Azido derivatives of germanium(II) and tin(II): Syntheses and characterization of [(Mes)2DAP]GeN3, [(Mes)2DAP]SnN3, and the corresponding chloro analogues featuring heterocyclic six-π-electron ring systems (where [(Mes)2DAP] = {N(Mes)C(Me)}2CH)

Article abstract of DOI:10.1021/ic001078j

Chloro and azido germanium(II) and tin(II) 1,5-diazapentadienyl complexes have been investigated. The treatment of GeCl₂·(1,4-dioxane) or SnCl₂ with [(Mes)₂DAP]Li in a 1:1 molar ratio gave the corresponding germanium(II) or tin(II) chloro complexes [(Mes)₂DAP]MCl (where [(Mes)₂DAP] = 2,4-dimethyl-N,N′-bis(2,4,6-trimethylphenyl)1,5-diazapentadienyl; M = Ge or Sn). [(Mes)₂DAP]GeCl and [(Mes)₂DAP]SnCl are monomeric in the solid state. The C₃N₂M rings adopt a flattened boat conformation. The metathesis reaction between [(Mes)₂DAP]MCl and sodium azide affords the azido compounds [(Mes)₂DAP]MN₃ in excellent yield. X-ray analysis revealed that [(Mes)₂DAP]GeN₃ features an essentially linear azide moiety and a nearly planar heterocyclic C₃N₂Ge ring system. The azide group occupies a site above the C₃N₂Ge ring. The solid-state structure of the tin azide [(Mes)₂DAP]-SnN₃ shows weak intermolecular Sn...N contacts. It features a linear azide moiety and a planar heterocyclic C₃N₂Sn ring system. Both azides have long (M)N-N(N) bonds and short (MN)N-N bonds. IR spectra of [(Mes)₂DAP]GeN₃ and [(Mes)₂DAP]SnN₃ display v_asym(N₃) bands at 2062 and 2060 cm^-1, respectively. ¹⁴N NMR spectroscopic data show three well-separated signals for the nitrogen atoms of the azide moieties. Structural and spectroscopic data suggest the presence of very similar azide groups in the Ge(II) and Sn(II) adducts. The dominant canonical form of the metal-azide moiety is M-N-N≡N.

Full text of DOI:10.1021/ic001078j

1000
Inorg. Chem. 2001, 40, 1000-1005
Azido Derivatives of Germanium(II) and Tin(II): Syntheses and Characterization of
[(Mes)2DAP]GeN3, [(Mes)2DAP]SnN3, and the Corresponding Chloro Analogues Featuring
Heterocyclic Six-π-Electron Ring Systems (where [(Mes)2DAP] ) {N(Mes)C(Me)}2CH)
Ashley E. Ayers,† Thomas M. Klapo1tke,‡ and H. V. Rasika Dias*,†,§
Department of Chemistry and Biochemistry, The University of Texas at Arlington,
Arlington, Texas 76019-0065, Institute of Fundamental Studies, Hantana Road, Kandy, Sri Lanka, and
Department of Chemistry, Ludwig-Maximilians University of Munich, Butenandtstrasse 5-13 (Haus D),
D-81377 Munich, Germany
ReceiVed September 25, 2000
Chloro and azido germanium(II) and tin(II) 1,5-diazapentadienyl complexes have been investigated. The treatment
of GeCl2‚(1,4-dioxane) or SnCl2 with [(Mes)2DAP]Li in a 1:1 molar ratio gave the corresponding germanium(II)
or tin(II) chloro complexes [(Mes)2DAP]MCl (where [(Mes)2DAP] ) 2,4-dimethyl-N,N′-bis(2,4,6-trimethylphenyl)-
1,5-diazapentadienyl; M ) Ge or Sn). [(Mes)2DAP]GeCl and [(Mes)2DAP]SnCl are monomeric in the solid state.
The C3N2M rings adopt a flattened boat conformation. The metathesis reaction between [(Mes)2DAP]MCl and
sodium azide affords the azido compounds [(Mes)2DAP]MN3 in excellent yield. X-ray analysis revealed that
[(Mes)2DAP]GeN3 features an essentially linear azide moiety and a nearly planar heterocyclic C3N2Ge ring system.
The azide group occupies a site above the C3N2Ge ring. The solid-state structure of the tin azide [(Mes)2DAP]-
SnN3 shows weak intermolecular Sn‚‚‚N contacts. It features a linear azide moiety and a planar heterocyclic
C3N2Sn ring system. Both azides have long (M)N-N(N) bonds and short (MN)N-N bonds. IR spectra of
[(Mes)2DAP]GeN3 and [(Mes)2DAP]SnN3 display νasym(N3) bands at 2062 and 2060 cm-1, respectively. 14N NMR
spectroscopic data show three well-separated signals for the nitrogen atoms of the azide moieties. Structural and
spectroscopic data suggest the presence of very similar azide groups in the Ge(II) and Sn(II) adducts. The dominant
canonical form of the metal-azide moiety is M-N-NtN.
Introduction
GeN3,12 and the aminotroponiminatogermanium(II) and tin(II)
complexes [(n-Pr)2ATI]GeN3 and [(n-Pr)2ATI]SnN3 are the
8
There is considerable current interest in both theoretical and
practical aspects of covalent azides. Azido derivatives of carbon
represent the most widely studied group of compounds among
this family.1,2 Related azides of heavier group 14 members such
as those of silicon(IV) and tin(IV) are also fairly well known.3-5
For example, the chemistry of trimethylsilyl and trimethylstannyl
azides has been investigated extensively.4,6,7 In contrast, very
little is known about the azides of low-valent group 14
elements.4,5,8 One of the difficulties in isolating such species is
their tendency to decompose with the elimination of nitrogen,
leading to high-valent group 14 compounds. Apart from Pb-
(N3)2 (a well-known primary explosive),4,9-11 the recently
reported [HB(3,5-(CH3)2Pz)3]GeN3,5 [(C5H5)Co{P(O)(OEt)2}3]-
only well-characterized compounds of this type in the literature
to our knowledge.
† The University of Texas at Arlington.
The scarcity of information on azides of low-valent group
14 elements prompted us to explore this area in more detail.
Recently, we demonstrated the successful utility of the ami-
notroponiminato ligand system,13-17 which features a delocalized
‡ Ludwig-Maximilians University of Munich.
§ Institute of Fundamental Studies.
(1) The Chemistry of the Azido Group; Patai, S., Ed.; Interscience: New
York, 1971.
(2) Azides and Nitrenes: ReactiVity and Utility; Scriven, E. F. V., Ed.;
Academic: New York, 1984.
(9) The Merck Index, 11th ed.; Budavari, S., Ed.; Merck & Co., Inc.: New
Jersey, 1989; p 5274, and references therein.
(10) Choi, C. S.; Prince, E.; Garrett, W. L. Acta Crystallogr. 1977, B33,
3536.
(3) Thayer, J. S. Organometal. Chem. ReV. 1966, 1, 157.
(4) Tornieporth-Oetting, I. C.; Klapo¨tke, T. M. Angew. Chem., Int. Ed.
Engl. 1995, 34, 511.
(5) Filippou, A. C.; Portius, P.; Kociok-Ko¨hn, G. Chem. Commun. 1998,
2327, and references therein.
(6) Banister, A. J.; Hauptman, Z. V.; Passmore, J.; Wong, C.-M.; White,
P. S. J. Chem. Soc., Dalton Trans. 1986, 2371.
(7) Kricheldorf, H. R.; Schwarz, G.; Kaschig, J. Angew. Chem., Int. Ed.
Engl. 1977, 16, 550.
(11) Greenwood, N. N.; Earnshaw, A. Chemistry of the Elements, 2nd ed.;
Butterworth-Heinemann: Woburn, MA, 1998; p 417.
(12) Filippou, A. C.; Portius, P.; Kociok-Ko¨hn, G.; Albrecht, V. J. Chem.
Soc., Dalton Trans. 2000, 1759.
(13) Dias, H. V. R.; Jin, W.; Ratcliff, R. E. Inorg. Chem. 1995, 34, 6100.
(14) Dias, H. V. R.; Wang, Z.; Jin, W. Coord. Chem. ReV. 1998, 176, 67.
(15) Dias, H. V. R.; Wang, Z. J. Am. Chem. Soc. 1997, 119, 4650.
(16) Dias, H. V. R.; Jin, W. Inorg. Chem. 1996, 35, 6546.
(8) Ayers, A. E.; Marynick, D. S.; Dias, H. V. R. Inorg. Chem. 2000, 39,
4147.
10.1021/ic001078j CCC: $20.00 © 2001 American Chemical Society
Published on Web 01/25/2001

Azido Derivatives of Ge(II) and Sn(II)
Inorganic Chemistry, Vol. 40, No. 5, 2001 1001
(s), 1475 (m), 1435 (m), 1375 (s), 1292 (m), 1246 (s), 1223 (w), 1195
(s), 1145 (s), 1017 (s), 959 (w), 866 (s), 789 (s), 723 (m), 653 (w),
635 (m), 597 (w), 566 (m), 502 (m). Anal. Calcd for C23H29N2GeCl:
C, 62.56; H, 6.62; N, 6.34. Found: C, 62.32; H, 6.58; N, 6.25.
[(Mes)2DAP]SnCl. A diethyl ether solution (25 mL) of [(Mes)2DAP]H
(850 mg, 2.54 mmol) was treated with n-BuLi (1.59 mL, 1.6 M hexane
solution) at -78 °C. It was stirred for 0.5 h, warmed to room
temperature, and stirred an additional 0.5 h. This pale yellow solution
was then slowly added to a suspension of SnCl2 (482 mg, 2.54 mmol)
in diethyl ether (20 mL) at -78 °C. The mixture immediately turned
yellow. The low temperature was kept for a further 1 h, then it was
allowed to warm to room temperature and stirred overnight. After
overnight stirring all volatiles were removed under vacuum. The
remaining solid was extracted into toluene and filtered through Celite.
The toluene was removed under vacuum to yield a pale yellow solid
(750 mg, 61%). Recrystallization from hexane-toluene (2:1) at room
temperature gave X-ray quality crystals of [(Mes)2DAP]SnCl. Mp:
10-π-electron ligand backbone, to stabilize germanium(II) and
tin(II) azido derivatives.8 Spectroscopic data and theoretical
work indicated that Ge(II) and Sn(II) have essentially the same
effect on the azide group. In this paper, we describe the use of
the diazapentadienyl (also known as â-diketiniminato, â-diimine,
or â-iminoamine) ligand system,18-22 which features a delo-
calized six-π-electron ligand backbone, to obtain thermally
stable covalent azides of Ge(II) and Sn(II).14 Syntheses and
characterization of [(Mes)2DAP]MN3 (where [(Mes)2DAP] )
2,4-dimethyl-N,N′-bis(2,4,6-trimethylphenyl)-1,5-diazapentadi-
enyl; M ) Ge or Sn) as well as the corresponding chloro
analogues [(Mes)2DAP]MCl are reported.
Experimental Section
General Procedures. All manipulations were carried out under an
atmosphere of purified nitrogen either using standard Schlenk techniques
or in a Vacuum Atmospheres single station drybox equipped with a
-25 °C refrigerator. Solvents were purchased from commercial sources
and distilled from conventional drying agents prior to use. Glassware
was oven-dried at 150 °C overnight. The NMR spectra were recorded
at room temperature on a JEOL Eclipse 500 (1H, 500.16 MHz; 13C,
125.78 MHz) or JEOL Eclipse 400 spectrometer (119Sn, 149.08 MHz;
14N, 28.89 MHz). Proton and carbon chemical shifts are reported in
parts per million vs Me4Si. 119Sn and 14N NMR chemical shifts were
referenced relative to external Me4Sn and MeNO2, respectively. Infrared
spectra were recorded on a JASCO FT-IR 410 spectrometer. Raman
spectra were recorded using the solid samples on a Perkin-Elmer 2000
NIR FT-Raman spectrometer with 100 mW laser power (1064 nm, 90°,
25 °C). Melting points were obtained on a Mel-Temp II apparatus.
Elemental analyses were performed at the University of Texas at
Arlington using a Perkin-Elmer Model 2400 CHN analyzer. [(Mes)2DAP]-
H23 and GeCl2‚(1,4-dioxane)24 were synthesized as reported previously.
n-BuLi, SnCl2, and NaN3 were purchased from commercial sources
and used as received.
1
155-160 °C. H NMR (CDCl3): δ 1.82 (s, 6H, DAP-CH3), 2.13 (s,
6H, o-CH3), 2.28 (s, 6H, p-CH3), 2.44 (s, 6H, o-CH3), 5.29 (s, 1H,
DAP-CH), 6.90 (s, 2H, m-CH), 6.96 (s, 2H, m-CH). 13C{1H} NMR
(CDCl3): δ 19.1 (o-CH3), 19.7 (o-CH3), 20.8 (p-CH3), 23.3 (DAP-
CH3), 99.9 (DAP-CH), 129.1 (m-CH), 130.1 (m-CH), 131.8 (o-CCH3),
134.3 (o-CCH3), 135.7 (p-CCH3), 141.3 (Cipso), 165.3 (DAP-CN). 14
N
NMR (CD2Cl2): δ -186 (Νring). 119Sn NMR (CD2Cl2): δ -236. IR
(KBr, cm-1): 3466 (w), 2998 (w), 2917 (s), 1760 (w), 1734 (w), 1608
(m), 1540 (s), 1450 (s), 1371 (s), 1266 (s), 1219 (w), 1199 (s), 1145
(s), 1023 (s), 958 (w), 932 (w), 856 (s), 833 (w), 801 (m), 786 (m),
723 (w), 650 (w), 626 (w), 567 (m), 501 (m). Raman (cm-1): 3112
(w), 3008 (m), 2918 (s), 2857 (m), 2739 (w), 1608 (s), 1575 (w), 1538
(m), 1475 (w), 1443 (m), 1384 (m), 1306 (s), 1280 (m), 1267 (m),
1220 (s), 1156 (m), 1028 (w), 964 (w), 934 (w), 853 (w), 787 (w), 723
(w), 654 (m), 592 (w), 576 (s), 501 (s), 409 (m), 396 (m), 384 (m),
360 (m), 326 (w), 281 (s), 249 (m), 225 (w), 203 (w), 139 (s), 112 (s).
Anal. Calcd for C23H29N2SnCl: C, 56.65; H, 5.99; N, 5.74. Found: C,
56.81; H, 5.74; N, 5.56.
[(Mes)2DAP]GeN3. [(Mes)2DAP]GeCl (200 mg, 0.45 mmol) and
NaN3 (29 mg, 0.45 mmol) were mixed in THF (10 mL) at room
temperature. After the solution was stirred for 3 h, the THF was
removed under vacuum. The remaining solid was extracted into toluene
and filtered through Celite. Removal of toluene under vacuum gave a
pale yellow solid (170 mg, 83%). X-ray quality crystals of [(Mes)2DAP]-
GeN3 were grown from hexane-toluene (2:1) at room temperature.
Mp: 164-166 °C. 1H NMR (CDCl3): δ 1.83 (s, 6H, DAP-CH3), 2.11
(s, 6H, o-CH3), 2.29 (s, 6H, p-CH3), 2.43 (s, 6H, o-CH3), 5.36 (s, 1H,
DAP-CH), 6.91 (s, 2H, m-CH), 6.99 (s, 2H, m-CH). 13C{1H} NMR
(CDCl3): δ 18.2 (o-CH3), 19.0 (o-CH3), 20.8 (p-CH3), 22.7 (DAP-
CH3), 99.7 (DAP-CH), 129.2 (m-CH), 130.0 (m-CH), 132.7 (o-CCH3),
Caution: Covalent and ionic azides are very toxic, and covalent
azides are potentially explosive. Appropriate safety precautions should
be taken.
[(Mes)2DAP]GeCl. A diethyl ether solution (25 mL) of [(Mes)2DAP]H
(700 mg, 2.09 mmol) was treated with n-BuLi (1.31 mL, 1.6 M hexane
solution) at -78 °C. The colorless solution was stirred for 0.5 h, warmed
to room temperature, and stirred an additional 0.5 h. This solution was
then slowly added to a suspension of GeCl2‚(1,4-dioxane) (650 mg,
2.09 mmol) in diethyl ether (15 mL) at -78 °C. The mixture slowly
turned cloudy yellow. The low temperature was kept for a further 1 h,
then it was allowed to warm to room temperature and stirred overnight.
After overnight stirring all volatiles were removed under vacuum. The
remaining solid was extracted into toluene and filtered through Celite.
The toluene was removed under vacuum to yield [(Mes)2DAP]GeCl
as a pale yellow solid (610 mg, 66%). It was recrystallized from toluene
at room temperature. Mp: 171-174 °C. 1H NMR (CDCl3): δ 1.85 (s,
6H, DAP-CH3), 2.12 (s, 6H, o-CH3), 2.27 (s, 6H, p-CH3), 2.45 (s,
6H, o-CH3), 5.49 (s, 1H, DAP-CH), 6.90 (s, 2H, m-CH), 6.96 (s, 2H,
m-CH). 13C{1H} NMR (CDCl3): δ 19.2 (o-CH3), 19.9 (o-CH3), 20.8
(p-CH3), 22.8 (DAP-CH3), 100.3 (DAP-CH), 129.1 (m-CH), 130.1
(m-CH), 132.6 (o-CCH3), 135.1 (o-CCH3), 136.3 (p-CCH3), 139.4
(Cipso), 164.5 (DAP-CN). IR (KBr, cm-1): 2915 (s), 1607 (m), 1526
134.9 (o-CCH3), 136.5 (p-CCH3), 139.6 (Cipso), 164.9 (DAP-CN). 14
N
NMR (CD2Cl2): δ -291 (N2), -136 (N3), -215 (N4), -196 (Nring).
IR (KBr, cm-1): 3308 (m), 2919 (s), 2732 (w), 2576 (w), 2062 (s,
asym N3), 1609 (m), 1531 (s), 1477 (m), 1442 (m), 1361 (s), 1271
(m), 1251 (m), 1223 (w), 1197 (s), 1146 (s), 1020(s), 901 (w), 888
(w), 860 (s), 783 (s), 722 (w), 647 (m), 604 (w), 568 (m), 499 (m).
Raman (cm-1): 3091 (w), 3018 (m), 2989 (m), 2923 (s), 2857 (w),
2732 (w), 2059 (w, asym N3), 1610 (s), 1569 (w), 1532 (m), 1480 (w),
1448 (w), 1384 (m), 1307 (s), 1272 (w), 1254 (m), 1225 (s), 1160 (m),
1020 (w), 969 (w), 939 (w), 838 (w), 784 (w), 651 (w), 597 (w), 578
(s), 501 (s), 410 (s), 371 (m), 354 (w), 328 (w), 292 (m), 210 (m), 114
(s). Anal. Calcd for C23H29N5Ge: C, 61.65; H, 6.52; N, 15.63. Found:
C, 61.28; H, 6.73; N, 15.49.
[(Mes)2DAP]SnN3. [(Mes)2DAP]SnCl (200 mg, 0.41 mmol) and
NaN3 (27 mg, 0.41 mmol) were mixed in THF (10 mL) at room
temperature. After the solution was stirred for 3 h, the THF was
removed under vacuum. The remaining solid was extracted into toluene
and filtered through Celite. Removal of toluene under vacuum gave
[(Mes)2DAP]SnN3 as a white solid (180 mg, 89%). It was recrystallized
from hexane-toluene (2:1) at room temperature. Mp: 146-148 °C.
1H NMR (CDCl3): δ 1.82 (s, 6H, DAP-CH3), 2.11 (s, 6H, o-CH3),
2.29 (s, 6H, p-CH3), 2.44 (s, 6H, o-CH3), 5.21 (s, 1H, DAP-CH), 6.91
(s, 2H, m-CH), 6.99 (s, 2H, m-CH). 13C{1H} NMR (CDCl3): δ 18.3
(o-CH3), 18.9 (o-CH3), 20.8 (p-CH3), 23.2 (DAP-CH3), 99.8 (DAP-
(17) Dias, H. V. R.; Jin, W. J. Am. Chem. Soc. 1996, 118, 9123.
(18) Clegg, W.; Cope, E. K.; Edwards, A. J.; Mair, F. S. Inorg. Chem.
1998, 37, 2317.
(19) Clegg, W.; Coles, S. J.; Cope, E. K.; Mair, F. S. Angew. Chem., Int.
Ed. 1998, 37, 796.
(20) Parks, J. E.; Holm, R. H. Inorg. Chem. 1968, 7, 1408.
(21) Hitchcock, P. B.; Lappert, M. F.; Liu, D.-S. J. Chem. Soc., Chem.
Commun. 1994, 1699.
(22) Radzewich, C. E.; Coles, M. P.; Jordan, R. F. J. Am. Chem. Soc. 1998,
120, 9384, and references therein.
(23) Budzelaar, P. H. M.; Oort, A. B. v.; Orpen, A. G. Eur. J. Inorg. Chem.
1998, 1485.
(24) Fjeldberg, T.; Haaland, A.; Schilling, B. E.; Lappert, M. F.; Thorne,
A. J. J. Chem. Soc., Dalton Trans. 1986, 1551.

1002 Inorganic Chemistry, Vol. 40, No. 5, 2001
Ayers et al.
Table 1. Crystal Data and Summary of Data Collection and Refinement
[(Mes)2DAP]GeCl
[(Mes)2DAP]SnCl
[(Mes)2DAP]GeN3
[(Mes)2DAP]SnN3
formula
fw
space group
a, Å
b, Å
C23H29ClN2Ge
441.52
C2/c
26.967(4)
12.369(4)
14.555(1)
90
114.144(6)
90
C23H29ClN2Sn
487.62
Pnma
6.881(1)
25.530(5)
12.770(3)
90
90
90
2243.5(8)
4
C23H29N5Ge
448.10
P21/n
7.469(2)
23.637(5)
12.788(4)
90
91.13(3)
90
C23H29N5Sn
494.20
P21/c
10.821(1)
15.254(2)
14.923(1)
90
108.285(9)
90
c, Å
R, deg
â, deg
γ, deg
vol, Å3
4430.2(17)
8
2257.4(10)
4
2338.8(5)
4
Z
T, K
203(2)
0.710 73
1.324
1.513
1.069
0.0306, 0.0794
0.0342, 0.0818
203(2)
0.710 73
1.444
1.268
1.032
0.0294, 0.0737
0.0373, 0.0778
203(2)
0.710 73
1.319
1.375
1.039
0.0473, 0.1130
0.0678, 0.1242
228(2)
0.710 73
1.404
1.110
1.058
0.0442, 0.1077
0.0464, 0.1098
λ (Mo KR ), Å
density (calc), g/cm3
abs coeff, mm-1
GOOF
R1, wR2a [I>2σ(I)]
R1, wR2 [all data]
a R1 ) ∑||Fo| - |Fc||/∑|Fo|. wR2 ) [∑[w(Fo - Fc2)2]/∑[w(Fo )2]]1/2
.
2
2
Table 2. Selected Bond Lengths [Å] and Angles [deg] for
[(Mes)2DAP]GeCl
CH), 129.2 (m-CH), 130.0 (m-CH), 131.8 (o-CCH3), 134.0 (o-CCH3),
135.9 (p-CCH3), 141.2 (Cipso), 165.8 (DAP-CN). 14N NMR (CD2Cl2):
δ -292 (N2), -136 (N3), -223 (N4), -186 (Nring). 119Sn NMR
(CD2Cl2): δ -276; IR (KBr, cm-1): 3347 (w), 2916 (s) 2060 (s, asym
N3), 1608 (m), 1531 (s), 1475 (m), 1450 (m), 1373 (s), 1310 (s), 1262
(s), 1220 (w), 1197 (s), 1146 (s), 1020 (s), 959 (w), 932 (w), 893 (w),
860 (s), 829 (w), 803 (m), 632 (w), 594 (w), 566 (m), 495 (m). Raman
(cm-1): 3102 (w), 3013 (m), 2919 (s), 2857 (m), 2731 (w), 2070 (w),
2058 (w, asym N3), 1609 (s), 1554 (m), 1478 (m), 1440 (m), 1382 (s),
1305 (s), 1279 (m), 1264 (m), 1222 (s), 1157 (m), 1024 (w), 963 (w),
934 (w), 827 (w), 722 (w), 652 (w), 595 (w), 577 (s), 496 (s), 403 (m),
359 (m), 330 (s), 279 (w), 258 (s), 235 (w), 174 (w), 133 (w), 109 (s).
Anal. Calcd for C23H29N5Sn: C, 55.90; H, 5.91; N, 14.17. Found: C,
55.63; H, 5.77; N, 13.94.
X-ray Structure Determination. A suitable crystal covered with a
layer of hydrocarbon oil was selected and attached to a glass fiber and
immediately placed in the low-temperature nitrogen stream. Data
collections were carried out at low temperature on a Siemens P4
diffractometer equipped with a LT-2A device for low-temperature work
and graphite-monochromated Mo KR radiation (λ ) 0.710 73 Å). The
unit cell parameters of [(Mes)2DAP]GeCl, [(Mes)2DAP]SnCl, [(Mes)2-
DAP]GeN3, and [(Mes)2DAP]SnN3 were determined by least-squares
refinement of 38, 56, 39, and 41 reflections, respectively. Three standard
reflections were measured at every 97 data points to check for crystal
deterioration and/or misalignment. No significant deterioration in
intensity was observed. Structures were solved by direct methods
followed by successive cycles of full-matrix least-squares refinement
on F2 and difference Fourier analysis. All the non-hydrogen atoms were
refined anisotropically. The hydrogen atoms were included at calculated
positions. Software programs and the sources of scattering factors are
contained in the Bruker SHELXTL 5.1 software package provided by
Bruker Analytical X-ray Instruments, Inc. Some details of data
collection and refinement are given in Table 1. Selected bond distances
and angles are given in Tables 2-5.
Ge-N(1)
Ge-N(5)
Ge-Cl
N(1)-C(2)
N(1)-C(8)
C(2)-C(3)
1.958(2)
1.980(2)
2.328(1)
1.348(4)
1.444(4)
1.382(4)
C(2)-C(6)
C(3)-C(4)
C(4)-N(5)
C(4)-C(7)
N(5)-C(17)
1.505(4)
1.399(4)
1.330(4)
1.501(4)
1.443(4)
N(1)-Ge-N(5)
N(1)-Ge-Cl
90.44(9)
96.19(7)
93.39(7)
120.0(2)
123.3(1)
116.7(1)
123.1(3)
118.8(3)
118.1(3)
126.3(3)
N(5)-C(4)-C(3)
N(5)-C(4)-C(7)
C(3)-C(4)-C(7)
C(4)-N(5)-C(17)
C(4)-N(5)-Ge
C(17)-N(5)-Ge
C(13)-C(8)-N(1)
C(9)-C(8)-N(1)
C(22)-C(17)-N(5)
C(18)-C(17)-N(5)
122.4(3)
119.2(3)
118.4(2)
121.5(2)
125.3(2)
113.3(2)
120.6(2)
118.7(2)
120.4(3)
118.4(3)
N(5)-Ge-Cl
C(2)-N(1)-C(8)
C(2)-N(1)-Ge
C(8)-N(1)-Ge
N(1)-C(2)-C(3)
N(1)-C(2)-C(6)
C(3)-C(2)-C(6)
C(2)-C(3)-C(4)
Table 3. Selected Bond Lengths [Å] and Angles [deg] for
[(Mes)2DAP]SnCl
Sn-N(0A)
Sn-N
2.162(3)
2.162(3)
2.468(1)
1.330(5)
N-C(5)
1.437(5)
1.392(4)
1.506(5)
1.392(4)
C(2)-C(3)
C(2)-C(4)
C(3)-C(2A)
Sn-Cl
N-C(2)
N(0A)-Sn-N
N(0A)-Sn-Cl
N-Sn-Cl
C(2)-N-C(5)
C(2)-N-Sn
C(5)-N-Sn
87.38(17)
90.52(9)
90.52(9)
119.6(3)
122.1(2)
118.3(2)
N-C(2)-C(3)
N-C(2)-C(4)
C(3)-C(2)-C(4)
C(2A)-C(3)-C(2)
C(10)-C(5)-N
C(6)-C(5)-N
124.9(4)
119.2(3)
115.7(4)
129.3(5)
119.2(3)
120.5(4)
position. Overall, the 1H NMR and 13C NMR spectra of [(Mes)2-
DAP]GeCl are consistent with a Cs-symmetric structure and
restricted rotation around the N-Mes bonds.
Crystals of [(Mes)2DAP]GeCl were studied by X-ray dif-
fraction, and the thermal ellipsoid plot is shown in Figure 1.
[(Mes)2DAP]GeCl has a monomeric structure. The heterocyclic
C3N2Ge ring is not planar. The germanium atom is displaced
from the diazapentadienyl ring plane by about 0.58 Å. The
Ge-Cl distance is slightly shorter than the corresponding
distance of [(i-Pr)2ATI]GeCl (2.368(2) Å),15 whereas the Ge-N
distances are essentially identical between the two systems.
The tin analogue [(Mes)2DAP]SnCl was synthesized from
SnCl2 and [(Mes)2DAP]Li. The 1H NMR and 13C NMR spectra
are essentially identical to those of [(Mes)2DAP]GeCl, suggest-
ing very similar solution structures. The 14N NMR spectrum
displays a broad peak at δ -186. It can be assigned to the
Results and Discussion
The synthesis of the chloro adduct [(Mes)2DAP]GeCl was
achieved by the treatment of GeCl2‚(1,4-dioxane) with [(Mes)2-
DAP]Li in a 1:1 molar ratio in Et2O. It was isolated as a pale
yellow solid in 66% yield (Scheme 1). The 1H NMR spectrum
of [(Mes)2DAP]GeCl taken in CDCl3 shows a singlet at δ 5.49,
which can be assigned to the diazapentadienyl ring proton. The
corresponding signal for the free ligand appears at a significantly
upfield position (δ 4.29).23 In contrast to the free ligand, the
ortho methyl groups of [(Mes)2DAP]GeCl appear as two broad,
1
well-separated singlets in the H NMR spectrum. A similar
pattern was observed for the signals due to protons at the meta-

Azido Derivatives of Ge(II) and Sn(II)
Inorganic Chemistry, Vol. 40, No. 5, 2001 1003
Table 4. Selected Bond Lengths [Å] and Angles [deg] for
[(Mes)2DAP]GeN3
Ge-N(1)
1.972(4)
1.975(4)
1.979(5)
1.199(7)
1.152(8)
1.322(6)
1.451(6)
N(5)-C(4)
N(5)-C(17)
C(2)-C(3)
C(2)-C(6)
C(3)-C(4)
C(4)-C(7)
1.323(6)
1.449(6)
1.396(7)
1.503(7)
1.388(7)
1.493(7)
Ge-N(5)
Ge-N(2)
N(2)-N(3)
N(3)-N(4)
N(1)-C(2)
N(1)-C(8)
N(1)-Ge-N(5)
N(1)-Ge-N(2)
N(5)-Ge-N(2)
N(3)-N(2)-Ge
N(4)-N(3)-N(2)
C(2)-N(1)-C(8)
C(2)-N(1)-Ge
C(8)-N(1)-Ge
90.13(17) N(1)-C(2)-C(3)
96.08(19) N(1)-C(2)-C(6)
96.45(19) C(3)-C(2)-C(6)
122.9(5)
119.2(4)
117.9(5)
127.3(5)
122.5(5)
118.9(4)
118.5(5)
120.7(4)
117.8(4)
Figure 1. Molecular structure of [(Mes)2DAP]GeCl. Hydrogen atoms
have been omitted for clarity.
121.1(4)
176.3(6)
121.2(4)
127.4(3)
111.3(3)
C(4)-C(3)-C(2)
N(5)-C(4)-C(3)
N(5)-C(4)-C(7)
C(3)-C(4)-C(7)
C(13)-C(8)-N(1)
C(9)-C(8)-N(1)
C(4)-N(5)-C(17) 121.0(4)
C(4)-N(5)-Ge
C(17)-N(5)-Ge
127.7(3)
111.2(3)
C(18)-C(17)-N(5) 118.2(4)
C(22)-C(17)-N(5) 120.5(4)
Table 5. Selected Bond Lengths [Å] and Angles [deg] for
[(Mes)2DAP]SnN3
Sn-N(1)
2.177(4)
2.198(5)
2.210(4)
1.332(7)
1.443(7)
1.208(8)
1.382(8)
C(2)-C(6)
N(3)-N(4)
C(3)-C(4)
C(4)-N(5)
C(4)-C(7)
N(5)-C(17)
1.514(8)
Sn-N(2)
1.109(8)
1.397(8)
1.318(7)
1.503(8)
1.442(7)
Figure 2. Molecular structure of [(Mes)2DAP]SnCl. Hydrogen atoms
have been omitted for clarity.
Sn-N(5)
N(1)-C(2)
N(1)-C(8)
N(2)-N(3)
C(2)-C(3)
[(Me3Si)2N]2Sn, δ 759),26 whereas four-coordinate chloro tin-
(II) complexes show 119Sn signals at relatively upfield regions
(e.g., [HB(Pz)3]SnCl, δ -569; [HB(3,5-Me2Pz)3]SnCl, δ -567).25
The X-ray crystal structure of [(Mes)2DAP]SnCl and the
atom-numbering scheme is shown in Figure 2. The [(Mes)2DAP]-
SnCl molecule has Cs symmetry with a crystallographically
imposed mirror plane containing Cl, Sn, and C3. The hetero-
cyclic C3N2Sn ring is not planar. The tin atom is displaced from
the diazapentadienyl ring plane by 0.70 Å. The Sn-Cl and
Sn-N distances are 2.468(1) and 2.162(3) Å, respectively. The
Sn-Cl distance is shorter than the corresponding distances of
[(i-Pr)2ATI]SnCl (2.542(2) Å)17 and [HB(3,5-Me2Pz)3]SnCl
(2.629(1) Å).27,28 There are no intermolecular interactions
between the Sn atoms (closest Sn‚‚‚Sn separation is about 5.63
Å) or Sn and Cl atoms (closest intermolecular Sn‚‚‚Cl contact
is about 5.54 Å) of neighboring [(Mes)2DAP]SnCl molecules.
The treatment of [(Mes)2DAP]GeCl or [(Mes)2DAP]SnCl
with NaN3 in THF led to the corresponding azide [(Mes)2DAP]-
GeN3 or [(Mes)2DAP]SnN3 in excellent yield (Scheme 2). These
Ge(II) and Sn(II) azides are stable in the absence of moisture
and air. They possess considerable thermal stability, with melting
points above 145 °C. Both [(Mes)2DAP]GeN3 and [(Mes)2DAP]-
SnN3 are very soluble in solvents such as toluene, CH2Cl2, and
THF.
N(1)-Sn-N(2)
N(1)-Sn-N(5)
N(2)-Sn-N(5)
C(2)-N(1)-C(8)
C(2)-N(1)-Sn
C(8)-N(1)-Sn
N(3)-N(2)-Sn
N(1)-C(2)-C(3)
N(1)-C(2)-C(6)
C(3)-C(2)-C(6)
94.49(19) C(2)-C(3)-C(4)
85.17(17) N(5)-C(4)-C(3)
88.69(18) N(5)-C(4)-C(7)
129.7(5)
123.8(5)
119.2(5)
116.9(5)
121.6(5)
127.7(4)
110.5(3)
121.5(5)
117.9(5)
119.5(5)
126.7(4)
113.3(3)
124.1(4)
125.6(5)
118.4(5)
115.8(5)
C(3)-C(4)-C(7)
C(4)-N(5)-C(17)
C(4)-N(5)-Sn
C(17)-N(5)-Sn
C(13)-C(8)-N(1)
C(9)-C(8)-N(1)
C(18)-C(17)-N(5) 118.5(5)
C(22)-C(17)-N(5) 120.6(5)
N(4)-N(3)-N(2) 176.0(7)
Scheme 1
[(Mes)2DAP]GeN3 and [(Mes)2DAP]SnN3 were characterized
1
by NMR and IR spectroscopy. H and 13C NMR spectra are
very similar to the corresponding spectra of the chloro adduct,
indicating the presence of a Cs-symmetric species in solution.
The 119Sn NMR spectrum of [(Mes)2DAP]SnN3 exhibits a
resonance at δ -276. This shows an upfield shift relative to
the chloro analogue [(Mes)2DAP]SnCl (δ -236), perhaps as a
result of the lower effective electronegativity of the azido moiety
nitrogens of the C3N2Sn ring. This may be compared to the
chemical shift of δ -199 for the nitrogen atoms of the
aminotroponiminato derivative [(n-Pr)2ATI]SnCl. This com-
pound features a heterobicyclic C7N2Sn ring system. The 119Sn
NMR spectrum of [(Mes)2DAP]SnCl shows a signal at δ
-236. This resonance appears at the region expected for
three-coordinate tin atoms, e.g., [(i-Pr)2ATI]SnCl, δ -68;17 [(n-
Pr)2ATI]SnCl, δ -84; [H2B(Pz)2]SnCl, δ -307.25 Two-
coordinate tin(II) adducts show 119Sn signals at significantly
higher chemical shift values (e.g., {[(i-Pr)2ATI]Sn}+, δ 734;17
(25) Reger, D. L.; Knox, S. J.; Huff, M. F.; Rheingold, A. L.; Haggerty,
B. S. Inorg. Chem. 1991, 30, 1754.
(26) Wrackmeyer, B.; Schiller, J. Z. Naturforsch. 1992, 47B, 662.
(27) Cowley, A. H.; Geerts, R. L.; Nunn, C. M.; Carrano, C. J. J.
Organomet. Chem. 1988, 341, C27.
(28) See also for a related Sn(II) chloride: Hitchcock, P. B.; Hu, J.; Lappert,
M. F.; Layh, M.; Liu, D.-S.; Severn, J. R.; Shun, T. Ann. Quim. Int.
Ed. 1996, 92, 186.

1004 Inorganic Chemistry, Vol. 40, No. 5, 2001
Ayers et al.
Scheme 2
Figure 3. Molecular structure of [(Mes)2DAP]GeN3. Hydrogen atoms
have been omitted for clarity.
Table 6. 14N NMR Data (CD2Cl2, 25 °C, Relative to δ(CH3NO2) )
0.00), 119Sn NMR Data (CD2Cl2, 25 °C, Relative to δ(Me4Sn) )
0.00), and Selected Infrared Spectroscopic Data (KBr Pellet, cm-1
)
of [(Mes)2DAP]MX and [(n-Pr)2ATI]MX Adducts (where M ) Ge
or Sn, X ) Cl or N3)a
compound
nitrogen-14
tin-119
ν
asym(N3)
2062
[(Mes)2DAP]GeN3 -291 (N2); -136 (N3);
-215 (N4); -196 (Nring
)
)
Figure 4. Molecular structure of [(Mes)2DAP]SnN3. Hydrogen atoms
have been omitted for clarity.
[(Mes)2DAP]SnN3 -292 (N2); -136 (N3);
-223 (N4); -186 (Nring
-276.2
-236.0
2060
[(Mes)2DAP]SnCl -186 (Nring
)
[(n-Pr)2ATI]GeN3 -250 (N2); -135 (N3);
2048
2039
-213, -230 (N4, Nring
)
)
[(n-Pr)2ATI]SnN3 -256 (N2); -136 (N3);
-202, -217 (N4, Nring
[(n-Pr)2ATI]SnCl -199 (Nring
-122.4
-83.7
)
a Connectivity: (Nring)2M-N(2)-N(3)-N(4).
compared to the chloride.29-31 A similar trend has been observed
in other tin compounds, e.g., [(n-Pr)2ATI]SnCl (δ -84), [(n-
Pr)2ATI]SnN3 (δ -122), [Fe(CO)2(Cp)]2SnCl2 (δ 550.5), and
[Fe(CO)2(Cp)]2Sn(N3)2 (δ 520.9).30
IR spectra of [(Mes)2DAP]GeN3 and [(Mes)2DAP]SnN3 in
KBr display strong absorption bands at 2062 and 2060 cm-1
,
respectively. These bands can be assigned to the N3 asymmetric
stretching vibrations.1,3 It is also possible to observe these bands
as very weak signals in the Raman spectra (2059 and 2058 cm-1,
respectively). The IR spectra of [(n-Pr)2ATI]GeN3 and [(n-Pr)2-
ATI]SnN3 also show νasym(N3) bands in the same region. Neither
infrared nor Raman spectra were useful for clearly identifying
the νsym(N3) band. This vibration is expected in the 1350-1250
cm-1 region.12,30 Raman spectra of the chloro and the azido tin
adducts [(Mes)2DAP]SnCl and [(Mes)2DAP]SnN3 show es-
sentially identical peaks in this region.
We have also studied [(Mes)2DAP]GeN3 and [(Mes)2DAP]-
SnN3 using 14N NMR spectroscopy. The 14N chemical shift
values are summarized in Table 6. The assignment of individual
resonances to different nitrogen atoms (connectivity (Nring)2M-
N2-N3-N4) was based on previous work on covalent azides.32
These spectra show three well-resolved signals for the azide
moiety. This suggests that the interaction between the azide
group and Ge(II) or Sn(II) is predominantly covalent in nature.
Figure 5. View of [(Mes)2DAP]SnN3 showing intermolecular Sn‚‚‚N
contacts. Only selected atoms have been included.
Furthermore, chemical shift values are nearly identical between
the germanium and tin adducts. This, combined with the IR
data, indicates that the Ge(II) and Sn(II) ions have similar effects
on the azide moiety. We have also examined the aminotropon-
iminato adducts [(n-Pr)2ATI]GeN3 and [(n-Pr)2ATI]SnN3 using
14N NMR spectroscopy (Table 6). Again, the three azide
nitrogens resonate at different chemical shift values. Due to peak
broadness and closeness, we could not assign chemical shift
values unambiguously to the N(ring) and N(4) atoms. However,
14N NMR spectroscopic data of [(n-Pr)2ATI]MN3 are in good
agreement with those of [(Mes)2DAP]MN3 adducts.
[(Mes)2DAP]GeN3 and [(Mes)2DAP]SnN3 were also char-
acterized by X-ray crystallography, and the molecular structures
are illustrated in Figures 3 and 4, respectively. [(Mes)2DAP]-
GeN3 has a monomeric structure. The six-membered C3N2Ge
ring is significantly more planar compared to that of the chloro
analogue. The germanium atom is displaced from the diaza-
pentadienyl ring plane by about 0.29 Å. The Ge-N(azide) and
(29) Li, Y.; Xiao, H. Huaxue Xuebao 1993, 51, 313.
(30) Hampden-Smith, M. J.; Lei, D.; Duesler, E. N. J. Chem. Soc., Dalton
Trans. 1990, 2953.
(31) Schulz, A.; Tornieporth-Oetting, I. C.; Klapo¨tke, T. M. Inorg. Chem.
1995, 34, 4343.
(32) Geissler, P.; Klapotke, T. M.; Kroth, H.-J. Spectrochim. Acta 1995,
51A, 1075.

Azido Derivatives of Ge(II) and Sn(II)
Inorganic Chemistry, Vol. 40, No. 5, 2001 1005
Figure 6. Side view of [(Mes)2DAP]GeCl (top left), [(Mes)2DAP]SnCl (top right), [(Mes)2DAP]GeN3 (bottom left), and [(Mes)2DAP]SnN3 (bottom
right) showing C3N2M ring and geometry at Ge and Sn. Only selected atoms have been included.
Ge-N(ring) bond distances are very similar. They are 1.972-
(4) Å and 1.975(4), 1.979(5) Å, respectively. The Ge-N(azide)
bond distance is shorter than those found in the three-coordinate
germanium adduct [(n-Pr)2ATI]GeN3 (2.047(2) Å)8 or four-
coordinate complexes [HB(3,5-(CH3)2Pz)3]GeN3 (2.262(2) Å)5
and [(C5H5)Co{P(O)(OEt)2}3]GeN3 (2.094(7) Å).12 The azide
group of [(Mes)2DAP]GeN3 is almost linear, as evident from
the N-N-N bond angles of 176.3(6)°. The N-N bond
distances of [(Mes)2DAP]GeN3 are 1.199(7) and 1.152(8) Å.
The corresponding N-N bond distances of [(n-Pr)2ATI]GeN3
are 1.197(3) and 1.144(4) Å.8
In contrast to the germanium adduct, the tin analogue
[(Mes)2DAP]SnN3 shows weak intermolecular Sn‚‚‚N2 contacts
(2.91 Å) in the solid state (Figure 5). This Sn‚‚‚N contact
between neighboring molecules is significantly longer than the
Sn-N2 bond distance (2.198(5) Å). The Sn-N(azide) bond
length is comparable to that observed for [(n-Pr)2ATI]SnN3
(2.241(4) Å). The six-membered C3N2Sn ring is planar. The
azide moiety is essentially linear (N-N-N 176.0(7)°). The two
N-N bond distances are 1.208(8) and 1.109(8) Å.
calculations on [(Me)2ATI]MN3 indicate that the trans arrange-
ments are only very slightly less stable.8 Overall, the structural
data of [(Mes)2DAP]GeN3 and [(Mes)2DAP]SnN3 suggest that
the dominant canonical form of the M-azide moiety is M-N-
NtN. This is consistent with the results from theoretical
calculations.8
In summary, this work shows that germanium(II) and tin(II)
azide derivatives can be isolated as thermally stable solids using
the [(Mes)2DAP]- ligand system. [(Mes)2DAP]GeN3 and [(Mes)2-
DAP]SnN3 represent a rare group of covalent azides that feature
low-valent group 14 elements. Both germanium(II) and tin(II)
ions have similar effects on the azide moiety. This is in good
agreement with the theoretical work.
Acknowledgment. We thank The Robert A. Welch Founda-
tion for support of this work. We also thank the National Science
Foundation (CHE-9601771) for providing funds to purchase the
500 MHz NMR spectrometer. We are deeply grateful to Dr.
Konstantin Karaghiosoff and Dr. Burkhard Krumm for recording
tin-119 NMR, nitrogen-14 NMR, and Raman spectra. We are
also thankful to Dr. Hongming Zhang (SMU) for collecting
X-ray data of [(Mes)2DAP]SnN3.
Figure 6 shows a side view of the four adducts described
above. The germanium and tin centers adopt a pyramidal
geometry, as evident from the sum of the bond angles at
germanium (281°) and tin (268°). The azido tin adduct has the
most planar C3N2M ring, whereas the corresponding chloride
shows the greatest deviation from planarity. The azide groups
occupy a site above the C3N2M ring system (cis). DFT
Supporting Information Available: X-ray crystallographic files
for [(Mes)2DAP]GeCl, [(Mes)2DAP]SnCl, [(Mes)2DAP]GeN3, and
[(Mes)2DAP]SnN3 in CIF format are available free of charge via the
Internet at http:// pubs.acs.org.
IC001078J