Synthesis and structures of aluminum and magnesium complexes of tetraimidophosphates and trisamidothiophosphates: EPR and DFT investigations of the persistent neutral radicals {Me2Al[(μ-NR)(μ-N tBu)P(μ-NtBu)2]Li(THF)2} ? (R = SiMe3, tBu)

Article abstract of DOI:10.1021/ic050689e

Reactions of (RNH)₃PNSiMe₃ (3a, R = ^tBu; 3b, R = Cy) with trimethylaluminum result in the formation of {Me ₂-Al(μ-N^tBu)(μ-NSiMe₃)P(NH ^tBu)₂]} (4) and the dimeric trisimidometaphosphate {Me₂Al[(μ-NCy)(μ-NSiMe³)P(μ-NCy) ₂P-(μ-NCy)(μ-NSiMe₃)]AlMe₂} (5a), respectively. The reaction of SP(NH^tBu)₃ (2a) with 1 or 2 equiv of AlMe₃ yields {Me₂Al[(μ-S)(μ-N ^tBu)P(NH^tBu)₂]} (7) and {Me₂Al[(μ -S)(μ-N^tBu)P(μ-NH^tBu)(μ-N^tBu)] AlMe₂} (8), respectively. Metalation of 4 with ⁿBuLi produces the heterobimetallic species {Me₂Al[(μ-N ^tBu)(μ-NSiMe₃)P(μ-NH^tBu)(μ-N ^tBu)]-Li(THF)₂} (9a) and {[Me₂Al][Li] ₂[P(N^tBu)₃(NSiMe₃)]} (10) sequentially; in THF solutions, solvation of 10 yields an ion pair containing a spirocyclic tetraimidophosphate monoanion. Similarly, the reaction of ( ^tBuNH)₃PN^tBu with AlMe₃ followed by 2 equiv of ⁿBuLi generates {Me₂Al[(μ-N ^tBu)₂P(μ₂-N^tBu) ₂(μ₂-THF)[Li(THF)]₂} (11a). Stoichiometric oxidations of 10 and 11a with iodine yield the neutral spirocyclic radicals {Me₂Al[(μ-NR)(μ-N^tBu)P(μ-N^tBu) ₂]Li-(THF)₂}^? (13a, R = SiMe₃; 14a, R = ^tBu), which have been characterized by electron paramagnetic resonance spectroscopy. Density functional theory calculations confirm the retention of the spirocyclic structure and indicate that the spin density in these radicals is concentrated on the nitrogen atoms of the PN₂Li ring. When 3a or 3b is treated with 0.5 equiv of dibutylmagnesium, the complexes {Mg[(μ-N^tBu)(μ-NH^tBu)P(NH^tBu)(NSiMe ₃)]₂} (15) and {Mg[(μ-NCy)(μ-NSiMe ₃)P(NHCy)₂]₂} (16) are obtained, respectively. The addition of 0.5 equiv of MgBu₂ to 2a results in the formation of {Mg[(μ-S)(μN^tBu)P(NH^tBu)₂]₂} (17), which produces the hexameric species {[MgOH]-[(μ-S)(μ-N ^tBu)P(NH^tBu)₂]}₆ (18) upon hydrolysis. Compounds 4, 5a, 7-11a, and 15-17 have been characterized by multinuclear (¹H, ¹³C, and ³¹P) NMR spectroscopy and, in the case of 5a, 9a·2THF, 11a, and 18, by X-ray crystallography.

Full text of DOI:10.1021/ic050689e

Inorg. Chem. 2005, 44, 5778−5788
Synthesis and Structures of Aluminum and Magnesium Complexes of
Tetraimidophosphates and Trisamidothiophosphates: EPR and DFT
Investigations of the Persistent Neutral Radicals
•
t
{
Me2Al[(µ-NR)(
µ
-NtBu)P(
µ
-NtBu)2]Li(THF)2
}
(R
)
SiMe3, Bu)
Andrea Armstrong, Tristram Chivers,* Heikki M. Tuononen, and Masood Parvez
Department of Chemistry, UniVersity of Calgary, Calgary, Alberta, Canada T2N 1N4
Received May 3, 2005
Reactions of (RNH)3PNSiMe3 (3a, R
Al( (4) and the dimeric trisimidometaphosphate
-NtBu)( -NSiMe3)P(NHtBu)2]
-NCy)( -NSiMe3)]AlMe2
(5a), respectively. The reaction of SP(NHtBu)3 (2a) with 1 or 2 equiv of AlMe3 yields
Me2Al[( -S)( (7) and Me2Al[( -S)( (8), respectively.
-NtBu)P(NHtBu)2] -NtBu)P( -NHtBu)( -NtBu)]AlMe2
Metalation of 4 with nBuLi produces the heterobimetallic species -NtBu)( -NHtBu)( -NtBu)]-
Me2Al[( -NSiMe3)P(
Li(THF)2 (9a) and (10) sequentially; in THF solutions, solvation of 10 yields an
[Me2Al][Li]2[P(NtBu)3(NSiMe3)]
ion pair containing a spirocyclic tetraimidophosphate monoanion. Similarly, the reaction of (tBuNH)3PNtBu with
AlMe3 followed by 2 equiv of nBuLi generates -NtBu)2P( 2-NtBu)2(
Me2Al[( 2-THF)[Li(THF)]2 (11a). Stoichiometric
Me2Al[( -NR)(
-NtBu)P( -NtBu)2]Li-
)
tBu; 3b, R
)
Cy) with trimethylaluminum result in the formation of
{Me2-
µ
µ
}
{
Me2Al[( -NCy)( -NSiMe3)P( -NCy)2P-
µ
µ
µ
(
µ
µ
}
{
µ
µ
}
{
µ
µ
µ
µ
}
{
µ
µ
µ
µ
}
{
}
{
µ
µ
µ
}
oxidations of 10 and 11a with iodine yield the neutral spirocyclic radicals
{
µ
µ
µ
•
(THF)2
}
(13a, R
)
SiMe3; 14a, R
)
tBu), which have been characterized by electron paramagnetic resonance
spectroscopy. Density functional theory calculations confirm the retention of the spirocyclic structure and indicate
that the spin density in these radicals is concentrated on the nitrogen atoms of the PN2Li ring. When 3a or 3b is
treated with 0.5 equiv of dibutylmagnesium, the complexes
Mg[( -NCy)( -NSiMe3)P(NHCy)2]2 (16) are obtained, respectively. The addition of 0.5 equiv of MgBu2 to 2a
results in the formation of Mg[( -S)( (17), which produces the hexameric species [MgOH]-
-NtBu)P(NHtBu)2]2
[( -S)( 11a, and 15 17 have been characterized
-NtBu)P(NHtBu)2]
2THF, 11a, and 18, by X-ray
{Mg[(µ µ } (15) and
-NtBu)( -NHtBu)P(NHtBu)(NSiMe3)]2
{
µ
µ
}
{
µ
µ
}
{
µ
µ
}
(18) upon hydrolysis. Compounds 4, 5a, 7
−
−
6
by multinuclear (1H, 13C, and 31P) NMR spectroscopy and, in the case of 5a, 9a
‚
crystallography.
Introduction
physical properties of these polyimido anions are dependent,
in large part, upon the ratio of imido/oxo units and the size
of the imido substituent.1
Numerous analogues of phosphorus oxoanions have been
prepared,3 including the trisimido(meta)phosphate4 [P(NR)3]-
and tetraimido(ortho)phosphate [P(NR)3(NR′)]3- (R ) R′ )
One of the more active areas of main-group chemistry
research over the past decade has been the synthesis and
characterization of imido analogues of simple oxoanions such
as carbonate, silicate, and phosphate.1 The underlying
principle of this work is that the oxo units [O]2- of these
species are formally isoelectronic2 with the imido [NR]2-
(R ) H, alkyl, aryl) group, and thus, a new class of p-block
polyanions can be generated by substituting some, or all, of
the oxygen atoms by imido groups. The chemical and
(2) The original definition of “isoelectronic” (isosteric) compounds restricts
the term to species having the same number of atoms and the same
number of electrons (Langmuir, I. J. Am. Chem. Soc. 1919, 41, 1543).
Thus, according to this definition, N3- is isoelectronic with O2-
.
However, nitrides are compositionally different from oxides as a result
of the different charges on the anions.
* 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. 2001, 40, 3960-3976. (b) Aspinall, G. M.; Copsey, M. C.;
Leedham, A. P.; Russell, C. A. Coord. Chem. ReV. 2002, 227, 217-
232.
(3) Chivers, T. Top. Curr. Chem. 2003, 229, 143-159.
(4) See, for example, (a) Niecke, E.; Frost, M.; Nieger, M.; von der Go¨nna,
V.; Ruban, A.; Schoeller, W. W. Angew. Chem., Int. Ed. Engl. 1994,
33, 2111. (b) Scherer, O. J.; Quintus, P.; Kaub, J.; Sheldrick, W. S.
Chem. Ber. 1987, 120, 1463. (c) Lief, G. R.; Carrow, C. J.; Stahl, L.;
Staples, R. J. Organometallics 2001, 20, 1629.
5778 Inorganic Chemistry, Vol. 44, No. 16, 2005
10.1021/ic050689e CCC: $30.25
© 2005 American Chemical Society
Published on Web 07/08/2005

Synthesis and Structures of Al and Mg Complexes
t
6
naphthyl;5 R ) Bu, R′ ) SiMe3 ) trianions. Heteroleptic
systems, such as the trisimidophosphate and -thiophosphate
trianions [EP(NR)3]3- (E ) O,7 S8), have also been reported
recently, and the first transition-metal derivatives of the
sulfur-containing ligand have been characterized.9
solution in heptane) were used as received from Aldrich. Iodine
t
was sublimed prior to use. (RNH)3PNSiMe3 (R ) Bu, Cy),6 SP-
(NHtBu)3,8 and OP(NHtBu)38 were prepared as described previously.
Instrumentation. 1H, 7Li, 13C, and 31P NMR spectra were
collected on a Bruker DRX-400 spectrometer with chemical shifts
reported relative to Me4Si in CDCl3 (1H and 13C), LiCl in D2O
(7Li), and 85% H3PO4 in D2O (31P). All spectra were collected at
22 °C. Infrared spectra were recorded as Nujol mulls on KBr plates
using a Nicolet Nexus 470 FTIR spectrometer in the range 400-
4000 cm-1. Electron paramagnetic resonance (EPR) spectra were
recorded at 22 °C on a Bruker EMX 113 spectrometer; spectral
simulations were carried out using XEMR14 and WINEPR Sim-
Fonia.15 Elemental analyses were provided by the Analytical
Services Laboratory, Department of Chemistry, University of
Calgary.
Previously, we have thoroughly investigated the reactivities
of a series of trisaminophosphates, OP(NHtBu)3 (1),6,8 SP-
(NHR)3 (2a, R ) Bu; 2b, R ) Pr; 2c, R ) p-tol),8,10 and
t
i
(RNH)3PNSiMe3 (3a, R ) Bu; 3b, R ) Cy),6,11 toward
t
alkyllithium reagents. It was found that the reactivity of these
aminophosphate species increases across the series 1 < 2 <
3. Specifically, 3-fold deprotonation of 1, 2a, or 2b is not
possible using n-butyllithium, whereas it does occur for 2c
and is readily effected for both 3a and 3b. More recently,
we have prepared a series of zinc imidophosphates by the
reactions of 1, 2a, 3a, and 3b with dimethylzinc.7 Interest-
ingly, the reaction of 1 with ZnMe2 generated several
products via at least two distinct reaction pathways, whereas
the reaction of 3a and dimethylzinc produced only {MeZn-
[(µ-NtBu)(µ-NSiMe3)P(NHtBu)2]}. In addition, two zinc
complexes were isolated that contained the trisimidophos-
phate trianion [OP(NtBu)3]3-, which had not been observed
in earlier reactions between 1 and n-butyllithium, trimeth-
ylaluminum, or lithium aluminum hydride.12
The only known main-group metal complexes of 2 and 3
are their lithium derivatives. In view of the current interest
in aluminophosphates,13 the development of synthetic routes
to a family of polyimidoaluminophosphates is certainly a
worthwhile endeavor. To this end, we have examined the
reactions of 2a and 3 with trimethylaluminum. While it is
not possible to effect the 3-fold deprotonation of 1 with
trimethylaluminum,12 the possibility of preparing trisimido-
(thio)- or tetraimidoaluminophosphates remains. Reactions
of 1-3 with MgBu2 have also been investigated in order to
gain a better understanding of the reactivity of these amido
reagents toward metal alkyls.
Preparation of {Me2Al[(µ-NtBu)(µ-NSiMe3)P(NHtBu)2]} (4).
A solution of AlMe3 (0.60 mL, 2.0 M, 1.2 mmol) in toluene was
added to a clear, colorless solution of (tBuNH)3PNSiMe3 (0.404 g,
1.21 mmol) in hexane (20 mL) at 22 °C. After 3 h, the solvent was
removed in vacuo, and the product was washed with hexane (5
mL), leaving 4 as an off-white powder (0.339 g, 0.868 mmol, 72%).
1H NMR (C6D6, δ): 1.8 (br, 2 H, NH), 1.29 (d, 9 H, NtBu), 1.16
(d, 18 H, NHtBu), 0.34 (s, 9 H, SiMe3), -0.22 (s, 6 H, AlMe2).
2
13C NMR (C6D6, δ): 51.76 [d, NCMe3, J(13C-31P) ) 10.9 Hz],
50.63 [d, NHCMe3, 2J(13C-31P) ) 15.2 Hz], 33.01 [d, NCMe3,
3J(13C-31P) ) 34.2 Hz], 32.30 [d, NHCMe3, 3J(13C-31P) ) 15.5 Hz],
3
3.57 [d, SiMe3, J(13C-31P) ) 14.9 Hz], 1.37 (s, AlMe2). 31P{1H}
NMR (C6D6, δ): 5.6 (s). IR (Nujol): 3404 cm-1 (ν N-H). Anal.
Calcd for C17H44N4AlPSi: C, 52.27; H, 11.35; N, 14.34. Found:
C, 52.16; H, 12.03; N, 13.92.
Preparation of {Me2Al[(µ-NCy)(µ-NSiMe3)P(µ-NCy)2P(µ-
NCy)(µ-NSiMe3)]AlMe2} (5a). A solution of AlMe3 (0.35 mL, 2.0
M, 0.70 mmol) in toluene was added to a clear, colorless solution
of (CyNH)3PNSiMe3 (0.286 g, 0.693 mmol) in hexane (20 mL) at
22 °C. The reaction mixture was stirred for 15 h; the volume of
the solution was then reduced to 1 mL and stored at -18 °C. After
48 h, colorless crystals of 5a were obtained (0.226 g, 0.306 mmol,
88.3%). 1H NMR (C6D6, δ): 0.8-1.9 (m, Cy), 0.22 (s, 18 H,
SiMe3), -0.37 (s, 6 H, AlMe2). 13C NMR (C6D6, δ): 51.68 (s,
CMe3), 50.05 (s, CMe3), 37.78 [d, NCCH2, 3J(13C-31P) ) 35.6 Hz],
36.91 [d, NCCH2, 3J(13C-31P) ) 19.2 Hz], 36.78 [d, NCCH2,
3J(13C-31P) ) 18.4 Hz], 26.18 (s, NCCH2CH2), 25.94 (s, NCCH2CH2),
Experimental Section
Reagents and General Procedures. All experiments were
carried out under an argon atmosphere using standard Schlenk
techniques. Toluene, n-hexane, diethyl ether, and tetrahydrofuran
(THF) were dried over Na/benzophenone, distilled, and stored over
molecular sieves prior to use. Trimethylaluminum (2.0 M solution
3
25.78 (s, p-CH2), 2.67 [d, SiMe3, J(13C-31P) ) 14.0 Hz], -6.81
(s, AlMe2). 31P{1H} NMR (C6D6, δ): 17.1 (s). CHN analyses gave
high C values owing to difficulties with the complete removal of
CyNH2.
n
in toluene), BuLi (2.5 M solution in hexanes), and MgBu2 (1.0
Preparation of {Me2Al[(µ-S)(µ-NtBu)P(NHtBu)2]} (7). A solu-
tion of AlMe3 (2.25 mL, 2.0 M, 4.5 mmol) in toluene was added
to a clear, colorless solution of SP(NHtBu)3 (1.24 g, 4.44 mmol)
in toluene (25 mL) at 22 °C. After 24 h, the solvent was removed
in vacuo, leaving a colorless oil; after storage for 12 h, the product
had solidified, giving 7 as a white powder (1.25 g, 3.73 mmol,
(5) Raithby, P. R.; Russell, C. A.; Steiner, A.; Wright, D. S. Angew. Chem.,
Int. Ed. Engl. 1997, 36, 649-650.
(6) Armstrong, A.; Chivers, T.; Krahn, M.; Parvez, M.; Schatte, G. Chem.
Commun. 2002, 2332-2333.
(7) Armstrong, A.; Chivers, T.; Krahn, M.; Parvez, M. Can. J. Chem.
2005, 83, in press.
1
82.8%). H NMR (C6D6, δ): 1.23 (s, 9 H, NtBu), 1.18 (s, 18 H,
(8) Chivers, T.; Krahn, M.; Schatte, G.; Parvez, M. Inorg. Chem. 2003,
42, 3994-4005.
(9) Rufanov, K. A.; Ziemer, B.; Meisel, M. Dalton Trans. 2004, 3808-
4
NHtBu), -0.24 [d, J(1H-31P) ) 1.8 Hz, 6 H, Me2Al]. 13C{1H}
2
NMR (C6D6, δ): 54.32 [d, CMe3, J(13C-31P) ) 37.2 Hz], 52.44
3809.
2
3
[d, CMe3, J(13C-31P) ) 9.0 Hz], 33.03 [d, CMe3, J(13C-31P) )
(10) Chivers, T.; Krahn, M.; Parvez, M.; Schatte, G. Chem. Commun. 2001,
1992-1993.
34.7 Hz], 31.42 [d, CMe3, 3J(13C-31P) ) 18.6 Hz], -5.20 (br, Me2-
(11) Armstrong, A.; Chivers, T.; Parvez, M.; Boere´, R. T. Inorg. Chem.
2004, 43, 3453-3460.
(12) Blais, P.; Chivers, T.; Krahn, M.; Schatte, G. J. Organomet. Chem.
2002, 646, 107-112.
(14) Eloranta, J. XEMR, version 0.7; University of Jyva¨skyla¨: Jyva¨skyla¨n,
Yliopisto, Finland.
(15) WINEPR SimFonia, version 1.25; Bruker Analytische Messtechnik
GmbH: Karlsruhe, Germany, 1996.
(13) For a recent review, see Kimura, T. Microporous Mesoporous Mater.
2005, 77, 97-107.
Inorganic Chemistry, Vol. 44, No. 16, 2005 5779

Armstrong et al.
Al). 31P{1H} NMR (C6D6, δ): 35.6 (s). Anal. Calcd for C14H35N3-
PSAl: C, 50.12; H, 10.52; N, 12.53. Found: C, 49.64; H, 10.97;
N, 12.63.
the solvent in vacuo. The product {[Me2Al][Li]2[P(NtBu)4]} was
isolated as a white powder (0.339 g, 0.887 mmol, 80%). Recrys-
tallization from THF/hexane produced colorless X-ray quality
crystals of {Me2Al[(µ-NtBu)2P(µ2-NtBu)2(µ2-THF)[Li(THF)]2} (11a).
1H NMR (d8-THF, δ): 1.34 (s, 36 H, NtBu), -0.96 (s, 6 H, AlMe2).
7Li (d8-THF, δ): 1.23 (s). 13C{1H} NMR (C6D6, δ): 50.90 (s,
NCMe3), 50.78 [d, NCMe3, 2J(13C-31P) ) 8.3 Hz], 36.41 [d, NCMe3,
3J(13C-31P) ) 34.9 Hz], 34.45 [d, NHCMe3, 3J(13C-31P) ) 25.4 Hz],
-4.0 (br, s, AlMe2). 31P{1H} NMR (d8-THF, δ): 12.4 (s).
Satisfactory CHN analyses could not be obtained because of the
extremely hygroscopic nature of this compound.
Preparation of {Me2Al[(µ-S)(µ-NtBu)P(µ-NHtBu)(µ-NtBu)]-
AlMe2} (8). A solution of AlMe3 (4.8 mL, 2.0 M, 9.6 mmol) in
toluene was added to a clear, colorless solution of SP(NHtBu)3 (1.30
g, 4.65 mmol) in toluene (20 mL) at 22 °C. After 40 h, the solvent
was removed in vacuo, leaving 8 as a white powder (1.74 g, 4.44
mmol, 95.5%). 1H NMR (C6D6, δ): 3.30 (br, d, NH), 1.33 [d, 4J(1H-
4
31P) ) 0.9 Hz, 9 H, NtBu], 1.23 [d, J(1H-31P) ) 0.7 Hz, 9 H,
4
NtBu], 1.20 [d, J(1H-31P) ) 0.9 Hz, 9 H, NHtBu], -0.25 (s, 3H,
Preparation of {Mg[(µ-NtBu)(µ-NHtBu)P(NHtBu)(NSiMe3)]2}
(15). A solution of MgBu2 (1.56 mL, 1.0 M, 1.56 mmol) in heptane
was added to a stirred solution of (tBuNH)3PNSiMe3 (1.05 g, 3.14
mmol) in hexane (15 mL) at 22 °C. After 18 h, the solvent was
removed in vacuo, leaving 15 as a white solid (0.986 g, 1.42 mmol,
Me2Al), -0.31 (s, 3 H, Me2Al), -0.39 (s, 3H, Me2Al), -0.54 (s,
2
3 H, Me2Al). 13C{1H} NMR (C6D6, δ): 59.09 [d, CMe3, J(13C-
2
31P) ) 12.9 Hz], 54.99 [d, CMe3, J(13C-31P) ) 39.3 Hz], 53.53
2
3
[d, CMe3, J(13C-31P) ) 8.8 Hz], 33.23 [d, CMe3, J(13C-31P) )
34.0 Hz], 32.33 [d, CMe3, 3J(13C-31P) ) 31.2 Hz], 30.05 [d, CMe3,
3J(13C-31P) ) 17.9 Hz], -5.20 (br, Me2Al), -6.09 (br, Me2Al).
31P{1H} NMR (C6D6, δ): 40.9 (s). Anal. Calcd for C16H40N3-
PSAl2: C, 49.08; H, 10.30; N, 10.73. Found: C, 49.05; H, 10.72;
N, 10.97.
1
91%). H NMR (C6D6, δ): 1.9 (br, d, NH), 1.8 (br, d, NH), 1.49
(s, 9 H, NtBu), 1.39 (s, 9 H, NHtBu), 1.32 (s, 9 H, NHtBu), 0.50
(s, 9 H, SiMe3). 13C{1H} NMR (d8-THF, δ): 51.52 (s, CMe3), 51.46
(s, CMe3), 51.40 (s, CMe3), 50.89 [d, CMe3, 2J(13C-31P) ) 3.0 Hz],
2
50.63 [d, CMe3, J(13C-31P) ) 15.0 Hz], 35.2 (s, CMe3), 33.4 [d,
Preparation of {[Me2Al][Li][P(NtBu)2(NHtBu)(NSiMe3)]} (9a).
A solution of AlMe3 (0.75 mL, 2.0 M, 1.50 mmol) in toluene was
added to a stirred solution of (tBuNH)3PNSiMe3 (0.502 g, 1.50
3
3
CMe3, J(13C-31P) ) 30.0 Hz], 33.2 [d, CMe3, J(13C-31P) ) 30.0
Hz], 32.3 [d, CMe3, 3J(13C-31P) ) 30.0 Hz], 5.7 [d, SiMe3, 3J(13C-
31P) ) 30.0 Hz], 4.3 [d, SiMe3, J(13C-31P) ) 30.0 Hz]. 31P{1H}
3
n
mmol) in hexane (20 mL) at 22 °C. After 1.5 h, BuLi (0.60 mL,
NMR(C6D6, δ): 5.2 (s). Anal. Calcd for C30H76N8MgP2Si2: C,
52.11; H, 11.08; N, 16.21. Found: C, 52.20; H, 10.19; N, 15.51.
Preparation of {Mg[(µ-NCy)(µ-NSiMe3)P(NHCy)2]2} (16). A
solution of MgBu2 (0.82 mL, 0.82 mmol) in heptane was added to
a stirred solution of (CyNH)3PNSiMe3 (0.677 g, 1.64 mmol) in
hexane (20 mL) at 22 °C. After 20 h, the solvent was removed in
vacuo, leaving 16 as an off-white solid (0.540 g, 0.637 mmol, 78%).
1H NMR (C6D6, δ): 1.0-3.2 (br, m, Cy), 0.40 (s, 9 H, SiMe3).
13C{1H} NMR (d8-THF, δ): 52.71 (s, CN), 50.03 [d, CNH, 2J(13C-
1.50 mmol) was added, resulting in a white slurry. After an
additional 3 h, the solvent was removed in vacuo, leaving 9a as a
white powder (0.582 g, 1.47 mmol, 98%). Colorless X-ray quality
crystals of {Me2Al[(µ-NtBu)(µ-NSiMe3)P(µ-NHtBu)(µ-NtBu)]Li-
(THF)2} (9a‚2THF) were obtained from a THF/hexane mixture at
1
t
-18 °C. H NMR (d8-THF, δ): 1.35 (s, 9 H, Bu), 1.31 (s, 9 H,
tBu), 1.29 (s, 9 H, tBu), 0.13 (s, 9 H, SiMe3), -0.89 (d, 6 H, Me2-
Al). 13C{1H} NMR (d8-THF, δ): 52.39 (s, CMe3), 51.14 [d, CMe3,
3
2J(13C-31P) ) 36.3 Hz], 36.70 [d, CMe3, J(13C-31P) ) 38.7 Hz],
3
3
36.09 [d, CMe3, J(13C-31P) ) 41.1 Hz], 34.11 [d, CMe3, J(13C-
31P) ) 29.1 Hz], 33.50 [d, CMe3, 3J(13C-31P) ) 19.2 Hz], 14.59 (s,
SiMe3), 4.26 (s, AlMe2). 31P{1H} NMR (d8-THF, δ): 8.2 (s). Anal.
Calcd for C17H43N4LiAlSiP: C, 51.49; H, 10.93; N, 14.13. Found:
C, 50.90; H, 10.73; N, 14.31.
3
31P) ) 30.4 Hz], 40.26 (s, CH2CN), 37.70 [d, CH2CNH, J(13C-
31P) ) 80.0 Hz], 26.73 (s, CHCH2), 26.31 (br, s, CH2CHCH2), 4.34
(s, SiMe3). 31P{1H} NMR (C6D6, δ): 19.6 (s). Anal. Calcd for
C42H88N8P2Si2Mg: C, 59.51; H, 10.46; N, 13.22. Found: C, 59.46;
H, 10.88; N, 12.53.
Preparation of {[Me2Al][Li]2[P(NtBu)3(NSiMe3)]} (10). A
solution of AlMe3 (0.60 mL, 2.0 M, 1.2 mmol) in toluene was added
to a stirred pale yellow solution of (tBuNH)3PNSiMe3 (0.404 g,
1.21 mmol) in hexane, resulting in a cloudy off-white solution. After
3h, BuLi (0.90 mL, 2.5 M, 2.3 mmol) in hexanes was added to
the reaction mixture, resulting in a white slurry. After an additional
Preparation of {Mg[(µ-S)(µ-NtBu)P(NHtBu)2]2} (17). A solu-
tion of MgBu2 (2.0 mL, 1.0 m, 2.0 mmol) was added to a stirred
solution of SP(NHtBu)3 (1.125 g, 4.026 mmol) in toluene (20 mL)
at 22 °C, resulting in a clear, colorless solution. After 20 h, the
solvent was removed in vacuo, leaving a colorless oil. After storage
for 24 h, 17 was obtained as a white powder (1.077 g, 1.850 mmol,
n
1
92.5%). H NMR(C6D6, δ): 2.03 (br, d, NH), 1.42 (s, 9H, NtBu),
3 h, the solvent was removed in vacuo, leaving 10 as a white powder
1
1.30 (s, 18H, NHtBu).13C{1H} NMR (C6D6, δ): 53.32 [d, CMe3,
(0.427 g, 1.06 mmol, 93%). H NMR (d8-THF, δ): 1.32 (s, 9 H,
NtBu), 1.30 (s, 18 H, NtBu), 0.08 (s, 9 H, SiMe3), -0.94 (s, 6 H,
AlMe2). 7Li (d8-THF, δ): 0.70 (s). 7Li (C6D6, δ): 1.44 (s), -2.71
(s). 13C{1H} NMR (C6D6, δ): 50.72 [d, NCMe3, 2J(13C-31P) ) 6.8
Hz], 36.58 [d, NCMe3, 3J(13C-31P) ) 36.2 Hz], 33.77 [d, NHCMe3,
3J(13C-31P) ) 27.2 Hz], 4.19 (s, SiMe3), -4.61 (s, AlMe2). 31P-
{1H} NMR (d8-THF, δ): 10.0 (s). Satisfactory CHN analyses could
not be obtained because of the extremely hygroscopic nature of
this compound.
2
2J(13C-31P) ) 46.7 Hz], 51.76 [d, CMe3, J(13C-31P) ) 8.8 Hz],
3
3
34.73 [d, CMe3, J(13C-31P) ) 41.0 Hz], 31.63 [d, CMe3, J(13C-
31P) ) 16.9 Hz]. 31P{1H} NMR (C6D6, δ): 38.8 (s). Anal. Calcd
for C24H58N6P2S2Mg: C, 49.60; H, 10.06; N, 14.46. Found: C,
50.89; H, 10.62; N, 13.69.
Storage of a solution of 17 in diethyl ether at -18 °C for one
week yielded colorless crystals of {[MgOH][(µ-S)(µ-NtBu)P-
(NHtBu)2]}6 (18).
Preparation of {Me2Al[(µ-NtBu)2P(µ2-NtBu)2(µ2-THF)[Li-
(THF)]2} (11a). A solution of AlMe3 (0.55 mL, 2.0 M, 1.10 mmol)
in toluene was added to a stirred clear, colorless solution of
(tBuNH)3PNtBu (0.353 g, 1.11 mmol) in hexane (15 mL), resulting
in an opaque white solution. After 3 h, nBuLi (1.4 mL, 1.6 M, 2.24
mmol) in hexanes was added to the reaction mixture, resulting in
a white slurry. After an additional 2.5 h, the white solid was allowed
to settle, and the supernatant liquid was decanted. The product was
washed with an additional 5 mL of hexane prior to the removal of
X-ray Analyses. Colorless crystals of 5a, 9a‚2THF, 11a, and
18 were coated with Paratone 8277 oil and mounted on a glass
fiber. All measurements were made on a Nonius Kappa CCD
diffractometer using graphite-monochromated Mo KR radiation.
Crystallographic data are summarized in Table 1. The structures
were solved by direct methods16 and refined by full-matrix least-
(16) Altomare, A.; Cascarano, M.; Giacovazzo, C.; Guagliardi, A. J. Appl.
Crystallogr. 1993, 26, 343.
5780 Inorganic Chemistry, Vol. 44, No. 16, 2005

Synthesis and Structures of Al and Mg Complexes
Table 1. Crystallographic Data
5a
9a‚2THF
11a
18
formula
fw, g
space group
a, Å
b, Å
c, Å
R, deg
â, deg
γ, deg
V, Å3
Z
C34H74Al2N6 P2Si2
739.07
P21/c
20.400(6)
16.813(4)
12.865(11)
90
92.31(3)
90
4409(4)
4
C25H59AlLiN4 O2PSi
540.74
P21/c
10.209(3)
17.616(4)
18.975(6)
90
91.218(9)
90
3411.7(17)
4
C34H74AlLi2N4 O4P
674.80
P21/c
10.876(2)
12.901(3)
29.422(7)
90
91.541(13)
90
4126.7(16)
4
C40H100Mg3N9O4P3S3
1033.31
P1h
14.993(4)
15.285(4)
15.535(4)
96.188(14)
102.701(16)
117.474(14)
2989.9(14)
2
T, K
λ, Å
173(2)
0.710 73
1.113
0.223
1616
173(2)
0.710 73
1.053
0.17
1192
100(2)
0.710 73
1.086
0.125
1488
173(2)
0.710 73
1.148
0.278
1128
d
calcd, g cm-3
µ, mm-1
F(000)
Ra
0.044,
0.107
0.081
0.203
0.23
0.55
0.042
0.096
b
Rw
a R ) [Σ||Fo| - |Fc||]/[Σ |Fo|] for reflections with I > 2.00σ(I). b Rw ) {[Σw(Fo - Fc )2]/[Σw(Fo )2]}1/2 for all reflections.
2
2
2
squares methods using SHELXL-97.17 Hydrogen atoms were
Results and Discussion
included at geometrically idealized positions and were not refined;
Synthesis and Characterization of {Me2Al[(µ-NtBu)(µ-
NSiMe3)P(NHtBu)2]} (4) and {Me2Al[(µ-NCy)(µ-NSiMe3)P-
(µ-NCy)2P(µ-NCy)(µ-NSiMe3)]AlMe2} (5a). The reaction
of (tBuNH)3PNSiMe3 (3a) with trimethylaluminum in a 1:1
molar ratio results in the elimination of 1 equiv of methane
and the formation of {Me2Al[(µ-NtBu)(µ-NSiMe3)P(NHt-
Bu)2]} (4) in good yield. On the basis of NMR data, complex
4 is assigned a monocyclic structure in which the aluminum
center is chelated by the two imido groups (Nt,Bu and
NSiMe3) of the monoanionic ligand (formally isoelectronic
with [H2PO4]2-), whereas the two NHtBu groups are in
the non-hydrogen atoms were refined anisotropically. A cyclohexyl
ring in 5a was disordered in one of the molecules; this was included
in the refinements using partial site occupancy factors. Only some
of the non-hydrogen atoms in 9a‚2THF were refined anisotropically.
The R carbon of the NtBu group and the silicon atom of the NSiMe3
group chelated to the Al atom showed positional disorder with the
two atoms occupying the same sites; the model was refined with
the C and Si atoms assigned partial occupancies that summed to
unity. Carbon atoms of both THF ligands were disordered over
two sites with equal site occupancy factors. The hydrogen atom
attached to N(4) was located from a difference map.
Computational Details. The structures of the model radicals
{Me2Al[(µ-NMe)(µ-NSiH3)P(µ-NMe)2]Li(OMe2)2}• (13b) and {Me2-
Al[(µ-NMe)2P(µ-NMe)2]Li(OMe2)2}• (14b) were optimized in their
doublet ground states using density functional theory (DFT) and
Cs and C2V symmetry, respectively. A hybrid PBE0 exchange-
correlation functional18,19 and Ahlrichs’ triple-ú valence basis set
augmented by one set of polarization functions (TZVP)20 were used
in the optimizations. Hyperfine coupling constants (HFCCs) were
then calculated by single-point calculations employing the optimized
geometries, PBE0 functional, and unrestricted Kohn-Sham formal-
ism. For P, N, Li, and Al, the single-point calculations utilized the
IGLO-III basis set21 in a completely uncontracted form and were
augmented with one additional steep s function as well as
f-polarization functions from the cc-pVTZ basis set.21 For Si, C,
and H, the calculations utilized the cc-pVTZ basis set21 in its
standard form. A pruned (99 590) integration grid was used in all
single-point calculations to ensure numerical convergence of
calculated HFCCs. All geometry optimizations were done with the
Turbomole 5.722 program package; Gaussian 0323 was used in all
single-point calculations.
1
exocyclic positions. The H NMR spectrum of 4 in C6D6
contains two tBu resonances at 1.16 and 1.29 ppm (relative
intensities 2:1), attributed to the NHtBu and NtBu groups,
respectively. Resonances due to the SiMe3 and AlMe2 units
with the appropriate intensities are observed at 0.34 and
-0.22 ppm, respectively. The 13C NMR spectrum of 4
exhibits resonances for two types of tBu groups, one SiMe3
group, and an AlMe2 unit, consistent with this structural
proposal; the 31P spectrum reveals a singlet at 5.6 ppm. Single
crystals of 4 could not be obtained owing to its high solubility
in organic solvents.
Interestingly, the reaction of the cyclohexyl derivative
(CyNH)3PNSiMe3 (3b) with AlMe3 proceeds in a different
manner. In this case, elimination of 1 equiv of cyclohex-
ylamine results in the nearly quantitative formation of
{Me2Al[(µ-NCy)(µ-NSiMe3)P(µ-NCy)2P(µ-NCy)(µ-NSiMe3)]-
AlMe2} (5a). An X-ray structure of 5a revealed a cen-
trosymmetric dimer in which the central feature is an
essentially planar P2N2 ring with the two phosphorus atoms
linked by NCy groups (Figure 1). Complex 5a is the
dimethylaluminum derivative of the trisimidometaphosphate
monoanion [P(NCy)2(NSiMe3)]-. Two closely related com-
(17) Sheldrick, G. M. SHELXL-97; University of Go¨ttingen: Go¨ttingen,
Germany, 1997.
(18) (a) Perdew, J. P.; Burke, K.; Ernzerhof, M. Phys. ReV. Lett. 1996, 77,
3865-3868. (b) Perdew, J. P.; Burke, K.; Ernzerhof, M. Phys. ReV.
Lett. 1997, 78, 1396-1396 (E).
(19) Perdew, J. P.; Ernzerhof, M.; Burke, K. J. Chem. Phys. 1996, 105,
9982-9985.
(20) The TZVP basis set was used as it is referenced in the Turbomole 5.7
internal basis set library.
(21) The basis set was taken from the EMSL basis set library: http://
www.emsl.pnl.gov/forms/basisform.html (accessed December 2004).
(22) TURBOMOLE, version 5.7. R. Theoretical Chemistry Group, Uni-
versity of Karlsruhe: Karlsruhe, Germany, 2004.
Inorganic Chemistry, Vol. 44, No. 16, 2005 5781

Armstrong et al.
[Al(1)-N(1) ) 1.9597(16) Å; Al(1)-N(2) ) 1.9251(16) Å],
with the shorter bond observed in the case of the more basic
NCy ligand.
A comparison of structural parameters of 5a and 5c4c
shows the expected similarities, with P-N single bond
distances of 1.701(2) Å observed within the P2N2 ring of 5c
[cf. 1.6816(16) Å in 5a] and the Al-N distances in 5a
[av ) 1.942(2) Å] slightly shorter than the average bond
length in 5c [1.958(2) Å]. Conversely, longer Al-C distances
are observed in 5a [1.961(2) Å] compared to those in 5c
[1.944(2) Å]. These minor differences can be attributed to
the more electron-donating character of the cyclohexylimido
t
substituents of 5a as compared to the NR (R ) Bu, p-tol)
groups of 5c.
The NMR spectra of 5a in C6D6 are consistent with the
retention of its dimeric structure in solution. In particular,
the 13C NMR spectrum contained two sets of cyclohexyl
resonances as well as signals attributed to the SiMe3 (2.67
ppm) and AlMe2 (-6.81 ppm) fragments. The 31P NMR
signal for 5a appears at 17.1 ppm. While the yields involved
in the two-step syntheses of the imidometaphosphate dimers
5b and 5c range from moderate to excellent,4c,24 the prepara-
tion of 5a requires only one step and does not involve the
use of potentially explosive organic azides.
Synthesis and NMR Characterization of {Me2Al[(µ-
S)(µ-NtBu)P(NHtBu)2]} (7) and {Me2Al[(µ-S)(µ-NtBu)P-
(µ-NHtBu)(µ-NtBu)]AlMe2} (8). In earlier attempts8 to
prepare a trisimido(thio)phosphate trianion [SP(NR)3]3-, it
was found that the reaction of SP(NHtBu)3 (2a) with 2 equiv
of n-butyllithium results in the extrusion of sulfur and the
formation of the cubic tris(imido)metaphosphate dimer
{[µ3-Li(THF)][P(µ3-NtBu)2(NtBu)]}2 (6) in 15% yield. In
light of the results described earlier, investigations into the
reactions of trisamino(thio)phosphates SP(NHR)3 (2) with
AlMe3 are of considerable interest, as three possible reaction
pathways can be envisioned: (i) monodeprotonation of 2 to
yield a [Me2Al]+ complex of the [SP(NR)(NHR)2]- anion,
(ii) deprotonation and loss of RNH2 to yield a bis(imido)-
(thio)metaphosphate [SP(NR)2]- monoanion, or (iii) depro-
tonation and sulfur extrusion to generate a tris(imido)-
metaphosphate [P(NR)3]- complex.
Figure 1. Thermal ellipsoid diagram of 5a (30% probability ellipsoids).
Hydrogen atoms omitted for clarity.
Table 2. Selected Bond Lengths (Å) and Angles (deg) for 5aa
P(1)-N(1)
P(1)-N(3)
Al(1)-C(5)
Al(1)-N(2)
1.5903(15) P(1)-N(2)
1.6816(16) Al(1)-C(4)
1.5952(15)
1.959(2)
1.9597(16)
96.55(9)
1.963(2)
Al(1)-N(1)
1.9251(16) P(1)-N(3)-P(1)*
N(3)-P(1)-N(3)* 83.45(9)
P(1)-N(1)-Al(1) 92.27(7)
N(1)-Al(1)-N(2) 76.40(6)
P(1)-N(2)-Al(1) 93.41(7)
a Symmetry transformations used to generate equivalent atoms: #1 -x,
-y, -z; #2 -x + 1, -y, -z + 1.
plexes have been isolated by Stahl et al.4c from the reaction
of the bis(amino)cyclodiphosph(V)azanes cis-{(tBuNH)-
(RNdPNtBu)2(NHtBu)} with trimethylaluminum. The gen-
eral structure of these tricyclic species is shown above (5a,
t
t
R ) Cy, R′ ) SiMe3; 5b, R ) Bu, R′ ) Ph; 5c, R ) Bu,
R′ ) p-tol).
Selected bond lengths and bond angles of 5a are shown
in Table 2. Each phosphorus atom is also part of a planar
four-membered PN2Al ring that is approximately perpen-
dicular to the P2N2 ring. The dimethylaluminum cations are
chelated by an NSiMe3 group and the NCy group that is not
involved in the central P2N2 ring. The P-N distances
involving these two imido ligands are very similar [P(1)-
N(1) ) 1.5903(15) Å; P(1)-N(2) ) 1.5952(15) Å] despite
their different substituents. These bond lengths are signifi-
cantly shorter than those in the P2N2 ring [P(1)-N(3) )
1.6816(16) Å], indicating a higher formal bond order in the
former. The two Al-N bond lengths also differ slightly
(23) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb,
M. A.; Cheeseman, J. R.; Montgomery, Jr., J. A.; Vreven, T.; Kudin,
K. N.; Burant, J. C.; Millam, J. M.; Iyengar, S. S.; Tomasi, J.; Barone,
V.; Mennucci, B.; Cossi, M.; Scalmani, G.; Rega, N.; Petersson, G.
A.; Nakatsuji, H.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.;
Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai,
H.; Klene, M.; Li, X.; Knox, J. E.; Hratchian, H. P.; Cross, J. B.;
Bakken, V.; Adamo, C.; Jaramillo, J.; Gomperts, R.; Stratmann, R.
E.; Yazyev, O.; Austin, A. J.; Cammi, R.; Pomelli, C.; Ochterski, J.
W.; Ayala, P. Y.; Morokuma, K.; Voth, G. A.; Salvador, P.;
Dannenberg, J. J.; Zakrzewski, V. G.; Dapprich, S.; Daniels, A. D.;
Strain, M. C.; Farkas, O.; Malick, D. K.; Rabuck, A. D.; Raghavachari,
K.; Foresman, J. B.; Ortiz, J. V.; Cui, Q.; Baboul, A. G.; Clifford, S.;
Cioslowski, J.; Stefanov, B. B.; Liu, G.; Liashenko, A.; Piskorz, P.;
Komaromi, I.; Martin, R. L.; Fox, D. J.; Keith, T.; Al-Laham, M. A.;
Peng, C. Y.; Nanayakkara, A.; Challacombe, M.; Gill, P. M. W.;
Johnson, B.; Chen, W.; Wong, M. W.; Gonzalez, C.; Pople, J. A.
Gaussian 03, revision C.02; Gaussian, Inc.: Wallingford, CT, 2004.
The reaction of SP(NHtBu)3 (2a) with 1 equiv of AlMe3
results in the formation of 7, a white powder, which has been
characterized by multinuclear NMR spectroscopy. The 31P
NMR spectrum of the product in C6D6 contained a single
resonance at 35.6 ppm (cf. 46.3 ppm for 2a), a strong
indication that a loss of sulfur has not occurred, since this
would be accompanied by a significant upfield shift as is
(24) Moser, D. F.; Carrow, C. J.; Stahl, L.; Staples, R. J. J. Chem. Soc.,
Dalton Trans. 2001, 8, 1246-1252.
5782 Inorganic Chemistry, Vol. 44, No. 16, 2005

Synthesis and Structures of Al and Mg Complexes
observed for 6 (31P NMR: -21 ppm).8 The 1H NMR
spectrum displayed two tert-butyl signals at 1.23 and 1.18
ppm in a 1:2 ratio, along with a peak at -0.24 ppm attributed
to a Me2Al+ cation; the corresponding signals were observed
in the 13C NMR spectrum. These NMR data are consistent
with the formation of {Me2Al[(µ-S)(µ-NtBu)P(NHtBu)2]} (7),
a monocyclic species that is isostructural with 4 and, like 4,
is the product of a simple deprotonation reaction.
Figure 2. Thermal ellipsoid diagram of 9a‚2THF (30% probability
t
ellipsoids). Only R-carbon atoms of the Bu and SiMe3 groups are shown;
only oxygen atoms of the THF molecules are shown.
lithium cation is coordinated to the remaining NtBu and NHt-
Bu groups and to two molecules of tetrahydrofuran. Pertinent
bond lengths and angles are given in Table 3 and are in good
agreement with metrical parameters calculated for the model
system {Me2Al[(µ-NMe)(µ-NSiH3)P(µ-NHMe)(µ-NMe)]Li-
(OMe2)2} (9b‚2OMe2), particularly when the difference in
the identities of the imido groups is taken into account.
The P-N distances in 9a‚2THF range from 1.588(3) to
1.716(3) Å, with identical bond lengths of 1.640(4) Å
observed for the two nitrogen atoms that chelate the
aluminum center. A longer P-N distance is present between
the phosphorus and the tert-butylamido nitrogen [1.716(3)
Å], while a significantly shorter distance is found for the
PdNtBu bond [1.588(3) Å], indicating the presence of
localized single and double phosphorus-nitrogen bonds for
N(4) and N(3), respectively. The mean Al-N distance in
9a‚2THF [1.899(4) Å] is slightly shorter than that observed
in 5a [1.9422(2) Å], presumably because of the larger formal
charge on each of the chelating imido groups of 9a‚2THF
as compared to those of 5a. As expected, the Li-N bond to
the monanion NHtBu ligand [2.178(7) Å] is substantially
longer than the Li-N linkage involving the dianionic NtBu
ligand [1.969(7) Å]. The angles about these two nitrogen
atoms are also significantly different [ PN(3)Li )
100.6(3)°; PN(4)Li ) 88.9(2)°] because of their different
hybridizations. In consequence, while the four-membered
AlN2P ring is essentially planar [ N(1)Al(1)N(2)P(1) )
-1.15(15)°], the LiN2P ring is puckered [ N(4)P(1)N(3)-
Li(1) ) 17.9(3)°]. This X-ray structure confirmed the
coordination mode of the ligand to the AlMe2 unit of 4 that
was deduced from the NMR data (vide supra).
The reaction of 2a with 2 equiv of AlMe3 yields a white
powder that has been identified as the spirocyclic complex
{Me2Al[(µ-S)(µ-NtBu)P(µ-NHtBu)(µ-NtBu)]AlMe2} (8) on
the basis of multinuclear NMR data. A single 31P resonance
was observed at 40.9 ppm, indicating that the P-S bond
remains intact (vide supra). The 1H NMR spectrum in C6D6
contained three tert-butyl resonances of equal intensities, as
well as four signals between -0.54 and -0.25 ppm attributed
to the methyl groups of the two inequivalent dimethyl-
t
aluminum cations. The corresponding Bu signals were
observed in the 13C NMR spectrum, along with two broad
resonances assigned to the Me2Al+ cations. The fact that the
four methyl groups resonate at different 1H NMR frequencies
is attributed to the lack of planarity in both the AlSNP and
AlN2P rings, resulting in a molecule with only C1 symmetry.
Further investigations of the reaction of 2a with AlMe3
as a function of stoichiometry, reaction time, and reaction
temperature did not yield any products other than 7 and 8.
Similarly, attempts to form a methylaluminum complex of
the amidotris(imido)phosphate dianion [P(NHtBu)(NtBu)2-
(NSiMe3)]2- by increasing the reaction time and temperature
or changing the stoichiometry of the reagents were not
successful; in all cases, only 4 was obtained. The nearly
quantitative formation of the simple dimethylaluminum
derivatives 4, 7, and 8 is in sharp contrast to our observations
for the reactions of OP(NHtBu)3 (1) with AlMe3 in which
products involving monoanionic and dianionic ligands, as
well as the neutral ligand 1, were obtained.12
Synthesis and NMR Characterization of {Me2Al[(µ-
NtBu)(µ-NSiMe3)P(µ-NHtBu)(µ-NtBu)]Li(THF)2} (9a‚2-
THF), {[Me2Al][Li]2[P(NtBu)3(NSiMe3)]} (10), and {Me2Al-
[(µ-NtBu)2P(µ2-NtBu)2(µ-THF)][Li(THF)]2} (11a); X-ray
Structures of 9a‚2THF and 11a. In view of the limited
reactivity of AlMe3 toward (tBuNH)3PNSiMe3 (3a), depro-
tonation of the dimethylaluminum complex 4 with nBuLi was
1
The H NMR spectrum of 9a in d8-THF contains three
tBu signals of equal intensity at 1.35, 1.31, and 1.29 ppm,
as well as a single SiMe3 resonance at 0.13 ppm and a singlet
at -0.89 ppm due to the two equivalent methyl groups of
the AlMe2 unit. The corresponding signals were observed
in the 13C NMR spectrum, while a single resonance at 8.2
ppm was observed in the 31P NMR spectrum. These
spectroscopic data are consistent with the retention of the
spirocyclic structure of 9a‚2THF in THF solution.
n
investigated. The treatment of 4 with 1 equiv of BuLi
resulted in the isolation of the heterobimetallic complex {-
[Me2Al][Li][P(NtBu)2(NHtBu)(NSiMe3)]} (9a) in essentially
quantitative yield. Recrystallization of 9a from THF/hexane
produced colorless crystals of 9a‚2THF; an X-ray structure
(Figure 2) revealed that this complex exists as the spirocycle
{Me2Al[(µ-NtBu)(µ-NSiMe3)P(µ-NHtBu)(µ-NtBu)]-
Li(THF)2} in which the dimethylaluminum cation is N,N′-
chelated by the NSiMe3 group and one NtBu unit, while the
In a similar manner, the dilithiated complex {[Me2Al][Li]2-
[P(NtBu)3(NSiMe3)]} (10) is recovered in excellent yield
from the reaction of 4, prepared in situ, with 2 equiv of
nBuLi (Scheme 1). An analogous synthesis of the sym-
Inorganic Chemistry, Vol. 44, No. 16, 2005 5783

Armstrong et al.
Table 3. Selected Bond Lengths (Å) and Angles (deg) for 9
X-ray data
calcd for
X-ray data
calcd for
atoms
for 9a‚2THF
9b‚2OMe2
atoms
for 9a‚2THF
9b‚2OMe2
P(1)-N(1)
1.640(4)
1.588(3)
1.911(5)
1.969(7)
1.980(5)
1.993(8)
71.6(2)
100.6(3)
94.9(2)
121.63(19)
1.642
1.611
1.966
1.933
1.983
1.974
75.8
97.0
95.3
123.2
P(1)-N(2)
1.640(4)
1.716(3)
1.886(4)
2.178(7)
1.989(5)
77.85(16)
88.9(2)
93.9(2)
93.3(2)
94.71(16)
1.643
1.755
1.922
2.137
1.986
76.8
86.0
93.4
94.5
96.1
P(1)-N(3)
P(1)-N(4)
Al(1)-N(1)
Al(1)-N(2)
Li(1)-N(3)
Li(1)-N(4)
Al(1)-C(1)
Al(1)-C(2)
Li(1)-O(1)
N(1)-Al(1)-N(2)
P(1)-N(4)-Li(1)
P(1)-N(1)-Al(1)
N(1)-P(1)-N(2)
N(3)-P(1)-N(4)
N(3)-Li(1)-N(4)
P(1)-N(3)-Li(1)
P(1)-N(2)-Al(1)
N(1)-P(1)-N(3)
Scheme 1. Stepwise Deprotonation of Trisamino(imino)phosphates to
signals in a 1:2 ratio at 1.32 and 1.30 ppm, as well as singlets
at 0.08 ppm and -0.94 ppm attributed to the SiMe3 and
AlMe2 groups, respectively; the corresponding signals are
observed in the 13C NMR spectrum. While the expected
singlet is observed at 10.0 ppm in the 31P NMR spectrum,
two resonances of approximately equal intensities are present
in the 7Li NMR spectrum at 1.44 and -2.71 ppm. The latter
observation suggests that, in THF solution, solvation of one
lithium cation occurs to produce the solvent-separated ion
pair {[Li(THF)4]}+{Me2Al[(µ-NtBu)(µ-NSiMe3)P(µ-NtBu)2]-
Li(THF)2}- (12), comprised of a spirocyclic monoanion and
a tetrasolvated lithium counterion. The related tetra(naph-
thylimido)phosphate {[Li(THF)4]}+{Li(THF)2[(µ-Nnaph)2P-
(µ-Nnaph)2]Li(THF)2]}- is known to have a spirocyclic
structure in the solid state.5
Mixed Me2Al+/Li+ Tetraimidophosphate Complexes and Subsequent
t
Oxidation to Yield Persistent Spirocyclic Radicals (R ) Bu; R′ )
t
SiMe3, Bu)
In contrast, the NMR data obtained for 11a in d8-THF
are consistent with its solid-state structure. The inequivalence
of the two types of tert-butyl groups is not apparent from
1
t
the H NMR spectrum, since only a single Bu resonance
(1.34 ppm) is observed, accompanied by a singlet at -0.96
ppm attributed to the Me2Al group. However, the 13C NMR
metrical tetraimidophosphate trianion [P(NtBu)4]3- as the
heterobimetallic complex {[Me2Al][Li]2[P(NtBu)4]} was car-
ried out by treating (tBuNH)3PNtBu first with AlMe3, then
with nBuLi. The structure of the THF adduct {Me2Al[(µ-Nt-
Bu)2P(µ2-NtBu)2(µ2-THF)][Li(THF)]2} (11a) was determined
by X-ray crystallography. This complex crystallizes with a
molecule of THF in its lattice, rendering the crystals unstable
toward solvent loss once removed from solution. Conse-
quently, the X-ray data are not of sufficient quality to allow
for a discussion of the bond lengths and angles of this
compound. However, the structural parameters are consistent
with the corresponding parameters that were calculated for
the model system {Me2Al[(µ-NMe)2P(µ2-NMe)2(µ2-OMe2)-
[Li(OMe2)]2} (11b) (Table 4).
t
spectrum clearly shows two sets of Bu signals (50.90 and
36.41 ppm; 50.78 and 34.45 ppm) with approximately equal
intensities. The 7Li NMR spectrum exhibits a singlet at 1.23
ppm, indicating the equivalence of the two lithium cations
and, thus, that formation of a solvent-separated ion pair does
not occur for 11a.
Reactions of 3a with AlMe3 and nBuLi in THF are readily
monitored by 31P NMR spectroscopy, as a downfield shift
is observed with each subsequent deprotonation of the ligand.
The signal at -15 ppm for (tBuNH)3PNSiMe3 disappears as
the dimethylaluminum complex 4 forms (5.6 ppm). Initially,
the addition of nBuLi results in the appearance of a peak at
8.2 ppm (9a); as more n-butyllithium is added, a signal for
the dilithiated complex 12 is observed at 10.0 ppm. A similar
trend in 31P NMR chemical shifts is observed when 3a is
reacted with 1, 2, and 3 equiv of n-butyllithium.11
EPR and DFT Characterization of the Persistent
Radicals {Me2Al[(µ-NR)(µ-NtBu)P(µ-NtBu)2]Li(THF)2}•
t
(13a, R ) SiMe3; 14a, R ) Bu). When exposed to air,
THF solutions of 12 turn a bright blue color, whereas
solutions of 11a become a deep teal color indicative of the
formation of radicals. In earlier studies, we have isolated
stable cubic tetraimidophosphate radicals by oxidization of
the dimeric lithium salt {Li3[P(NtBu)3(NSiMe3)]}2 with 1
equiv of iodine or bromine.25 Oxidations of the dimethyl-
Complexes 10 and 11a have been characterized by
multinuclear (1H, 7Li, 13C, and 31P) NMR spectroscopy. The
t
1H NMR spectrum of 10 in d8-THF consists of two Bu
5784 Inorganic Chemistry, Vol. 44, No. 16, 2005

Synthesis and Structures of Al and Mg Complexes
Table 4. Selected Bond Lengths (Å) and Angles (deg) for 11
X-ray data
calcd for
X-ray data
calcd for
atoms
for 11a
11b
atoms
for 11a
11b
P(1)-N(1)
P(1)-N(2)
P(1)-N(3)
P(1)-N(4)
Al(1)-N(1)
Al(1)-N(2)
Li(1)-N(3)
Li(2)-N(3)
Li(1)-N(4)
Li(2)-N(4)
1.668(9)
1.671(9)
1.645(9)
1.597(10
1.881(10)
1.877(10)
2.07(2)
2.01(2)
2.13(2)
1.98(2)
1.661
1.661
1.668
1.668
1.918
1.918
2.009
2.009
2.009
2.009
Li(1)-O(1)
2.03(2)
2.15(2)
2.09(2)
2.00(2)
77.4(4)
91.7(5)
89.4(5)
91.0(7)
91.1(7)
67.1(8)
1.960
2.126
2.126
1.960
76.7
93.2
91.5
86.4
86.4
Li(1)-O(2)
Li(2)-O(2)
Li(2)-O(3)
N(1)-Al(1)-N(2)
N(3)-P(1)-N(4)
N(1)-P(1)-N(2)
Li(1)-N(3)-P(1)
Li(2)-N(4)-P(1)
Li(1)-O(2)-Li(2)
66.4
aluminum complexes 11a and 12 are expected to yield
neutral spirocyclic radicals via the elimination of 1 equiv of
THF-solvated lithium halide (Scheme 1). In practice, the
addition of 0.5 equiv of iodine to a colorless solution of 12
in THF results in an intense blue color, which persists for
several hours in solution. In the solid state, this mixed
heterobimetallic tetraimidophosphate radical 13a is stable for
only a few minutes; however, it has been identified by its
solution EPR spectrum (Figure 3). The observed pattern is
To aid in the interpretation of this complex spectrum, the
model system {Me2Al[(µ-NMe)(µ-NSiH3)P(µ-NMe)2]Li-
(Me2O)2}• (13b) was examined by means of DFT calcula-
tions. The optimized molecular structure displays Cs sym-
metry, with the AlN2P and LiN2P rings perpendicular to one
another. The two NMe groups that chelate the lithium cation
have equivalent P-N bond lengths of 1.668 Å, while slightly
shorter P-N bond distances are observed for the remaining
P-NMe unit (1.655 Å) and the P-NSiH3 (1.650 Å)
fragment. The four metal-nitrogen distances are quite
similar, with an average N-Al bond length of 1.958 Å and
identical Li-N distances (2.030 Å).
Single-point calculations on 13b indicated that the singly
occupied molecular orbital (SOMO) is primarily a linear
combination of nitrogen p orbitals (Figure 4). For symmetry
reasons, the contributions from the nitrogen atoms in the
AlN2P and LiN2P rings are not equivalent; a Mulliken
population analysis of the atomic spin densities revealed that
the spin density is concentrated on the nitrogen atoms of
the LiN2P ring. Although the SOMO has only minor
contributions from phosphorus, lithium, and aluminum, these
atoms have nonzero spin densities owing to spin polarization
effects. In consequence, the EPR spectrum of 13b, and hence
that of its parent system 13a, is expected to show large
hyperfine couplings to one phosphorus and two equivalent
nitrogen atoms. Smaller couplings to the other two nitrogen
atoms and the metal centers should also be present and are
responsible for the extensive hyperfine structure seen in the
experimental EPR spectrum. While the calculations indicate
that the Me2Al+ cation also contributes to the SOMO,
coupling to the methyl protons is expected to be so small as
to be unobservable.
Figure 3. Experimental (top) and simulated (bottom) EPR spectra of 13a
in THF.
An excellent simulation of the experimental EPR spectrum
was obtained by including hyperfine couplings to one
phosphorus atom (29.29 G), one lithium cation (1.43 G), one
aluminum atom (1.39 G), a pair of equivalent nitrogen nuclei
(7.20 G), and two unique nitrogen atoms (1.61 and 0.27 G)
(Figure 3). These hyperfine couplings are consistent with
the retention of the spirocyclic arrangement of 12 upon
oxidation and the formation of the neutral radical {Me2Al-
[(µ-NtBu)2P(µ-NtBu)2]Li(THF)2}• (13a) (Scheme 1). To
confirm the relative magnitudes of the HFCCs used to create
the spectral simulation, the calculated data for 13b were
examined more closely. The differing spin densities on the
primarily a doublet due to coupling of the unpaired electron
to the phosphorus atom (31P, 100%, I ) 1/2), with a total of
approximately 50 lines due to additional hyperfine coupling
to the nitrogen (14N, 99%, I ) 1), lithium (7Li, 92.5%, I )
3/2), and aluminum (27Al, 100%, I ) 5/2) nuclei.
(25) Armstrong, A.; Chivers, T.; Parvez, M.; Boere´, R. Angew. Chem., Int.
Ed. 2004, 43, 502-505.
Inorganic Chemistry, Vol. 44, No. 16, 2005 5785

Armstrong et al.
Figure 4. SOMO of 13b (left) and 14b (right).
Table 5. Experimental and Calculated HFCCs (G) for 13 and 14
nucleus
spin
13aa
13bb
14aa
14bb
5
27Al
/
/
/
1.39
1.43
29.29
7.20
1.61
0.27
-1.22
-1.67
-30.72
6.61
-1.29
-0.07
1.99
1.40
28.45
6.44
-2.03
-1.58
-30.96
5.76
2
3
7Li
2
1
31P
2
14NtBu‚‚‚Li
14NtBu‚‚‚Al
14NSiMe3
1
1
1
1.67
0.50
a Values used to simulate the experimental spectrum. b Values calculated
for the model systems.
nitrogen atoms are reflected in the 14N HFCCs, which were
calculated to be largest for the two equivalent NtBu ligands
that chelate the lithium cation (6.61 G), smallest for the
NSiMe3 group (-0.07 G), and of an intermediate size for
the unique NtBu nitrogen atom (-1.29 G). The calculated
HFCCs are shown in Table 5, along with the values used to
create the spectral simulation shown in Figure 3. The largest
calculated HFCC was to the phosphorus nucleus (-30.72
G), while the much smaller aluminum (-1.22 G) and lithium
(-1.67 G) couplings are calculated to be fairly similar. These
calculated HFCCs provide good support for the proposed
spirocyclic structure of the radical 13a.
The one-electron oxidation of 11a with halogens yields
the persistent teal radical {Me2Al[(µ-NtBu)2P(µ-NtBu)2]Li-
(THF)2}• (14a) with a stability similar to that of 13a: it
persists in solution for approximately 3 h but cannot be
isolated in the solid state. The solution EPR spectrum of this
radical is shown in Figure 5. DFT calculations were carried
out on the model system {Me2Al[(µ-NMe)2P(µ-NMe)2]-
Li(Me2O)2}• (14b). The geometry-optimized structure of this
molecule has C2V symmetry, with the two MN2P (M ) Li,
Al) rings perpendicular to one another. The two pairs of P-N
bond lengths in this structure are equivalent within the
accuracy of the calculations, at 1.650 and 1.653 Å for the
P-N-Al and P-N-Li distances, respectively. As was seen
for 13b, the Al-N bonds (1.936 Å) are slightly shorter than
the Li-N bonds (1.984 Å).
Figure 5. Experimental (top) and simulated (bottom) EPR spectra of 14a
in THF.
spectrum was obtained by including hyperfine couplings to
two pairs of equivalent 14N atoms (6.44 G, 1.67 G), one
lithium cation (1.40 G), one dimethylaluminum cation (1.99
G), and the phosphorus atom (28.45 G). The close agreement
of the experimental and calculated HFCCs, which are shown
in Table 5, confirms that the oxidation product of 11a is
indeed the neutral spirocycle radical {Me2Al[(µ-NtBu)2P(µ-
NtBu)2]Li(THF)2}• (14a). Unlike other related tetraimi-
dophosphate radicals,25 the EPR spectra of 13a and 14a are
not dependent on sample concentration, indicating that
dissociation of these spirocyclic radicals (e.g., by solvation
of the lithium cations) does not occur even in very dilute
solutions.
Synthesis and Characterization of {Mg[(µ-NtBu)-
(µ-NHtBu)P(NHtBu)(NSiMe3)]2} (15), {Mg[(µ-NCy)(µ-
NSiMe3)P(NHCy)2]2} (16), {Mg[(µ-S)(µ-NtBu)P(NHtBu)2]2}
(17), and {[MgOH][(µ-S)(µ-NtBu)P(NHtBu)2]}6 (18). The
reaction of MgBu2 with 2 equiv of (tBuNH)3PNSiMe3 (3a)
produces a complex in which a magnesium dication is bis-
chelated by two imidophosphate monoanions {Mg[(µ-NtBu)-
(µ-NHtBu)P(NHtBu)(NSiMe3)]2} 15. This compound has
been characterized by multinuclear NMR spectroscopy and
displays a single resonance in its 31P spectrum at 5.2 ppm.
Further examination of the data indicated that the com-
position of the SOMO (Figure 4) of 14b is similar to that of
13b. An excellent simulation of the experimental EPR
1
The H NMR spectrum of 15 in C6D6 is interesting in that
it consists of three tBu signals of equal intensities, one SiMe3
5786 Inorganic Chemistry, Vol. 44, No. 16, 2005

Synthesis and Structures of Al and Mg Complexes
resonance, and two broad doublets that are attributable to
two inequivalent NH protons. These data indicate that the
imidophosphate ligand is coordinated to the magnesium atom
through one NHtBu and one NtBu group. This is somewhat
surprising, considering the well-established structures of the
dimethylaluminum complexes 4, 9a, 10, and 11a, in which
the aluminum atom is chelated by the two imido groups,
while the amido substituents remain noncoordinated. This
preference is attributed to the fact that Mg2+ is a harder acid
than Me2Al+ and will, therefore, prefer coordination to the
harder base NHtBu over coordination to the NSiMe3 nitrogen
atom.
Figure 6. Thermal ellipsoid diagram of 18 (30% probability ellipsoids).
Only R-carbons of the tert-butyl groups are shown.
Table 6. Selected Bond Lengths (Å) and Angles (deg) for 18a
P(1)-N(1)
1.6078(16) P(1)-N(2)
1.6721(18) P(1)-S(1)
2.0266(15) Mg(1)-O(2)
2.0030(16) Mg(2)-O(1)
2.0042(15) Mg(2)-O(3)
2.0039(15) Mg(3)-O(2)
2.1208(15) Mg(1)-N(1)
2.6290(10) Mg(2)-N(4)
2.6166(11) Mg(3)-N(7)
2.6237(11) Mg(1)-Mg(2)
1.6532(17)
2.0112(8)
2.1191(15)
2.1198(15)
2.0325(15)
2.0346(16)
2.0675(17)
2.0686(18)
2.0677(18)
3.0317(12)
75.56(3)
P(1)-N(3)
Mg(1)-O(1)
The reaction of MgBu2 with the cyclohexyl derivative
(CyNH)3PNSiMe3 (3b) in a 1:2 molar ratio produces a
complex that was identified as {Mg[(µ-NCy)(µ-NSiMe3)P-
(NHCy)2]2} (16) on the basis of NMR data and CHN
analysis. The appearance of resonances for only two cyclo-
hexyl environments in a 2:1 ratio in the 13C NMR spectrum
(in C6D6) suggests coordination of two imido groups
(NSiMe3 and NCy) to the magnesium center and two
exocyclic cyclohexylamido groups.
Mg(1)-O(3)
Mg(2)-O(2)
Mg(3)-O(1)
Mg(3)-O(3)
Mg(1)-S(1)
Mg(2)-S(2)
Mg(3)-S(3)
N(2)-P(1)-N(3)
P(1)-N(1)-Mg(1) 102.69(8)
O(1)-Mg(1)-O(2) 83.08(6)
100.60(9)
P(1)-S(1)-Mg(1)
S(1)-Mg(1)-N(1)
74.47(5)
Mg(1)-O(1)-Mg(2) 93.94(6)
O(1)-Mg(3)-O(2*) 103.21(6)
S(1)-P(1)-N(1)
O(2)-Mg(2)-O(3) 102.40(6)
104.74(6)
O(1)-Mg(2)-O(2)
83.60(6)
Attempts to effect further deprotonation by changing the
reaction conditions and stoichiometry were unsuccessful; the
only products observed by 31P NMR were the monoanionic
complexes 15 and 16. Similar low reactivities were observed
for these species toward dimethylzinc and trimethylalumi-
num. However, the trisamino(thio)phosphate SP(NHtBu)3
(2a) was previously found to be slightly more reactive than
(RNH)3PNSiMe3 toward ZnMe2.7 Consequently, reactions
between MgBu2 and 2a were explored using various sto-
ichiometries and reaction conditions.
a Symmetry transformations used to generate equivalent atoms: #1 -x,
-y + 1, -z.
that prolonged storage of this complex in Et2O leads to the
of the hexameric complex {[Mgµ3-OH][(µ-S)(µ-NtBu)P(NH-
tBu)2]}6 (18), presumably via the partial hydrolysis of 17.
An X-ray structure of 18 (Figure 6) revealed that the core
of this complex is composed of six [Mgµ3-OH]+ cations
linked together via Mg-O bonds to form two stacked six-
membered Mg3O3 rings (or a Mg6O6 hexagonal prism). Each
magnesium center is also N,S-chelated by the monoanionic
ligands [SP(NHtBu)2(NtBu)]-, rendering the Mg2+ cations
pentacoordinate. The bis(amido)imido(thio)phosphate ligands
When 0.5 equiv of MgBu2 was employed, a white powder
was recovered that gave rise to only one 31P NMR signal
1
(38.8 ppm). The H NMR and 13C NMR spectra of the
product in C6D6 indicated the presence of two inequivalent
tBu environments. The 1:2 integration of the 1H NMR peaks
(at 1.56 and 1.45 ppm), and the absence of any resonances
attributable to a BuMg+ cation, is consistent with the
formation of the N,S-chelated complex {Mg[(µ-S)(µ-NtBu)P-
(NHtBu)2]2} (17).
t
radiate outward from the Mg6O6 core, with the two BuNH
groups of each ligand remaining noncoordinated. Selected
bond lengths and bond angles for 18 are summarized in Table
6. The three Mg-O bonds in the center of the molecule are
inequivalent: each magnesium atom has one short bond [e.g.,
Mg(1)-O(3) ) 2.0030(16) Å], which can be considered a
discrete [MgOH]+ unit; one slightly weaker bond [Mg(1)-
O(1) ) 2.0266(15) Å] to a second oxygen atom within a
Mg3O3 ring; and a third, longer distance [Mg(1)-O(2) )
2.1191(15) Å] between the magnesium of one Mg3O3 ring
and an oxygen atom in the other six-membered ring. The
average Mg-O bond distance in 18 is 2.054(15) Å, compare
1.9473(13)-2.0020(14) Å for the related complex {[NaMg-
Attempts to grow single crystals of 17 from a variety of
organic solvents were unsuccessful; however, it was found
Inorganic Chemistry, Vol. 44, No. 16, 2005 5787

Armstrong et al.
Table 7. Reactivities of EP(NHR)3 toward Metal Alkyl Reagents MRx
(E, R) ZnMe2
nBuLi
O, tBu
1- or 2-fold
AlMe3
1- or 2-fold
deprotonationc
MgBu2
3-fold
Possibly 3-fold
deprotonationa
deprotonation;
multiple products
formedb
deprotonation;
multiple products
formedd
monodeprotonation;
sulfur extrusion at
high temperaturesd
S, tBu
1- or 2-fold
monodeprotonationb
1- or 2-fold
deprotonation;
deprotonationd
sulfur extrusion
and dimerization
to a metaphosphatee
NSiMe3, Cy
NSiMe3, tBu
3-fold
monodeprotonationb
dimerization to
metaphosphated
monodeprotonation;
NCy, NSiMe3
chelationd
monodeprotonation;
NtBu, NHtBu
chelationd
deprotonationf
3-fold
deprotonationf
monodeprotonation;
NtBu, NSiMe3
chelationb
monodeprotonation;
NtBu, NSiMe3
chelationd
a References 6 and 8. b Reference 7. c Reference 12. d This work. e References 8 and 10. f Reference 6.
(NiPr)2(O)‚THF}6, which also contains a core of two stacked
Mg3O3 rings.26 The bis(amido)imido(thio)phosphate ligand,
as expected, contains one short P-N bond to the tert-
butylimido nitrogen atom [P(1)-N(1) ) 1.6078(16) Å],
while longer distances are observed to the two tert-butyl-
amido groups [P(1)-N(2) ) 1.6532(17) Å; P(1)-N(3) )
1.6721(18) Å].
Conclusions
The trisamidophosphates EP(NHR)3 (E ) O, S, NR′;
R ) alkyl) display similar reactivities toward AlMe3 as they
do toward ZnMe2, with the highest reactivity observed for
E ) O and the lowest reactivity for E ) NR′. Three-fold
deprotonation of these species to form imido analogues of
the well-known aluminophosphates does not occur. In the
case of E ) NR′, two different reaction pathways can occur
to yield imido analogues of ortho- or meta-phosphate,
depending on the identity of the R group employed.
Reactions of AlMe3 with SP(NHtBu)3 yield N,S-chelated
complexes. Lithiation of aluminum bis(amido)bis(imido)-
phosphates produces heterobimetallic complexes that form
persistent radicals upon oxidation with iodine. Reactions with
MgBu2 lead to multiple products for E ) O and S, but only
a simple monoanionic complex of E ) NR′. The different
behaviors of 1-3 toward various organometallic (metal alkyl)
reagents are summarized in Table 7.
The deliberate hydrolysis of 17 with 1 equiv of H2O was
attempted in both diethyl ether and toluene. Reaction times
of more than 10 min result in the complete hydrolysis of
17, and a mixture of SP(NHtBu)3 (2a) and magnesium oxide
was recovered. Over shorter reaction times, two signals of
equal intensity attributable to 2a and 17 are observed in the
31P NMR spectrum of the product mixture. It is thought that
removal of the solvent under a vacuum facilitates the loss
of water from 18 so that the hydroxide complex is not
observed.
The reaction of 2a and MgBu2 in a 1:1 stoichiometry gave
a complex mixture of products, as revealed by 31P NMR
spectra. The marked increase in the number of products
formed from the reaction of EP(NHtBu)3 (E ) O, S) with
dibutylmagnesium as compared to dimethylzinc7 can be
attributed to the higher electrophilicity of the magnesium
cations and their tendency to adopt octahedral rather than
tetrahedral coordination modes.
Acknowledgment. We thank the University of Calgary
and the Natural Sciences and Engineering Research Council
of Canada for funding and Helsingin Sanomain 100-
vuotissa¨a¨tio¨ for a scholarship (H.M.T.).
Supporting Information Available: Crystallographic CIF files
are included in the Supporting Information. This material is
available free of charge via the Internet at http://pubs.acs.org.
(26) Drummond, A. M.; Gibson, L. T.; Kennedy, A. R.; Mulvey, R. E.;
O’Hara, C. T.; Rowlings, R. B.; Weightman, T. Angew. Chem., Int.
Ed. 2002, 41, 2382-2384.
IC050689E
5788 Inorganic Chemistry, Vol. 44, No. 16, 2005