Facile formation of rare terminal chalcogenido germanium complexes with alkylamidinates as supporting ligands

Article abstract of DOI:10.1021/ja9719891

The first characterized amidinate complexes of Ge have been prepared using alkylamidinates as ancillary ligands. Spectroscopic and structural characterization of the two complexes, (CyNC(Me)NCy)₂Ge(II) (1) and (CyNC((t)Bu)NCy)₂Ge(II) (2) (Cy = cyclohexyl), revealed that the Ge coordination geometry is distorted tetrahedral in which one of the vertices is occupied by a lone pair of electrons. Both 1 and 2 exhibited one bidentate and one monodentate ('dangling') ligand. Rapid oxidative addition of chalcogen atom sources (styrene sulfide and Se) to these complexes resulted in a series of rare terminal chalcogenido complexes with the formulas (CyNC(R)NCy)₂Ge=Ch [R = Me, Ch = S (3), Se(4); R = (t)Bu, Ch = S (5), Se(6)]. The spectroscopic data and X-ray structure of G revealed a terminal Ge=Se complex. Mixed amidinato-amido analogues were similarly obtained. For example, [(CyNC(R)NCy)Ge(II)[N(SiMe₃)₂] (R = Me, (t)Bu) react to yield the corresponding terminal chalcogenido complexes. In the case of [(CyNC(Me)NCy)Ge(II)[N(SiMe₃)₂]Se (10), a crystallographic study confirmed the presence of a terminal Ge=Se bond.

Full text of DOI:10.1021/ja9719891

J. Am. Chem. Soc. 1997, 119, 10359-10363
10359
Facile Formation of Rare Terminal Chalcogenido Germanium
Complexes with Alkylamidinates as Supporting Ligands
Stephen R. Foley, Corinne Bensimon, and Darrin S. Richeson*
Contribution from the Department of Chemistry, UniVersity of Ottawa,
Ottawa, Ontario, Canada K1N 6N5
ReceiVed June 16, 1997X
Abstract: The first characterized amidinate complexes of Ge have been prepared using alkylamidinates as ancillary
ligands. Spectroscopic and structural characterization of the two complexes, (CyNC(Me)NCy)2GeII (1) and
(CyNC(tBu)NCy)2GeII (2) (Cy ) cyclohexyl), revealed that the Ge coordination geometry is distorted tetrahedral in
which one of the vertices is occupied by a lone pair of electrons. Both 1 and 2 exhibited one bidentate and one
monodentate (“dangling”) ligand. Rapid oxidative addition of chalcogen atom sources (styrene sulfide and Se) to
these complexes resulted in a series of rare terminal chalcogenido complexes with the formulas (CyNC(R)-
NCy)2GedCh [R ) Me, Ch ) S (3), Se(4); R ) tBu, Ch ) S (5), Se(6)]. The spectroscopic data and X-ray structure
of 6 revealed a terminal GedSe complex. Mixed amidinato-amido analogues were similarly obtained. For example,
[(CyNC(R)NCy)GeII[N(SiMe3)2] (R ) Me, tBu) react to yield the corresponding terminal chalcogenido complexes.
In the case of [(CyNC(Me)NCy)GeII[N(SiMe3)2]Se (10), a crystallographic study confirmed the presence of a terminal
GedSe bond.
Introduction
reported, and the Se and Te derivatives have been structurally
characterized.5 Bulky alkylamidinate ligands have been dem-
onstrated to provided the supporting environment for a structur-
ally characterized terminal SndS complex, SdSn(CyNC(tBu)-
NCy)2, which is unique in the absence of macrocyclic supporting
ligation.6
Coincident with our interest in the formation of multiple
bonds between the heavy main group elements, we are exploring
the effects of ligand geometry on the coordination environments
of post transition elements. Part of this systematic study is based
on the use of amidinate ligands in the chemistry of group 14
metals. Specifically, we have been exploring the ability of these
ligands to stabilize unusual structures and functions in Ge(II/
IV) and Sn(II/IV) complexes. Amidinate anions exhibit ver-
satility in binding modes (Chart 1) and, through changes of
substituents, should present a flexible system for tuning the
effects of changes in steric bulk and electronic properties of
the supporting ligand on the product compounds.9
Amidinato complexes of tin have been prepared with the
metal in both the divalent and tetravalent oxidation states.6,10-18
However, to our knowledge, there are no structurally character-
ized germanium analogues. Moreover, these results have been,
by and large, limited to use of N,N′-bis(trimethylsilyl)benza-
midinate-based ligands, [Me3SiNC(C6H4R)NSiMe3].10-17 We
were interested in the possibility of overcoming this limitation
and investigating the effects of changing the various substitu-
Recent advances in the preparation of complexes with
terminal multiple bonds between the chalcogen elements and
Ge or Sn have provided significant results to challenge the idea
that such features are unique to the lighter congeners of these
elements.1-7 For example, isolation and structural characteriza-
tion of species possessing GedS, GedSe, and GedTe moieties
have been achieved by virtue of the kinetic stabilization provided
by having sterically protecting groups on the Ge center (e.g.,
Tbt(CH(SiMe3)2)GedTe).2,8 Additional thermodynamic stabil-
ity has been applied through the coordination of a base to the
group 14 center and was employed to stabilize [η3-{(µ-tBuN)2-
(SiMeNtBu)2}]GeS.3 A series of Sn and Ge terminal chalco-
genido complexes were prepared with the versatile supporting
ligand octamethyldibenzotetraaza[14]annulene (Me8taa2-).4 The
complexes [η4-Me8taa]GedE (E ) S, Se, Te) were all structur-
ally characterized.4b The series of compounds bis[(2-pyridyl)-
bis(trimethylsilyl)methyl]GedE (E ) S, Se, Te) has been
X Abstract published in AdVance ACS Abstracts, October 15, 1997.
(1) For general reviews of multiple bonding to Ge, see: (a) Escudie, J.;
Couret, C.; Ranaivonjatovo, H.; Satge, J. Coord. Chem. ReV. 1994, 130,
427. (b) Barrau, J.; Escudie, J.; Satge, J. Chem. ReV. 1990, 90, 283. (c)
Baines, K. W.; Stibbs, W. G. AdV. Organomet. Chem. 1996, 39, 275.
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Int. Ed. Engl. 1994, 33, 2316. (c) Tokitoh, N.; Matsumoto, T.; Manmaru,
K.; Okazaki, R. J. Am. Chem. Soc. 1993, 115, 8855. (d) Tokitoh, N.;
Matsuhashi, Y.; Shibata, K.; Matsumoto, T.; Suzuki, H.; Saito, M.;
Manmaru, K.; Okazaki, R. Main Group Met. Chem. 1994, 17, 55. (e)
Tokitoh, N.; Matsumoto, T.; Ichida, H.; Okazaki, R. Tetrahedron Lett. 1991,
32, 6877. (f) Tokitoh, N.; Saito, M.; Okazaki, R. J. Am. Chem. Soc. 1993,
115, 2065.
(3) Veith, M.; Becker, S.; Huch, V. Angew. Chem., Int. Ed. Engl. 1989,
28, 1237.
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1351. (c) Kuchta, M. C.; Parkin, G. J. Am. Chem. Soc. 1994, 116, 8372.
(5) Ossig, G.; Meller, A.; Bronneke, C.; Muller, O.; Schafer, M.;
Herbstirmer, R. Organometallics 1997, 16, 2116.
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(10) Dehnicke, K.; Ergezinger, C.; Hartmann, E.; Zinn, A.; Ho¨sler, K.
J. Organomet. Chem. 1988, 352, C1.
(11) Roesky, H. W.; Meller, B.; Noltemeyer, M.; Schmidt, H.-G.; Scholz,
U.; Sheldrick, G. M. Chem. Ber. 1988, 121, 1403.
(12) Ergezinger, C.; Weller, F.; Dehnicke, K. Z. Naturforsch. 1988, 43B,
1621.
(13) Kidea, J. D.; Hiller, W.; Borgsen, B.; Dehnicke, K. Z. Naturforsch.
1989, 44B, 889.
(14) Appel, S.; Weller, F.; Dehnicke, K. Z. Anorg. Allg. Chem. 1990,
583, 7.
(6) Zhou, Y.; Richeson, D. S. J. Am. Chem. Soc. 1996, 118, 10850.
(7) Examples of structurally characterized polyselenoanions of germa-
nium which have terminal GedSe bonds include [GeSe44-] (2.35 Å) and
[Ge4Se104-] (2.26 Å): Krebs, B. Angew. Chem., Int. Ed. Engl. 1983, 22,
113.
(15) Borgsen, B.; Dehnicke, K.; Fenske, D.; Baum, G. Z. Anorg. Allg.
Chem. 1991, 596, 133.
(16) Kilimann, U.; Noltemeyer, M.; Edelmann, F. T. J. Organomet.
Chem. 1993, 443, 35.
(17) Edelmann, F. T. Coord. Chem. ReV. 1994, 137, 403.
(18) Zhou, Y.; Richeson, D. S. Inorg. Chem. 1997, 36, 501.
(8) Tbt ) 2,4,6-[(SiMe3)2CH]3C6H2.
S0002-7863(97)01989-6 CCC: $14.00 © 1997 American Chemical Society

10360 J. Am. Chem. Soc., Vol. 119, No. 43, 1997
Foley et al.
Chart 1
the Cy and Me protons. In this case, a variable-temperature
1H NMR study for 1 over the temperature range 200-300 K
showed only a small amount of line broadening which could
be attributed to solvent viscosity effects.
Due to these apparently conflicting results, X-ray diffraction
studies were undertaken to clarify the geometry of both 1 and
2 (Table 1). Compounds 1 and 2 possess similar geometries
which are based on distorted tetrahedra in which one of the
vertices is occupied by a stereochemically active lone pair of
electrons.20,21 There were no anomalously short intermolecular
contacts. The molecular geometries and atom-numbering
schemes are shown in Figures 1 and 2. In contrast to the
previously reported Sn[CyNC(tBu)NCy]2, in which both amidi-
nates were bidentate, 1 and 2 exhibited one bidentate and one
monodentate (“dangling”) ligand.6 The free imine nitrogen does
not exhibit any obvious interaction with an adjacent metal center.
Taking into account the smaller radius of Ge, the structural
features within the bidentate ligand are similar to those of
reported Sn(II) and Sn(IV) complexes of related ligands:6,18 the
two nitrogens and bridging carbon atoms for the amidinate
ligand lie in a plane which includes the Ge atom with
comparable internal angles. The slight differences between the
methyl (1) and butyl (2) analogues (e.g., the angles around N1
and N2) appear to be consistent with the bulk of the group on
the methyne carbon.
Scheme 1
The Ge-N3 (mondentate ligand) distances are consistently
shorter than the Ge-N distances of the bidentate ligand. In
addition, the N3 atom is approximately equally disposed with
regard to N1 and N2.
1
The results of these analyses clearly explain the H NMR
ents.6,18 Our investigation of the coordination chemistry of
amidinate anions has relied on their generation by the addition
of alkyl anion equivalents to carbodiimides.18,19
results for 2 and indicate that although 1 exhibits three distinct
Cy groups in the solid state, the solution structure is fluxional.
Although the mechanism for interconversion of the amidinate
groups in complex 1 is not yet clear, it appears that substitution
of the methyl group in 1 with a tert-butyl group substantially
slows this process.18
Terminal S and Se Complexes of Ge. Treatment of the
two new complexes 1 and 2 with chalcogen sources (e.g., styrene
sulfide or Se) followed the redox pathway outlined in Scheme
2. In both cases, the reaction was rapid and complete.
Spectroscopic and microanalytical data for both products
confirmed the formulas for compounds 3-6. Specifically, the
1H NMR spectra of [CyNC(Me)NCy]2GeS (3) and [CyNC(Me)-
NCy]2GeSe (5) compared favorably to that of the parent 1.
Similarly, the NMR spectra of [CyNC(tBu)NCy]2GeS (4) and
[CyNC(tBu)NCy]2GeSe (6) indicated coordinations of the
amidinate ligands similar to that observed above for 2.
Furthermore, both COSY and heteroatom (13C/1H) correlation
NMR experiments for 4 were consistent with the structure
In this report we describe the synthesis of a unique family of
bis(amidinato)germanium(II) and mixed (amidinato)(amido)-
germanium(II) species. These compounds are easily converted
to terminal germanium chalcogenido complexes (GedCh; Ch
) S, Se) through oxidation with chalcogen atom sources. These
results contribute to the limited number of structurally character-
ized terminal chalcogenido complexes, and the addition of these
new species may help to delineate the features which stabilize
and affect the reactivity of such species.
Results and Discussion
Ge(II) Complexes of the (CyNC(R)NCy)- Anions (R )
CH3, CMe3). The in situ preparation of (CyNC(R)NCy)Li (R
) Me, tBu; Cy ) cyclohexyl) followed by subsequent addition
of 0.5 equivalents of GeCl2(dioxane) generated the Ge(II)
complexes 1 and 2 in excellent isolated yields (Scheme 1). Both
of these compounds have been characterized by spectroscopic
means, microanalysis, subsequent reactivity and single crystal
X-ray analysis.
(20) The structure of 1 was refined with observed and unobserved
reflections to obtain a better ratio of reflections to parameters (2373/298 )
7.96). Although the crystal quality was not ideal, a higher quality crystal
was not available. This analysis established the essential molecular structure
which was comparable to that of 2. Selected bond distances (Å) and bond
angles (deg) for 1: Ge1-N1, 2.037(11); Ge1-N2, 2.158(13); Ge1-N3,
1.935(12); N1-C7, 1.302(19); N2-C7, 1.329(18); N3-C21, 1.364(20);
N4-C21, 1.327(18); N1-Ge1-N2, 62.4(4); N1-Ge1-N3, 101.2(5);
N2-Ge1-N3, 96.0(4); Ge1-N1-C1, 137.3(10); Ge1-N1-C7, 95.6(9);
Ge1-N2-C7, 89.4(9); Ge1-N2-C9, 139.0(9); Ge1-N3-C15, 128.1(10);
Ge1-N3-C21, 104.4(9); N1-C7-N2, 111.6(13); N3-C21-N4, 111.4-
(12).
(21) Selected bond distances (Å) and bond angles (deg) for 2:
Ge1-N1, 2.040(9); Ge1-N2, 1.993(10); Ge1-N3, 1.903(9); Ge2-N5,
2.043(9); Ge2-N6, 2.090(9); Ge2-N7, 1.898(9); N1-C7, 1.299(15);
N2-C7, 1.420(15); N3-C24, 1.419(15); N4-C24, 1.282(16);
N1-Ge1-N2, 65.6(4); N1-Ge1-N3, 107.0(4); N2-Ge1-N3, 108.1(4);
Ge1-N1-C1, 129.7(7); Ge1-N1-C7, 93.4(7); Ge1-N2-C7, 91.8(7);
Ge1-N2-C12, 135.7(7); Ge1-N3-C18, 133.6(7); Ge1-N3-C24, 112.5-
(7); N1-C7-N2, 106.8(10); N3-C24-N4, 125.0(11).
The first indication that these compounds were not isostruc-
tural with the previously reported Sn(II) analogues was provided
1
by the room-temperature H NMR spectrum of 2.6 Unlike
Sn[CyNC(tBu)NCy]2, which displayed one environment for both
t
the Cy and Bu groups, Ge[CyNC(tBu)NCy]2 gave two mul-
tiplets for the cyclohexyl protons R to nitrogen in a 1:2:1 ratio
and two well-separated singlets in a 1:1 ratio for the tBu groups.
1
No coalescence of these signals was observed in the H NMR
spectra of 2 up to 375 K.
In contrast, the NMR spectrum for the methyl analogue,
Ge[CyNC(Me)NCy]2, exhibited a single environment for both
(19) (a) Zhou, Y.; Richeson, D. S. Inorg. Chem. 1996, 35, 1423. (b)
Zhou, Y.; Richeson, D. S. Inorg. Chem. 1996, 35, 2448.

Terminal Chalcogenido Germanium Complexes
J. Am. Chem. Soc., Vol. 119, No. 43, 1997 10361
Table 1. Crystallographic Data for [CyNC(Me)NCy]2Ge (1), [CyNC(tBu)NCy]2Ge (2), [CyNC(tBu)NCy]2GedSe (6), and
C6H11NC(Me)NC6H11]Ge[N(SiMe3)2]Se (10)
1
2
6
10
empirical formula
fw
GeN4C28H50
515.31
GeN4C34H62
597.46
SeGeN4C34H62
678.43
GeSeSi2N3C20H43
533.29
crystal system, space group
no. of reflns used for unit cell dimens
monoclinic, P21/c
24
monoclinic, Pc
24
monoclinic, P21/c
24
monoclinic, P21/a
8192
2θ range (deg)
lattice params
a (Å)
b (Å)
c (Å)
â (deg)
Z value
80-100
40.0-50.0
80-100
3.00-57.0
15.1666(6)
11.5652(4)
16.0374(6)
99.856(3)
4
17.2075(21)
11.055
18.223(3)
97.029(12)
2
17.806(3)
9.900(2)
20.425(5)
94.920(16)
4
8.8803(1)
16.5932(2)
18.2614(3)
97.186(1)
4
F(000)
1110
1.235
1.62
1.540 56
2509
648
1.157
1.37
1.540 56
3690
3690
1434
1.256
2.52
1.540 56
3740
3588
1998
102
1114
1.327
2.61
0.070 93
18456
6781
5253
70
Dcalc(g‚cm-3
)
µ (mm-1
λ (Å)
no. of reflns measd
no. of unique reflns
no. of reflns obsd
no. of atoms
)
2373
112920
83
3416
202
no. of variables
for significant reflections
R
298
702
361
417
0.074
0.052
0.057
0.043
0.111
0.087
0.027
0.024
Rw
Figure 1. Molecular structure and atom-numbering scheme for [CyNC-
(Me)NCy]2Ge (1) (Cy ) cyclohexyl).20 Hydrogen atoms have been
omitted for clarity.
Figure 2. Molecular structure and atom-numbering scheme for one
of the two molecules in the asymmetric unit for the structure of [CyNC-
(tBu)NCy]2Ge (2) (Cy ) cyclohexyl).21 Hydrogen atoms have been
omitted for clarity.
proposed in Scheme 2. Finally, the 77Se NMR spectrum (δ )
1023.8 vs Me2Se) of 6 is comparable to that of a structurally
characterized germaselenone which appeared at δ ) 940.6.2b
In order to validate the terminal GedCh bond in these
materials, we undertook an investigation of the structure of 6
by single-crystal X-ray diffraction (Table 1). These structural
results demonstrate the salient bonding features shown in Figure
3.22 From Figure 3 it is clear that the most outstanding structural
feature in this molecule is the terminal GedSe bond. The Ge-
Se bond length of 2.196 Å correlates favorably with the comp-
arable reports in the literature of (cf. 2.247 and 2.180 Å).2b,4b
The distorted tetrahedral Ge coordination geometry in this
complex is similar to that of the Ge(II) starting material (2)
with the Ge-Se vector residing in the site previously occupied
by the lone electron pair. The coordination sphere of Ge is
completed by the nitrogen atoms of one bidentate (N3, N4) and
one monodentate amidinate (N1). The gross features (e.g.,
internal angles of the Ge-N3-C24-N4 cycle) of both amidi-
nate ligands and their relative disposition are very similar to
those of 2. Not surprisingly, the three Ge(IV)-N bonds for 6
are shorter than those of the Ge(II) starting material. The Se-
Ge-N angles range from 120.0(5) to 122.3(4)°.
Ge(II) Complexes with Mixed-Ligand Systems. The obser-
vation that one of the amidinate ligands in both the Ge(II)
complexes and the terminal GeIVdCh complexes is monodentate
prompted us to consider substitution of this ligand with a simple
amido ligand. Complexes 1-6 appear to be essentially equal
to mixed amidinato-amido species. On the basis of acces-
sibility and the previous synthesis of GeII[N(SiMe3)2]2, we chose
to investigate the substitution of the dangling amidinate with
the N(SiMe3)2 moiety. It should be noted that reaction of GeII-
[N(SiMe3)2]2 with a chalcogen is rapid and yields the expected
bridging system (µ-Ch)2{Ge[N(SiMe3)2]2}2.23
(22) Selected bond distances (Å) and bond angles (deg) for 6: Ge-Se,
2.196(4); Ge-N1, 1.86(1); Ge-N3, 2.01(1); Ge1-N4, 1.99(1); N1-C7,
1.42(2); N2-C7, 1.27(2); N3-C24, 1.29(2); N4-C24, 1.35(2);
N1-Ge-N3, 106.4(6); N1-Ge-N4, 108.9(6); N3-Ge-N4, 65.6(6);
Ge-N1-C7, 119.8(11); C1-N1-C7, 123.9(13); Ge-N3-C24, 92.4(11);
Ge-N4-C24, 91.7(11); N3-C24-N4, 109.9(16); Se1-Ge1-N1, 120.0-
(5); Se1-Ge1-N3, 122.3(4); Se1-Ge1-N4, 121.4(4).
The mixed-ligand species 7 and 9 were obtained by the
stepwise reaction of GeCl2(dioxane) with 1 equiv of lithium
(23) Hitchcock, P. B.; Jang, E.; Lappert, M. F. J. Chem. Soc., Dalton
Trans. 1995, 3179. Hitchcock, P. B.; Jasim, H. A.; Lappert, M. F.; Leung,
W.-P.; Rai, A. K.; Taylor, R. E. Polyhedron 1991, 10, 1203.

10362 J. Am. Chem. Soc., Vol. 119, No. 43, 1997
Foley et al.
Figure 4. Molecular structure and atom-numbering scheme for [C6H11-
NC(Me)NC6H11]Ge[N(SiMe3)2]Se (10) (Cy ) cyclohexyl).24
Figure 3. Molecular structure and atom-numbering scheme for [CyNC-
(tBu)NCy]2GedSe (6) (Cy ) cyclohexyl).22 Hydrogen atoms have been
omitted for clarity.
distorted tetrahedron with the Ge-Se vector residing on one of
the vertices at a slightly longer distance (2.2212(3) Å) than in
6 but comparable to those of literature species.2b,4b The
coordination sphere of Ge is completed by the nitrogen atoms
of one bidentate (N1, N2) amidinate and the bis(trimethyl-
silyl)amido nitrogen (N3). The internal angles of the planar
Ge-N1-C7-N2 cycle are reminiscent of those in the biden-
tate ligands in 1, 2, and 6. The amido nitrogen (N3) is planar
with the plane of this ligand rotated out of the plane of the
amidinate ligand (torsional angles: N1-Ge-N3-Si1 ) 165.2°,
N1-Ge-N3-Si2 ) -9.04°, Se-Ge-N3-Si1 ) 21.72°). The
three Ge(IV)-N bonds are very similar to those of 6, and
the Se-Ge-N angles are slightly smaller and range from
115.18(5) to 121.03(5)°.
Scheme 2
Conclusion
Terminal chalcogenido germanium complexes have been
prepared from a unique family of bis(amidinato)germanium-
(II) and mixed (amidinato)(amido)germanium(II) compounds.
These results add significantly to the limited number of struc-
turally characterized terminal chalcogenido complexes. These
new species will help to delineate the steric and electronic fea-
tures which stabilize and influence the reactivity of such species.
The structural studies presented above show that Ge(II) and
Ge(IV) complexes with these ligand environments have a strong
disposition toward a tetrahedral coordination geometry. This
tendency led to the systematic observation of dangling ligands
in the bis(amidinate) systems. This contrasts with reported
Sn(II/IV) analogues. In addition, amidinate anions have been
shown to be excellent ancillary ligands for Ge complexes with
fairly well-defined structural features.
amidinate followed by addition of 1 equiv of lithium amide
(Scheme 1). Only in the case of CyNC(tBu)NCy]2GeCl (8) was
1
the intermediate species isolated and characterized. The H
NMR spectrum of CyNC(tBu)NCy]2GeN(SiMe3)2 (9) displays
a broadened singlet for the trimethylsilyl groups relative to that
of CyNC(Me)NCy]2GeN(SiMe3)2 (7), indicative of hindered
rotation of the amido ligand.
Preparation of these relatively stable GedCh species is
allowing a thorough study of their reactivity. Our preliminary
efforts in this regard (i.e., investigation of 2+2 cycloadditions
and atom transfer reactions) are promising and will be the
subject of future reports.
These Ge(II) species also readily react with elemental selen-
ium to yield the chalcogenido complexes [CyNC(Me)NCy]2Ge-
[N(SiMe3)2]Se (10) [CyNC(tBu)NCy]2Ge[N(SiMe3)2]Se (11).
Both COSY and heteroatom (13C/1H) correlation NMR experi-
ments for 11 were consistent with the connectivity shown in
Scheme 2. As in the case of 9, the NMR spectrum of 11 indi-
cates that there is hindered rotation around Ge-N(SiMe3)2 bond.
The appearance of a 77Se NMR resonance at δ ) 1115.6 vs
Me2Se for 10 is similar to the case of 6 and appropriate for a
terminal function.2b
Experimental Section
General Considerations. All manipulations were carried out in a
Vacuum Atmospheres drybox or on a vacuum line using standard
(24) Selected bond distances (Å) and bond angles (deg) for 10:
Ge-Se, 2.2212(3); Ge-N1, 1.9946(15); Ge-N2, 1.9572(15); Ge-N3,
1.8410(15); N1-C7, 1.3367(24); N2-C7, 1.3209(24); N3-Si1,
1.7723(15); N3-Si2, 1.7542(15); ; Se-Ge-N1, 115.18(5); Se-Ge-N2,
121.03(5); Se-Ge-N3, 120.52(5); N1-Ge-N2, 67.14(6); N1-Ge-N3,
114.05(6); N2-Ge-N3, 107.42(6); Ge-N1-C7, 92.12(11); Ge-N2-C7,
92.06(11); N1-C7-N2, 108.54(16).
A single-crystal X-ray diffraction analysis provided the
detailed connectivity of 10 (Table 1). From Figure 4 it is clear
that 10, like 6, is a terminal Ge chalcogenido species.24 Again,
the Ge coordination geometry in this complex is that of a

Terminal Chalcogenido Germanium Complexes
J. Am. Chem. Soc., Vol. 119, No. 43, 1997 10363
Schlenk techniques. Solvents were distilled under nitrogen from Na/K
alloy. GeCl2(dioxane)25 was prepared by literature procedures. tBuLi,
MeLi, LiN(SiMe3)2, and dicyclohexylcarbodiimide were used as
received from Aldrich.
NMR spectra were run on a Gemini 200 MHz or Bruker 500MHz
spectrometer with deuterated benzene as a solvent and internal standard.
All elemental analyses were run on a Perkin-Elmer PE CHN 4000
elemental analysis system. Satisfactory CHN microanalysis was
obtained for all products.
Ge[C6H11NC(Me)NC6H11]2 (1). To a solution of dicyclohexylcar-
bodiimide (0.889 g, 4.32 mmol) in diethyl ether (40 mL) was added
MeLi (3.08 mL, 1.4 M, 4.32 mmol). After 30 min, GeCl2(diox) (0.50
g, 2.16 mmol) was added. The solution was stirred for 12 h, filtered
to remove the white LiCl precipitate, and evaporated to dryness.
Colorless crystals were obtained from hexanes at -34 °C (1.73 g, 78%
yield). 1H NMR (C6D6, ppm): 3.29 (br, C6H11, 4H); 2.02-1.16 (m,
C6H11, 40H); 1.64 (s, Me, 6H). 13C NMR (C6D6, ppm): 163.0 (s,
NCN); 56.3, 35.8, 26.5, 26.3 (4s, C6H11); 12.6 (s, Me).
Ge[C6H11NC(CMe3)NC6H11]2 (2). To a solution of dicyclohex-
ylcarbodiimide (1.24 g, 6.00 mmol) in diethyl ether (50 mL) was
added tBuLi (3.55 mL, 1.7 M, 6.00 mmol). After 30 min, GeCl2(diox)
(0.700 g, 3.00 mmol) was added. The solution was stirred for 12 h,
filtered to remove the white LiCl precipitate, and evaporated to dry-
ness. Pale yellow crystals were obtained from a 50:50 mixture of
hexamethyldisiloxane/hexanes at -34 °C (3.05 g, 85% yield). 1H
NMR (C6D6, ppm): 4.10 (br, C6H11, 1H); 3.77 (br, C6H11, 2H); 3.50
(br, C6H11, 1H); 2.35-1.17 (m, C6H11, 40H); 1.61 (s, CMe3, 9H); 1.17
(s, CMe3, 9H).
[C6H11NC(Me)NC6H11]2GeS (3). To a solution of 1 (0.152 g, 0.30
mmol) in hexanes (5 mL) was added styrene sulfide (0.061 g, 0.45
mmol). Product slowly precipitated out of solution. The solution was
stirred for 12 h and filtered, and the product was crystallized from ether
at -34 °C (0.12 g, 75% yield of colorless crystals of 3). 1H NMR
(C6D6, ppm): 3.27 (br, C6H11, 4H); 2.12-1.04 (m, C6H11, 40H); 1.49
(s, Me, 6H).
[C6H11NC(CMe3)NC6H11]2GeS (4). To a solution of 2 (0.110 g,
0.184 mmol) in hexanes (5 mL) was added styrene sulfide (0.037 g,
0.28 mmol). Product slowly precipitated out of solution. The solution
was stirred for 12 h, filtered, and crystallized from ether at -34 °C
(0.087 g, 75% yield of colorless crystals of 4). 1H NMR (C6D6, ppm):
4.07 (br, C6H11, 1H); 3.71 (br, C6H11, 2H); 3.22 (br, C6H11, 1H); 2.67-
0.90 (m, C6H11, 40H); 1.70 (s, CMe3, 9H); 1.07 (s, CMe3, 9H).
[C6H11NC(Me)NC6H11]2GeSe (5). To a solution of 1 (1.00 g, 1.94
mmol) in ether (15 mL) was added 1 equiv of selenium (0.154 g, 1.94
mmol). The solution was stirred for 12 h and evaporated to dryness.
Colorless crystals were obtained from ether at -34 °C (1.02 g, 89%
yield). 1H NMR (C6D6, ppm): 3.30 (br, C6H11, 4H); 2.15-0.85 (m,
C6H11, 40H); 1.50 (s, Me, 6H).
[C6H11NC(CMe3)NC6H11]2GeSe (6). To a solution of 2 (0.300 g,
0.500 mmol) in ether (10 mL) was added 1 equiv of selenium (0.040
g, 0.500 mmol). The solution was stirred for 12 h and evaporated to
dryness. Crystals were obtained from ether at -34 °C (0.25 g, 85%
yield of colorless crystals of 6). 1H NMR (C6D6, ppm): 4.03 (br, C6H11,
1H); 3.75 (br, C6H11, 2H); 3.23 (br, C6H11, 1H); 2.70-0.90 (m, C6H11,
40H); 1.71 (s, CMe3, 9H); 1.07 (s, CMe3, 9H). 13C NMR (C6D6,
ppm): 178.7 (s, NCN); 162.5 (s, NCN); 32.2 (s, Me); 28.6 (s, Me).
77Se NMR (C6D6, ppm vs Me2Se): 1023.8 (s, GeSe).
[C6H11NC(CMe3)NC6H11]GeCl (8). To a solution of dicyclohexyl-
carbodiimide (0.267 g, 1.30 mmol) in diethyl ether (20 mL) was added
tBuLi (0.76 mL, 1.7M, 1.30 mmol). After 30 min, 1 equiv of GeCl2-
(diox) (0.300 g, 1.30 mmol) was added. The solution was stirred for
12 h, filtered to remove the white LiCl precipitate, and evaporated to
dryness to give a white solid. 1H NMR (C6D6, ppm): 3.62 (br, C6H11,
2H); 2.12-0.90 (m, C6H11, 20H); 1.20 (s, CMe3, 9H).
[C6H11NC(CMe3)NC6H11]GeN(SiMe3)2 (9). To a solution of 8
(0.130 g, 0.350 mmol) in ether (10 mL) was added 1 equiv of lithium
bis(trimethylsilylamide) (0.217 g, 0.350 mmol). The solution was
stirred for 12 h, filtered, and evaporated to dryness. White crystals
were obtained from ether at room temperature (0.13 g, 77% yield). 1H
NMR (C6D6, ppm): 3.72 (br, C6H11, 2H); 2.20-0.95 (m, C6H11, 20H);
1.11 (s, CMe3, 9H); 0.50 (br s, SiMe3, 18H).
[C6H11NC(Me)NC6H11]Ge[N(SiMe3)2]Se (10). To a solution of 7
(0.98 g, 2.15 mmol) in diethyl ether (30 mL) was added 1 equiv of
selenium (0.17 g, 2.15 mmol). The solution was stirred for 24 h and
evaporated to dryness, leaving behind a yellow powder. Clear, color-
less crystals were obtained from 75:25 diethyl ether/hexanes at
-34 °C (0.85 g, 74% yield). 1H NMR (C6D6, ppm): 2.98 (br, C6H11,
2H); 2.10-0.85 (m, C6H11, 20H); 1.16 (s, Me, 3H); 0.53 (s, SiMe3,
18H). 13C NMR (C6D6, ppm): 170.0 (s, NCN); 55.3, 35.1, 33.6, 25.4
(4s, C6H11); 11.8 (s, Me); 6.1 (s, SiMe3). 77Se NMR (C6D6, ppm vs
Me2Se): 1115.6 (s, GeSe).
[C6H11NC(CMe3)NC6H11]Ge[N(SiMe3)2]Se (11). To a solution of
9 (0.050 g, 0.101 mmol) in C6D6 (0.5 mL) was added 1 equiv of
selenium (0.008 g, 0.101 mmol). 1H NMR (C6D6, ppm): 3.67 (br,
C6H11, 2H); 2.75-0.90 (m, C6H11, 20H); 1.11 (s, CMe3, 9H); 0.84 (b,
SiMe3, 9H); 0.33 (b, SiMe3, 9H). 13C NMR (C6D6, ppm): 175.7 (s,
NCN); 57.7, 37.1, 34.3, 25.9, 25.4 (5s, C6H11); 38.1 (s, CMe3); 28.0
(s, Me); 7.0, 5.8 (br s, SiMe3).
X-ray Crystallography. For compounds 1, 2, and 6 a summary of
the data collection is provided in Table 1. Intensity data were collected
on a Rigaku diffractometer at -153 °C using the θ-2θ scan technique
for crystals mounted on glass fibers. The structures were solved by
direct methods. The non-hydrogen atoms were refined anisotropically.
Hydrogen atom positions were located in the difference Fourier maps
and refined isotropically in the case of a favorable observation/parameter
ratio. The final cycle of full-matrix least-squares refinement was based
on the number of observed reflections with [I > 2.5σ(I)]. Anomalous
dispersion effects were included in the Fc values. All calculations were
performed using the NRCVAX package. Full details of the data
collection and refinement and final atomic coordinates are reported in
the Supporting Information.
For compound 7, a summary of the data collection is provided in
Table 1. Intensity data were collected on a Siemens SMART CCD
diffractometer at -153 °C using the ω (0.3° scans) scan technique for
crystals mounted on glass fibers. The structures were solved by direct
methods. The non-hydrogen atoms were refined anisotropically.
Hydrogen atom positions were located in the difference Fourier maps
and refined isotropically in the case of a favorable observation/parameter
ratio. The final cycle of full-matrix least-squares refinement was based
on the number of observed reflections with [I > 2.5σ(I)]. Anomalous
dispersion effects were included in the Fc values. All calculations were
performed using the NRCVAX package. Full details of the data
collection and refinement and final atomic coordinates are reported in
the Supporting Information.
[C6H11NC(Me)NC6H11]GeN(SiMe3)2 (7). To a solution of dicy-
clohexylcarbodiimide (0.445 g, 2.16 mmol) in diethyl ether (25 mL)
was added MeLi (1.54 mL, 1.4 M, 2.16 mmol). After 30 min, the
solution was added to 1 equiv of GeCl2(diox) (0.500 g, 2.16 mmol) in
diethyl ether (25 mL). The solution was stirred for 6 h, and 1 equiv of
lithium bis(trimethylsilylamide) (0.361 g) was then added. The solution
was stirred for another 12 h and filtered to remove the white LiCl
precipitate. The solvent was removed under vacuum, at which point
an intractable yellow oil was observed as the sole product (0.90 g,
92% yield). 1H NMR (C6D6, ppm): 3.05 (br, C6H11, 2H); 2.00-1.02
(m, C6H11, 20H); 1.29 (s, Me, 3H); 0.46 (s, SiMe3, 18H).
Acknowledgment. This work was supported by the Natural
Sciences and Engineering Research Council of Canada.
Supporting Information Available: COSY and HETCOR
spectra for compounds 4 and 11, listings providing crystal-
lographic data and details of the structural solutions, tables of
atomic positions, thermal parameters, and bond distances and
angles, and ORTEP drawings and unit cell diagrams for
compounds 1, 2, 6, and 10 (60 pages). See any current masthead
page for ordering and Internet access instructions.
(25) Fjeldberg, T.; Haaland, A.; Schilling, B. E. R.; Lappert, M. F.;
Thorne, A. J. J. Chem. Soc., Dalton Trans. 1986, 1551.
JA9719891