N-H and N=C bond formation via germanium(III) diradicaloid intermediates and C-S bond cleavage in reactions of the digermyne Ar'GeGeAr' (Ar' = C 6H3-2,6-(C6H3-2,6-Pr i2)2) with a

Article abstract of DOI:10.1021/ic801713v

Reactions of the digermyne Ar'GeGeAr' (Ar' = C₆H3-2,6(C ₆H₃-2,6-Pr'₂)2) (1) with four different azides R'N₃ (R = Me₃Sn, ⁿBu₃Sn, PhSCH ₂, or 1-adamantanyl) a

Full text of DOI:10.1021/ic801713v

Inorg. Chem. 2009, 48, 2464-2470
N-H and N)C Bond Formation via Germanium(III) Diradicaloid
Intermediates and C-S Bond Cleavage in Reactions of the Digermyne
Ar′GeGeAr′ (Ar′ ) C6H3-2,6-(C6H3-2,6-Pri2)2) with Azides
Xinping Wang, Chengbao Ni, Zhongliang Zhu, James C. Fettinger, and Philip P. Power*
Department of Chemistry, UniVersity of California, DaVis, One Shields AVenue, California 95616
Received September 5, 2008
Reactions of the digermyne Ar′GeGeAr′ (Ar′ ) C6H3-2,6(C6H3-2,6-Pri2)2) (1) with four different azides R′N3 (R )
Me3Sn, nBu3Sn, PhSCH2, or 1-adamantanyl) are described. Treatment of 1 with Me3SnN3 or nBu3SnN3 afforded the
low-valent germanium (II) parent amido derivative, Ar′Ge(µ2-NH2)2GeAr′ (3) or the high-valent germanium (IV)
parent imido derivative, Ar′(nBu3Sn)Ge(µ2-NH)2Ge(SnnBu3)Ar′ (4), respectively. Addition of AdN3 (Ad )1-admantanyl)
yielded a monoimide bridged species Ar′Ge(µ2-NAd)GeAr′ (5). The structure of 5 differs from that of the diradicaloid
Ar′Ge(µ2-NSiMe3)2GeAr′ (2), which was previously obtained from the analogous reaction of 1 with Me3SiN3. The
reaction of 1 with PhSCH2N3 afforded the germanium ketimide Ar′Ge(SPh)2(N)CH2) (6) containing the imino
-N)CH2 functional group. These reactions demonstrate a remarkable product dependence on the azide substituent.
All compounds were spectroscopically and structurally characterized. Both 3 and 4 feature a four-membered Ge2N2
core. The structure of 5 is stabilized by CH-π interactions while 6 features a rare example of a π-π interaction
between an aromatic ring and a non-aromatic double bond (N)C). The mechanism of formation of 3-6 are
discussed. It is proposed that 3 and 4 are obtained via diradical imido intermediates followed by H-abstraction from
solvents, whereas 6 was formed by the activation of azide group in concert with C-S bond cleavage.
Introduction
imido bridged Ar′Ge(µ2-NSiMe3)2GeAr′ (Ar′ ) C6H3-2,6-
(C6H3-2,6-Pri2)2) (2), which was obtained from the reaction
of digermyne Ar′GeGeAr′ (1) with Me3SiN3.4a We observed
that a solution of 2 in several solvents (benzene, toluene,
and cyclohexane) gradually faded to pale yellow over time
and speculated that hydrogen abstraction from the solvent
was the cause. However, we were unable to characterize the
product of this reaction adequately. We decided to synthesize
a series of imido complexes with different nitrogen substit-
uents related to 2 to throw further light on their reactions
with solvents. We also wished to explore the range of imido
derivatives of the class Ar′Ge(µ2-NR′)2GeAr′ to test their
Diradicals are thought to play a crucial role in bond
breaking and formation processes.1 Although diradicals are
generally highly unstable, the discovery of stable singlet
diradicals or diradicaloids based on heavier main group
elements has been one of the most interesting recent
developments in inorganic main group chemistry.2-5 Re-
cently we reported the synthesis and characterization of the
non-Kekule´ singlet diradicaloid, the germanum-centered,
* To whom correspondence should be addressed. E-mail: pppower@
ucdavis.edu. Fax: (+01) 530-752-8995.
(1) (a) Borden, W. T. Diradicals; Wiley-Interscience: New York, 1998;
p 708. (b) Jain, R.; Sponsler, M. B.; Coms, F. D.; Dougherty, D. A.
J. Am. Chem. Soc. 1988, 110, 1356. (c) Nguyen, K. A.; Gordon, M. C.;
Boatz, J. A. J. Am. Chem. Soc. 1994, 116, 9241. (d) Gru¨tzmacher,
H.; Breher, F. Angew. Chem., Int. Ed. 2002, 41, 4006.
(2) (a) Niecke, E.; Fuchs, A.; Baumeister, F.; Nieger, M.; Schoeller, W. W.
Angew. Chem., Int. Ed. Engl. 1995, 34, 555. (b) Baumgartner, T.;
Gudat, D.; Nieger, M.; Niecke, E.; Schiffer, T. J. J. Am. Chem. Soc.
1999, 121, 5953. (c) Niecke, E.; Fuchs, A.; Nieger, M. Angew. Chem.,
Int. Ed. 1999, 38, 3028. (d) Niecke, E.; Fuchs, A.; Nieger, M.; Schmidt,
O.; Schoeller, W. W. Angew. Chem., Int. Ed. 1999, 38, 3031. (e)
Niecke, E.; Fuchs, A.; Schmidt, O.; Nieger, M. Phosphorus, Sulfur
Silicon Relat. Elem. 1999, 146, 41. (f) Sugiyama, H.; Ito, S.; Yoshifuji,
M. Angew. Chem., Int. Ed. 2003, 42, 3802.
(3) (a) Scheschkewitz, D.; Amii, H.; Gornitzka, H.; Schoeller, W. W.;
Bourissou, D.; Bertrand, G. Science 2002, 295, 1880. (b) Schoeller,
W. W.; Rozhenko, A.; Bourissou, D.; Bertrand, G. Chem.sEur. J.
2003, 9, 3611. (c) Scheschkewitz, D.; Amii, H.; Gornitzka, H.;
Schoeller, W. W.; Bourissou, D.; Bertrand, G. Angew. Chem., Int.
Ed. 2004, 43, 385. (d) Amii, H.; Vranicar, L.; Gornitzka, H.; Bourissou,
D.; Bertrand, G. J. Am. Chem. Soc. 2004, 126, 1344. (e) Niecke, E.;
Fuchs, A.; Baumeister, F.; Nieger, M.; Schoeller, W. W. Angew.
Chem., Int. Ed. Engl. 1995, 34, 555.
(4) (a) Cui, C.; Brynda, M.; Olmstead, M.; Power, P. P. J. Am. Chem.
Soc. 2004, 126, 6510. (b) Cox, H.; Hitchcock, P. B.; Lappert, M. F.;
Pierssens, L. J.-M. Angew. Chem., Int. Ed. 2004, 43, 4500.
(5) Breher, F. Coord. Chem. ReV. 2007, 251, 1007.
2464 Inorganic Chemistry, Vol. 48, No. 6, 2009
10.1021/ic801713v CCC: $40.75  2009 American Chemical Society
Published on Web 02/17/2009

Reactions of the Digermyne Ar′GeGeAr′
125.4 (Me3SnN3), 139.4 (Ar′Ge(µ2-NSnMe3)2GeAr′) ppm. A similar
reactivity with various small molecules. It is noteworthy that,
in parallel work, it has been shown that various imido
derivatives of transition metals involving Fe(III),6a Fe(IV),6b
and Co(III)6c abstract H atoms from reagents or solvents to
form iron or cobalt amido complexes. The formation of Ni(II)
ketimido complexes via transient Ni(III) imides has also been
reported.7 However, to our knowledge, no similar phenomena
have been disclosed for main group 14 imido complexes. In
this paper we show that the reactions of Ar′GeGeAr′ with
various azides afforded an unexpected variety of products
3-6 (Scheme 1), none of which resembles 2. The common
feature of these reactions is the high likelihood of radical
involvement.
1
NMR experiment was carried out in d6-benzene. H NMR (300
MHz, C6D6, 25 °C): δ 1.00 (m, CH(CH3)2, Ar′Ge(µ2-ND2)2GeAr′
and Ar′Ge(µ2-NSnMe3)2GeAr′), 1.31 (m, CH(CH3)2, Ar′Ge(µ2-
NSnMe3)2GeAr′), 2.86 (m, CH(CH3)2, Ar′Ge(µ2-ND2)2GeAr′ and
Ar′Ge(µ2-NSnMe3)2GeAr′), 6.93-7.30 (m, Ar-H) ppm. 2D NMR
(600 MHz, C6H6, 25 °C): δ 0.98 ppm (weak, Ar′Ge(µ2-ND2)2GeAr′).
Ar′(nBu3Sn)Ge(µ2-NH)2Ge(SnnBu3)Ar′ (4). To a red solution
of 1 (0.198 g, 0.210mmol) in hexane (50 mL) was added dropwise
nBu3SnN3 (0.5 mL, 1.8mmol) in hexane (20 mL) at 0 °C with
vigorous stirring. The reaction mixture was warmed to room
temperature and further stirred for 1d. The resulting yellow solution
was concentrated to about 20 mL and stored at about -18 °C for
2 weeks to afford yellow, X-ray-quality crystals of 4. Yield: 0.065
1
g, 20%. mp 232 °C (decomp.). NMR: H NMR (300 MHz, C6D6,
25 °C): δ 0.87 (t, JH-H ) 7.5 Hz, 3H, CH2CH2CH2CH3), 1.03 (t,
Experimental Section
JH-H ) 7.8 Hz, 2H, CH2CH2CH2CH3), 1.27 (sext., JH-H ) 7.5 Hz,
General Procedures. All manipulations were carried out by
using modified Schlenk techniques under an atmosphere of argon
or nitrogen or in a Vacuum Atmospheres HE-43 drybox. Solvents
were dried over an alumina column and degassed prior to use.
Ar′GeGeAr′8 and (C6H3-2, 6-Mes2)N3 (Mes ) C6H2-2,4,6-Me3)9
were synthesized by literature methods. Me3SnN3 (Aldrich, 97%),
nBu3SnN3 (Aldrich, 98%), PhSCH2N3 (Aldrich, 95%), and 1-ada-
mantyl azide (AdN3, Ad ) 1-adamantanyl, Aldrich, 97%) were
2H, CH2CH2CH2CH3), 1.52 (quint, JH-H
) 7.2 Hz, 2H,
CH2CH2CH2CH3), 2.92 (m, br., CHMe2), 3.08 (sept, CHMe2),
3.57(m, br., CHMe2), 6.94-7.36(m, 9H, Ar-H) (N-H resonance
not observed). 13C{1H} NMR (100.6 MHz, C6D6, 25 °C): δ 11.37
(nBu), 15.83 (nBu), 22.95 (CH(CH3)2), 25.39 (CH(CH3)2), 26.18
(nBu), 26.53 (nBu), 30.13 (CH(CH3)2), 123.50 (m-Dipp), 127.54
(p-C6H3), 128.18 (m-C6H3) ppm. 119Sn{1H} NMR (224 MHz, C6D6,
25 °C): δ 99.1 ppm.
Ar′Ge(µ2-NAd)GeAr′ (5). To a red solution of 1 (0.298 g,
0.316mmol) in hexane (50 mL) was added dropwise AdN3 (0.128
g, 0.722 mmol) in hexane (10 mL) at 0 °C. After the reaction
mixture had been stirred at room temperature for 1 d, the volume
of the solution was reduced to about 10 mL under reduced pressure.
Overnight storage of the orange solution at about -18 °C afforded
orange X-ray-quality crystals of 5. Yield: 0.217 g, 63%; mp
254-256 °C. NMR: 1H NMR (300 MHz, C6D6, 25 °C): δ 0.86 (d,
JH-H ) 6.0 Hz, 24H, CH(CH3)2), 0.91 (d, JH-H ) 6.3 Hz, 24H,
CH(CH3)2), 1.23-1.42 (m), 1.74(m), 3.11 (br) (15H, Ad), 3.57(sept.,
JH-H ) 6.0 Hz, 8H, CH(CH3)2), 6.92 (d, 6H, Ar-H), 7.09-7.16
(m, 12H, Ar-H) ppm. 13C{1H} NMR (100.6 MHz, C6D6, 25 °C):
δ 22.89 (CH(CH3)2), 25.66 (CH(CH3)2), 30.80 (CH(CH3)2), 35.79
(CH(CH3)2), 48.27 (Ad), 63.77 (Ad), 123.66 (m-Dipp), 127.57 (p-
C6H3), 128.21 (m-C6H3), 130.59 (p-C6H3-2,6-Pri2) ppm.
1
used as received without further purification. H and 13C NMR
spectra were recorded on a Varian 300 MHz instrument and
referenced to known standards. 2D NMR spectra were recorded on
a Bruker Avance 500 MHz spectrometer equipped with a multi-
nuclear probe tuned to 2D. 119Sn NMR spectra were recorded on a
Varian Inova 600 MHz spectrometer (224.2 MHz) and referenced
externally to neat SnMe4. The melting points were recorded using
a Meltemp apparatus and were not corrected. Infrared data were
recorded as Nujol mulls on a Perkin-Elmer PE-1430 instrument.
Ar′Ge(µ2-NH2)2GeAr′ (3). To a red solution of 1 (0.201 g,
0.213mmol) in hexane (40 mL) was added dropwise a Me3SnN3
(0.137 g, 0.659 mmol) slurry in hexane (20 mL) at 0 °C. The slurry
was warmed, and it rapidly gave an orange solution. After further
stirring for 1d, unreacted Me3SnN3 was recovered by filtration. The
filtrate was reduced to dryness, and the yellow powder was
redissolved in toluene. Storage of the solution at about -18 °C for
one week afforded X-ray-quality crystals of 3. Yield: 0.097 g, 47%;
Ar′Ge(SPh)2(N)CH2) (6). To a red solution of 1 (0.176 g, 0.187
mmol) in hexane (40 mL) was added dropwise PhSCH2N3 (0.5 mL,
3.53 mmol) slurry in hexane (20 mL). After the reaction mixture
was stirred at room temperature for 1 d, the yellow solution was
concentrated to about 10 mL and stored at -15 °C for 1 week to
yield colorless, X-ray-quality crystals of 6. Yield: 0.02 g, 15%;
mp 180-182 °C. NMR: 1H NMR (300 MHz, C6D6, 25 °C): δ 1.07
(d, JH-H ) 6.9 Hz, 12H, CH(CH3)2), 1.59 (d, JH-H ) 6.9 Hz, 12H,
CH(CH3)2), 3.06 (sept, JH-H ) 6.9 Hz, 4H, CH(CH3)2), 4.42 (s,
2H, NCH2), 6.74-6.81 (10H, SPh-H), 6.98 (m, 3H, Ar-H), 7.16
(m, 6H, Ar-H)ppm. 13C{1H} NMR (100.6 MHz, C6D6, 25 °C): δ
23.16 (CHMe2), 26.10 (CHMe2), 31.82 (CHMe2), 122.65, 123.38,
126.92, 128.63, 129.12, 131.28 (SPh-C and Ar-C), 136.59 (NCH2),
146.15, 147.64 (SPh-C and Ar-C). IR: 1579 cm-1 (νN)C, weak).
Reaction of 1 with (C6H3-2, 6-Mes2)N3. To a red solution of 1
(0.183 g, 0.194 mmol) in hexane (40 mL) was added dropwise
(C6H3-2, 6-Mes2)N3 (0.145 g, 0.408mmol) solution in hexane (20
mL). The reaction mixture was stirred at room temperature for 1 d
and no color changes were observed. After removal of the solvent
under reduced pressure, 1 and (C6H3-2, 6-Mes2)N3 were recovered
1
its melting point, H NMR, and IR spectra are identical to the
literature values.10 mp: 86-88 °C. H NMR (300 MHz, C6D6, 25
1
°C): δ 0.89 (s, 2H, NH2), 0.97 (d, JH-H ) 6.8 Hz, 12H, CH(CH3)2),
1.11 (d, JH-H ) 7.2 Hz, 12H, CH(CH3)2), 2.96 (sept, JH-H ) 6.8
Hz, 4H, CH(CH3)2), 6.95 (d, JH-H ) 7.6 Hz, 6H, Ar-H), 7.09-7.13
(m, 12H, Ar-H) ppm. IR (Nujol): ν ) 3380 and 3309 cm-1 (νNH
,
2
weak). A typical NMR experiment involving 1 (0.108 g, 0.114
mmol) and Me3SnN3 (0.051 g, 0.245 mmol) was carried out in
benzene solvent (50 mL), which, after 1 day, afforded the signals:
119Sn{1H} NMR (224 MHz, C6D6, 25 °C): δ -33.3 (Me3SnPh),
(6) (a) Eckert, N. A.; Vaddadi, S.; Stoian, S.; Lachicotte, R. J.; Cundari,
T. R.; Holland, P. L. Angew. Chem., Int. Ed. 2006, 45, 6868. (b) Lucas,
R. L.; Powell, D. R.; Borovik, A. S. J. Am. Chem. Soc. 2005, 127,
11596. (c) Thyagarajan, S.; Shay, D. T.; Incarvito, C. D.; Rheingold,
A. L.; Theopold, K. H. J. Am. Chem. Soc. 2003, 125, 4440.
(7) Bai, G.; Stephan, D. Angew. Chem., Int. Ed. 2007, 46, 1856.
(8) Stender, M.; Phillips, A. D.; Wright, R. J.; Power, P. P. J. Am. Chem.
Soc. 2005, 127, 17530.
(9) (a) Gavenonis, J.; Tilley, T. D. Organometallics 2002, 21, 5549. (b)
Wright, R. J.; Steiner, J.; Beaini, S.; Power, P. P. Inorg. Chim. Acta
2006, 359, 1939.
(10) Stanciu, C.; Hino, S. S.; Stender, M.; Richards, A. F.; Olmstead, M. M.;
Power, P. P. Inorg. Chem. 2005, 44, 2774.
1
on the basis of H NMR spectroscopy.
X-ray Crystallography. Crystals of 3, 4, 5, and 6 were removed
from the Schlenk tube under a stream of argon and immediately
Inorganic Chemistry, Vol. 48, No. 6, 2009 2465

Wang et al.
Table 1. Selected X-ray Crystallographic Data for 3, 4, 5, and 6
cmpd
3·4C7H8
4
5·C6H14
6·0.5C6H14
formula
C88H110Ge2N2
1341.00
C84H130N2Ge2Sn2
1550.46
yellow block
orthorhombic
Pbca
23.066(1)
21.095(1)
32.251(1)
C76H103NGe2
1175.82
orange block
monoclinic
P2(1)/c
23.594(1)
12.983(1)
22.881(1)
C46H56NS2Ge
759.67
colorless plate
monoclinic
C2/c
42.263(4)
9.943(1)
19.481(1)
formula wt
color, habit
crystal system
space group
a [Å]
b [Å]
c [Å]
R [deg]
ꢀ [deg]
γ [deg]
V [Å3]
colorless block
triclinic
j
P1
12.072(2)
13.241(3)
13.719(3)
109.60(3)
102.81(3)
103.69(3)
1895.4(10)
1
1.175
90(2)
0.838
18192
112.27(1)
91.44(1)
15693(1)
8
6485.9(9)
4
1.204
90(2)
0.969
14980
11937
0.0378
0.1058
8183.5(3)
8
1.233
90(2)
0.883
9108
7834
0.0385
0.1113
Z
F
calc.[g cm-3
]
1.313
90(2)
1.431
10723
8162
T [K]
µ, mm-1
no. of reflns
no. of obsd reflns
R1, obsd reflns
wR2, all
9096
0.0344
0.0964
0.0344
0.0736
Scheme 1
covered with a thin layer of hydrocarbon oil. A suitable crystal
was selected, attached to a glass fiber, and quickly placed in a low
temperature N2 stream. The data for 3 and 4 were collected on a
Bruker APEX (Mo KR radiation (λ ) 0.71073 Å) and a CCD area
detector), while 5 and 6 were recorded near on a Bruker SMART
1000 (Mo KR radiation (λ ) 0.71073) and a CCD area detector).
For all crystals the SHELX version 6.1 program package was used
for the structure solutions and refinements. Absorption corrections
were applied using the SADABS program.11 The crystal structures
were solved by direct methods and refined by full-matrix least-
squares procedures. All non-H atoms were refined anisotropically.
H atoms were included in the refinement at calculated positions
produced rapid color changes from the intense red color of
the precursors to colorless (3 or 6), yellow (4) or orange
(5). This is in sharp contrast to the reaction of 1 with Me3SiN3
in which a color change from red to deep violet was
observed.4a The reaction of 1 with terphenyl azide (C6H3-2,
6-Mes2)N3 (Mes ) C6H2-2,4,6-Me3), however, produced no
color change indicating that no reaction had occurred, which
1
was further confirmed by H NMR spectroscopy.
Treatment of 1 with Me3SnN3 afforded a low-valent
germanium (II) derivative of the parent amide group -NH2
(3), while the reaction with nBu3SnN3 afforded a high-valent
germanium (IV) derivative of the parent imide group -NH
(4) (Scheme 2). It can be reasoned that the reactions of 1
with Me3SnN3 probably proceeds via the initial formation
of a diradicaloid intermediate Ar′Ge(µ2-NSnMe3)2GeAr′, an
using a riding model included in the SHELXTL program.12
A
summary of the data collection parameters for 3-6 is provided in
Table 1.
Results and Discussion
(11) SADABS, an empirical absorption correction program from the
SAINTPlus NT, version 5.0 package; Bruker AXS: Madison, WI, 1998.
(12) SHELXTL, version 5.1; Bruker AXS: Madison, WI, 1998.
Reactions. The reactions of 1 with RN3 (R ) SnMe3,
SnnBu3, Ad (1-adamantanyl), and PhSCH2) in hexane
2466 Inorganic Chemistry, Vol. 48, No. 6, 2009

Reactions of the Digermyne Ar′GeGeAr′
Scheme 2
Scheme 3
analogue of the silicon congener 2. This is followed by Sn-N
bond cleavage and loss of the Me3Sn · radical, whereupon
H-atom transfer from the solvent to the nitrogens occurs to
afford 3 (Scheme 2b). The tin radical Me3Sn · is then trapped
by H abstraction from benzene or toluene solvent to afford
Me3SnPh or Me3SnCH2Ph. This reaction pathway is sup-
solvent. However, a signal due to -ND2 (δ ) 0.98 ppm)
was observed in the 2D NMR spectrum. The reaction
sequence is also supported by our previous isolation of the
silicon analogue (2) of Ar′Ge(µ2-NSnMe3)2GeAr′,4a and by
work that described the ready formation of metal amido
moieties via an H-atom abstraction from solvents by transi-
tion metal imido intermediates.6 In addition, several recent
reports have described the H-abstraction by a variety of
aminyl radicals.14 Similarly, a diradicaloid analogue of 2 is
formed in the initial step of the reaction of 1 with nBu3SnN3.
1
2
ported by 119Sn, H, and D NMR spectroscopy.
The reaction mixture of 1 and Me3SnN3 displayed 119Sn
NMR signals due to Me3SnN3 (δ ) 125.4 ppm), Ar′Ge(µ2-
NSnMe3)2GeAr′ (δ ) 139.4 ppm), and Me3SnPh (δ ) -33.3
ppm) immediately upon mixing the reagents.13 A signal due
to -NH2 (δ ) 0.89 ppm) was not observed in the 1H NMR
spectrum when the reaction was performed in the deuterated
(14) (a) Kogut, E.; Wiencko, H. L.; Zhang, L. B.; Cordeau, D. E.; Warren,
T. H. J. Am. Chem. Soc. 2005, 127, 11248–11249. (b) Buttner, T.;
Geier, J.; Frison, G.; Harmer, J.; Calle, C.; Schweiger, A.; Schonberg,
H.; Gru¨tzmacher, H. Science 2005, 307, 235–238. (c) Huang, W.;
Henry-Riyad, H.; Tidwell, T. T. J. Am. Chem. Soc. 1999, 121, 3939–
3943.
(13) Me3SnPh in CH2Cl2: δ119Sn ) -28.6 ppm. Wrackmeyer, B. Annu.
Rep. NMR Spectrosc. 1985, 16, 73; Me3SnN3 in C6D6: δ119Sn ) 126.0
ppm (this work).
Inorganic Chemistry, Vol. 48, No. 6, 2009 2467

Wang et al.
Figure 1. Thermal ellipsoid (50%) drawing of 4. Hydrogen atoms (except
NH) are not shown. Only carbons directly attached to Sn in the SnnBu3
moieties are shown. Selected bond distances (Å) and angles (deg) for 4:
C1-Ge1 2.000(2), Ge1-N2 1.856(2), Ge1-N1 1.841(2), Ge1-Sn1
2.666(1), Ge2-N2 1.856(2), Ge2-N1 1.838(2), Ge2-Sn2 2.636(1),
Ge2-C31 1.993(2), C1-Ge1-N1 109.71(1), C1-Ge1-N2 106.50(1),
N1-Ge1-N2 83.87(1), Ge1-N1-Ge2 95.34(1), Ge1-N2-Ge2 96.61(1),
N1-Ge2-C25 113.16(1), N2-Ge2-C25 109.04(1), Ge1-N1-H2 116.5(1),
Ge2-N1-H2 138.8(1), Ge1-N2-H1 132.3(1), Ge2-N2-H1 130.2(1).
Figure 2. Thermal ellipsoid (50%) drawing of 5. Hydrogen atoms and C6H3-
2,6-Pri2 (except ipso carbon atoms) are not shown. Selected bond distances
(Å) and angles (deg): C1-C2 1.426(3), C1-C6 1.424(3), Ge1-C1 2.049(2),
Ge1-N 1.849(1), Ge2-N 1.891(2), N-C61 1.502(3), C31-C32 1.411(3),
C31-C36 1.418(3), C61-C62 1.540(3), C61-C63 1.532(3), N-C61 1.502(3),
C6-C1-C2 116.38(9), Ge1-C1-C2 128.00(6), Ge1-C1-C6 107.55(4),
C1-Ge1-N 118.82(8), Ge1-N-C61 134.09(4), Ge2-N-C61 114.15(3),
Ge1-N-Ge2 111.38(9), N-Ge2-C31 104.99(8), Ge2-C31-C32 112.04(5),
Ge2-C31-C36 127.73(6), C36-C31-C32 118.02(9).
This is also followed by N-Sn bond cleavage and the
formation of a new aminyl diradical14,15 {nBu3Sn(Ar)′Ge(µ-
N · )}2, which forms 4 via H-atom abstraction (Scheme 2c).
The reasons why these reactions produce 3 and 4 from the
addition of the Me3SnN3 and Bu3SnN3 to 1 are unclear at
present.
(MN)CR2) (M ) metal). 6 is the first example of a main-
group metal ketimide featuring the parent -N)CH2 group.19
Structures. The molecular structure of 3 is essentially
identical to that previously reported. However, in the earlier
report 3 was obtained by a straightforward route involving
treatment of Ar′GeCl with liquid NH3.10 For the current
structure, the compound crystallized in a different space
group with a different number of toluene solvate molecules
(4 vs 1.5). Otherwise there are no significant differences (see
Supporting Information for more details). The structure of
4, Ar′nBu3SnGe(µ2-NH)2GeSnnBu3Ar′(Figure 1), is dimeric
with a Ge2N2 core that has an almost planar arrangement
with a rhombohedral shape and with an acute angle near
84° at the germaniums and a wider angle near 97° at the
nitrogens. The germanium centers have tetrahedral coordina-
tion geometries, and the terphenyl groups are arranged in a
trans fashion across the ring. The nitrogen centers have
trigonal planar coordination in the case of N1 and a
somewhat pyramidalized coordination in the case of N2 as
shown by the sum of the angles at N1 of 359° and at N2 of
349°. The Ge-N1 bond lengths (1.841 (2), 1.838 (2) Å) are
slightly shorter than Ge-N2 bond lengths (1.856 (2), 1.856
(2) Å) consistent with the different nitrogen coordination
geometries. The Ge-N distances are slightly longer than the
reported range 1.801-1.829 Å in several Ge(IV)-NH imido
species, for example, the Ge-N(H) bond lengths of
1.811-1.818 Å in [iPrC6H3NSiMe3Ge(NH2)2]2NH20 or
1.807-1.828 Å in [iPrC6H3NSiMe3Ge(NH2)2NH]3,21 in
n
Reaction of 1 with excess AdN3 yielded a novel monoim-
ido bridged species 5 (Scheme 1). It seems that steric
crowding prevents the isolation of a cyclic Ge2N2 diradicaloid
species analogous to 2. It is noteworthy that 1 displays no
reaction with the even bulkier terphenyl azide (C6H3-2,
6-Mes2)N3. The structure of 5 resembles that of Ar′Sn(µ2-
NSiMe3)SnAr′, which was obtained by the reaction of
Me3SiN3 with Ar′SnSnAr′.16
Reaction of 1 with excess PhSCH2N3 afforded a germa-
nium (IV) ketimide 6 featuring the imino -N)CH2 group.
It is proposed (without mechanistic evidence) that this
reaction proceeds via the sequence given in Scheme 3, during
which the cleavage of C-S bond occurs in the conversion
of 7 to 8 followed by dissociation of 8 to afford 9 and 10.
The C-S bond is readily cleaved by numerous transition
metal complexes,17 but a similar reaction for multiple bonded
compounds of main group elements is unknown.18 This
reaction has provided a new route to a metal ketimide
(15) For a stable aminyl diradical, see: (a) Rajca, A.; Shiraishi, K.; Pink,
M.; Rajca, S. J. Am. Chem. Soc. 2007, 129, 7232–7233.
(16) Cui, C.; Olmstead, M.; Fettinger, J.; Spikes, G. H.; Power, P. P. J. Am.
Chem. Soc. 2005, 127, 17530. For other -NR bridged derivatives of
Ge(II), see: (a) Hitchcock, P. B.; Lappert, M. F.; Thorne, A. J. Chem.
Commun. 1990, 1587. (b) Barlett, R. A.; Power, P. P. J. Am. Chem.
Soc. 1990, 112, 3660. (c) Veith, M. Angew. Chem., Int. Ed. Engl.
1987, 26, 1.
(17) Recent references: (a) Reynolds, M. A.; Guzei, L. A.; Angelici, R. J.
J. Am. Chem. Soc. 2002, 124, 1689. (b) Chung, M.; Schlaf, M. J. Am.
Chem. Soc. 2004, 126, 7386. (c) O’Connor, J. M.; Bunker, K. D.;
Rheingold, A. L.; Zakharov, L. J. Am. Chem. Soc. 2005, 127, 4180–
4181. (d) Li, M.; Ellern, A.; Espenson, J. H. J. Am. Chem. Soc. 2005,
127, 10436–10447. (e) Goh, L. Y.; Weng, Z.; Leong, W. K.; Leung,
P. H. Angew Chem., Int. Ed. 2001, 40, 3236. (f) Shimizu, D.; Takeda,
N.; Tokitoh, N. Chem. Commun. 2006, 177–179.
(19) Two structurally characterized transition metal complexes containing
-N)CH2 group: (a) Sceats, E. L.; Figueroa, J. S.; Cummins, C. C.;
Loening, N. M.; Van der Wel, P.; Griffin, R. G. Polyhedron 2004,
23, 2751. (b) Herrmann, W. A.; Bell, L. K.; Ziegler, M. L.; Pfisterer,
H.; Pahl, C. J. Organomet. Chem. 1983, 247, 39; For examples that
have only been spectroscopically characterized, see: (c) Pombeiro,
A. J. L.; Hughes, D. L.; Richards, R. L. Chem. Commun. 1988, 1052.
(d) Chatt, J.; Dosser, R. J.; Leigh, G. J. Chem. Commun. 1972, 1243.
(20) Wraage, K.; Lameyer, L.; Stalke, D.; Roesky, H. W. Angew. Chem.,
Int. Ed. 1999, 38, 522–523.
(18) The C-S bond can be cleaved by alkali metals and Lewis acids. (a)
Tarbell, D. S.; Harnish, D. P. Chem. ReV. 1951, 49, 1–90. (b) Schmidt,
M.; Rittig, F. R. Angew Chem., Int. Ed. Engl. 1970, 9, 738–739.
(21) Wraage, K.; Schmidt, H.-G.; Noltemeyer, M.; Roesky, H. W. Eur.
J. Inorg. Chem. 1999, 863.
2468 Inorganic Chemistry, Vol. 48, No. 6, 2009

Reactions of the Digermyne Ar′GeGeAr′
Figure 3. Intramolecular CH-π interactions in 5 between (a) two Ar′ ligands (2.48-3.10 Å); (b) Ar′ and the adamantanyl ligand (2.64-2.82 Å).
which the nitrogens bridge two germaniums, and have planar
coordination geometry.
The structure of 5 is illustrated in Figure 2. It can be seen
that an adamantanyl imido unit bridges two Ar′Ge moieties.
The two Ge-N lengths (Ge1-N 1.849(1), Ge2-N 1.891(2)
Å) are slightly different but similar to those in 4 and are
consistent with single bonding. The Ge1 · · · Ge2 separation
(3.089(1) Å) is much longer than a normal Ge-Ge single
bond (average 2.44 Å).22 The coordination geometry at the
nitrogen atom is planar (sum of interligand angles ) 359.6°).
The Ge1-N-C61 (134.09°) and Ge2-N-C61 (114.15°)
angles are dissimilar, and the shorter Ge1-N bond is
associated with the wider Ge1-N-C61 angle. Significantly,
deformations of the trigonal planar geometries at the ipso
C1 and C31 atoms are also observed. The C1-Ge1 bond
subtends an angle of about 35.7° with respect to the averaged
plane of the C1 aryl ring. The corresponding Ge2-C31
deviation is about 12.8°. As a result, the corresponding
phenyl ring geometries are distorted with some C-C bond
lengthening. The C1-C2 (1.426 (3) Å) and C1-C6 (1.424
(3) Å) bond lengths are marginally longer than those of
C31-C32 (1.411 (3) Å) and C31-C36 (1.418 (3) Å),
consistent with the higher degree of distortion (35.7° vs
12.8°). The preference of the singly bridged imido structure
and the distortion of the geometry at the ipso C atoms are
likely a result of crowding as is evident from the intramo-
lecular interactions involving CH(CH3 or CH2)-π electron
interactions in the range 2.48-3.10 Å between terphenyl and
adamantanyl substitutents as shown in Figure 3. The exist-
ence of CH-π interactions in a range of molecules is well-
known and could be a controlling influence in the observed
structural conformations.23
Figure 4. Thermal ellipsoid (50%) drawing of 6. Hydrogen atoms (except
N)CH2 hydrogen atoms) and C6H3-2,6-Pri2 (except ipso carbon atoms) are
not shown. Selected bond distances (Å) and angles (deg) for 6: C1-C2
1.407(2), C1-C6 1.412(3), C1-Ge1 1.970(2), Ge1-N1 1.862(2), N1-C43
1.258(3), Ge1-S1 2.253(6), Ge1-S2 2.223(6), C2-C1-C6 119.16(6),
C2-C1-Ge1 121.05(3), C6-C1-Ge1 119.66(3), C1-Ge1-N1 111.52(7),
Ge1-N1-C43 120.28(6), N1-Ge1-S1 112.70(6), N1-Ge1-S2 105.44(6),
S1-Ge1-S2 111.43(2).
The structure of 6 (Figure 4) shows that the coordination
geometry at germanium is tetrahedral with a terminal
-N)CH2 group bound to Ge. The Ge-N (1.862 (2) Å) is
close to that found in Ar′Ge-N(Ph)CC(Ph)N-GeAr′ and
Ar′Ge{(TCNE)}3{(GeAr′)}3 (Ge-N 1.801 (4)-1.859 (4)),16
which contain -N)CRR′ (R, R′ ) organic) groups. The
N-C bond length (1.258 (3) Å) is consistent with an N)C
double bond.24 The Ge1-N1-C43 bond angle (120.28(6)°)
is quite different from the Mo-N-C angles, for example,
163.20(1)° in (η5-C5Me5)2Mo2(CO)3(µ1-NCH2) (µ2-NCH2)
and 177.99(2)° in H2CNMo(N[tBu]Ar)3 (Ar ) 3,5-
(CH3)2C6H3),19a consistent with the presence of a stere-
ochemically active lone pair at N (1). This is consistent with
a shorter N-C bond length (1.258(3) Å) in 6, which may
be comparable to those in the linear Mo)N)C units (N-C
1.275(1) Å in (η5-C5Me5)2Mo2(CO)3(µ1-NCH2) (µ2-NCH2)
and 1.299(7) Å in Mo(N[tBu]Ar)3(µ1-NCH2) (Ar ) 3,5-
(CH3)2C6H3)).19b
(22) (a) Mackay, K. M. The Chemistryof Organic Germanium, Tin, and
Lead Coumpounds; Patai, S., Ed.; Wiley: Chichester, 1995; Chapter
2. (b) Baines, K. M.; Stibbs, W. G. AdV. Organomet. Chem. 1996,
39, 275.
(23) For a discussion of the nature of CH-π bond and induced structural
conformational changes, see: (a) Nishio, M.; Hirota, M.; Umezawa,
Y. The CH/π Interaction. EVidence, Nature, and Consequences; Wiley-
VCH, 1998; (b) Desiraju, G. R.; Steiner, T. The Weak Hydrogen Bond
in Structural Chemistry and Biology; Oxford University Press: Oxford,
1999.
(24) Wells, A. F. Structural Inorganic Chemistry, 5th ed.; Clarendon:
Oxford, 1984; p 807.
Inorganic Chemistry, Vol. 48, No. 6, 2009 2469

Wang et al.
experimental and theoretical attention has been focused on
aromatic pairs as model systems for π-π interactions.
However, studies of non-aromatic species have largely been
limited to systems with interactions to tetracyanoethene
(TCNE).25 Compound 6 is a rare example that contains an
interaction between an aromatic ring and a non-aromatic π
bond.27 Figure 5 shows two molecular orbitals exhibiting
π(N)C)-π(arene) interaction in a similar but simpler mol-
ecule Ar#Ge(SH)2NCH2 (Ar# ) (C6H3-2, 6-Mes2)).
Conclusion
This work has demonstrated that a diversity of germanium-
nitrogen compounds, a germanium amide, two imido deriva-
tives, or a ketimide, can be synthesized by the treatment of
the multiple bonded digermyne Ar′GeGeAr′ (1) with a
variety of azides. The results indicate that several different
processes involving unusual intermediates, for example, a
Ge(III) imido diradicaloid, Ge(IV) aminyl radical, C-S bond
cleavage, N-H and N)C bond formation, and intra CH-
π(arene) and π(N)C)-π(arene) interactions probably occur.
It also suggests that a wider range of Ge-N compounds
could be made by the treatment of digermynes with other
azides. The isolation of a large range of other heavier main
group element or even transition metal element amido or
imido by reactions of the recently synthesized species REER
Figure 5. Two molecular orbitals of Ar#Ge(SH)2NCH2 (HF/3-21G)28
showing π(N)C)-π(arene) interactions. The red and blue colors represent
two different phases and the blue (a) and red (b) colored regions indicated
by the arrows represent the interaction overlaps. Color code for atoms: gray
(C), blue (N), white (H), yellow (S), and black (Ge).
The plane of the -N)CH2 moiety is approximately
parallel to that of one phenyl (the angle between planes is
ca. 10.7°), and the distance between the N atom and phenyl
ring is about 3.2 Å, suggesting a π-π interaction between
the N)C unit and the phenyl ring.25 Attractive interactions
between π-systems have been recognized for over 20 years
as important factors in the structure of biological systems,
crystal packing, and molecular recognition.26 To date, most
(E )Si,29 Sn,29 Pb,29 Cr,30 Fe,31 Co,31 Zn,32 Cd,32 Hg,32
R
) alkyl, aryl, and silyl groups) with a variety of azides R′N3
n
(e.g., R′ ) Me3Si, Me3Sn, Bu3Sn, PhSCH2, 1-adamantyl,
C6H5, C6H3-2,6-Pri2) is probable.
Acknowledgment. We are grateful to the National Science
Foundation (CHE-0641020) for financial support.
(25) Harris, L. D.; Platts, J. A.; Tomkinson, N. C. O. Org. Biomol. Chem.
2003, 1, 457–459.
(26) Hunter, C. A.; Sanders, J. K. M. J. Am. Chem. Soc. 1990, 112, 5525–
5534; this reference to π-π interactions has been cited over 2100 times
to date.
Supporting Information Available: X-ray data (CIFs) for 3,
4, 5, and 6. This material is available free of charge via the Internet
at http://pubs.acs.org.
j
(27) (a) Oki, M.; Shionoiri, K.; Otake, K.; Ono, M.; Toyota, S. Bull. Chem.
j
Soc. Jpn. 1993, 66, 589–597. (b) Oki, M.; Hirose, T.; Maeda, K.;
Yanagawa, M.; Kataoka, Y.; Kojima, H.; Morita, N.; Toyota, S. Bull.
Chem. Soc. Jpn. 1997, 70, 859–868.
IC801713V
(28) Calculations were performed with the Gaussian 03 package (see below
for citation) and the representation of the molecular orbitals was
generated with the Chem3D program. Frisch, M. J.; Trucks, G. W.;
Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.;
Montgomery, J. A.; Vreven, Jr. 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.; Toyata, 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.; 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.; Ciolowski, 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 A.1.; Gaussian, Inc.: Pittsburgh,
PA, 2003.
(29) (a) Pu, L.; Twamley, B.; Power, P. P. J. Am. Chem. Soc. 2000, 122,
3524. (b) Phillips, A. D.; Wright, R. J.; Olmstead, M. M.; Power,
P. P. J. Am. Chem. Soc. 2002, 124, 5930. (c) Sekiguchi, A.; Kinjo,
R.; Ichinohe, M. Science. 2004, 305, 1755.
(30) Nguyen, T.; Sutton, A. D.; Brynda, M.; Fettinger, J. C.; Long, G. J.;
Power, P. P. Science. 2005, 310, 844.
(31) Nguyen, T.; Merrill, A.; Ni, C.; Lei, H.; Fettinger, J. C.; Ellis, B. D.;
Long, G. J.; Brynda, M.; Power, P. P. Angew. Chem., Int. Ed. 2008,
47, 9115.
(32) (a) Resa, I.; Carmona, E.; Gutierrez-Puebla, E.; Angeles, M. Science.
2004, 305, 1136. (b) Wang, Y.; Quillan, B.; Wei, P.; Wang, X.-J.;
Xie, Y.; King, R. B.; Schleyer, P. V. R.; Schaeffer, H. F.; Robinson,
G. H. J. Am. Chem. Soc. 2005, 758, 127. (c) Zhu, Z.; Wright, R. J.;
Olmstead, M. M.; Rivard, E.; Brynda, M.; Power, P. P. Angew. Chem.,
Int. Ed. 2006, 45, 5807. (d) Zhu, Z.; Brynda, M.; Fettinger, J. C.;
Power, P. P. J. Am. Chem. Soc. 2006, 128, 15068. (e) Zhu, Z.; Brynda,
M.; Wright, R. J.; Fischer, R. C.; Merrill, W. A.; Rivard, E.; Wolf,
R.; Fettinger, J. C.; Olmstead, M. M.; Power, P. P. J. Am. Chem. Soc.
2007, 129, 10847.
2470 Inorganic Chemistry, Vol. 48, No. 6, 2009