Imide transfer properties and reactions of the magnesium imide ((THF)MgNPh)6: A versatile synthetic reagent

Article abstract of DOI:10.1021/ic951510a

Imide transfer properties of ((THF)MgNPh)₆ (1) and the synthesis of the related species {(THF)MgN(1-naphthyl)}₆-2.25THF (2), via the reaction of dibutylmagnesium with H₂N(1-naphthyl), in a THF/heptane mixture are described. Treatment of 1 with Ph₂CO, 4-Me₂NC₆H₄NO, t-BuNBr₂ (3), PCl₃, or MesPCl₂ (Mes = 2,4,6-Me₃C₆H₂-) leads to the isolation of Ph₂CNPh (4), 4-Me₂NC₆H₄NNPh (5), t-BuNNPh (6), (PhNPCl)₂ (7), or (MesPNPh)₂ (8) in moderate yield. Reaction between 1 and GeCl₂·dioxane, SnCl₂, or PbCl₂ affords the M₄N₄ (M = Ge, Sn, Pb) cubane imide derivative (GeNPh)₄ (9), [(SnNPh)₄·{MgCl₂(THF)₄}]∞ (10), (SnNPh)₄-0.5PhMe (11), or (PbNPh)₄·0.5PhMe (12). Interaction of 1 with Ph₃PO, (Me₂N)₃PO, or Ph₂SO furnishes the complex (Ph₃POMgNPh)₆ (13), {(Me₂N)₃POMgNPh}₆·₂PhMe (14), or (Ph₂SOMgNPh)₆ (15). The addition of 3 equiv of MgBr₂ to 1 gives 1.5 equiv of ((THF)Mg)₆(NPh)₄Br₄ (16) in quantitative yield, whereas treatment of 16 with 4 equiv of 1,4-dioxane is an alternative synthetic route to 1. Compounds 2, 3, 9, 10, and 14 were characterized by X-ray crystallography. The reactions demonstrate that 1 is a versatile and useful reagent for the synthesis of a variety of main group imides. Crystal data at 130 K with Mo Kα (λ = 0.710 73 A?) radiation for 3 or Cu Kα (λ = 1.541 78 A?) radiation for 2, 9, 10, and 14: 2, C₉₃H₁₀₈Mg₆N₆O_7.25, a = 28.101(7) A?, b = 35.851(7) A?, c = 36.816(7) A?, Z = 2, space group Fddd, R = 0.068 for 3500 (I > 2σ(I)) data; 3, C₄H₉Br₂N, a = 6.682(2) A?, b = 10.834(3) A?, c = 11.080(3) A?, a = 66.25(2)°, β = 89.88(2)°, γ = 82.53(2)°, Z = 4, space group P1?, R = 0.038 for 2043 (I > 2σ(I)) data; 9, C₂₄H₂₀Ge₄N₄, a = 10.749(2) A?, b = 12.358(3) A?, c = 35.818(7) A?, Z = 8, space group Pbca, R = 0.040 for 2981 (I > 2σ(I)) data; 10, C₄₀H₅₂Cl₂MgN₄O₄Sn ₄, a = 12.770(3) A?, b = 13.554(3) A?, c = 25.839(5) A?, Z = 4, space group P2₁2₁2₁, R = 0.040 for (I > 2σ(I)) data: 14, C₈₆H₁₅₄-Mg₆N₄O₆P ₆, a = 22.478(4) A?, b = 16.339(3) A?, c = 29.387(6) A?, Z = 4, space group Pbcn, R = 0.081 for 4696 (I > 2σ(I)) data.

Full text of DOI:10.1021/ic951510a

3254
Inorg. Chem. 1996, 35, 3254-3261
Imide Transfer Properties and Reactions of the Magnesium Imide ((THF)MgNPh)6: A
Versatile Synthetic Reagent
Warren J. Grigsby, Tony Hascall, Jeffrey J. Ellison, Marilyn M. Olmstead, and
Philip P. Power*
Department of Chemistry, University of California, Davis, California 95616
ReceiVed NoVember 22, 1995X
Imide transfer properties of ((THF)MgNPh)6 (1) and the synthesis of the related species {(THF)MgN(1-
naphthyl)}6‚2.25THF (2), via the reaction of dibutylmagnesium with H2N(1-naphthyl), in a THF/heptane mixture
are described. Treatment of 1 with Ph2CO, 4-Me2NC6H4NO, t-BuNBr2 (3), PCl3, or MesPCl2 (Mes ) 2,4,6-
Me3C6H2-) leads to the isolation of Ph2CNPh (4), 4-Me2NC6H4NNPh (5), t-BuNNPh (6), (PhNPCl)2 (7), or
(MesPNPh)2 (8) in moderate yield. Reaction between 1 and GeCl2‚dioxane, SnCl2, or PbCl2 affords the M4N4
(M ) Ge, Sn, Pb) cubane imide derivative (GeNPh)4 (9), [(SnNPh)4‚{MgCl2(THF)4}]∞ (10), (SnNPh)4‚0.5PhMe
(11), or (PbNPh)4‚0.5PhMe (12). Interaction of 1 with Ph3PO, (Me2N)3PO, or Ph2SO furnishes the complex
(Ph3POMgNPh)6 (13), {(Me2N)3POMgNPh}6‚2PhMe (14), or (Ph2SOMgNPh)6 (15). The addition of 3 equiv of
MgBr2 to 1 gives 1.5 equiv of ((THF)Mg)6(NPh)4Br4 (16) in quantitative yield, whereas treatment of 16 with 4
equiv of 1,4-dioxane is an alternative synthetic route to 1. Compounds 2, 3, 9, 10, and 14 were characterized by
X-ray crystallography. The reactions demonstrate that 1 is a versatile and useful reagent for the synthesis of a
variety of main group imides. Crystal data at 130 K with Mo KR (λ ) 0.710 73 Å) radiation for 3 or Cu KR (λ
) 1.541 78 Å) radiation for 2, 9, 10, and 14: 2, C93H108Mg6N6O7.25, a ) 28.101(7) Å, b ) 35.851(7) Å, c )
36.816(7) Å, Z ) 2, space group Fddd, R ) 0.068 for 3500 (I > 2σ(I)) data; 3, C4H9Br2N, a ) 6.682(2) Å, b )
10.834(3) Å, c ) 11.080(3) Å, R ) 66.25(2)°, â ) 89.88(2)°, γ ) 82.53(2)°, Z ) 4, space group P1h, R ) 0.038
for 2043 (I > 2σ(I)) data; 9, C24H20Ge4N4, a ) 10.749(2) Å, b ) 12.358(3) Å, c ) 35.818(7) Å, Z ) 8,
space group Pbca, R ) 0.040 for 2981 (I > 2σ(I)) data; 10, C40H52Cl2MgN4O4Sn4, a ) 12.770(3) Å, b )
13.554(3) Å, c ) 25.839(5) Å, Z ) 4, space group P212121, R ) 0.040 for (I > 2σ(I)) data; 14, C86H154
-
Mg6N4O6P6, a ) 22.478(4) Å, b ) 16.339(3) Å, c ) 29.387(6) Å, Z ) 4, space group Pbcn, R ) 0.081 for
4696 (I >2σ(I)) data.
THF
Introduction
((THF)MgNPh)
6Et2Mg + 6H2NPh
8
6 + 12EtH (3)
Magnesium imides have their origin in reactions between
Grignard reagents and primary arylamines which were originally
described by Meunier in 1903, eq 1.1
1
In addition to the characterization of the imide species
themselves, there have been some investigations of the reactions
of ArN(MgBr)2 compounds (Ar ) variously substituted aromatic
rings) with a variety of reagents such as ketones, bifunctional
nitroarenes, oxidizing agents, nitrobenzothiazoles, and nitroben-
zenes.5 These reactions were carried out with an “ArN(MgBr)2”
species that was not isolated but generated in situ. In contrast,
with the exception of some reactions involving cyclopentadienyl
halides of titanium or zirconium,6 there is no information
available on the chemistry of the simpler ((THF)MgNPh)6
species 1. In this paper the reactions of this interesting
compound with a variety of substrates are reported. In addition
an alternative method for the synthesis of 1 by the reaction of
readily available 16, i.e. ((THF)Mg)6(NPh)4Br4, with 4 equiv
of 1,4-dioxane is described.
X ) halide
PhNH2 + 2RMgX ) R ) alkyl group8 “PhN(MgX)2” + 2RH
(1)
Since that time, magnesium imides have only received
intermittent attention,2 and it was not until 1994 that the structure
of an “RN(MgX)2” species was shown to have an adamantyl
framework of formula (Et2OMg)6(NR)4Br4 (R ) Ph)3 which
presumably arises from the disproportionation shown in eq 2.
4“PhN(MgBr)”2 L ) Et O or THF8
2
(LMg)6(NPh)4Br4 + 2MgBr2 (2)
L ) THF (16)
Experimental Section
Parallel work showed that the reaction between aniline and
MgEt2 affords the new halide-free imide species ((THF)-
MgNPh)6 (1),4 featuring a hexagonal prismatic Mg6N6 cage
structure as shown in eq 3.
General Procedures. All reactions were performed by using
modified Schlenk techniques under an inert atmosphere of N2 or in a
Vacuum Atmospheres HE43-2 drybox. Solvents were freshly distilled
(5) For example: (a) Okubo, M.; Hayashi, S.; Matsunaga, M.; Uematsu,
Y. Bull. Chem. Soc. Jpn. 1981, 54, 2337. (b) Okubo, M.; Aratani,
H.; Gondo, T.; Koga, K. Ibid. 1983, 56, 788. (c) Okubo, M.; Yoshida,
S.; Egami, Y.; Matsuo, K.; Nagase, S. Ibid. 1987, 60, 1741. (d) Okubo,
M.; Asao, K.; Hyakutake, H. Ibid. 1987, 60, 3781. (e) Okubo, M.;
Inatomi, Y.; Taniguchi, N.; Imamura, K. Ibid. 1988, 61, 3881.
(6) Grigsby, W. J.; Olmstead, M. M.; Power, P. P. J. Organomet. Chem.,
in press.
X Abstract published in AdVance ACS Abstracts, April 1, 1996.
(1) Meunier, L. C. R. Hebd. Seances Acad. Sci. 1903, 136, 758.
(2) Petyunin, P. A. Russ. Chem. ReV. (Engl. Transl.) 1962, 31, 100.
(3) Hascall, T.; Olmstead, M. M.; Power, P. P. Angew. Chem., Int. Ed.
Engl. 1994, 33, 1000.
(4) Hascall, T.; Ruhlandt-Senge, K.; Power, P. P. Angew. Chem., Int. Ed.
Engl. 1994, 33, 356.
S0020-1669(95)01510-2 CCC: $12.00 © 1996 American Chemical Society

Imide Transfer Properties of a Magnesium Imide
Inorganic Chemistry, Vol. 35, No. 11, 1996 3255
under N2 from Na/K or Na/K/benzophenone ketyl and degassed twice
before use. NMR spectra were obtained on a General Electric QE-
300 NMR spectrometer and referenced to an internal standard. 31P
NMR spectra were referenced to an external standard, 85% H3PO4. IR
spectra were obtained by using a Perkin-Elmer 1430 spectrometer.
SnCl2, PbCl2, Ph2CO, Ph2SO, 4-(Me2N)C6H44NO, Ph3PO, and Bu2Mg
(1:1 mixture of n- and sec-Bu 1.0 M in heptane) were purchased
commercially and used as received. Aniline and (Me2N)3PO were
distilled from calcium hydride before use. The compound ((THF)-
MgNPh)6 (1), which was used in the reactions described below, was
synthesized by the reaction of Bu2Mg and aniline in THF/heptane
solution.6 PCl3 was distilled prior to use. t-BuNBr2 (3)7, MesPCl2,8
and GeCl2‚dioxane9 were synthesized by literature procedures. 1-Naph-
thylamine was used as received.
{(THF)MgN(1-naphthyl)}6‚2.25THF (2). 1-Naphthylamine (0.72
g, 5 mmol) dissolved in THF (30 mL) was treated with MgBu2 (5 mmol
in heptane solution, 5.0 mL). The solution was refluxed for 15 h and
filtered through a pad of Celite. The solution was then concentrated
to ca. 20 mL and cooled in a -20 °C freezer for 2 days to give yellow
crystals of {(THF)MgN(1-naphthyl)}6‚2.25THF (2) (0.82 g, 0.5 mmol,
62% based on Mg): 1H NMR (300 MHz, C7D8) δ 9.37 (s, br, 1H,
H8), 7.70 (d, J ) 7.8 Hz, 1H, H3), 7.23 (m, 3H, H5-H7), 6.98 (m,
2H, H2, H4), 3.54 (s, 4H, OCH2), 1.45 (s, 4H, CH2); 13C NMR (300
MHz, C7D8) δ 165.2 (s, C1), 133.3 (s, C5), 129.2 (d), 122.3 (d), 116
(d, C4), 110.3 (d, C2); IR (Nujol) ν 1605 (w), 1565 (m), 1550 (s),
1500 (s), 1280 (s, br), 1220 (m), 1160 (m), 1130 (w), 1080 (ms), 1050
(m), 1020 (ms), 890 (m), 790 (m, sh), 770 (s), 720 (ms), 660 (m), 610
(m), 570 (m), 515 (ms), 425 (m), 390 (m) cm-1. Desolvation problems
involving THF did not permit an accurate elemental analysis of this
compound.
cis-(PhNPCl)2 (7). ((THF)MgNPh)6 (0.93 g, 0.83 mmol) was
dissolved in THF (30 mL). Dioxane (1 mL, 11.7 mmol) and freshly
distilled PCl3 (0.29 mL, 3.32 mmol) were added via syringe. The
solution immediately turned yellow with warming. After 18 h of
stirring, all volatile material was removed under reduced pressure, and
the resulting white solid was extracted with warm toluene (40 mL).
The solution was filtered through a frit and concentrated to ca. 5 mL.
Slow cooling yielded fine white crystals of cis-(PhNPCl)2 (7) (0.23 g,
0.73 mmol, 27% based on phosphorus): mp ) 110-112 °C (lit. 153-
154 °C);13 1H NMR (300 MHz, C6D6) δ 6.97 (t, J ) 8.1 Hz, 2H, m-H),
6.83 (m, 3H, o, p-H); 13C NMR (300 MHz, C6D6) δ 138.1 (s, JP-C
)
10.0 Hz, ipso-C), 130.1 (d, m-C), 123.9 (d, p-C), 117.1 (d, JP-C ) 6.9
Hz, o-C); 31P NMR (300 MHz, C6D6) δ 199.8 (s); IR (Nujol) ν 1590
(s), 1485 (s), 1264 (vs), 1095 (w), 1072 (w), 1030 (w), 915 (vs), 745
(ms), 680 (m), 470 (m), 390 (mw) cm-1
.
(MesPNPh)2 (8). ((THF)MgNPh)6 (0.75 g, 0.67 mmol) was
dissolved in THF. Dioxane (1 mL, 11.7 mmol) and MesPCl2 (0.29
mL, 3.32 mmol) (Mes ) 2,4,6-Me3C6H2-) were added via syringe. The
solution immediately turned yellow with warming. After 18 h of
stirring, all volatile materials were removed under reduced pressure,
and the resulting yellow solid was extracted with warm toluene (40
mL). The solution was filtered twice through Celite and concentrated
to ca. 10 mL. Slow cooling yielded a yellow oil (0.40 g) which was
identified spectroscopically as a cis/trans mixture (1:2) of the diaza-
diphosphetidine (MesPNPh)2 (8) (0.83 mmol, 50% based on phospho-
rus): 1H NMR (300 MHz, C6D6) δ 7.08 (t, J ) 8.1 Hz, 4H, m-H, Ph),
6.90-6.68 (m, 13H), 6.56 (s, 4H, m-H, Mes), 2.49 (s, 6H, CH3), 2.43
(s, 12H, CH3), 2.19 (s, 3H, CH3), 2.00 (s, 6H, CH3); 31P NMR (300
2
2
MHz, C6D6) δ 220.4 (t, JPP ) 30.2 Hz, cis isomer), 196.6 (d, JPP
26.5 Hz, trans isomer).
)
(GeNPh)4 (9). GeCl2‚dioxane (0.93 g, 4.0 mmol) was dissolved in
THF (30 mL), and 1,4-dioxane (1 mL, 11.7 mmol) was added via
syringe. ((THF)MgNPh)6 (0.75 g, 0.67 mmol) was then added slowly
via a solids-addition tube, after which the orange solution was heated
to reflux for 14 h. The solution was then filtered through a frit, and
all volatile materials were removed under reduced pressure. The
resulting dark yellow oil was dissolved in toluene (10 mL), and the
solution was concentrated to ca. 5 mL. Cooling to -20 °C yielded
large pale yellow plates of (GeNPh)4 (9) (0.20 g, 0.31 mmol, 31% based
Ph2CdNPh (4). Benzophenone (0.58 g, 3.2 mmol) was dissolved
in diethyl ether (40 mL). ((THF)MgNPh)6(0.60 g, 0.53 mmol) was
added via a solids-addition funnel, and the solution was stirred for 16
h. The pale yellow solution was filtered through Celite and then
concentrated to incipient crystallization. Cooling the solution in a -20
°C freezer yielded colorless crystals of triphenylimine (4) (0.60 g, 2.3
mmol, 73%): mp 112-113 °C (lit. 109 °C);10 1H NMR (300 MHz,
CDCl3) δ 7.86 (d, J ) 7.2 Hz, 2H, o-H), 7.52 (m, 3H), 7.34 (m, 4H),
7.23 (m, 3H), 7.01 (t, J ) 7.2 Hz, 1H, p-H), 6.82 (d, J ) 7.2 Hz, 2H,
o-H).
1
on germanium): mp 214-215 °C; H NMR (300 MHz, C6D6) δ 7.19
(d, J ) 7.2 Hz, 2H, o-H), 7.12 (t, J ) 6.9 Hz, 2H, m-H), 6.88 (t, 7.2
Hz, 1H, p-H); 13C NMR (300 MHz, C6D6) δ 150.1 (s, ipso-C), 130.0
(d, o-C), 122.8 (d, p-C), 121.6 (d, m-C); IR (Nujol) ν 1595 (s), 1490
(s), 1375 (mw), 1260 (sh, ms), 1220 (br, ms), 1100 (br, ms), 1030
4-Me2NC6H4NdNPh (5). N,N-Dimethyl-4-nitrosoaniline (0.60 g,
4.0 mmol) dissolved in diethyl ether (25 mL) was added to a solution
of ((THF)MgNPh)6 (0.75 g, 0.67 mmol) dissolved in diethyl ether (25
mL). The green solution rapidly became orange. After 2 h of stirring,
the solution was filtered through Celite and concentrated to incipient
crystallization. Cooling in a -20 °C freezer over several days yielded
yellow crystals of N,N-dimethyl-4-phenylazoaniline (5) (0.60 g, 2.7
mmol, 67%): mp 115 °C (lit. 115 °C);11 1H NMR (300 MHz, C6D6) δ
8.21 (d, J ) 9.0 Hz, 2H, o-H), 8.15 (d, J ) 7.5 Hz, 2H, o-H), 7.24 (d,
J ) 7.2 Hz, 2H, m-H), 7.09 (t, J ) 7.5 Hz, 1H, p-H), 6.44 (d, J ) 9.0
Hz, 2H, m-H).
t-BuNdNPh (6). ((THF)MgNPh)6 (0.86 g, 0.76 mmol) was
dissolved in diethyl ether (40 mL). Dioxane (1 mL, 11.7 mmol) was
added and the solution cooled with a dry ice/acetone bath. t-BuNBr2
(3) (1.06 g, 4.59 mmol) dissolved in diethyl ether (20 mL) was added
dropwise, and the solution was allowed to warm to room temperature
and stirred for a further 12 h. The dark brown solution was filtered
through Celite, and the solvent was removed under reduced pressure.
Distillation of the remaining dark brown residue afforded an orange
oil identified as 1-tert-butyl-2-phenyldiazene (6) (0.20 g, 1.23 mmol,
27%): bp (70-74 °C/2.0 mmHg; lit. 32-35 °C/0.05 Torr);12 1H NMR
(300 MHz, CDCl3) δ 7.93 (d, J ) 8.1 Hz, 2H, o-H), 7.50 (m, 3H,
m-H, p-H), 1.31 (s, 9H, t-Bu).
(ms), 805 (s), 690 (sh, ms), 450 (br, m) cm-1
.
[(SnNPh)4‚{MgCl2(THF)4}]∞ (10). ((THF)MgNPh)6 (0.75 g, 0.67
mmol) was dissolved in THF (40 mL). Dioxane (1 mL, 11.7 mmol)
was added via syringe. SnCl2 (0.76 g, 4.0 mmol) was then added via
a solids-addition tube, and the solution was heated to ca. 50 °C for
14 h. The solvent was removed under reduced pressure, and the residue
was extracted with toluene (50 mL). After filtration through a frit, the
solution was concentrated to incipient crystallization under reduced
pressure. Cooling to -20 °C yielded small, pale, yellow crystals.
Recrystallization from THF/toluene (1:1) afforded colorless needles of
[(SnNPh)4‚{MgCl2(THF)4}]∞ (10) (0.38 g, 0.31 mmol, 31% based on
1
tin): mp 310 °C dec; H NMR (300 MHz, C6D6) δ 7.17 (t, J ) 7.6
Hz, 2H, m-H), 6.94 (d, J ) 7.5 Hz, 2H, o-H), 6.84 (t, J ) 7.4 Hz, 1H,
p-H), 3.64 (s, 4H, THF), 1.37 (s, 4H, THF); IR (Nujol) ν 1580 (w),
1260 (s), 1215 (w), 1095 (br, s), 1020 (s), 800 (s), 680 (w) 565 (br, w)
cm-1
.
(SnNPh)4‚0.5PhMe (11). ((THF)MgNPh)6 (0.75 g, 0.67 mmol) was
dissolved in THF (20 mL), and 1,4-dioxane (2 mL, 23 mmol) was added
via syringe. Then SnCl2 (0.76 g, 4.0 mmol) was added via a solids-
addition tube, and the solution was heated to reflux for 18 h. The
solvent was removed under reduced pressure, and the yellow residue
was extracted into hot (ca. 70 °C) toluene (40 mL). The solution was
filtered through a frit and concentrated to ca. 5 mL. Cooling to -20
°C yielded small, yellow crystals. Recrystallization from toluene
afforded fine yellow needles of (SnNPh)4‚0.5PhMe (11) (0.35 g, 0.42
(7) Gottardi, W. Monatsh. Chem. 1973, 104, 1681.
(8) Oshikawa, T.; Yamashita, M.; Chem. Ind. (Tokyo) 1985, 126.
(9) Fjeldberg, T.; Haaland, A.; Schilling, B. E. R.; Lappert, M. F.; Thorne,
A. J. J. Chem. Soc., Dalton Trans. 1986, 8, 1551.
(10) Pauly, W. Justus Liebigs Ann. Chem. 1877, 187, 199. Beilstein 1929,
12, 201.
(11) Knoevenagel, H. J. Prakt. Chem. 1914, 89, 50. Beilstein 1934, 16,
310.
(12) Kirch, K.; Riesser, P.; Knock, F. Chem. Ber. 1991, 124, 1143.
(13) Davies, A. R.; Dronsfield, A. T.; Hazeldine, R. N. J. Chem. Soc.,
Perkin Trans. 1973, 1, 379.

3256 Inorganic Chemistry, Vol. 35, No. 11, 1996
Grigsby et al.
Table 1. Selected Crystallographic and Refinement Data for 2, 3, 9, 10, and 14a
2
3
9
10
14
formula
Mr
C93H108Mg6N6O7.25
1587.5
C4H9Br2N
230.9
C24H20Ge4N4
6548
C40H52Cl2MgN4O4Sn4
1222.83
C86H154Mg6N24O6P6
1952.02
a, Å
b, Å
c, Å
28.101(7)
35.851(7)
36.816(7)
6.682(2)
10.834(3)
11.080(3)
66.25(2)
89.88(2)
82.53(2)
726.9(3)
4
10.749(2)
12.358(3)
35.818(7)
12.770(3)
13.554(3)
25.839(5)
22.478(4)
16.339(3)
29.387(6)
R, deg
â, deg
γ, deg
V, Å3
37091(14)
2
4758(2)
8
4472(2)
4
10793(4)
4
Z
space group
Fddd
1.541 78
1.251
0.995
3500
P1h
Pbca
1.541 78
1.828
5.990
2981
289
0.040
0.108
1.097
P212121
1.541 78
1.816
19.143
3190
Pbcn
1.541 78
1.201
1.733
4696
λ, Å
0.710 73
2.110
d(calc), g cm-3
µ, mm-1
11.045
2043
135
0.038
0.044
no. of reflns with I > 2σ(I)
no. of paramtrs refnd
584
256
644
Rb
Rw
0.068
0.090
1.31
0.040
0.101
1.070
0.081
0.173
1.060
GOF
0.74
a Data collections were carried out at 130 K. b R ) ∑(|Fo| - |Fc|)/∑|Fo|; Rw ) ∑(|Fo| - |Fc|)xw/∑|Fo|xw.
1
mmol, 42% based on tin): mp 91-92 °C dec; H NMR (300 MHz,
C6D6) δ 7.18 (t, J ) 7.5 Hz, 2H, m-H), 6.94 (d, J ) 7.5 Hz, 2H, o-H),
6.84 (t, J ) 7.5 Hz, 1H, p-H); 13C NMR (300 MHz, C6D6) δ 153.9 (s,
ipso-C), 129.8 (d, m-C), 120.9 (d, o-C), 120.6 (d, p-C); IR (Nujol) ν
1585 (s), 1480 (s), 1260 (m), 1215 (br, s), 1150 (w), 1100 (m), 1075
(ms), 1030 (ms), 995 (sh, w), 880 (ms), 840 (s), 810 (br, m), 760 (s),
735 (mw), 690 (s), 630 (m), 575 (br, ms), 430 (br, ms) cm-1. Anal.
Calcd for C27.5H24N4Sn4: C, 37.31; H, 2.73; N, 6.32. Found: C, 36.34;
H, 2.91; N, 6.09.
(Ph2SOMgNPh)6 (15). ((THF)MgNPh)6 (0.87 g, 0.77 mmol) was
dissolved in toluene (60 mL). Diphenyl sulfoxide (0.94 g, 4.6 mmol)
was added via a solids-addition funnel. The initial yellow precipitate
dissolved when the solution was heated to reflux. After refluxing for
16 h, the solution was filtered through Celite. The dark yellow solution
was concentrated to ca. 15 mL and layered with hexane (5 mL). Slow
cooling in a -20 °C freezer yielded a dark orange oil (ca. 0.40 g).
This was identified spectroscopically as (Ph2SOMgNPh)6 (15) (0.21
mmol, 27%). Further attempts to crystallize this oil were unsuccess-
ful: 1H NMR (300 MHz, C6D6) δ 7.25 (m, 4H), 7.08 (m, 5H), 6.96
(m, 3H), 6.79 (t, J ) 7.6 Hz, 2H), 6.53 (t, J ) 7.6 Hz, 1H); 13C NMR
(300 MHz, CDCl3) δ 145.2 (s, ipso-C, NPh), 142.5 (s, ipso-C, SPh),
132.2 (d, o-C, SPh), 130.2 (d, m-C, SPh), 128.9 (d, m-C, NPh), 126.2
(d, p-C, SPh), 120.9 (d, p-C, NPh), 116.2 (d, o-C, NPh).
Alternative Synthesis of ((THF)Mg)6(NPh)4Br4 (16). ((THF)-
MgNPh)6 (1) (0.75 g, 0.66 mmol) was dissolved in a diethyl ether/
THF solution (4:1, 50 mL), and MgBr2 (0.36 g, 2.0 mmol) was added
via a solids-addition funnel. The solution was stirred for 12 h and
then refluxed for a further 16 h. The solvent was removed under
reduced pressure and the resulting residue extracted with toluene (30
mL). The solution was filtered through a pad of Celite and then
concentrated to ca. 10 mL and layered with hexane (2 mL). Slow
cooling in a -20 °C freezer yielded large colorless crystals of ((THF)-
Mg)6(NPh)4Br4 (16) (0.57 g, 0.45 mmol, 69% based on magnesium):
mp (does not melt <325 °C); 1H NMR (300 MHz, C6D6) δ 7.42 (d, J
) 7.8 Hz, 2H, o-H), 7.17 (t, J ) 7.2 Hz, 2H, m-H), 6.69 (t, J ) 6.9
Hz, 1H, H4), 4.02 (s, 6H, OCH2), 1.22 (s, 6H, CH2); 13C NMR (300
MHz, C6D6) δ 165.5 (s, ipso-C), 129.1 (d, o-C), 124.7 (d, m-C), 113.2
(d, p-C), 71.5 (t, OCH2), 25.2 (t, CH2). These spectra were identical
to those of an authentic sample prepared from PhNH2 and EtMgBr.3
Alternative Synthesis of ((THF)MgNPh)6 (1). ((THF)Mg)6-
(NPh)4Br4 (16) (1.50 g, 1.2 mmol) was dissolved in diethyl ether (80
mL). Dioxane (0.4 mL, 4.8 mmol) was added, and the solution was
stirred for 16 h. The solution was filtered through a pad of Celite and
then concentrated to incipient crystallization. Cooling in a -20 °C
freezer yielded very fine crystals of ((THF)MgNPh)6 (1) (0.81 g, 0.90
mmol, 60% based on magnesium). This product was shown to be
identical spectroscopically to the previously reported ((THF)MgNPh)6
(1) prepared by the reaction of MgBu2 with aniline in THF.6
(PbNPh)4‚0.5PhMe (12). ((THF)MgNPh)6 (0.75 g, 0.67 mmol) was
dissolved in THF (40 mL), and 1,4-dioxane (1 mL, 11.7 mmol) was
added via syringe. PbCl2 (1.12 g, 4.0 mmol) was added via a solids-
addition tube. The solution was then refluxed for 18 h, whereupon
the solvent was removed under reduced pressure the resulting orange
residue was dissolved in hot toluene (50 mL), and the solution was
quickly filtered. Cooling the solution to ambient temperature yielded
fine orange crystals of (PbNPh)4‚0.5PhMe (12) (0.53 g, 0.27 mmol,
1
40% based on lead): mp 278 °C dec; H NMR (300 MHz, C6D6) δ
7.49 (t, J ) 7.2 Hz, 2H, m-H), 6.66 (t, J ) 7.4 Hz, 1H, p-H), 6.23 (d,
J ) 7.4 Hz, 2H, o-H); IR (Nujol) ν 1575 (ms), 1260 (mw), 1215 (vs),
1180 (w), 1150 (w), 1100 (w, br), 1070 (mw), 1020 (m), 990 (sh, w),
835 (m), 800 (br, m), 760 (sh, ms), 730 (w), 690 (m), 560 (w), 410
(w), 385 (w) cm-1. Anal. Calcd for C27.5H24N4Pb4: C, 26.65; H, 1.95;
N, 4.52. Found: C, 26.81; H, 2.06; N, 4.19.
(Ph3POMgNPh)6 (13). ((THF)MgNPh)6 (1) (0.30 g, 0.27 mmol)
was dissolved in toluene (30 mL). Triphenylphosphine oxide (0.45 g,
1.62 mmol) was added via a solids-addition funnel, and the solution
was refluxed for 18 h. The yellow solution was then filtered through
Celite and concentrated to ca. 10 mL. After layering with hexane (5
mL), the solution was cooled in a -20 °C freezer overnight to yield
triphenylphosphine oxide (0.10 g). The remaining solution was pumped
to dryness under reduced pressure to yield a dark yellow oil. 31P NMR
(300 MHz, C6D6) spectroscopy of this oil gave a minor resonance peak
at δ ) 25.1 (Ph3PO) and a major (>90%) peak at δ ) 35.0 ((Ph3-
POMgNPh)6 (13), ca. 25% based on P).
{(Me2N)3POMgNPh}6‚2PhMe (14). ((THF)MgNPh)6 (1.00 g, 0.88
mmol) was dissolved in toluene (40 mL). Hexamethylphosphorylamide
(0.93 mL, 5.33 mmol) was added via syringe and the solution heated
to reflux for 4.5 h. The solution was filtered through Celite. Slow
cooling of the solution to room temperature yielded colorless crystals
of {(Me2N)3POMgNPh}6‚2PhMe (14) (0.55 g, 0.32 mmol, 36%): mp
X-ray Crystallography. Crystals of 2, 3, 9, 10, or 14 were coated
with hydrocarbon oil. Suitable crystals for data collection were selected
and then mounted in the cold stream (130 K) of the diffractometer.
Data for 2 were collected on a Siemens P4/RA diffractometer employing
nickel-monochromated Cu KR (λ ) 1.541 78 Å) radiation and operating
at 15 kW. Data for 3 were collected as a Siemens R3m/V diffracto-
meter employing graphite-monochromated Mo KR (λ ) 0.710 73 Å)
radiation and operating at 2 kW. Data for 9, 10, and 14 were collected
on a Syntex P21 diffractometer employing graphite-monochromated Cu
KR (λ ) 1.541 78 Å) radiation and operating at 2 kW.
1
240 °C; H NMR (300 MHz, C6D6) δ 6.95 (t, J ) 8.4 Hz, 2H, m-H),
6.86 (d, J ) 8.4 Hz, 2H, o-H), 6.32 (t, J ) 6.6 Hz, 1H, p-H), 2.35 (s,
JP-H ) 9.6 Hz, 18H, NMe): 13C NMR (300 MHz, C6D6) δ 172.10 (s,
ipso-C), 127.54 (d, m-C), 127.14 (d, o-C), 105.86 (d, p-C), 36.73 (q,
JP-C ) 4.5 Hz, NMe); 31P NMR (300 MHz, C6D6) δ 21.75 (JP-H
)
9.6 Hz); IR (Nujol) ν 1570 (m), 1450 (s), 1300 (br, ms), 1200 (br, s),
1070 (sh, m), 970 (br, s), 855 (sh, m), 830 (sh, m), 745 (s), 690 (sh, s),
560 (br, ms), 450 (br, ms) cm-1
.

Imide Transfer Properties of a Magnesium Imide
Inorganic Chemistry, Vol. 35, No. 11, 1996 3257
Table 2. Selected Atomic Coordinates (×104) and Equivalent Isotropic Displacement Parameters (Å2 × 103) for Compounds 2, 3, 9, 10, and
14
x
y
z
U(eq)a
Compound 2
x
y
z
U(eq)a
Mg(1)
Mg(2)
Mg(3)
N(1)
N(2)
N(3)
C(1)
C(2)
C(3)
C(4)
C(5)
4180(1)
4179(1)
3596(1)
4042(2)
4319(2)
3458(2)
4254(2)
3985(2)
4195(2)
4677(2)
4973(2)
1114(1)
2081(1)
1592(1)
1099(1)
1598(1)
2086(1)
871(2)
680(2)
465(2)
417(2)
596(2)
3547(1)
3554(1)
3142(1)
4086(1)
3270(1)
3398(1)
4348(2)
4609(2)
4878(2)
4906(2)
4640(2)
31(1)
32(1)
31(1)
31(2)
32(2)
32(2)
33(2)
34(2)
47(3)
57(3)
46(3)
C(6)
C(7)
C(8)
C(9)
C(10)
C(11)
C(21)
O(1)
O(2)
O(3)
4766(2)
5076(2)
5561(2)
5761(2)
5476(2)
4701(2)
3220(2)
4558(2)
4584(1)
3450(2)
822(2)
1005(2)
957(2)
720(2)
551(2)
1561(2)
2361(2)
659(1)
2511(1)
1643(1)
4366(2)
4123(2)
4133(2)
4402(2)
4645(2)
3040(2)
3210(2)
3401(1)
3386(1)
2606(1)
28(2)
31(2)
42(2)
56(3)
60(3)
35(2)
34(2)
44(2)
41(2)
40(2)
Compound 3
Br(1)
Br(2)
Br(3)
N(1)
C(1)
C(2)
C(3)
C(4)
4467.2(10)
3130.9(11)
3639(6)
2583(7)
438(9)
239(11)
-876(10)
-133(11)
1381.6(6)
4458.5(7)
2678(4)
2709(5)
2460(6)
1058(7)
3556(7)
2560(8)
3700.7(6)
2179.2(7)
759(5)
2316(5)
2643(6)
2684(7)
1453(7)
3931(6)
30.0(3)
23.6(3)
27.0(11)
19(2)
Br(4)
Br(5)
Br(6)
N(2)
C(5)
C(6)
C(7)
C(8)
4309.9(11)
8279.8(11)
6520(6)
2681.9(7)
1649.3(7)
4662(5)
2919(5)
2675(7)
3762(7)
2940(8)
1272(7)
-24.4(7)
-943.9(7)
-2028(4)
-1563(5)
-2613(6)
-3042(7)
-3779(7)
-2139(8)
24.7(3)
36.3(3)
27.0(11)
25(2)
28(2)
34(3)
5826(8)
24(2)
4671(10)
2792(10)
6055(13)
4071(13)
33(3)
32(3)
41(3)
41(3)
33(3)
Compound 9
Ge(1)
Ge(2)
Ge(3)
Ge(4)
N(1)
2201(1)
1501(1)
-119(1)
2418(1)
1502(4)
888(4)
9252(1)
9425(1)
8121(1)
7277(1)
7725(3)
7872(3)
4174(1)
3361(1)
3887(1)
3671(1)
4132(1)
3426(1)
25(1)
25(1)
24(1)
25(1)
24(1)
24(1)
N(3)
N(4)
C(1)
C(7)
C(13)
C(19)
691(4)
2935(4)
1607(5)
318(5)
-112(5)
4150(5)
9606(3)
8866(3)
7124(4)
7404(4)
10482(4)
9195(4)
3859(1)
3676(1)
4472(2)
3101(1)
3967(2)
3564(2)
23(1)
23(1)
28(1)
25(1)
25(1)
27(1)
N(2)
Compound 10
Sn(1)
Sn(2)
Sn(3)
Sn(4)
Mg(1)
Cl(1)
Cl(2)
N(1)
2170(1)
3619(1)
1199(1)
2987(1)
2843(3)
2690(2)
2951(3)
3643(8)
2059(8)
1490(8)
-1359(1)
-402(1)
377(1)
5817(1)
6805(1)
6667(1)
5737(1)
3756(2)
4712(1)
2806(1)
5933(4)
6680(4)
5816(4)
10(10)
N(4)
C(1)
C(7)
C(13)
C(19)
O(1)
O(2)
O(3)
O(4)
2808(8)
4606(9)
1779(10)
672(9)
3131(10)
3240(7)
1295(7)
4420(7)
2374(7)
965(7)
-724(8)
-1830(9)
457(9)
1875(9)
-1840(7)
-750(7)
3(7)
6597(4)
5685(5)
6997(5)
5472(5)
6850(5)
3679(4)
3672(4)
3842(4)
3844(4)
7(2)
7(3)
10(10)
11(1)
10(10)
12(1)
17(1)
21(1)
9(2)
12(3)
11(3)
11(3)
16(2)
19(2)
19(2)
21(2)
933(1)
-352(3)
-546(2)
-169(2)
-516(7)
-1024(7)
137(7)
N(2)
N(3)
8(2)
1128(7)
10(2)
Compound 14
Mg(1)
O(1)
P(1)
N(1)
N(2)
N(3)
N(4)
C(7)
Mg(2)
852(1)
1629(2)
2181(1)
2779(2)
2125(3)
2308(3)
897(2)
5531(1)
5868(2)
6171(1)
5642(4)
6122(4)
7097(4)
5226(3)
5201(4)
4308(1)
-301(1)
-547(2)
-763(1)
-658(2)
-1313(2)
-597(2)
378(2)
19(1)
O(2)
P(2)
703(2)
1071(5)
-351(2)
-623(3)
190(1)
278(2)
381(1)
3685(2)
3086(8)
5126(3)
5329(3)
6031(1)
6937(2)
7650(1)
6398(3)
7218(4)
1114(1)
1379(4)
759(2)
1161(2)
493(1)
41(1)
30(2)
20(1)
23(1)
19(1)
27(1)
28(1)
20(1)
22(1)
34(1)
31(1)
61(2)
53(2)
62(2)
21(1)
24(1)
21(1)
N(8)
C(19)
Mg(3)
O(3)
929(1)
P(3)
1226(1)
-182(2)
-264(2)
1469(2)
346(1)
540(2)
617(1)
N(12)
C(31)
171(2)
185(2)
a U(eq) is defined as one-third of the trace of the orthogonalized Uij tensor.
The structure of 2 was solved in space group Fddd using direct and
difference Fourier methods, developed, and refined routinely.14 Dis-
order was observed for one of the solvent THF molecules. It was
refined using partial occupancies of 56.7% for C(52), C(53), C(54)
and 43.3% for C(52B), C(53B), C(54B). There is also a disordered
THF molecule located on a special position (0.625, 0.125, z). The
atoms are labeled C(S2) and C(S3); 25% of the molecule is present in
the asymmetric unit. Hydrogen atoms were added geometrically and
refined using a riding model with fixed thermal parameters equal to
0.05 Å2. An absorption correction (XABS)15 was applied. Refinement
was by full-matrix least-squares methods based on F, with anisotropic
parameters for all non-hydrogen atoms. The final difference map
unit which pack, along with two symmetrically equivalent molecules,
in a square arrangement around a center of symmetry. This gives rise
to an unusual disorder in which the bromine atoms positions are
interchanged with “lone-pair” positions in a ratio of 84.5(2)% and 15.5-
(2)%. Thus, of the four bromine atoms in the asymmetric unit, two
are fully present, two are at 0.845 occupancy, and two are in the
alternative at 0.155 occupancy. The last two bromines were refined
with their isotropic thermal parameters linked together. The other four
were refined with their thermal parameters free. Hydrogen atoms were
added as rigid groups, assuming C-H of 0.96 Å, and refined by use
of a riding model and fixed isotropic thermal parameters equal to 0.030
Å2. An absorption correction (XABS)15 was applied. In the final cycles
of refinement, all non-hydrogen atoms were refined anisotropically
except for the minor bromines. The largest peak in the difference map
had a value 0.67 e Å-3, adjacent to Br(4).
showed no features greater than 0.94 and -0.29 e Å-3
.
The structure of 3 was solved in space group P1h using Patterson
and difference methods.14 There are two molecules in the asymmetric
(14) Sheldrick, G. M. SHELXTL-PLUS: A Program for Crystal Structure
Determination; Version 4.2; Siemens Analytical X-ray Instruments:
Madison, WI, 1990.
(15) Program XABS provides an empirical correction based on Fo and Fc
differences: H. Hope and B. Moezzi, Department of Chemistry,
University of California, Davis.

3258 Inorganic Chemistry, Vol. 35, No. 11, 1996
Grigsby et al.
The structure of 9 was solved in space group Pbca using direct and
difference Fourier methods.16 The initial solution located all non-
hydrogen atoms. Hydrogen atoms were added in calculated positions,
with C-H equal to 0.95 Å, and refined using a riding model with fixed
thermal parameters equal to 0.05 Å2. An absorption correction
(XABS2)17 was applied. Refinement was by full-matrix least-squares
methods based on F2, with anisotropic parameters for all non-hydrogen
atoms. The final difference map showed no features greater than 0.673
and -1.054 e Å-3
.
The structure of 10 was solved in space group P212121 using direct
and difference Fourier methods.16 The initial solution located a partial
structure, and the remaining non-hydrogen atoms were located in a
subsequent difference map. Hydrogen atoms were added in calculated
positions and refined using a riding model with fixed thermal parameters
equal to 0.05 Å2. An absorption correction (XABS2)17 was applied.
Refinement was by full-matrix least-squares methods based on F2, with
anisotropic parameters for all Sn, Mg, and Cl atoms. The final difference
map showed no features greater than 0.922 and -0.774 e Å-3
.
The structure of 14 was solved in space group Pbcn using direct
and difference Fourier methods,16 developed, and refined routinely. The
structure shows two disorder problems which were sufficiently modeled
with split occupancies. The P(NMe2)3 group involving atoms between
P(2) and C(18) showed rotational disorder and was modeled with split
occupancies of 53.3(8)% for P(2) to C(18) and 46.7(8)% for P(2A) to
C(18A). The toluene solvent molecule was found to be disordered on
two partially overlapping positions and refined isotropically with 63.2-
(12)% occupancy for C(37) to C(43) and 37.8(12)% occupancy for
C(44) to C(50). The aromatic ring of the toluene molecule was con-
strained as a rigid hexagon. Hydrogen atoms were added geometrically
and refined by use of a riding model and fixed isotropic thermal
parameters equal to 0.05 Å2. An absorption correction (XABS2)17 was
made. Refinement was by full-matrix least-squares methods based on
F2, with anisotropic thermal parameters for all non-hydrogen atoms
except those of the toluene solvent molecule. The final difference map
Figure 1. Thermal ellipsoid plot (30%) of 2. For clarity, neither
solvating THF carbons nor hydrogen atoms nor any atoms of the THF
molecules of crystallization are shown.
acidic alkylamines have not yet yielded readily characterizable
products other than the less novel intermediate amide deriva-
tives. In the case of the structure of [{(1-naphthyl)NLi2}10-
(Et2O)6]‚Et2O (17), the N10Li14 core consists of two rhombic
dodecahedra sharing a common face.19 In contrast to 2, it was
obtained by double deprotonation of 1-naphthylamine with
n-BuLi.
The structure of 2 as shown in Figure 1 has a crystallographi-
cally imposed center of symmetry. The central Mg6N6 frame-
work consists of a slightly distorted hexagonal prism containing
alternating magnesium and nitrogen atoms. Each magnesium
is solvated by a single THF molecule whereas each nitrogen
bears a naphthyl group. As found for the structure of 1, the
Mg-N distances within the hexagonal rings (2.05 Å average)
are slightly shorter than those which join the rings (2.09 Å
average).4 These Mg-N distances are similar to those observed
for 1, as are the Mg-N-Mg (117.6(2)°) and N-Mg-N (121.5-
(2)°) angles. Similarly, both the Mg-O (2.02 Å average) and
N-C (1.38 Å average) distances are also comparable to those
found for 1.
The synthetic utility of the magnesium imide ((THF)MgNPh)6
(1) as an imide transfer agent has only been demonstrated in
the case of a few reactions with some early metal cyclopenta-
dienyl derivatives. For example, when 1 was treated with (η5-
C5H5)TiCl3, the bridged titanium imide {(η5-C5H5)Ti(Cl)(NPh)}2
was obtained in good yield.6 A much greater range of reactions,
summarized in Scheme 1, is now discussed here.
Reaction between 1 and benzophenone proceeded in a clean,
straightforward manner to give the expected triphenylimine
product, Ph2CdNPh (4), in good isolated yield. A similar
reaction between 1 and the nitroso compound 4-Me2N(C6H4)-
NO gave the azo compound 4-Me2N(C6H4)NdNPh (5) also in
good yield. Diimine compounds could also be synthesized via
the reaction of 1 with alkyldibromoamines. Treatment of 1 with
the alkyldibromoamine t-BuNBr2 (3) gave the expected diimine
product t-BuNdNPh (6). The yield of this reaction was only
27%, however. This is probably a consequence of the fact that
showed no features greater than 0.571 and -0.316 e Å-3
.
Results and Discussion
The magnesium imide ((THF)MgNPh)6 (1) was originally
synthesized (eq 1) by the reaction between MgEt2 and H2NPh.4
A more convenient route, however, involves the use of the
readily available dibutylmagnesium (supplied commercially as
a 1:1 mixture of n-butyl and sec-butyl groups in heptane solvent)
instead of MgEt2. This affords the product 1 in 84% yield.6
The slightly more crowded 1-naphthyl derivative {(THF)MgN-
(1-naphthyl)}6‚2.25THF (2) can be synthesized by the same
method, and its hexameric structure (Figure 1) is very similar
to that originally reported for 1 in spite of the larger size of the
nitrogen substituent. At present, homometallic magnesium
imide structures are confined to these two aryl derivatives and
to species which may be in equilibrium with “ArN(MgX)2” in
solution, i.e. ((THF)Mg)6(NPh)4Br4. The only other instance
of the involvement of a magnesium atom in an imide cage
structure concerns the compound {HAlN(t-Bu)}3{N(t-Bu)}-
{MgTHF}, in which one of the AlH corners is replaced by a
Mg(THF) moiety.18 The Mg-N distance 2.09 Å in this species
and those found in 1 and 2 are very similar.
An interesting aspect of the double deprotonation of primary
amines by electropositive main group 1 or 2 elements is that it
has only been authenticated structurally for a few aromatic amine
derivatives such as 1, 2, 16, and 17 and [{(1-naphthyl)NLi2}]10-
(Et2O)6]‚Et2O (17).19 Apparently, the acidity20 of the arylamines
readily permits the generation of the imides whereas the less
(16) SHELXTL-PLUS: A Program for Crystal Structure Determination,
Version 5.02; Siemens Analytical X-ray Instruments: Madison, WI,
1994.
(17) Parkin, S. R.; Moezzi, B.; Hope, H. XABS2: an empirical absorption
correction program. J. Appl. Crystallogr. 1995, 28, 53.
(18) Del Piero, G.; Cesari, M.; Cucinella, S.; Mazzei, A. J. Organomet.
Chem. 1977, 137, 265.
(19) Armstrong, D. R.; Barr, D.; Clegg, W.; Drake, S. R.; Singer, R. J.;
Snaith, R.; Stalke, D.; Wright, D. S. Angew. Chem., Int. Ed. Engl.
1991, 30, 1707.
(20) March, J. AdVanced Organic Chemistry, 4th ed.; Wiley: New York,
1992; p 250.

Imide Transfer Properties of a Magnesium Imide
Inorganic Chemistry, Vol. 35, No. 11, 1996 3259
Table 3. Selected Bond Lengths (Å) and Angles (deg) for Compounds 2, 3, 9, 10, and 14
Compound 2
Mg(1)-N(1)
Mg(1)-N(2)
Mg(1)-O(1)
Mg(1)-N(1A)
2.022(5)
2.053(5)
2.019(5)
2.090(5)
Mg(2)-N(3)
Mg(2)-O(2)
Mg(2)-N(3A)
Mg(3)-N(2)
2.105(5)
2.012(5)
2.054(5)
2.084(5)
Mg(3)-O(3)
Mg(3)-N(1A)
N(1)-C(1)
2.025(5)
2.066(5)
1.397(8)
2.090(5)
N(1)-Mg(3A)
N(2)-C(11)
N(3)-C(21)
N(3)-Mg(2A)
2.066(5)
1.373(8)
1.378(8)
2.054(5)
N(1)-Mg(1A)
N(1)-Mg(1)-N(2)
N(1)-Mg(1)-O(1)
N(2)-Mg(1)-O(1)
N(1)-Mg(1)-N(1A)
N(2)-Mg(1)-N(1A)
123.2(2) N(2)-Mg(2)-N(3A) 122.7(2) Mg(1)-N(1)-C(1)
110.0(2) N(3)-Mg(2)-N(3A) 95.0(2) Mg(1)-N(1)-Mg(1A)
127.5(4) Mg(1)-N(2)-C(11)
87.4(2) Mg(2)-N(2)-C(11)
126.2(4) Mg(3)-N(2)-C(11)
119.3(2) Mg(2)-N(3)-Mg(3)
104.3(4) Mg(2)-N(3)-C(21)
84.8(2) Mg(3)-N(3)-C(21)
114.9(2) Mg(2)-N(3)-Mg(2A)
111.9(4)
122.9(4)
128.4(4)
86.3(2)
127.5(4)
118.7(4)
85.0(2)
116.8(2) O(2)-Mg(2)-N(3A) 113.7(2) C(1)-N(1)-Mg(1A)
92.5(2) N(2)-Mg(3)-N(3)
95.1(2) N(2)-Mg(3)-O(3)
94.1(2) Mg(1)-N(1)-Mg(3A)
114.6(2) C(1)-N(1)-Mg(3A)
109.4(2) Mg(1A)-N(1)-Mg(3A)
94.9(2) Mg(1)-N(2)-Mg(2)
O(1)-Mg(1)-N(1A) 115.3(2) N(3)-Mg(3)-O(3)
N(2)-Mg(2)-N(3)
N(2)-Mg(2)-O(2)
N(3)-Mg(2)-O(2)
93.0(2) N(2)-Mg(3)-N(1A)
112.3(2) N(3)-Mg(3)-N(1A) 118.7(2) Mg(1)-N(2)-Mg(3)
117.1(2) O(3)-Mg(3)-N(1A) 120.8(2) Mg(2)-N(2)-Mg(3)
85.3(2) Mg(3)-N(3)-Mg(2A) 118.8(2)
86.5(2) C(21)-N(3)-Mg(2A) 114.1(4)
Compound 3
Br(1)-N(1)
Br(2)-N(1)
Br(3)-N(1))
1.941(4)
1.923(6)
1.874(8)
C(1)-C(2)
C(1)-C(4)
Br(4)-N(2)
1.524(11)
1.518(11)
1.925(6)
Br(5)-N(2)
Br(6)-N(2)
1.926(5)
1.869(8)
N(2)-C(5)
C(5)-C(7)
1.525(10)
1.540(10)
Br(1)-N(1)-Br(2)
Br(2)-N(1)-Br(3)
Br(2)-N(1)-C(1)
Br(3)-Br(4)-N(2)
105.5(3)
101.0(3)
113.7(4)
171.2(3)
Br(4)-N(2)-Br(5)
Br(5)-N(2)-Br(6)
Br(5)-N(2)-C(5)
106.0(2)
107.2(3)
111.0(4)
Br(1)-N(1)-Br(3)
Br(1)-N(1)-C(1)
Br(3)-N(1)-C(1)
103.8(3)
110.3(3)
121.0(5)
Br(4)-N(2)-Br(6)
Br(44)-N(2)-C(5)
Br(6)-N(2)-C(5)
102.0(3)
112.7(4)
117.0(4)
Compound 9
Ge(1)-N(4)
Ge(1)-N(3)
Ge(1)-N(1)
Ge(2)-N(3)
2.006(4)
2.025(4)
2.036(4)
1.997(4)
Ge(2)-N(4)
Ge(2)-N(2)
Ge(3)-N(2)
2.032(4)
2.042(4)
1.999(4)
Ge(3)-N(1)
Ge(3)-N(3)
Ge(4)-N(1)
2.011(4)
2.033(4)
2.001(4)
Ge(4)-N(2)
Ge(4)-N(4)
N-C
2.005(4)
2.042(4)
1.433(7) (av)
N(4)-Ge(1)-N(3)
N(4)-Ge(1)-N(1)
N(3)-Ge(1)-N(1)
N(3)-Ge(2)-N(4)
N(3)-Ge(2)-N(2)
N(4)-Ge(2)-N(2)
82.6(2)
81.9(2)
82.1(2)
82.7(2)
82.1(2)
82.1(2)
N(2)-Ge(3)-N(1)
N(2)-Ge(3)-N(3)
N(1)-Ge(3)-N(3)
N(1)-Ge(4)-N(2)
N(1)-Ge(4)-N(4)
N(2)-Ge(4)-N(4)
81.6(2)
Ge(4)-N(1)-Ge(3)
Ge(4)-N(1)-Ge(1)
Ge(3)-N(1)-Ge(1)
Ge(3)-N(2)-Ge(4)
Ge(3)-N(2)-Ge(2)
Ge(4)-N(2)-Ge(2)
97.7(2)
Ge(2)-N(3)-Ge(1)
Ge(2)-N(3)-ge(3)
Ge(1)-N(3)-Ge(3)
Ge(1)-N(4)-Ge(2)
Ge(1)-N(4)-Ge(4)
Ge(2)-N(4)-Ge(4)
97.1(2)
97.5(2)
96.9(2)
96.6(2)
97.5(2)
96.6(2)
82.3(2)
82.6(2)
81.7(2)
81.9(2)
82.8(2)
97.8(2)
97.2(2)
97.9(2)
97.1(2)
97.4(2)
Compound 10
Sn(1)-N(3)
Sn(1)-N(1)
Sn(1)-N(2)
Sn(2)-N(2)
Sn(2)-N(4)
Sn(2)-N(1)
Sn(3)-N(2)
2.205(9)
Sn(3)-N(4)
Sn(3)-N(3)
Sn(4)-N(1)
Sn(4)-N(3)
Sn(4)-N(4)
Mg(1)-O(2)
2.210(10)
2.252(11)
2.195(10)
2.205(10)
2.234(10)
2.060(10)
Mg(1)-O(1)
Mg(1)-O(4)
Mg(1)-Cl(2)
Mg(1)-Cl(1)
N(1)-C(1)
2.089(10)
N93)-C(13)
1.44(2)
1.46(2)
3.132(2)
3.363(2)
3.151(2)
3.343(2)
2.221(10)
2.278(10)
2.188(10)
2.191(9)
2.258(10)
2.193(10)
2.106(10)
2.471(5)
2.491(5)
1.41(2)
N(4)-C(19)
Sn(1)- - -Cl(1)
Sn(2)- - -Cl(2A)
Sn(3)- - -Cl(2A)
Sn(4)- - -Cl(1)
N(2)-C(7)
1.41(2)
N(3)-Sn(1)-N(1)
N(3)-Sn(1)-N(2)
N(1)-Sn(1)-N(2)
N(2)-Sn(2)-N(4)
N(2)-Sn(2)-N(1)
N(4)-Sn(2)-N(1)
N(2)-Sn(3)-N(4)
N(2)-Sn(3)-N(3)
N(4)-Sn(3)-N93)
N(1)-Sn(4)-N(3)
82.0(4)
78.1(4)
79.6(4)
81.9(4)
80.7(4)
79.6(4)
81.3(4)
78.9(4)
79.6(4)
82.7(4)
N(1)-Sn(4)-N(4)
N(3)-Sn(4)-N(4)
N(4)-Sn(4)-Sn(1)
O(2)-Mg(1)-O(3)
O(2)-Mg(1)-O(1)
O(3)-Mg(1)-O(1)
O(2)-Mg(1)-O(4)
O(4)-Mg(1)-O(4)
O(1)-Mg(1)-O(4)
O(2)-Mg(1)-Cl(2)
80.1(3)
80.2(4)
85.6(2)
178.2(4)
88.3(4)
89.9(4)
89.3(4)
92.5(4)
177.4(4)
88.5(3)
O(3)-Mg(1)-Cl(2)
O(1)-Mg(1)-Cl(2)
O(4)-Mg(1)-Cl(2)
O(2)-Mg(1)-Cl(1)
O(3)-Mg(1)-Cl(1)
O(1)-Mg(1)-Cl(1)
O(4)-Mg(1)-Cl(1)
Cl(2)-Mg(1)-Cl(1)
Sn(4)-N91)-Sn(1)
Sn(4)-N(1)-Sn(2)
91.6(3)
Sn(1)-N(1)-Sn(2)
Sn(2)-N92)-Sn(3)
Sn(2)-N(2)-Sn(1)
Sn(3)-N(2)-Sn(1)
Sn(4)-N(3)-Sn(1)
Sn(4)-N(3)-Sn(3)
Sn(1)-N(3)-Sn(3)
Sn(2)-N94)-Sn(3)
Sn(2)-N(4)-Sn(4)
Sn(3)-N(4)-Sn(4)
99.1(4)
97.2(4)
99.5(4)
100.9(4)
96.2(4)
99.3(4)
101.3(4)
96.6(4)
100.3(4)
99.7(4)
89.4(3)
91.5(3)
90.1(3)
89.7(3)
90.7(3)
88.4(3)
178.7(2)
96.0(4)
99.4(4)
Compound 14a
Mg(1)-O(1)
Mg(1)-N(8)#1
Mg(1)-N(4)
Mg(1)-N(12)
O(1)-P(1)
1.968(4)
2.056(5)
2.061(5)
2.115(5)
1.479(4)
N(4)-Mg(2)
N(4)-Mg(3)
Mg(2)-O(2)
Mg(2)-N(12)#1
2.068(5)
2.091(5)
1.954(4)
2.077(5)
O(2)-P(2A)
1.48(2)
1.50(2)
2.056(5)
2.067(5)
Mg(3)-O(3)
Mg(3)-N(12)
O(3)-P(3)
1.968(4)
2.070(5)
1.474(4)
2.077(5)
O(2)-P(2)
N(8)-Mg(1)#1
N(8)-Mg(3)
N(12)-Mg(2)#1
N(8)#1-Mg(1)-N(4) 122.3(2) Mg(2)-N(4)-Mg(3)
86.9(2) P(2)-O(2)-Mg(2)
162.9(5) N(8)-Mg(3)-N(4)
93.3(2)
92.5(2)
174.8(3)
87.2(2)
N(8)#1-Mg(1)-N(12) 93.6(2) N(4)-Mg(2)-N(12)#1 121.9(2) Mg(1)#1-N(8)-Mg(3) 116.6(2) N(12)-Mg(3)-N(4)
N(4)-Mg(1)-N(12)
P(1)-O(1)-Mg(1)
Mg(1)-N(4)-Mg(2)
92.1(2) N(4)-Mg(2)-N(8)
174.6(3) N(12)#1-Mg(2)-N(8) 93.4(2) Mg(3)-N(8)-Mg(2)
118.3(2) P(2A)-O(2)-Mg(2) 176.0(6) N(8)-Mg(3)-N(12)
93.0(2) Mg(1)#1-N(8)-Mg(2) 86.9(2) P(3)-O(3)-Mg(3)
86.7(2) Mg(3)-N(12)-Mg(1)
123.9(2) Mg(2)#1-N(12)-Mg(1) 86.0(2)
a Symmetry transformation used to generate equivalent atoms.
side reactions such as bromination of the aryl ring can also
occur. The structure of the alkyldibromoamine t-BuNBr2 is
shown in Figure 2. It represents a relatively rare instance of a
solid state structure featuring nitrogen bound to more than one
halogen. The N-Br distances in 3 are in the range 1.869(8)-
1.941(4) Å. These values are close to the sum (1.87 Å) of the
covalent radii of nitrogen (0.73 Å) and bromine (1.14 Å). They
are slightly longer than the 1.843(3) Å N-Br distance observed
in N-bromobenzamide or the 1.817(7) Å seen in N-bromosuc-
cinimide.21 The difference may be due to the fact that in these

3260 Inorganic Chemistry, Vol. 35, No. 11, 1996
Grigsby et al.
Scheme 1. Summary of the Reactions of ((THF)MgNPh)6
(1)
Figure 2. Thermal ellipsoid plot (30%) of the unit cell of 3 illustrating
the structural disorder. Hydrogen atoms are not shown.
molecules the nitrogens are sp2 hybridized in contrast to the
sp3 hybridization observed in 3. The nitrogen centers have
pyramidal coordination with average interligand angles at N(1)
and N(2) of 109.8 and 109.9°, respectively. These are only
slightly greater than the value found for NH3. This is surprising
in view of the larger sizes of the substituents in 3. However,
it is probable that the electronegative bromines keep the
interligand angles from becoming too wide since they tend to
raise the inversion barrier at nitrogen.22
The reaction between 1 and 4 equiv of phosphorus trichloride
led to the isolation of the diazadiphosphetidine cis-(PhNPCl)2
(7). The presence of 7 was verified by a comparison of the
crystallographic lattice parameters and the 31P NMR data with
those of the reported structure.23 The reaction with MesPCl2
(Mes ) 2,4,6-Me3C6H2) gave, however, a mixture of the cis/
trans (1:2) diazadiphosphetidine product (MesPNPh)2 (8) in
good yield.24,25 The isomers were not separated.
The reaction between 1 and the main group 4 dihalides
GeCl2‚dioxane, SnCl2, and PbCl2 afforded the corresponding
tetrameric metal imides in good to moderate yields. The
reaction of 1 with GeCl2‚dioxane gave the germanium imide
(GeNPh)4 (9), whose structure is illustrated Figure 3. It
possesses a distorted Ge4N4 cubane core consisting of alternating
germanium and nitrogen atoms, each nitrogen being substituted
by a phenyl ring. The N-Ge-N angles are less than 90° (82.2-
(2)° average), whereas the corresponding Ge-N-Ge angles are
97.3(2)° (average). The cubane structural type has not been
structurally authenticated for germanium imides. Nonetheless
the Ge4N4 core bears a close resemblance to Sn4N4 and Pb4N4
imido structures which are now well established.26 The Ge-N
bond distances are essentially equivalent and have an average
length of 2.02(2) Å. This distance is longer than those reported
for the related trimeric and dimeric imides [GeN(2,6-i-
Figure 3. Thermal ellipsoid plot (30%) of 9. Hydrogen atoms are
not shown.
Pr2C6H3)]3 (1.86 Å)27 and [GeN(2,4,6-t-Bu3C6H2)]2 (1.85 Å),28
where the germaniums and nitrogens are two- and three-
coordinate, respectively. The isolation of a tetrameric 9 instead
of a dimeric or trimeric species illustrates the importance of
steric effects in the determination of the structure of this class
of compound.
A similar reaction between 1 and SnCl2 or PbCl2 affords
(SnNPh)4 (11) or (PbNPh)4 (12). Each of these compounds
crystallizes with 0.5 equiv of PhMe per tetramer. Since the
structures of other tetrameric Sn(II) and Pb(II) imides have
already been reported,26 it was decided not to determine their
structures. Nonetheless the presence of a tetrameric (SnNPh)4
was verified in the unusual structure observed for {(SnNPh)4‚
MgCl2(THF)4}∞ (10) (Figure 4), which was isolated using a
workup procedure different from that for 11. The main
structural motif in 10 consists of chains formed of alternating
(SnNPh)4 and MgCl2(THF)4 units. The halides act as bridges
between the tin and magnesium centers; however, the Sn- - -Cl
interactions are rather long (3.13-3.36 Å) so that the bridging
is weak. Not surprisingly the Sn-N bond lengths, which
average 2.22(2) Å, are similar to those previously reported for
other tetrameric tin(II) imides.26 The average Mg-Cl and
Mg-O distances of 2.08(1) and 2.481(5) Å are well within the
known range.29
(21) Jabay, O.; Pritzkow, H.; Jander, J. Z. Naturforsch., B 1977, 32, 1416.
(22) Lambert, J. B. In Topics in Stereochemistry; Allinger, N. L., Eliel, E.
L., Eds.; Wiley: New York, 1971; Vol. 6, p 19.
(23) Chen, H.-J.; Haltiwanger, R. C.; Hill, T. G.; Thompson, M. L.; Coons,
D. E.; Norman, A. D. Inorg. Chem. 1985, 24, 4725.
(24) Scherer, O. J.; Schnabl, G. Angew. Chem., Int. Ed. Engl. 1976, 15,
772.
(25) Lehousse, C.; Haddad, M.; Barrans, J. Tetrahedron Lett. 1982, 23,
4171.
(26) For example: (a) Veith, M.; Sommer, M.-L.; Ja¨ger, D. Chem. Ber.
1979, 112, 2581. (b) Veith, M.; Recktenwald, O. Z. Naturforsch., B
1983, 34, 1054. (c) Veith, M. Angew. Chem., Int. Ed. Engl. 1987,
26, 1. (d) Veith, M. Coord. Chem. ReV. 1990, 90, 1. (e) Chen, H.;
Bartlett, R. A.; Dias, H. V. R.; Olmstead, M. M.; Power, P. P. Inorg.
Chem. 1991, 30, 3390. (f) Allan, R. E.; Beswick, M. A.; Edwards,
A. J.; Paver, M. A.; Rennie, M.-A.; Raithby, P. R.; Wright, D. S. J.
Chem. Soc., Dalton Trans. 1995, 1991.
It was also hoped that 1 would readily convert phosphine
oxides to phosphinimines. However, when 1 was treated with
the phosphine oxide Ph3PO or (Me2N)3PO, the corresponding
iminophosphorane, R3PdNPh, was not formed even in the
(27) Bartlett, R. A.; Power, P. P. J. Am. Chem. Soc. 1990, 112, 3660.
(28) Hitchcock, P. B.; Lappert, M. F.; Thorne, A. J. J. Chem. Soc., Chem.
Commun. 1990, 1587.
(29) Holloway, C. E.; Melnik, M. J. Organomet. Chem. 1994, 465, 1.

Imide Transfer Properties of a Magnesium Imide
Inorganic Chemistry, Vol. 35, No. 11, 1996 3261
reduction in the electron density at the phosphorus center owing
to the complexation of the oxygen. A similar 31P downfield
shift was observed for 13 which was obtained when Ph3PO was
added to 1. Formation of the adduct 14, instead of the imino-
phosphorane R3PdNPh, from the reaction of HMPA with 1 is
consistent with a strong PdO bond. The robust nature of the
P-O bond is also reflected in the fact that it often maintains
its integrity in the presence of quite reactive substrates. For
instance, it is possible to form stable HMPA complexes of
aryllithium compounds32 without the formation of coupled
products.
Reaction of 1 with Ph2SO also did not give the corresponding
sulfinimide. The adduct {(Ph2SO)MgNPh}6 (15) was the only
product isolated from this reaction. The reaction of 1 with [(η5-
C5H5)Fe(CO)2]2 with the intention of converting metal-bound
CO to PhNC (bound or unbound) did not result in any detectable
reaction. Reaction between 1 and 3 equiv of MgBr2 afforded
1.5 equiv of ((THF)Mg)6(NPh)4Br4 (16) (eq 4). It can be
Figure 4. Thermal ellipsoid plot (30%) of 10 illustrating the association
of the (SnNPh)4 and MgCl2(THF)4 units. Hydrogen atoms are not
shown.
((THF)MgNPh)6
1.5((THF)Mg) (NPh) Br
6 4
+ 3MgBr2 f
4
1
16
(4)
demonstrated (13C NMR and X-ray data) that this product is
similar to the corresponding Et2O-solvated compound previously
crystallized3 from “PhN(MgBr)2” solutions. This Et2O-solvated
species has been shown to have an adamantyl Mg6N4 core with
doubly deprotonated nitrogens.3 It is probable that the THF-
solvated 16 has a similar structure which, like the Et2O-solvated
analogue, results from disproportionation of the “PhN(MgBr)2”
species to give 16 and MgBr2 as already shown in eq 2.
Compound 16 may be reconverted to 1 by the removal of MgBr2
as described by eq 5. The data thus show that 1 and 16 are
1,4-dioxane8
Figure 5. Thermal ellipsoid plot (30%) of 14 showing the disorder in
one of the (Me2N3)PO solvating molecules. Only oxygens and ipso-
carbon atoms are shown for three of the (Me2N)3PO and three of the
phenyl donors. Hydrogen atoms are omitted for clarity.
((THF)Mg)6(NPh)4Br4
4 equiv
16
2/3((THF)MgNPh)6 + 2MgBr2‚2(1,4-dioxane) (5)
1
refluxing solvent. Instead, substitution of the THF’s took place
and the adduct {(Ph3PO)MgNPh}6 (13) or [{(Me2N)3PO}-
MgNPh]6‚2PhMe (14) was formed.
readily interconvertible by simple addition or removal of the
appropriate number of equivalents of magnesium halide.
Conclusions
The structure of [{(Me2N)3PO}MgNPh]6‚2PhMe (14) was
determined and is shown in Figure 5. The Mg6N6 molecules
are located on crystallographic centers of symmetry. As with
2, the core of 14 consists of alternating magnesium and nitrogen
atoms in an hexagonal prismatic cage. Each nitrogen bears a
phenyl substituent, while the magnesiums are solvated through
oxygen by a (Me2N)3PO group. Though the Mg-N-Mg
(117.3(2)°) and N-Mg-N (122.7(2)°) angles of the Mg6N6 cage
are comparable to those of 1,4 the Mg-N distances within the
hexagonal rings (2.07(1) Å average) and the Mg-N bonds
linking the rings (2.10(1) Å average) show a slight lengthening
with respect to those in 1 (2.05(1) and 2.08(1) Å, respectively).
The average N-C distance (1.37(1) Å average), however, is
the same as that found in 1. The Mg-O distances (1.96(1) Å
average) in 14 are significantly shorter (1.96(1) Å in 12 vs 2.04-
(1) Å in 1). The P-O distances (1.48(1) Å average) are similar
to those observed in other HMPA complexes, and the slight
deviation from linearity of the Mg-O-P angles is not unusual30
and has been observed in other HMPA metal complexes.
The 31P NMR chemical shift of [{(Me2N)3PO}MgNPh]6 (14)
is ca. 3 ppm downfield from that in free (Me2N)3PO (HMPA)
(δ ) 24.3).31 This is, of course, consistent with a slight
The reactions described here have shown 1 to be a capable
imide transfer agent for the synthesis of a wide variety of main
group imido compounds. While it was shown the reaction of
1 with ketone and nitroso compounds led to the formation of
the corresponding imine and diimine products 4 and 5, the
synthetic utility of 1 as an imide transfer is perhaps best
demonstrated in its reactions with main group 14 and 15
substrates. Formation of the diazadiphosphetidines 7 and 8 and
the tetrameric group 14 imides 9, 11, and 12 is an indication of
the potential of magnesium imides as versatile imide transfer
agents especially in main group chemistry.
Acknowledgment. We are grateful to the donors of the
Petroleum Research Fund, administered by the American
Chemical Society, for financial support.
Supporting Information Available: Full tables of data collection
and refinement parameters, atom coordinates, bond distances and angles,
anisotropic thermal parameters, and hydrogen coordinates and isotropic
thermal parameters (54 pages). Ordering information is given on any
current masthead page.
IC951510A
(31) (a) Muller, N.; Lauterbur, P. C.; Goldenson, J. J. Am. Chem. Soc.
1956, 478, 3557. (b) Van Wazer, J. R.; Callis, C. F.; Shoolery, J. N.;
Jones, R. C. J. Am. Chem. Soc. 1956, 78, 5715.
(30) For example: (a) Sinha, S. P.; Pakkann, T. T.; Pakkanen, T. A.;
Niinisto, L. Polyhedron 1982, 1, 355. (b) Tursina, A. I.; Yatsen, Ko,
A. V.; Medvedev, S. V.; Aslanov, L. A. Koord. Khim. 1987, 13, 401.
(32) Reich, H. J.; Green, D. P. J. Am. Chem. Soc. 1989, 111, 8729.