glassware.
X-ray Structures and NMR Characterization of
{(THF)2Li2[PhP(S)(NtBu)2]}2 (2b), {(THF)2Li2[PhP(Se)-
(NtBu)2]}2 (2c) and {(THF)2Li2[PhP(Te)(NtBu)2]}2 (2d).
The molecular geometry and atomic numbering schemes for
2b and 2c are shown in Figures 3 and 4. The structure of 2d
is similar to that of 2c. Pertinent structural parameters for
2b-d are compared in Table 4. All three compounds form
dimers that are linked through Li-E (E ) S, Se, Te)
interactions. The selenide and telluride, 2c and 2d, contain
central transoid Li2E2 rings, while the sulfide 2b has only
very weak transannular interactions. The structures all contain
(N,N′)- and (N,E)-chelated lithium ions. The (N,N′)-chelated
Table 4. Selected Bond Lengths (Å) and Bond Angles (deg) for
{(THF)2Li2[PhP(S)(NtBu)2]}2 (2b), {(THF)2Li2[PhP(Se)(NtBu)2]}2 (2c),
and {(THF)2Li2[PhP(Te)(NtBu)2]}2 (2d)
2b
2c
2d
E(1)-P(1)
E(1)-Li(1)*
E(1)-Li(1)
P(1)-N(2)
P(1)-N(1)
O(1)-Li(1)
O(1)-Li(2)
O(2)-Li(2)
N(1)-Li(1)
N(1)-Li(2)
N(2)-Li(2)
2.040(5)
2.406(4)
3.172(5)
1.6092(16)
1.6256(16)
2.065(4)
2.087(4)
1.936(4)
2.058(4)
2.060(4)
1.960(4)
2.2371(5)
2.564(4)
2.637(4)
1.6011(17)
1.6198(17)
2.034(4)
2.235(5)
1.938(4)
2.027(4)
2.066(4)
2.006(4)
2.4935(12)
2.792(9)
2.848(9)
1.597(4)
1.619(4)
2.104(9)
2.140(10)
1.937(9)
2.010(10)
2.106(9)
2.005(9)
P(1)-E(1)-Li(1)*
P(1)-E(1)-Li (1)
Li(1)-E(1)-Li(1)*
N(2)-P(1)-N(1)
N(2)-P(1)-E(1)
N(1)-P(1)-E(1)
Li(1)-O(1)-Li(2)
P(1)-N(1)-Li(1)
P(1)-N(1)-Li(2)
Li(1)-N(1)-Li(2)
P(1)-N(2)-Li(2)
N(1)-Li(1)-E(1)*
N(1)-Li(1)-E(1)
E(1)*-Li(1)-E(1)
N(2)-Li(2)-N(1)
124.68(10)
118.51(9)
67.53(8)
115.24(18)
63.00(18)
64.6(3)
105.1(2)
113.29(15)
106.68(15)
82.8(4)
100.8(3)
85.4(3)
86.0(4)
89.5(3)
126.6(4)
85.0(3)
115.4(3)
76.8(3)
55.86(8)
69.35(14)
98.82(8)
67.46(13)
104.31(9)
112.82(7)
108.19(7)
82.09(15)
96.27(13)
86.40(13)
86.61(17)
88.97(14)
124.43(17)
83.69(13)
112.54(13)
77.31(15)
115.81(7)
115.00(7)
76.51(15)
90.72(13)
89.74(12)
77.25(16)
93.90(13)
143.7(2)
69.07(15)
110.65(16)
75.29(14)
lithium is solvated by one molecule of THF, while a second
molecule of THF bridges these two lithium ions.
The P-E distances of 2.040(5), 2.2371(5), and
2.4935(12) Å for 2b, 2c, and 2d, respectively, are all closer
to single bond values rather than double bonds.18-25 The P-N
bond lengths are in the narrow range 1.60-1.62 Å for all
three compounds. The transannular Li-E distance is slightly
(17) Dissociation of the tetrameric cluster {Li[P(NtBu)2]}4 into smaller
aggregates has been established by VT NMR studies. Brask, J. K.;
Chivers, T.; Krahn, M. L.; Parvez, M. Inorg. Chem. 1999, 38, 290.
Inorganic Chemistry, Vol. 41, No. 25, 2002 6813

Briand et al.
longer than the Li-E* distance for 2c and 2d, whereas this
difference is ca. 0.77 Å for the sulfide 2b. Consistently, the
N(1)-P(1) -E(1) bond angle is substantially larger for the
sulfide [115.00(7)°, 2b; 108.19(7)°, 2c; 106.68(15)°, 2d]. No
structural information is available for the alkali-metal deriva-
tives of the related [PhP(NtBu)3]2- dianion for comparison,7
although the structure of a spirocyclic tellurium(IV) complex
has been reported.26
The 1H NMR spectra for 2b-d in THF-d8 at room
temperature all show single NtBu resonances at δ 1.06, 1.08,
and 1.12, respectively, in addition to the resonances for the
phenyl substituents and coordinated THF molecules. The 31P
NMR spectra consist of singlets at δ 39.5, 27.6, and -14.4
for 2b, 2c, and 2d, respectively. The 77Se and 125Te NMR
spectra reveal doublets at δ -45.7 and -333 for 2c and 2d,
with 1J(31P-77Se) ) 513 Hz and 1J(31P-125Te) ) 1212 Hz,
Figure 5. X-ray structure of {Me2Al[PhP(Se)(NtBu)(NHtBu]} (4c) show-
ing the numbering scheme (30% probability ellipsoids). Only the carbon
t
atoms of the Bu, phenyl, and methyl groups are shown.
1
respectively. The decrease in the value of J(31P-77Se) by
Table 5. Selected Bond Lengths (Å) and Bond Angles (deg) for
{Me2Al[PhP(Se)(NtBu)(NHtBu]} (4c)
273 Hz in 2c compared to 1c indicates a substantially lower
P-Se bond order as expected from the structural data. Taken
together, the NMR data suggest that 2b-d have a higher
degree of symmetry in solution than in the solid state. Since
only one NtBu resonance is observed in the 1H NMR spectra
of 2b-d, even at -100 °C, and only one 7Li NMR
environment is indicated, it is likely that a facile fluxional
process involving exchange between Li(1)-N(1) and Li(1)-
N(2) interactions occurs. Such fluxional processes are
common for polycylic species involving polyimido anions
of p-block elements.1a
Synthesis and X-ray Structures of {Me2Al[PhP(S)-
(NtBu)(NHtBu]} (4b) and {Me2Al[PhP(Se)(NtBu)(NHtBu]}
(4c). Stahl et al. have shown that cyclodiphosph(V)azanes
cis-[tBu(H)N(E)P(µ-NtBu)2P(E)N(H)tBu] (E ) O, S, Se)
react with trimethylaluminum to form the bis(dimethyl-
aluminum) complexes {(Me2Al)[tBuN(E)P(µ-NtBu)2P(E)Nt-
Bu](AlMe2)} in which the ligand is bis(N,E)-chelated to
aluminum.27 Related mononuclear dimethylaluminum com-
plexes have been prepared from [Me2Si(µ-NtBu)2P(E)-
(NHPh)] and trimethylaluminum.28 In the present work it
was of interest to determine whether the reaction of PhP-
(E)(NHtBu)2 (1b, E ) S; 1c, E ) Se) with trimethylalumi-
num results in double deprotonation to give the dianions 3b,c
or monodeprotonation to give the monoanions 5b,c.
Se(1)-P(1)
Se(1)-Al(1)
P(1)-N(1)
P(1)-N(2)
2.1865(7)
2.5103(10)
1.611(2)
Al(1)-N(1)
Al(1)-C(16)
Al(1)-C(15)
1.900(3)
1.959(4)
1.965(4)
1.653(3)
P(1)-Se(1)-Al(1)
N(1)-P(1)-N(2)
N(1)-P(1)-Se(1)
N(2)-P(1)-Se(1)
N(1)-P(1)-Al(1)
72.94(3)
117.91(14)
99.55(9)
116.02(10)
40.72(9)
N(2)-P(1)-Al(1)
Se(1)-P(1)-Al(1)
N(1)-Al(1)-Se(1)
P(1)-N(1)-Al(1)
C(5)-N(2)-P(1)
135.44(10)
58.86(3)
81.75(8)
105.70(13)
131.1(2)
The reaction of 1b or 1c with 1 equiv of trimethylalumi-
num in boiling toluene for 18 h yields the complexes 4b
and 4c, which exhibit similar NMR spectra. The H NMR
1
spectra contain two equally intense resonances in the NtBu
region (δ 1.28 and 1.08, 4b and 4c), two equally intense
methylaluminum resonances (δ -0.01 and -0.03, 4b; 0.10
and 0.07, 4c), and an amido NH resonance (δ 2.38, 4b; 2.35,
4c), suggesting formation of a monodeprotonated complex.
The 31P NMR spectra reveal singlets at δ 38.4 (4b) and δ
29.1 (4c); the latter resonance shows selenium satellites. The
77Se NMR spectrum of 4c contains a doublet at δ -102.4
with 1J(31P-77Se) ) 497 Hz (cf. 468 and 463 Hz for {[MeP-
(N(TMS)2)(NtBu)(Se)](AlMe2)} and {MeP[N(TMS)(tBu)]-
[(NtBu)(Se)](AlMe2)}, respectively).29,30
The X-ray structure of 4c is shown in Figure 5 and
pertinent structural parameters are summarized in Table 5.
In view of the congruence in the NMR spectra, it is likely
that 4b has a similar structure. Consistent with the NMR
data, the monoanion 5c coordinates the dimethylaluminum
fragment through (N,Se)-chelation. The methyl groups on
aluminum are oriented perpendicular to the plane of the
distorted AlNPSe ring. The tBu substituent of the exocyclic
N(H)tBu group is in an exo position with respect to the
PNAlSe ring.
(18) The PdS double bond in SPPh2NHPh2PS19 is 1.936(1) Å and a typical
single bond value is 2.100(1) Å. Corbridge, D. E. C. In The Structural
Chemistry of Phosphorus; Elsevier: New York, 1994.
(19) No¨th, H. Z. Naturforsch. 1982, 37b, 1491.
(20) Typical single and double PSe bond distances are 2.238 and 2.093 Å,
respectively.21, 22
(21) Burford, N.; Spence, R. E.v. H.; Rogers, R. D. J. Chem. Soc., Dalton
Trans. 1990, 3611.
(22) Allen, F. H.; Kennard, O.; Watson, D. G.; Brammer, L.; Orpen, A.
G.; Taylor, R. J. Chem. Soc., Perkin Trans. 2, 1987, S1.
(23) Typical single and double PTe bond distances are 2.50 and 2.37 Å,
respectively.24,25
The P-Se distance of 2.1865(7) Å is significantly shorter
than that observed in 2c (2.2371(5) Å), indicating a higher
(24) Kuhn, N.; Schumann, H.; Boese, R. J. Chem. Soc., Chem. Commun.
1987, 1257.
(25) Kuhn, N.; Schumann, H.; Wolmersha¨user, G. Z. Naturforsch. 1987,
42b, 674.
(26) Chivers, T.; Gao, X.; Parvez, M. Angew. Chem., Int. Ed. Engl. 1995,
34, 2549.
(27) Lief, G. R.; Carrow, C. J.; Stahl, L. Organometallics 2001, 20, 1629.
(28) Haagenson, D. C.; Moser, D. F.; Stahl, L. Inorg. Chem. 2002, 41,
1245.
(29) (a) Romanenko, V. D.; Shul’gin, V. F.; Skopenko, V. V.; Markovskii,
L. N. Zh. Obshch. Khim. 1985, 55, 538. (b) Romanenko, V. D.;
Shul’gin, V. F.; Skopenko, V. V.; Chernega, A. N.; Antipin, M. Yu.;
Struchkov, Yu. T.; Boldeskul, I. E.; Markovskii, L. N. Zh. Obshch.
Khim. 1985, 55, 282.
(30) Bauer, T.; Schulz, S.; Nieger, M. Z. Anorg. Allg. Chem. 2001, 627,
266.
6814 Inorganic Chemistry, Vol. 41, No. 25, 2002

Synthesis and X-ray Structures of Dilithium Complexes
P-Se bond order in 4c. However, the values of J(31P-
77Se) exhibit the opposite trend (497 Hz, 4c; 513 Hz, 2c).
The reasons for this discrepancy are not clear, but it is
apparent that the correlation between bond length (or bond
order) and the value of 1J(31P-77Se) is only approximate for
this series of compounds. The endocyclic P-N distance of
1.611(2) Å is significantly shorter than the exocyclic P-N
distance of 1.653(3) Å. The disparity of ca. 0.6 Å in the
Al-Se and Al-N distances results in a distorted four-
membered AlNPSe ring with endocyclic bond angles
P-Se-Al ) 72.94(3)° and P-N-Al ) 105.70(13)°. The
Al-Se distance of 2.510(1) Å is somewhat longer than the
range of values (2.34-2.44 Å) found for recently reported
four-coordinate aluminum complexes.31-33 The Al-N dis-
tance of 1.900(3) Å can be compared with values in the range
1.84-1.89 Å for four-coordinate aluminum complexes.34,35
Thus the structural data indicate, as expected, that the
selenium atom is less strongly bonded than nitrogen to the
aluminum center.
Conclusions
1
The dilithium salts of the phosphonate dianions 3a-c are
generated by the lithiation of the appropriate chalcogenido
bis(amido)phosphonate 1a-c with LinBu. The preparation
of the corresponding telluride requires lithiation of PhP-
(NHtBu)2 prior to oxidation with elemental tellurium. The
formation of a Li2O-templated complex provides another
example of the creation of a cluster with a central OLi6 core
caused by the presence of adventitious water. Isostructural
dimethylaluminum complexes of the monoanions 5b,c can
be generated by the reactions of trimethylaluminum with
1b,c, respectively. The novel polydentate dianions 3b-d and
5b,c are potentially versatile tripodal or bidentate ligands
with both hard (N) and soft (S, Se, Te) donor centers that
merit further investigation, especially in the context of
transition-metal complexes.
Acknowledgment. We thank the NSERC (Canada) for
(31) Harlan, C. J.; Gillan, E. G.; Bolt, S. G.; Barron, A. R. Organometallics
1996, 15, 5479.
financial support.
(32) Cui, C.; Roesky, H. W.; Noltemeyer, M.; Schmidt, H.-G. Organo-
metallics 1999, 18, 5120.
(33) Cui, C.; Roesky, H. W.; Noltemeyer, M.; Schmidt, H.-G. Inorg. Chem.
2000, 39, 3678.
(34) Brask, J. K.; Chivers, T.; Schatte, G.; Yap, G. P. A. Organometallics
2000, 19, 5683.
(35) Blais, P.; Chivers, T.; Schatte, G.; Krahn, M. J. Organomet. Chem.
2002, 646, 107.
Supporting Information Available: X-ray crystallographic
files, in CIF format for complexes 2a‚Li2O, 2a′, 2b, 2c, 2d, and
4c. This material is. avaliable free of charge via the Internet at
http://pubs.acs.org.
IC020471H
Inorganic Chemistry, Vol. 41, No. 25, 2002 6815