Heteroleptic germanium(II) and tin(II) chlorides supported by anionic ligands derived from 2,3-dimethyl-1,4-diaza-1,3-butadiene

Article abstract of DOI:10.1002/ejic.201300830

The syntheses and structures of heteroleptic germanium(II) and tin(II) chlorides supported by anionic ligands derived from 2,3-dimethyl-1,4-diaza-1,3- butadiene are described. The reaction of ArN=C(Me)C(Me)=NAr (L, Ar = 2,6-iPr₂C₆H

Full text of DOI:10.1002/ejic.201300830

FULL PAPER
DOI:10.1002/ejic.201300830
Heteroleptic Germanium(II) and Tin(II) Chlorides
Supported by Anionic Ligands Derived from
2,3-Dimethyl-1,4-diaza-1,3-butadiene
Siew-Peng Chia,[a] Yongxin Li,[a] Rakesh Ganguly,[a] and
Cheuk-Wai So*[a]
Keywords: Carbene homologues / Germanium / Tin / Chlorides / N ligands
The syntheses and structures of heteroleptic germanium(II)
and tin(II) chlorides supported by anionic ligands derived
from 2,3-dimethyl-1,4-diaza-1,3-butadiene are described.
ArN=C(Me)C(=CH2)NAr] reacted with GeCl2·dioxane in
Et2O to form [{C(=CH)NAr}{C(Me)=NAr}]2(GeCl)2 (3). The
byproducts are [{C(CH2)NAr}{C(Me)=NAr}Ge]2 (4) and L2H
(5). Furthermore, the reaction of L with LiNiPr2 in Et2O, fol-
lowed by treatment with SnCl2, afforded [L2SnCl] (6). Com-
pounds 1–4 and 6 have been characterized by NMR spec-
troscopy and X-ray crystallography.
The reaction of ArN=C(Me)C(Me)=NAr (L, Ar
= 2,6-
iPr2C6H3) with MeLi in Et2O, followed by treatment with
GeCl2·dioxane or SnCl2, afforded [L1ECl] [L1 = ArN=C(Me)-
C(Me)2NAr; E = Ge (1), Sn (2)]. Moreover, L2Li [L2
=
effect of the latter, which determine the nucleophilic attack
or the deprotonation. We anticipate that both lithiated spe-
cies L1Li and L2Li may have potential to be useful ligands
for the stabilization of main-group elements and transition
metals.
Introduction
Enormous effort has been invested in the design of li-
gands with new electronic and steric features to improve the
reactivities of metal complexes. Various multidentate ancil-
lary ligands with ketimine donors such as aminotropon-
iminates, amidinates, guanidinates, β-diketiminates, and bis-
(imino)phenyl have been developed.[1] The cooperation of a
metal ion and the ligand leads to an amazingly broad array
of geometries and reactivities of the corresponding com-
plexes.[2] Another member of this family is 1,4-diaza-1,3-
butadiene ligands (DABs).[3] Owing to their inherent tun-
able and flexible coordination modes, DABs are widely uti-
lized not only for transition metals and f-block metals,[4]
but also for s-block and p-block main-group elements.[5]
The resulting complexes exhibit extraordinary electronic
structures and catalytic activities.
Our interest in the DAB family of ligands was initiated
by the reactivity of a substituted 2,3-dimethyl-1,4-diaza-1,3-
butadiene compound, L, with lithium reagents to give the
anionic ligands L1Li and L2Li (Scheme 1). L1Li was pre-
pared by the nucleophilic attack at one of the imine carbon
atoms of L with MeLi, whereas L2Li was afforded by the
deprotonation of a methyl group at the imine carbon atom
of L with LiNiPr2.[6] The different reactivity of L with lith-
ium reagents is probably caused by the basicity and steric
Scheme 1. Substituted 2,3-dimethyl-1,4-diaza-1,3-butadiene (L)
and the lithiated imine/amide complexes L1Li and L2Li.
We are interested in employing the anionic ligands L1
and L2 to synthesize base-stabilized germanium(II) and
tin(II) chlorides, because germylenes and stannylenes con-
taining functionalized substituents such as H, OH, and Cl
can be versatile building blocks for the synthesis of new
derivatives with low-valent germanium and tin atoms and
synthons for the activation of small molecules.[2d–2h,7]
In this paper, we report the syntheses and structures of
the organogermanium(II) and -tin(II) chloride complexes
[L1ECl] [L1 = ArN=C(Me)C(Me)2NAr; E = Ge (1), Sn (2);
Ar
=
2,6-iPr2C6H3], [{C(=CH)NAr}{C(Me)=NAr}]2-
(GeCl)2 (3) and [L2SnCl] [6, L2 = ArN=C(Me)C(=CH2)-
NAr].
[a] Division of Chemistry and Biological Chemistry, Nanyang
Technological University,
Results and Discussion
21 Nanyang Link, 637371 Singapore
Synthesis of [L1ECl] (E = Ge, Sn)
E-mail: CWSo@ntu.edu.sg
http://www.spms.ntu.edu.sg/cbc/
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.201300830.
The reaction of L with MeLi in Et2O at 0 °C, followed by
treatment with GeCl2·dioxane or SnCl2, afforded [L1ECl]
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[E = Ge (1), Sn (2), Scheme 2]. Compounds 1 and 2 were [(N,N-dimethylamino)methyl]phenyl,
270.26°},[9]
and
isolated as highly air- and moisture-sensitive yellow crystal- [{dpp-bian(nBu)}GeCl] {dpp-bian = 1,2-bis[(2,6-diisoprop-
line solids. They are soluble in hydrocarbon solvents and ylphenyl)imino]acenaphthene, 277.20°}.[10] The geometry at
have been characterized by NMR spectroscopy. The 1H the Ge atom indicates that it is almost nonhybridized and
NMR spectra of 1 and 2 show two singlets (1: δ = 0.78 and possesses a lone pair of electrons with high s character. The
1.38 ppm; 2: δ = 0.83 and 1.39 ppm) corresponding to the N1–Ge1 bond length [1.8804(17) Å] is comparable with
nonequivalent gem-dimethyl groups and a singlet (1: δ = those in [Me2Si(NtBu)(NtBuH)GeCl] [1.894(3) Å][11] and
1.71 ppm; 2: δ = 1.80 ppm) attributable to the methyl group [(Me3Si)2N)2Ge] [1.873(5) and 1.878(5) Å].[12] The Ge1–N2
at the imine skeleton. For 1, eight doublets at δ = 0.88– bond length [2.0634(18) Å] is comparable with those of the
1.55 ppm and four septets at δ = 3.16–4.52 ppm for the iPr N–Ge coordinative bonds in N-donor-stabilized chloro-
groups of the Ar substituents are observed. For 2, five germylenes such as [{C5H4N-2-C(SiMe3)2}GeCl] [2.082(4),
broad signals at δ = 0.91–1.51 ppm and four broad signals 2.075(4) Å][13] and [(Mamx)GeCl] [2.0936(13) Å].[9] The
at δ = 2.97–4.57 ppm for the iPr groups of the Ar substitu- Ge1–Cl1 bond length [2.3397(6) Å] is comparable with
1
ents are observed. The H NMR spectra of 1 and 2 also those in the bis(chlorogermyl) complex [ClGe(dipp-tip)-
show one set of resonances of the phenyl protons. More- GeCl] {dipp-tip
= 1,2-tetrakis[(2,6-diisopropylphenyl)-
over, the 119Sn{1H} NMR spectrum of 2 displays a singlet imino]pyracene, 2.278(2) Å}[14] and [{dpp-bian(nBu)}GeCl]
at δ = –40 ppm, which is in the range of the 119Sn NMR [2.3500(7) Å].[10]
resonances of heteroleptic tin(II) halides supported by ket-
The molecular structure of 2 shows (Figure 2) that the
Sn atom adopts a distorted trigonal-pyramidal geometry
(sum of bond angles 265.61°), which is comparable with
that of [SnCl{(S)-box-Ph}] {266.55°, (S)-box-Ph = 1,1-
bis[(4S)-4-phenyl-1,3-oxazolin-2-yl]ethane}.[8h] The geome-
try of the Sn atom indicates that it is almost nonhybridized
and possesses a lone pair of electrons with high s character.
The Sn1–Cl1 bond [2.5011(5) Å] is longer than that in base-
stabilized chlorostannylenes [2.440(5)–2.488(3) Å],[7c,15] but
is shorter than that in [2,6-(CH=NtBu)2C6H3SnCl]
[2.5624(5) Å].[2h] The Sn1–N2 bond [2.0676(13) Å] is
slightly shorter than those in [SnCl{(S)-box-Ph}]
[2.134(3) Å],[8h] [DIPY-SnCl] [DIPY = dipyrromethene,
2.1802(16) Å],[8b] and [C6H4-2-CH2N(CH3)2-1-N(GePh3)-
SnCl] [2.107(2) Å].[8d] The Sn1–N1 bond [2.2741(13) Å] is
significantly longer than the Sn1–N2 bond, which indicates
that the Sn1–N1 bond is a coordinative bond.
imine-containing ligands (δ = –266–69.7 ppm).[2d,8]
Scheme 2. Synthesis of 1 and 2.
Compounds 1 and 2 have been characterized by X-ray
crystallography. The molecular structure of 1 (Figure 1)
shows that the Ge atom adopts a distorted trigonal-pyrami-
dal geometry (sum of bond angles 275.95°), which is com-
parable with those of [2,6-(CH=NAr)2C6H3GeCl]
(267.40°),[2g] [(Mamx)GeCl] {Mamx = 2,4-di-tert-butyl-6-
Figure 1. Molecular structure of 1 (ellipsoids set at 50% prob-
ability). Hydrogen atoms and solvent molecules are omitted for
clarity. Selected bond lengths [Å] and angles [°]: Ge1–Cl1 2.3397(6),
Figure 2. Molecular structure of 2 (ellipsoids set at 50% prob-
ability). Hydrogen atoms are omitted for clarity. Selected bond
Ge1–N1 1.8804(17), Ge1–N2 2.0634(18), C15–N1 1.457(3), C15– lengths [Å] and angles [°]: Sn1–Cl1 2.5011(5), Sn1–N1 2.2741(13),
C16 1.512(3), C16–N2 1.290(3), C16–C17 1.487(4), C15–C14 Sn1–N2 2.0676(13), C13–N1 1.2897(19), C13–C15 1.523(2), C15–
1.558(4), C15–C13 1.538(3), N1–Ge1–N2 79.99(7), N1–Ge1–Cl1 N2 1.456(2), C13–C14 1.488(2), C15–C16 1.537(2), C15–C17
102.04(6), N2–Ge1–Cl1 93.93(6), C15–N1–Ge1 119.83(13), C16– 1.555(2), N1–Sn1–N2 73.62(5), N1–Sn1–Cl1 89.68(3), N2–Sn1–Cl1
C15–N1 106.48(18), N2–C16–C15 116.7(2), C16–N2–Ge1
114.88(15).
102.31(4), C13–N1–Sn1 116.32(10), C15–C13–N1 117.15(14), N2–
C15–C13 108.35(12), C15–N2–Sn1 120.39(10).
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Synthesis of [{C(=CH)NAr}{C(Me)=NAr}]2(GeCl)2 (3) and
[{C(CH2)NAr}{C(Me)=NAr}Ge]2 (4).
The reaction of L2Li with GeCl2·dioxane in Et2O at 0 °C
afforded
a mixture of [{C(=CH)NAr}{C(Me)=NAr}]
2(GeCl)2 (3), [{C(CH2)NAr}{C(Me)=NAr}Ge]2 (4), and
L2H (5, Scheme 3),[16] as confirmed by NMR spectroscopy.
Other byproducts such as [L2 Ge] could not be observed.
2
The reaction mixture was then filtered, and the filtrate was
concentrated to give a mixture of 3 and 4 as highly air-
and moisture-sensitive yellow crystalline solids. The mother
liquor was further concentrated to afford pure 3 as yellow
crystals. However, an attempt to isolate pure 4 by
recrystallization failed. Moreover, the reaction of L2Li with
GeCl2·dioxane in tetrahydrofuran (THF) at –78 or 0 °C af-
forded 3 as the major product, as confirmed by NMR spec-
troscopy. Compounds 3 and 4 (Figures 3 and 4) have been
analyzed by X-ray crystallography. However, the mecha-
nism for the formation of 3 and 4 remains unknown. We
propose that the reaction may proceed through the forma-
tion of an intermediate [L2GeCl], which may then undergo
a ligand coupling reaction with L2Li and GeCl2·dioxane,
followed by rearrangement to form 3–5.
Figure 3. Molecular structure of 3 (ellipsoids set at 50% prob-
ability). Hydrogen atoms and a solvent molecule are omitted for
clarity. Selected bond lengths [Å] and angles [°]: Ge1–Cl1 2.2924(9),
Ge1–N1 1.931(2), Ge1–N2 2.019(2), C13–N1 1.366(4), C13–C15
1.467(4), C15–N2 1.308(4), C15–C16 1.494(4), C13–C14 1.385(4),
C14–C14A 1.414(6), N1–Ge1–N2 79.57(10), N1–Ge1–Cl1 97.91(8),
N2–Ge1–Cl1 95.76(7), C13–N1–Ge1 117.83(19), C15–C13–N1
112.1(2), N2–C15–C13 114.7(3), C15–N2–Ge1 115.7(2), C13–C14–
C14A 127.9(3), N1A–Ge1A–N2A 79.57(10).
Figure 4. Molecular structure of 4 (ellipsoids set at 50% prob-
ability). Hydrogen atoms except H16A and H16B atoms are omit-
ted for clarity. Selected bond lengths [Å] and angles [°]: Ge1–N1
1.859(6), Ge1–N2 1.872(6), C13–N1 1.395(9), C13–C15 1.367(10),
C15–N2 1.396(9), C13–C14 1.509(10), C15–C16 1.492(10), C16–
C16A 1.508(14), N1–Ge1–N2 83.4(3), C13–N1–Ge1 125.1(5), C15–
Scheme 3. Synthesis of 3–6.
Compound 3 was isolated as a highly air- and moisture-
sensitive yellow crystalline solid, which is soluble in hydro-
1
carbon solvents. The H NMR spectrum shows two dou- C13–N1 113.6(7), N2–C15–C13 113.6(6), C15–N2–Ge1 114.5(5),
C15–C16–C16A 112.3(8).
blets at δ = 1.17 and 1.25 ppm and one septet at δ =
3.07 ppm, which correspond to the iPr groups of the Ar
substituents. The spectrum also shows a singlet at δ = correspond to the methyl protons at the alkene skeleton and
1.79 ppm and a broad signal at δ = 5.93 ppm for the methyl methylene protons, respectively. Moreover, there is a mul-
protons at the imine skeleton and methine protons, respec- tiplet at δ = 7.07–7.25 ppm for the phenyl protons.
tively. Moreover, there is a multiplet at δ = 7.06–7.26 ppm
for the phenyl protons. Furthermore, the H NMR spec- Ge atoms adopt a distorted trigonal-pyramidal geometry
The molecular structure of 3 (Figure 3) shows that the
1
trum acquired at –60 °C is same as that at room tempera- (sum of bond angles 273.24°), which is comparable with
ture.
that of 1. This indicates that the Ge atoms possess a lone
1
With the NMR spectroscopic data of 3 in hand, the H pair of electrons with high s character. The N1–Ge1
NMR spectroscopic data of 4 in the mixture of 3 and 4 can [1.931(2) Å], Ge1–Cl1 [2.2924(9) Å], and N2–Ge1
be identified. Compound 4 shows four doublets at δ = 1.12, [2.019(2) Å] bonds are comparable to those in 1 [N1–Ge1:
1.21, 1.24, and 1.25 ppm and two septets at δ = 2.97 and 1.8804(17); Ge1–Cl1: 2.3397(6); N2–Ge1: 2.0634(18) Å].
3.07 ppm attributable to the iPr groups of the Ar substitu- The C14–C14A [1.414(6) Å], C13–C15 [1.467(4) Å], and
ents. There are also singlets at δ = 1.33 and 2.43 ppm, which C13–C14 [1.385(4) Å] bonds are shorter than a typical C–
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pared as described in the literature.[3] The 1H, 13C, and 119Sn NMR
spectra were recorded with a JEOL ECA 400 spectrometer. The
chemical shifts (δ) are relative to SiMe4 for 1H and 13C and SnMe4
for 119Sn. Elemental analyses were performed by the Division of
Chemistry and Biological Chemistry, Nanyang Technological Uni-
versity. Melting points were measured in sealed glass tubes.
C single bond (1.53 Å) but are longer than a typical C–C
double bond (1.34 Å). The C15–N2 [1.308(4) Å] bond lies
between a typical C–N single bond (1.47 Å) and C–N
double bond (1.27 Å). These results indicate that there is an
appreciable electron delocalization in the ligand skeleton.
In the molecular structure of 4 (Figure 4), the N1–Ge1–
N2 bite angle [83.4(3)°] is comparable with those of the N- [L1GeCl] (1): MeLi (0.75 mL, 1.6 m in Et2O, 1.2 mmol) was added
dropwise to a stirred solution of L (0.41 g, 1.01 mmol) in Et2O
(10 mL) at 0 °C. The reaction mixture was warmed to room tem-
perature and stirred for 1 h. The resulting yellow solution was then
added dropwise to a solution of GeCl2·dioxane (0.27 g, 1.17 mmol)
in Et2O (5 mL) at –78 °C. The resulting red suspension was warmed
to room temperature and stirred for 15 h. After filtration and con-
centration of the filtrate, 1 was obtained as yellow crystals, yield
0.35 g (64.7%), m.p. 184 °C. 1H NMR (395.9 MHz, [D6]benzene,
25 °C): δ = 0.78 [s, 3 H, (CH3)2CN], 0.89 [d, 3JH,H = 6.77 Hz, 3 H,
heterocyclic germylenes derived from 1,2-bis(arylimino)-
acenaphthenes [85.0(2)–85.2(1)°].[17] Moreover, the Ge–N,
N–C, and C–C bond lengths in the Ge1–N1–C13–C15–N2
metallacycle are similar to those in the N-heterocyclic
germylenes (Ge–N: average 1.886 Å, N–C: average 1.375 Å,
C–C: average 1.388 Å).[17] The C16–C16A bond
[1.492(10) Å] is a C–C single bond.
3
CH(CH3)2], 1.10 [d, JH,H = 7.24 Hz, 3 H, CH(CH3)2], 1.16 [d,
Synthesis of [L2SnCl] (6)
3
3JH,H = 6.81 Hz, 3 H, CH(CH3)2], 1.20 [d, JH,H = 6.81 Hz, 3 H,
3
CH(CH3)2], 1.23 [d, JH,H = 6.81 Hz, 3 H, CH(CH3)2], 1.38 [s, 3
The reaction of L with LiNiPr2 in Et2O at 0 °C, followed
by treatment with SnCl2, afforded [L2SnCl] (6, Scheme 3).
Compound 6 was isolated as a highly air- and moisture-
sensitive yellow crystalline solid, which is soluble in hydro-
3
H, (CH3)2CN], 1.43 [d, JH,H = 7.24 Hz, 3 H, CH(CH3)2], 1.44 [d,
3
3JH,H = 6.81 Hz, 3 H, CH(CH3)2], 1.54 [d, JH,H = 6.81 Hz, 3 H,
3
CH(CH3)2], 1.71 [s, 3 H, (CH3)C=N], 3.16 [sept, JH,H = 6.81 Hz,
1 H, CH(CH3)2], 3.25 [sept, 3JH,H = 6.81 Hz, 1 H, CH(CH3)2], 3.40
1
3
3
carbon solvents. The H NMR spectrum of 6 displays four
[sept, JH,H = 6.81 Hz, 1 H, CH(CH3)2], 4.52 [sept, JH,H
=
doublets (δ = 1.18–1.31 ppm) and two broad signals (δ = 6.81 Hz, 1 H, CH(CH3)2], 7.00–7.31 ppm (m, 6 H, Ar) ppm.
13C{1H} NMR (99.6 MHz, [D6]benzene, 25 °C): δ = 18.0, 23.0,
23.3, 24.1, 24.2, 24.6, 24.7, 26.7, 28.19, 28.21, 28.3, 28.4, 29.5, 29.6,
29.8 [iPr, (CH3)2CN, (CH3)C=N], 75.2 [(CH3)2CN], 123.6, 124.2,
124.9, 125.8, 126.7, 128.6, 137.0, 138.2, 140.9, 142.6, 150.4, 153.8
(Ar), 195.1 (C=N) ppm. C29H43ClGeN2 (527.72): calcd. C 65.98,
H 8.22, N 5.31; found C 65.64, H 8.11, N 5.13.
3.11 and 3.46 ppm) corresponding to the iPr groups of the
Ar substituents. Moreover, there are two signals (δ = 3.90
and 4.88 ppm) attributable to the vinylic protons. The
119Sn{1H} NMR resonance of 6 (δ = –88 ppm) is compar-
able with that of 2. Single crystals of 6 have been analyzed
by X-ray crystallography, but the X-ray crystal structure
shows serious disorder (Figure S1), in which the methyl Crystallographic Data for 1: C29.67H43ClGeN2O0.33; M = 541.03;
¯
trigonal; R3; a = 26.6462(6), b = 26.6462(6), c = 21.6114(6) Å; γ =
group (C1/C1A) is disordered over two positions with occu-
pancies of 0.5. This results in an averaging of the bond
lengths of the ligand, and these data are unsuitable for any
meaningful discussion. Although there is disorder, it is still
clear that the Sn atom adopts a distorted trigonal-pyrami-
dal geometry and is coordinated to two nitrogen atoms of
120°; V = 13288.7(6) Å3; Z = 18; ρcalcd. = 1.217 mgm–3; 52998 mea-
sured reflections; 9025 independent reflections; 321 refined param-
eters; R1 = 0.0457, wR2 = 0.1312 [IϾ2σ(I)].
[L1SnCl] (2): MeLi (0.75 mL, 1.6 m in Et2O, 1.2 mmol) was added
dropwise to a stirred solution of L (0.41 g, 1.01 mmol) in Et2O
the ligand and the chlorine atom. Attempts to isolate single (10 mL) at 0 °C. The reaction mixture was warmed to room tem-
perature and stirred for 1 h. The resulting yellow solution was then
added dropwise to a solution of SnCl2 (0.23 g, 1.21 mmol) in Et2O
(5 mL) at –78 °C. The reaction mixture was warmed to room tem-
perature, and the resulting orange suspension was stirred for 15 h.
crystals without disorder failed.
Conclusions
After filtration and concentration of the filtrate, 2 was obtained as
1
Heteroleptic germanium(II) and tin(II) chlorides sup- yellow crystals, yield 0.36 g (62.7%), m.p. 157 °C (dec). H NMR
(395.9 MHz, [D6]benzene, 25 °C): δ = 0.83 [s, 3 H, (CH3)2CN], 0.91
[br., 3 H, CH(CH3)2], 1.12 [br., 6 H, CH(CH3)2], 1.24 [br., 6 H,
CH(CH3)2], 1.39 [s, 3 H, (CH3)2CN], 1.43 [br., 6 H, CH(CH3)2],
1.51 [br., 3 H, CH(CH3)2], 1.80 (s, 3 H, CH3C=N), 2.97 [br., 1 H,
CH(CH3)2], 3.34 [br., 1 H, CH(CH3)2], 3.47 [br., 1 H, CH(CH3)2],
4.56 [br., 1 H, CH(CH3)2], 7.02–7.28 ppm (m, 6 H, Ar) ppm.
13C{1H} NMR (99.6 MHz, [D6]benzene, 25 °C): δ = 19.0, 23.0,
23.7, 24.0, 24.2, 24.6, 25.1, 26.5, 27.9, 28.0, 28.3, 28.6, 29.1, 29.5,
31.6 [iPr, (CH3)2CN, (CH3)C=N], 75.2 [(CH3)2CN], 123.4, 124.1,
124.7, 125.8, 125.9, 126.6, 138.9, 140.0, 141.3, 141.8, 149.8, 153.1
(Ar), 197.3 (C=N) ppm. 119Sn{1H} NMR (147.6 MHz, [D6]-
benzene, 25 °C): δ = –40 ppm. C29H43ClN2Sn (573.79): calcd. C
60.68, H 7.56, N 4.88; found C 60.38, H 7.21, N 4.75.
ported by anionic ligands derived from 2,3-dimethyl-1,4-di-
aza-1,3-butadiene were synthesized. The X-ray crystal
structures of 1–3 and 6 show that the germanium(II) or
tin(II) atom adopts a distorted trigonal-pyramidal geome-
try and is bonded to the bidentate ligand and a chlorine
atom. The results indicate that the Ge and Sn atoms possess
a lone pair of electrons with high s character. The mecha-
nism for the formation of 3 and 4 is currently under investi-
gation.
Experimental Section
General: All manipulations were performed under an inert atmo-
sphere of argon by using standard Schlenk techniques. Solvents
were dried and distilled from Na/K alloy prior to use. L was pre-
Crystallographic Data for 2: C29H43ClN2Sn; M = 573.79; mono-
clinic; P21/c; a = 17.8671(2), b = 10.6751(2), c = 16.9547(3) Å; β =
118.0080(10)°; V = 2855.08(8) Å3; Z = 4; ρcalcd. = 1.335 mgm–3;
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56625 measured reflections; 14648 independent reflections; 309 re-
δ = –88.0 ppm. C28H39ClN2Sn (557.77): calcd. C 60.24, H 6.99, N
fined parameters; R1 = 0.0345, wR2 = 0.0814 [IϾ2σ(I)].
5.02; found C 59.96, H 6.54, N 4.87.
[{C(=CH)NAr}{C(Me)=NAr}]2(GeCl)2 (3) and [{C(CH2)NAr}-
X-ray Data Collection and Structural Refinement: The intensity data
for 1–4 and 6 were collected with a Bruker APEX II diffractometer.
The data were collected at 103(2) K. The structures were solved by
direct phase determination (SHELXS-97) and refined for all data
by full-matrix least-squares methods on F2.[18] All non-hydrogen
atoms were subjected to anisotropic refinement. The hydrogen
atoms were generated geometrically and allowed to ride on their
respective parents atoms; they were assigned appropriate isotopic
thermal parameters and included in the structure-factor calcula-
tions.
{C(Me)=NAr}Ge]2 (4):
A
solution of L2Li·Et2O (0.49 g,
1.01 mmol) in Et2O (10 mL) was added dropwise to a stirred solu-
tion of GeCl2·dioxane (0.27 g, 1.17 mmol) in Et2O (5 mL) at
–78 °C. The reaction mixture was warmed to room temperature,
and the resulting dark green suspension was stirred for 15 h. After
filtration and concentration of the filtrate, a mixture of 3 and 4
was obtained. The mother liquor was further concentrated to af-
ford pure 3 as yellow crystals, yield 0.37 g (35.9%), m.p. 162 °C.
3
1H NMR (395.9 MHz, [D6]benzene, 25 °C): δ = 1.17 [d, JH,H
=
3
7.24 Hz, 24 H, CH(CH3)2], 1.25 [d, JH,H = 7.24 Hz, 24 H,
CH(CH3)2], 1.79 (s, 6 H, CH3C=N), 3.07 [sept, JH,H = 6.81 Hz, 8
CCDC-947516 (for 1), -947517 (for 2), -947518 (for 3), -959344 (for
4), and -947519 (for 6) contain the supplementary crystallo-
graphic data for this paper. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
3
H, CH(CH3)2], 5.93 (br., 2 H, CH=CH), 7.06–7.26 (m, 12 H, Ar)
ppm. 13C{1H} NMR (99.6 MHz, [D6]benzene, 25 °C): δ = 14.1,
19.4, 23.2, 24.3, 25.3, 26.5, 28.3 (iPr, CH3C=N), 49.2 (C=CN), 67.0
(C=CN), 112.5, 123.5, 127.3, 128.7, 139.5, 145.7 (Ar), 172.3 (C=N)
ppm. C56H76Cl2Ge2N4 (1021.33): calcd. C 65.83, H 7.50, N 5.49;
found C 65.48, H 7.14, N 5.14.
Supporting Information (see footnote on the first page of this arti-
cle): X-ray crystal structure of 6.
With the NMR spectroscopic data of 3 in hand, the NMR spectro-
scopic data of 4 in the mixture of 3 and 4 could be identified. 4:
Acknowledgments
3
1H NMR (395.9 MHz, [D6]benzene, 25 °C): δ = 1.12 [d, JH,H
=
3
6.77 Hz, 12 H, CH(CH3)2], 1.21 [d, JH,H = 6.77 Hz, 12 H,
This work was supported by the Academic Research Fund Tier 1
(RG22/12).
3
CH(CH3)2], 1.24 [d, JH,H = 6.33 Hz, 12 H, CH(CH3)2], 1.25 [d,
3JH,H = 6.77 Hz, 12 H, CH(CH3)2], 1.33 (s, 3 H, CH3C=N), 2.43
3
(s, 4 H, CH2CH2), 2.97 [sept, JH,H = 6.81 Hz, 4 H, CH(CH3)2],
3.07 [sept, JH,H = 6.81 Hz, 4 H, CH(CH3)2], 7.07–7.25 (m, 12 H,
3
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13.09, 22.66, 23.19, 26.36, 27.91, 28.26, 28.32, 28.43 (iPr, CH3C=N,
NCCCCN), 123.59 (N=CCH3), 127.31, 128.42, 130.89, 139.28,
139.31, 145.75 (Ar) ppm.
Crystallographic Data for 3: C70H92Cl2Ge2N4; M = 1205.56; tri-
¯
clinic; P1; a = 11.6097(4), b = 11.6803(4), c = 13.1414(5) Å; α =
90.528(2), β = 101.511(2), γ = 110.985(2)°; V = 1624.02(10) Å3; Z
= 1; ρcalcd. = 1.233 mgm–3; 7758 measured reflections; 7758 inde-
pendent reflections; 362 refined parameters; R1 = 0.0424, wR2
0.1031 [IϾ2σ(I)].
=
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Crystallographic Data of 4: C56H78Ge2N2; M = 952.40; monoclinic;
P21/n; a = 13.121(3), b = 11.775(3), c = 17.909(4) Å; β =
103.455(7)°; V = 2690.9(10) Å3; Z = 2; ρcalcd. = 1.175 mgm–3; 25280
measured reflections; 5520 independent reflections; 289 refined pa-
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[L2SnCl] (6): LiNiPr2 (0.6 mL, 2.0 m in THF/heptane/ethylbenzene,
1.2 mmol) was added dropwise to a stirred solution of L (0.41 g,
1.01 mmol) in Et2O (10 mL) at 0 °C. The reaction mixture was
warmed to room temperature and stirred for 15 h. The resulting
yellow solution was added dropwise to a stirred solution of SnCl2
(0.23 g, 1.21 mmol) in Et2O (5 mL) at –78 °C. The reaction mixture
was warmed to room temperature, and the resulting dark yellow
suspension was stirred for 15 h. After filtration, the filtrate was
concentrated to afford 6 as yellow crystals, yield 0.32 g (57.4%),
m.p. 167 °C (dec). 1H NMR (395.9 MHz, [D8]THF, 25 °C): δ =
1.18 [d, 3JH,H = 6.73 Hz, 6 H, CH(CH3)2], 1.19 [d, 3JH,H = 6.73 Hz,
3
6 H, CH(CH3)2], 1.22 [d, JH,H = 6.73 Hz, 6 H, CH(CH3)2], 1.31
[d, 3JH,H = 6.73 Hz, 6 H, CH(CH3)2], 2.21 (s, 3 H, CH3C=N), 3.11
[br., 2 H, CH(CH3)2], 3.46 [br., 2 H, CH(CH3)2], 3.90 [s, 1 H,
(CH2)CN], 4.88 [s, 1 H, (CH2)CN], 7.00–7.33 (m, 6 H, Ar) ppm.
13C{1H} NMR (99.6 MHz, [D6]benzene, 25 °C): δ = 18.4, 22.7,
23.2, 24.3, 25.4, 28.7, 29.0 (iPr, CH3C=N), 66.0 (CH2=CN), 97.6
(CH2=CN), 123.5, 126.6, 135.1, 138.6, 140.1, 156.0 (Ar), 179.5
(C=N) ppm. 119Sn{1H} NMR (147.63 MHz, [D6]benzene, 25 °C):
Eur. J. Inorg. Chem. 2014, 526–532
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[L H] (5) can be afforded by the reaction of [L Li] with water
1
in Et2O. H NMR (395.9 MHz, D6[benzene], 25 °C): δ = 1.14
[d, 3JH,H = 7.24 Hz, 6 H, CH(CH3)2], 1.21 [overlapping d, 3JH,H
3
= 6.81 Hz, 12 H, CH(CH3)2], 1.31 [d, JH,H = 7.24 Hz, 6 H,
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7.24 Hz, 2 H, CH(CH3)2], 3.46 [sept, JH,H = 6.81 Hz, 2 H,
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3
=
3
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FULL PAPER
7.27 (m, 6 H, Ar) ppm. With the NMR spectroscopic data
of [L2H] in hand, its presence in the reaction of [L2Li] with
GeCl2·dioxane in Et2O can be identified.
[18]
G. M. Sheldrick, SHELXL-97, University of Göttingen, Ger-
many, 1997.
Received: July 1, 2013
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Published Online: December 6, 2013
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© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim