Synthesis and characterization of extremely bulky amido-germanium(II) halide complexes

Article abstract of DOI:10.1139/cjc-2013-0394

The extremely bulky aryl/silyl secondary amines, HN(Ar)(SiMe₃), Ar = C₆H₂-i-Pr₂(CPh₃)-2,6,4 (L ^DipH), C₆H₂{C(H)Ph₂} ₂-i-Pr-2,6,4 (L^?H)

Full text of DOI:10.1139/cjc-2013-0394

427
ARTICLE
Synthesis and characterization of extremely bulky
amido-germanium(II) halide complexes
Terrance J. Hadlington, Jiaye Li, and Cameron Jones
Abstract: The extremely bulky aryl/silyl secondary amines, HN(Ar)(SiMe3), Ar = C6H2-i-Pr2(CPh3)-2,6,4 (LDipH), C6H2{C(H)Ph2}2-i-
Pr-2,6,4 (L†H), or C6H2{C(H)Ph2}2-t-Bu-2,6,4 (Lt-BuH), have been synthesized via salt metathesis reactions between the appropriate
lithium anilide complex and ClSiMe3. The related diaryl secondary amines, HN(Ar*)(R), Ar* = C6H2{C(H)Ph2}2Me-2,6,4 and R =
C6H3Me2-3,5 (LMeH), C6H3(CF3)2-3,5 (LCF3H), or C6H2-i-Pr3-2,4,6 (LTripH), were prepared via palladium catalyzed cross-coupling
reactions. Three of the amines were crystallographically characterized. Treatment of GeCl2·dioxane with 1 equiv. of each of the
deprotonated amines led to the isolation of the amido-germanium(II) chloride complexes, [LGeCl] (L = L†, Lt-Bu, LCF3, or LTrip).
Similarly, reaction of the known amido-digermyne, [L*Ge–GeL*] (L* = –N(Ar*)(SiMe3)), with I2 resulted in the oxidative cleavage of
the Ge–Ge bond of the digermyne, and the formation of the first two-coordinate amido-germanium(II) iodide complex, [L*GeI].
Crystallographic characterization of [Lt-BuGeCl] and [L*GeI] revealed both to have similar monomeric structures. The compounds
described in this study should prove useful as synthons for synthetic chemists working in the field of low oxidation state main
group chemistry.
Key words: germylene, steric bulk, amide, germanium, crystal structure.
Résumé : On a synthétisé les arylsilylamines secondaires très encombrées, HN(Ar)(SiMe3), Ar = C6H2-i-Pr2(CPh3)-2,6,4 (LDipH),
C6H2{C(H)Ph2}2-i-Pr-2,6,4 (L†H), ou C6H2{C(H)Ph2}2-t-Bu-2,6,4 (Lt-BuH), par des réactions de métathèse entre le complexe anilide
lithium approprié et le ClSiMe3. On a préparé les diarylamines secondaires apparentées, HN(Ar*)(R), Ar* = C6H2{C(H)Ph2}2Me-2,6,4
et R = C6H3Me2-3,5 (LMeH), C6H3(CF3)2-3,5 (LCF3H), ou C6H2-i-Pr3-2,4,6 (LTripH), par des réactions de couplage croisé catalysées par
le palladium. Trois de ces amines ont été caractérisées par cristallographie. Le traitement du GeCl2·dioxane avec 1 equiv. de
chacune des amines déprotonées a permis d’isoler les complexes chlorure de germanium(II) amido, [LGeCl] (L = L†, L-t-Bu, LCF3 ou
LTrip). Similairement, la réaction de l’amidodigermyne connu, [L*Ge–GeL*] (L* = –N(Ar*)(SiMe3)), avec I2 a donné lieu au clivage
oxydatif de la liaison Ge–Ge du digermyne et a` la formation du premier complexe a` deux coordinats iodure de germanium(II)
amido, [L*GeI]. La caractérisation du [L-t-BuGeCl] et du [L*GeI] par cristallographie a révélé qu’ils possèdent des structures
monomériques similaires. Les composés décrits dans la présente étude devraient être des synthons utiles pour les spécialistes de
la chimie de synthèse dont le travail porte sur les éléments du groupe principal dans un faible état d’oxydation. [Traduit par la
Rédaction]
Mots-clés : germylène, encombrement stérique, amide, germanium, structure crystalline.
Our contributions to the design and synthesis of kinetically
stabilizing ligands have largely centered on bulky anionic, bidentate
Introduction
The chemistry of compounds containing the main group ele-
ments in very low oxidation states and (or) with very low coordi-
nation numbers has rapidly expanded over the past 20 years.1–4
The growing interest in this area has largely been driven by ad-
vances it has offered to our fundamental understanding of bond-
ing, structure, and compound stability. More recently, however,
the recognition that low oxidation state main group compounds
can possess electronic structures similar to those of d-block metal
complexes has led to the former finding a variety of “transition
metal-like” synthetic applications.5–8 Pertinent examples here are
the, sometimes reversible, activations of small molecules, e.g., H2,
CO2, C2H4, NH3, etc., that are central to many catalytic processes.
Most developments in this aspect of the field have occurred with
low oxidation state group 14 element complexes, the kinetic sta-
bilization of which has been permitted by the growing number of
sterically encumbered ligands that are available to the synthetic
inorganic chemist.
N-donor ligands. Of most note are the very hindered guanidi-
nate and amidinate ligand systems, [(DipN)2CR]– (Dip = C6H3-i-Pr2-
2,6 and R = bulky amino, alkyl, aryl), which we have applied to the
stabilization of a variety of metallacycles containing metal cen-
ters in the +1 (or +2) oxidation state, not only from the s- and
p-blocks,9 but also from the d- and f-blocks.10,11 Over the past two
years, we have extended this study to the preparation of a new
class of monodentate amide ligands of unprecedented steric bulk,
e.g., –N(Ar)(R) (Ar = C6H2{C(H)Ph2}2R=-2,6,4; R= = Me (Ar*) or i-Pr
(Ar†); and R = SiMe3, SiPh3, SiPri3, Ph, or mesityl (Mes)).12–14 These
have been used to stabilize a variety of one- and two-coordinate
p-block (and d-block) metal(I or II) complexes, which, in many
cases, display fascinating reactivity.12–21 Most success has been
had with low-valent germanium systems such as the amido-
digermynes, [L*Ge–GeL*]17 and [L=Ge=GeL=]21 (L* = –N(Ar*)(SiMe3)
and L= = –N(Ar†)(Si-i-Pr3)), which are closely related to Power’s22
celebrated bulky terphenyl substituted digermynes, e.g.,
Received 29 August 2013. Accepted 8 October 2013.
T.J. Hadlington, J. Li, and C. Jones. School of Chemistry, Monash University, P.O. Box 23, Melbourne, Victoria 3800, Australia.
Corresponding author: Cameron Jones (e-mail: cameron.jones@monash.edu).
This article is part of a Special Issue commemorating the 14th International Conference on the Coordination and Organometallic Chemistry of Germanium, Tin, and Lead
(ICCOC-GTL 2013) held in Baddeck, NS, July 2013.
Can. J. Chem. 92: 427–433 (2014) dx.doi.org/10.1139/cjc-2013-0394
Published at www.nrcresearchpress.com/cjc on 15 October 2013.

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Can. J. Chem. Vol. 92, 2014
Scheme 1. Synthesis of bulky secondary amines.
[Ar=Ge=GeAr=] (Ar= = –C6H3(C6H3-i-Pr2-2,6)2-2,6). Not only can the
Ge–Ge bond order in these systems be readily controlled by subtle
variations in amido ligand bulk, but they can also activate both H2
and CO2 at temperatures well below 0 °C, and at atmospheric
pressure.16,17,21 To extend the range of amido-digermynes, and to
explore the effects that ligand (L) sterics and electronics have on
their properties and reactivity, new germanium(II) halide precur-
sors, [LGeX] (X = halide), to these complexes need to be available.
Herein, we describe the development of several new bulky sec-
ondary amine proligands, and the use of these in the preparation
of a number of monomeric amido-germanium(II) halide com-
plexes.
amines (range: ␦ 3.30–18.01 ppm, cf. ␦ 3.20 ppm for L*H) and the
19F{1H} NMR spectrum of LCF3H (␦ –62.7 ppm).
Three of the secondary amines (LDipH, LCF3H, and LTripH) were
crystallographically characterized, and their molecular structures
can be found in Fig. 1. The increasing steric bulk around the N
center of this series of amines is clear, with the bulk of LTrip
H
being especially significant. Despite this, the C/Si–N–C angles of
the compounds fall in a fairly narrow range (121.22(10)–124.44(18)°)
and their N–C/Si bond lengths are unexceptional. One feature of
the solid state structure of LTripH that is worth mentioning is that
one of its ortho-isopropyl groups appears to be sandwiched be-
tween two phenyl groups of its benzhydryl substituents. However,
the simplicity of the 1H NMR spectrum of the compound suggests
that this does not greatly hinder rotation of the Ar* and Trip
groups, relative to each other, in solution.
Attempts were made to prepare amido-germanium(II) chloride
complexes, [LGeCl], by deprotonating all of the secondary amines
with Li-n-Bu, followed by treatment of tetrahydrofuran (THF)
solutions of GeCl2·(dioxane) with the in situ generated lithium
amides (Scheme 2). These reactions afforded moderate to good
yields of the expected compounds from all of the lithium amides,
except LiLDip and LiLMe, for which intractable product mixtures
were obtained. It is perhaps not surprising that [LDipGeCl] could not
be readily accessed, as the closely related system [(Dip)(Me3Si)NGeCl]
can only be prepared in very low yield.20 It is, however, worth
noting that from one attempted crystallization of [LDipGeCl] from
a diethyl ether extract of the reaction mixture, a few crystals of
the cocrystallized, lithium amide complexes, [LDipLi(THF)(OEt2)]
[LDipLi(THF)3], were obtained. Details of the molecular structure of
the [LDipLi(THF)(OEt2)] component of this cocrystal can be found in
the Supplementary data.
While compounds 1–4 will likely prove useful as precursors to a
variety of lower oxidation state systems via reduction methodol-
ogies, it would be useful to be able to access the iodo-germylene
analogues of these species. One reason for this is that it is well
known that reductions of p-block metal iodide complexes are
typically more facile and higher yielding than those of metal chlo-
rides.1–8 While it is likely that compounds of the type [LGeI] should
be easily synthesized from reactions of lithium amides with GeI2,
the very high cost of the latter reagent makes this route prohibi-
tive. As a demonstration of the feasibility of an alternative route
to amido-germanium(II) iodide complexes, we carried out the re-
action of the known digermyne [L*Ge–GeL*]17 with 1 equiv. of I2.24
This, indeed, afforded a moderate yield of the monomeric amido-
germanium(II) iodide compound, [L*GeI] (5), via oxidative cleavage
of the Ge–Ge bond of the digermyne. The spectroscopic data for
Results and discussion
At the outset of this study, it was decided to target two specific
variations of the general class of bulky amido ligands, –N(Ar)(R),
which we have previously developed.12–14 The first group of these,
–N(Ar)(SiMe3), Ar = C6H2-i-Pr2(CPh3)-2,6,4 (Dip*), Ar†, or C6H2{C(H)Ph2}2-
t-Bu-2,6,4 (Art-Bu), is related to the well-used –N(Ar*)(SiMe3) (L*) li-
gand,12 but has both less bulky (Dip*) and more bulky (Ar† or
Art-Bu) aryl substituents. The second group of ligands, –N(Ar*)(R),
R = C6H3Me2-3,5 (ArMe), C6H3(CF3)2-3,5 (ArCF3), or C6H2-i-Pr3-2,4,6
(ArTrip), is related to the previously employed diaryl amide li-
gands, –N(Ar*)(Ph) and –N(Ar*)(Mes),13 but have varying steric bulk
and electronic properties. With respect to the latter property, the
ArCF3 substituted ligand might be expected to be more electron
withdrawing than the other diaryl amides.
Two synthetic routes were employed to synthesize the second-
ary amine proligands in moderate to high yields (Scheme 1). The
silyl substituted amines, HN(Ar)(SiMe3), Ar = Dip* (LDipH), Ar†
(L†H), or Art-Bu (Lt-BuH), were readily prepared by quenching the
in situ generated lithiated anilines, “LiN(Ar)H”, with chlorotri-
methylsilane. In contrast, the diaryl amines, HN(Ar*)(R), R = ArMe
(LMeH), ArCF3 (LCF3H), or Trip (LTripH), were synthesized by palla-
dium catalyzed cross-coupling reactions, based on a literature pro-
cedure,23 between ArBr and the aniline Ar*NH2. A gauge of the
acidity of the amino protons of these ligands can be drawn from
1
the chemical shifts of their H NMR signals. Those for both the
silyl substituted amines (␦ 1.65–2.05 ppm) and the diaryl amines
(␦ 4.46–4.59 ppm) fall in narrow, but distinct, ranges that are
comparable to chemical shifts reported for related systems, e.g.,
HN(Ar*)(SiMe3) (␦ 1.75 ppm) and HN(Ar*)(Mes) (␦ 4.32 ppm), respec-
tively. It is of note that the fluorine substitution in LCF3H appears
to have little effect on the acidity of its amine proton, relative to
those in LMeH and LTripH. It is also worthy to mention that singlet
resonances were observed in the 29Si{1H} NMR spectra of the silyl
Published by NRC Research Press

Hadlington et al.
429
Fig. 1. Thermal ellipsoid plot (25% probability surface) of the
molecular structures of (a) LDipH, (b) LCF3H, and (c) LTripH. Hydrogen
atoms (except amino protons) are omitted. C/Si–N–C angles (°):
121.22(10) for LDipH, 124.44(18) for LCF3H, and 124.05(11) for LTripH.
closest C···E interactions in these complexes involve the ipso- and
one ortho-aromatic carbon atom of each flanking phenyl group
(ϳ3.17–3.40 Å for 2 and 3.08–3.10 Å for 5), which are well outside
the sum of the covalent radii for Ge and C (1.90 Å).26 An examina-
tion of the N–Ge–halide angles of 2 (99.19(5)°) and 5 (102.02(9)°)
shows them to be similar to each other, and to that for [L*GeCl]
(98.85(9)°).12 Moreover, the Si–N–Ge halide fragment of each com-
pound is essentially planar, which could suggest some overlap of
the N p-orbital lone pair with the empty p-orbital at Ge, as has
been postulated for [L*GeCl]. Indeed, the Ge–N distances in 2 and
5 are at the short end of the known range of distances for GeII–N
(mean: 1.979 Å) interactions.27
Conclusions
In summary, a range of extremely bulky secondary amines have
been synthesized and fully characterized. The majority of these
have been utilized in the preparation of new amido-germanium(II)
chloride complexes, one of which has been crystallographically
characterized and shown to be monomeric in the solid state. A
related monomeric amido-germanium(II) iodide compound has
been prepared in good yield via the oxidative cleavage of the
Ge–Ge bond of an amido-digermyne with I2. The amide ligands
and the amido-germanium(II) halide complexes described in this
study should prove useful synthons for synthetic inorganic chem-
ists, especially those with an interest in the chemistry of low
oxidation state/low coordination number metal complexes.
Experimental section
General methods
All manipulations were carried out using standard Schlenk and
glove box techniques under an atmosphere of high purity dini-
trogen. THF, hexane, and toluene were distilled over potassium,
whilst diethyl ether was distilled over a Na/K alloy (1:1). Dichlo-
Scheme 2. Synthesis of compounds 1–5.
1
romethane was distilled over CaH2. H and 13C{1H} NMR spectra
were recorded on Bruker Avance III 400 or Varian Inova 500 spec-
trometers and were referenced to the resonances of the solvent
used. 29Si{1H} and 19F{1H} NMR spectra were recorded on a Bruker
Avance III 400 spectrometer and were referenced to external
SiMe4 and CFCl3, respectively. Mass spectra were obtained from
the Engineering and Physical Sciences Research Council (EPSRC)
National Mass Spectrometric Service Centre at Swansea Univer-
sity. FT-IR spectra were recorded using a PerkinElmer RX1 spec-
trometer as Nujol mulls between NaCl plates, or on solid samples
protected from the atmosphere with a film of Nujol using an
Agilent Cary 630 attenuated total reflectance (ATR) spectrometer.
Microanalyses were carried out by the Science Centre, London
Metropolitan University. Reproducible microanalyses of the ma-
jority of the germylene halide complexes could not be acquired as
they could either not be obtained as crystalline solids or their
recrystallization consistently led to contamination with small
amounts (ϳ5%) of the free secondary amine proligands, which
have similar solubilities to the germylene complexes. Melting
points were determined in sealed glass capillaries under dini-
trogen and are uncorrected. The compounds Ar*NH2, [(IPr)Pd(Im)]
(IPr = C{N(Dip)C(H)}2 and Im = 1-methylimidazole),23 Dip*NH2,28
and [L*GeGeL*]17 were prepared by literature procedures. All other
reagents were used as received.
this compound are very similar to those for [L*GeCl], and are con-
sistent with its proposed structure. This is also the case for the
data for 1–4, though it is noteworthy that the spectra for 4 display
a number of very broad resonances, which suggests that, unlike
for the free amine LTripH, the Ar* and Trip substituents of the
compound cannot freely rotate in solution at room temperature.
Variable temperature solution state NMR studies did not lead to
any significant sharpening of these signals.
Although it only proved possible to obtain X-ray crystal struc-
tures of 2 and 5 (see Fig. 2), it is very likely that compounds 1, 3,
and 4 have related monomeric structures in the solid state.25
Moreover, the structures of 2 and 5 are very similar to that of
[L*GeCl],12 while compound 5 represents the first crystallographi-
cally characterized two-coordinate amido-germanium(II) iodide
species. It is clear from Fig. 2 that the reluctance of 2 and 5 to
dimerize is partly due to the Ge centers of the complexes being
sandwiched by two phenyl substituents of their Ar moieties. The
Ar†NH2
Diphenylmethanol (10.0 g, 74 mmol), 4-isopropylaniline (27.3 g,
148 mmol), ZnCl2 (5.0 g), and 8.3 mL of 34% aqueous HCl were
added to a flask under dinitrogen, vented to a bubbler, and the
mixture was heated at 160 °C for 3 h before being cooled to room
temperature. The mixture was then extracted with dichlorometh-
ane (100 mL) and the extract washed with a saturated aqueous
solution of K2CO3. The dichloromethane layer was separated and
then evaporated to dryness. The solid residue was washed with
Published by NRC Research Press

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Can. J. Chem. Vol. 92, 2014
Fig. 2. Thermal ellipsoid plot (25% probability surface) of the molecular structures of (a) [Lt-BuGeCl] (2) and (b) [L*GeI] (5). Hydrogen atoms are
omitted. Selected bond lengths (Å) and angles (°) for 2: Ge(1)–N(1) 1.8481(15), Ge(1)–Cl(1) 2.2374(7), Si(1)–N(1) 1.7642(16), N(1)–C(1) 1.448(2),
N(1)–Ge(1)–Cl(1) 99.19(5), C(1)–N(1)–Si(1) 119.15(12), C(1)–N(1)–Ge(1) 108.87(11), Si(1)–N(1)–Ge(1) 131.98(9). Selected bond lengths (Å) and angles (°) for
5: I(1)–Ge(1) 2.6641(4), Ge(1)–N(1) 1.865(3), Si(1)–N(1) 1.753(3), N(1)–C(1) 1.453(4), N(1)–Ge(1)–I(1) 102.02(9), C(1)–N(1)–Si(1) 118.8(2), C(1)–N(1)–Ge(1)
106.2(2), Si(1)–N(1)–Ge(1) 134.95(17).
ethyl acetate (ϳ25 mL) and then dried under vacuum to give
mixture allowed to warm to room temperature, after which time
it was stirred for 4 h. Volatiles were then removed in vacuo to
afford a gummy solid. The residue was extracted with dichlo-
romethane (60 mL), the extract filtered, and then evaporated to
dryness. The solid residue was washed with hexane (ϳ15 mL) and
then dried under vacuum to give L†H as a colorless solid (3.29 g,
57%); mp 118–120 °C. IR (Nujol, cm−1) ␯: 3357 (N-H str., m). 1H NMR
(400 MHz, CDCl3, 298 K) ␦: 0.14 (s, 9H, SiC(CH3)3), 0.98 (d, J = 6.9 Hz,
6H, CH(CH3)2), 1.65 (s, 1H, NH), 2.61 (sept, J = 6.9 Hz, 1H, CH(CH3)2),
5.94 (s, 2H, CHPh2), 6.56 (s, 2H, m-Ar-H), 6.98–7.26 (m, 20H, Ar-H).
13C{1H} NMR (101 MHz, C6D6, 298 K) ␦: 1.4 (Si(CH3)3), 24.1 (CH(CH3)2),
33.3 (CH(CH3)2), 52.7 (CHPh2), 126.1, 126.5, 126.6, 128.2, 128.5, 129.1,
Ar†NH2 as a colorless solid (23.5 g, 68%); mp 165–168 °C. IR (ATR,
1
cm−1) ␯: 3427 (N-H str., m), 3365 (N-H str., m). H NMR (400 MHz,
CDCl3, 298 K) ␦: 0.93 (d, J = 6.9 Hz, 6H, CH(CH3)2), 2.53 (br m, 1H,
CH(CH3)2), 3.26 (s, 2H, NH2), 5.44 (s, 2H, CHPh2), 6.42 (s, 2H, m-Ar-H),
7.04–7.32 (m, 20H, Ar-H). 13C{1H} NMR (101 MHz, CDCl3, 298 K) ␦:
24.1 (CH(CH3)2), 33.3 (CH(CH3)2), 52.7 (CHPh2), 126.5, 126.6, 128.5, 129.1,
129.6, 137.9, 140.0, 143.0 (Ar-C). ESI-MS m/z (%): 468.2 (Ar†NH3+, 100).
Accurate (acc.) mass ESI-MS calcd. for C35H34N (Ar†NH3+): 468.2691;
found: 468.2684.
Art-BuNH2
A similar procedure was used as for the preparation of Ar†NH2,
except 4-tert-butylaniline was employed (yield 31%); mp 195–
200 °C. IR (Nujol, cm−1) ␯: 3421 (N-H str.), 3358 (N-H str., m). 1H NMR
(400 MHz, CDCl3, 298 K) ␦: 0.97 (s, 9H, C(CH3)3), 3.33 (s, 2H, NH2),
5.47 (s, 2H, CHPh2), 6.58 (s, 2H, m-Ar-H), 7.08–7.29 (m, 20H, Ar-H).
13C{1H} NMR (101 MHz, CDCl3, 298 K) ␦: 31.4 (C(CH3)3), 34.0 (C(CH3)3),
52.8 (CHPh2), 125.6, 126.6, 128.5, 128.6, 129.6, 139.6, 140.1, 143.0
(Ar-C). ESI-MS m/z (%): 482.2 (Art-BuNH3+, 100). Acc. mass ESI-MS
calcd. for C36H36N (Art-BuNH3+): 482.2848; found: 482.2843.
129.6, 137.9, 140.0, 141.0, 143.0, 144.4 (Ar-C). 29Si{1H} NMR (80 MHz,
+
C6D6, 298 K) ␦: 18.0 (s). ESI-MS m/z (%): 541.3 (MH+, 2), 468.2 (Ar†NH3
,
100).
Lt-Bu
H
Li-n-Bu (3.5 mL of a 1.6 mol/L solution in hexane) was added to a
solution of Art-BuNH2 (2.50 g, 5.19 mmol) in THF (40 mL) at –80 °C.
The resultant solution was warmed to room temperature and
stirred for 1 h before being cooled again to –80 °C. Neat SiMe3Cl
(0.75 mL, 0.642 g, 5.87 mmol) was added to this solution and the
reaction mixture allowed to warm to room temperature, after
which time it was stirred for 4 h. Volatiles were then removed in
vacuo to afford a solid residue. This was extracted with dichlo-
romethane (50 mL), the extract filtered, and evaporated to dry-
ness. The residue was washed with hexane (ϳ10 mL) and the
remaining solid dried under vacuum to give Lt-BuH as a colorless
solid (1.97 g, 71%); mp 165–170 °C. IR (Nujol, cm−1) ␯: 3360 (N-H str.,
m). 1H NMR (400 MHz, C6D6, 298 K) ␦: 0.12 (s, 9H, SiC(CH3)3), 1.06 (s,
9H, C(CH3)3), 1.83 (s, 1H, NH), 6.19 (s, 2H, CHPh2), 7.02–7.23 (m, 22H,
Ar-H). 13C{1H} NMR (101 MHz, C6D6, 298 K) ␦: 1.3 (Si(CH3)3),
31.3 (C(CH3)3), 34.4 (C(CH3)3), 53.2 (CHPh2), 126.3, 126.5, 128.6, 130.0,
140.4, 141.1, 144.9, 145.7 (Ar-C). 29Si{1H} NMR (80 MHz, CDCl3, 298 K)
␦: 3.53. ESI-MS m/z (%): 554.5 (MH+, 17), 482.2 (Art-BuNH3+, 100).
LDip
H
Li-n-Bu (1.5 mL of a 1.6 mol/L solution in hexane) was added to a
solution of Dip*NH2 (1.0 g, 2.38 mmol) in THF at –80 °C. The resul-
tant solution was warmed to room temperature and stirred for 1 h
before being cooled again to –80 °C. Neat ClSiMe3 (0.30 mL,
0.257 g, 2.38 mmol) was added to this solution and the reaction
mixture allowed to warm to room temperature, after which time
it was stirred for an additional 3 h. Volatiles were then removed in
vacuo to afford a viscous oil. This was extracted with toluene
(10 mL), the extract filtered, and hexane (5 mL) added to the fil-
trate. The resultant solution was placed at –20 °C overnight afford-
ing colorless crystals of LDipH (0.57 g, 48%); mp 120–124 °C. IR
(Nujol, cm−1) ␯: 3376 (N-H str., m). 1H NMR (400 MHz, C6D6, 298 K)
␦: 0.10 (s, 9H, Si(CH3)3), 1.08 (d, J = 6.9 Hz, 12H, CH(CH3)2), 2.05 (s, 1H,
NH), 3.39 (sept, J = 6.9 Hz, 2H, CH(CH3)2), 6.96–7.45 (m, 17H, Ar-H).
13C{1H} NMR (151 MHz, C6D6, 298 K) ␦: 0.8 (Si(CH3)3), 23.8 (CH(CH3)2),
28.5 (CH(CH3)2), 65.6 (CPh3), 126.1, 126.9, 127.7, 131.7, 137.7, 141.7, 143.0,
148.0 (Ar-C). 29Si{1H} NMR (80 MHz, C6D6, 298 K) ␦: 3.33 (s). ESI-MS m/z(%):
491.3 (M+, 2), 420.2 (Dip*NH2+, 100).
LMe
H
A suspension of Ar*NH2 (5.0 g, 11.4 mmol), KO-t-Bu (1.78 g,
15.9 mmol), [(IPr)Pd(Im)] catalyst (184 mg, 2.5 mol%), and 3,5-
dimethylbromobenzene (1.11 mL, 8.20 mmol) in toluene (60 mL) was
heated at reflux for 2 h. The reaction mixture was allowed to cool
to room temperature, whereupon further portions of [(IPr)Pd(Im)]
catalyst (184 mg, 2.5 mol%) and 3,5-dimethyl bromobenzene
(0.74 mL, 5.47 mmol) were added, and the reaction mixture heated
again under reflux. The mixture was then cooled to room temper-
ature and all volatiles were removed in vacuo. The residue was
extracted with dichloromethane (3 × 25 mL), the combined
L†H
Li-n-Bu (6.7 mL of a 1.6 mol/L solution in hexane) was added to a
solution of Ar†NH2 (5.0 g, 10.7 mmol) in THF (40 mL) at –80 °C. The
resultant solution was warmed to room temperature and stirred
for 1 h before being cooled again to –80 °C. Neat SiMe3Cl (1.42 mL,
1.22 g, 11.1 mmol) was added to this solution and the reaction
Published by NRC Research Press

Hadlington et al.
431
Table 1. Summary of crystallographic data for LDipH, LCF3H, LTripH, 2, and 5.
LDip LCF3 LTrip
H
H
H
2
5
Empirical formula
Formula weight
Crystal system
Space group
a (Å)
b (Å)
c (Å)
␣ (°)
C34H41NSi
491.77
Monoclinic
P21/c
9.6943(2)
14.2774(3)
20.9242(6)
90
93.024(2)
90
2892.07(12)
4
C41H31F6N
651.67
Triclinic
P-1
13.5647(6)
15.8217(7)
16.2151(8)
88.585(2)
69.334(2)
89.568(2)
3255.1(3)
4
C48H51
641.90
Monoclinic
P21/n
12.608(3)
16.096(3)
18.938(4)
90
98.95(3)
90
3796.4(13)
4
1.123
0.064
1384
N
C39H42ClGeNSi
660.87
Monoclinic
P21/n
10.6827(3)
16.8010(5)
20.0684(6)
90
103.594(3)
90
3500.97(18)
4
C36H36GeINSi
710.24
Orthorhombic
Pmn21
17.4012(6)
9.2802(2)
9.9933(3)
90
90
90
1613.78(8)
2
1.462
␤ (°)
␥ (°)
Volume (Å3)
Z
␳ (calcd.) (g cm−3
)
1.129
0.103
1064
1.330
0.101
1352
1.254
1.013
1384
␮ (mm−1
F (000)
)
1.968
716
Reflections collected
Unique reflections
Rint
R1 indices (I > 2␴(I))
wR2 indices (all data)
CCDC No.
18863
5664
0.0300
0.0423
0.1048
957840
28039
11222
0.0259
0.0491
0.1279
48942
6664
0.1114
0.0556
0.1493
957845
22660
6886
0.0271
0.0325
0.0817
11153
3612
0.0302
0.0249
0.0512
957843
957839
957844
extracts filtered, and volatiles removed in vacuo to afford an off-
white solid. This residue was washed with hexane (10 mL) to give
LMeH as an off-white powder (4.33 g, 70%); mp 113–116 °C. IR (ATR,
cm−1) ␯: 3288 (N-H str., m). 1H NMR (C6D6, 400 MHz, 298 K) ␦: 1.54 (s,
6H, ArMe-m-CH3), 1.87 (s, 3H, Ar*-p-CH3), 4.46 (s, 1H, NH), 5.93 (s, 2H,
ArMe-o-CH), 6.07 (s, 2H, CHPh2), 6.41 (s, 1H, ArMe-p-CH), 6.99–
7.09 (m, 22H, Ar-H). 13C{1H} NMR (C6D6, 75.5 MHz, 298 K) ␦:
21.5 (ArMe-m-CH3), 30.1 (Ar*-p-CH3), 52.3 (CHPh2), 111.2, 120.6, 126.6,
128.6, 129.8, 130.4, 136.1, 136.6, 139.0, 144.3, 144.6, 147.6 (Ar-C).
3H, p-CH3), 2.85 (sept, J = 6.9 Hz, 1H, p-CH(CH3)2), 2.87 (sept, J =
6.9 Hz, 2H, o-CH(CH3)2), 4.66 (s, 1H, NH), 5.93 (s, 2H, CHPh2), 6.94 (s,
2H, Ar*-m-CH), 6.98–7.10 (m, 22H, Ar-H). 13C{1H} NMR (C6D6,
75.5 MHz, 298 K) ␦: 21.7 (p-CH(CH3)2), 24.3 (o-CH(CH3)2), 25.2 (o-
CH(CH3)2), 29.0 (p-CH(CH3)2), 35.2 (Ar*-p-CH3), 53.0 (s, 2H, CHPh2),
122.3, 127.1, 129.2, 130.5, 131.4, 132.0, 137.7, 139.0, 140.9, 141.7, 144.1,
145.1 (Ar-C). IR (ATR, cm−1) ␯: 3411 (N-H str., w). EI-MS m/z (%): 642.4
(MH+, 4), 440.2 (Ar*NH+, 28). Acc. mass calcd. for C48H52N (MH+):
642.4099; found: 642.4095.
EI-MS m/z (%): 544.1 (MH+, 95). Acc. mass ESI-MS calcd. for C41H37
N
[L†GeCl] (1)
(M+): 543.2926; found: 543.2895.
Li-n-Bu (2.4 mL of a 1.6 mol/L solution in hexane) was added to
a solution of L†H (2.0 g, 3.9 mmol) in THF (25 mL) at –80 °C. The
resultant red solution was warmed to room temperature and
stirred for 1 h. This solution was added to a solution of
GeCl2·dioxane (0.95 g, 4.1 mmol) in THF (10 mL) at –80 °C. The
mixture was then warmed to room temperature and stirred over-
night. Volatiles were then removed in vacuo, the residue ex-
tracted with toluene (50 mL), the extract filtered, and volatiles
removed from the filtrate in vacuo. The residue was washed with
hexane (ϳ10 mL) and the remaining solid dried under vacuum
yielding 1 as a colorless solid (1.92 g, 81%); mp 208–212 °C (de-
comp.). IR (ATR, cm−1) ␯: 1600 (m), 1378 (s), 1252 (s), 1204 (m), 1076 (m),
LCF3
H
This compound was prepared similarly to LMeH, except Ar*NH2
(5.0 g, 11.4 mmol), KO-t-Bu (1.78 mg, 15.9 mmol), [(IPr)Pd(Im)] cata-
lyst (184 mg, 2.5 mol%), and 3,5-bis(trifluoromethyl)bromobenzene
(1.41 mL, 8.20 mmol) were used in the initial stage of the reaction.
[(IPr)Pd(Im)] (184 mg, 2.5 mol%) and 3,5-bis(trifluoromethyl)
bromobenzene (0.94 mL, 5.47 mmol) were used in the latter stage of
the reaction. LCF3H was obtained by extraction of the crude reac-
tion mixture into hexane, followed by slow evaporation to afford
colorless crystals (2.38 g, 32%); mp 102–108 °C. IR (ATR, cm−1) ␯:
1
3387 (N-H str., m). H NMR (C6D6, 400 MHz, 298 K) ␦: 1.78 (s, 3H,
1
p-CH3), 4.53 (s, 1H, NH), 5.54 (s, 2H, CHPh2), 6.41–7.16 (m, 25H, Ar-H).
13C{1H} NMR (C6D6, 75.5 MHz, 298 K) ␦: 21.4 (p-CH3), 52.5 (CHPh2),
112.0 (CF3), 126.8, 127.9, 128.7, 129.6, 130.6, 132.4, 132.8, 133.3, 138.2,
143.2, 144.8, 148.4. 19F{1H} NMR (C6D6, 282 MHz, 298 K) ␦: –62.74 (s).
EI-MS m/z (%): 652.1 (MH+, 27). Acc. mass ESI-MS calcd. for
C41H30F6N (M+-H): 650.2282; found: 650.2278.
891 (m), 699 (s). H NMR (400 MHz, C6D6, 298 K) ␦: 0.72 (s, 9H,
Si(CH3)3), 0.94 (d, J = 6.9 Hz, 6H, CH(CH3)2), 2.47 (sept, J = 6.9 Hz, 1H,
CH(CH3)2), 5.92 (s, 2H, CHPh2), 6.79–7.26 (m, 22H, Ar-H). 13C{1H}
NMR (101 MHz, C6D6, 298 K) ␦: 4.4 (Si(CH3)3), 24.0 (CH(CH3)2),
33.8 (CH(CH3)2), 53.8 (CHPh2), 126.8, 126.9, 127.9, 128.8, 129.9, 130.0,
131.1, 142.2, 143.3, 143.4, 144.7, 145.2 (Ar-C). 29Si{1H} NMR (80 MHz,
C6D6, 298 K) ␦: 6.04 (s). EI-MS m/z (%): 647.2 (M+, 3, correct isotopic
distribution), 539.3 (L†+, 40), 467.2 (Ar†NH3+, 100).
LTrip
H
This compound was prepared similarly to LMeH, except Ar*NH2
(5.0 g, 11.4 mmol), KO-t-Bu (1.78 mg, 15.9 mmol), [(IPr)Pd(Im)] cata-
lyst (184 mg, 2.5 mol%), and 2,4,6-triisopropylbromobenzene
(2.08 mL, 8.20 mmol) were used in the initial stage of the reaction.
[(IPr)Pd(Im)] (184 mg, 2.5 mol%) and 2,4,6-triisopropylbromoben-
zene (1.39 mL, 5.47 mmol) were used in the latter stage of the
reaction. LTripH was obtained by extraction of the crude reaction
mixture into dichloromethane, filtration, and removal of all vola-
tiles from the filtrate in vacuo. The residue was recrystallized
from diethyl ether to afford LTripH as colorless crystals (1.78 g,
24%); mp 178–182 °C. 1H NMR (C6D6, 400 MHz, 298 K) ␦: 0.96 (d, J =
6.9 Hz, 12H, o-CH(CH3)2), 1.29 (d, J = 6.9 Hz, 6H, p-CH(CH3)2), 1.87 (s,
[Lt-BuGeCl] (2)
Li-n-Bu (1.3 mL of a 1.6 mol/L solution in hexane) was added to a
solution of Lt-BuH (1.0 g, 1.81 mmol) in THF (25 mL) at –80 °C. The
resultant solution was warmed to room temperature and stirred
for 1 h. This was added to a solution of GeCl2·dioxane (0.46 g,
1.99 mmol) in THF (10 mL) at –80 °C. The reaction mixture was
then warmed to room temperature, after which it was stirred
overnight. Volatiles were subsequently removed in vacuo and the
residue extracted with toluene (50 mL). The extract was filtered,
the filtrate evaporated to dryness, and the residue washed with
hexane (ϳ10 mL). This left 2 as an off-white solid (0.60 g, 50%).
Published by NRC Research Press

432
Can. J. Chem. Vol. 92, 2014
X-ray quality crystals of the compound were grown from a tolu-
ene/hexane solution; mp 230–234 °C (decomp.). IR (ATR, cm−1) ␯:
1600 (s), 1076 (s), 1030 (s), 891 (s), 765 (w). 1H NMR (400 MHz, C6D6,
298 K) ␦: 0.72 (s, 9H, SiC(CH3)3), 1.06 (s, 9H, C(CH3)3), 5.93 (s, 2H,
CHPh2), 6.79–7.27 (m, 22H, Ar-H). 13C{1H} NMR (101 MHz, C6D6,
298 K) ␦: 4.4 (Si(CH3)3), 31.2 (C(CH3)3), 34.6 (C(CH3)3), 53.9 (CHPh2),
126.0, 126.8, 128.7, 128.2, 129.8, 130.0, 131.1, 141.9, 143.4, 143.5, 147.4,
144.3 (Ar-C). 29Si{1H} NMR (80 MHz, C6D6, 298 K) ␦: 6.0. EI-MS m/z (%):
661.2 (M+, 13, correct isotopic distribution), 552.3 (Lt-Bu+, 100). Anal.
calcd. for C39H42ClGeNSi (%): C, 70.87; H, 6.41; N, 2.12; found: C,
70.94; H, 6.38; 2.17.
866 (w), 700 (s). EI-MS m/z (%): 710.0 (M+, 1, correct isotopic distri-
bution), 584.1 (L*Ge+, 100), 511.2 (L*+, 41).
X-ray crystallography
Crystals of LDipH, LCF3H, LTripH, 2, 5, [LDipLi(THF)(OEt2)][LDipLi(THF)3],
[L*Ge-GeL*], and [L†SiBr3] suitable for X-ray structural determina-
tion were mounted in silicone oil. Crystallographic measure-
ments were made using either Oxford Gemini Ultra or Bruker
Apex X8 diffractometers using a graphite monochromator with
MoK␣ radiation (␭ = 0.71073 Å) or the MX1 beamline of the Austra-
lian Synchrotron (␭ = 0.71080 Å, LTripH) at 123 K. The software
package Blu-Ice29 was used for synchrotron data acquisition,
while the program XDS30 was employed for synchrotron data re-
duction. The structures were solved by direct methods and refined
on F2 by full-matrix least-squares (SHELX97)31 using all unique
data. All nonhydrogen atoms are anisotropic with hydrogen
atoms included in calculated positions (riding model). Two crys-
tallographically independent molecules were refined in the asym-
metric unit of the crystal structure of LCF3H. There are no significant
geometric differences between them. The absolute structure pa-
rameter for the crystal structure of 5 was refined at –0.003(10).
Crystal data, details of data collections, and refinement are given
in Table 1 and Table S1 of the Supplementary data.
[LCF3GeCl] (3)
Li-n-Bu (0.53 mL, 1.6 mol/L in hexane) was added to a solution of
LCF3H (0.50 g, 0.77 mmol) in THF (30 mL) at –80 °C. The reaction
mixture was warmed to room temperature and stirred for 2 h. The
resultant solution was then added to a solution of GeCl2·dioxane
(0.20 g, 0.85 mmol) in THF (5 mL) at –80 °C. The resultant solution
was warmed to room temperature over 16 h, whereupon volatiles
were removed in vacuo. The residue was extracted with warm
toluene (20 mL), the extract filtered, and volatiles removed in
vacuo to give a yellow-brown oil. The residue was washed with
hexane (5 mL) and dried in vacuo to give 3 as a pale brown powder
(321 mg, 55%); mp 142–145 °C. IR (ATR, cm−1) ␯: 3062 (w), 3026 (w),
1610 (m), 1032 (m), 995 (m), 956 (s), 864 (m), 748 (m). 1H NMR (C6D6,
400 MHz, 298 K) ␦: 1.78 (s, 3H, p-CH3), 5.48 (s, 2H, CHPh2), 6.41–
7.68 (m, 25H, Ar-H). 13C{1H} NMR (C6D6, 75.5 MHz, 298 K) ␦: 25.2
(p-CH3), 52.7 (CHPh2), 69.0 (m-CF3), 114.2, 117.7, 129.8, 130.4, 132.3,
132.7, 137.9, 138.0, 142.1, 143.8, 144.4, 150.6 (Ar-C). 19F{1H} NMR
(C6D6, 282 MHz, 298 K) ␦: –62.8. EI-MS m/z (%): 759.0 (M+, <1, correct
isotopic distribution), 651.1 (LCF3+, 100).
Supplementary data
Supplementary data are available with the article through
the journal Web site at http://nrcresearchpress.com/doi/suppl/
10.1139/cjc-2013-0394. CCDC 957838-957845 contain the X-ray
data in CIF format for this manuscript. These data can be ob-
tained, free of charge, via http://www.ccdc.cam.ac.uk/products/
csd/ request (Or from the Cambridge Crystallographic Data
Centre, 12 Union Road, Cambridge CB2 1E2, UK; fax: +44 1223
33603; e-mail: deposit@ccdc.cam.ac.uk).
[LTripGeCl] (4)
Li-n-Bu (1.07 mL, 1.6 mol/L in hexane) was added to a solution of
LTripH (1.00 g, 1.56 mmol) in THF (30 mL) at –80 °C. The reaction
mixture was warmed to room temperature and stirred for 2 h. The
resultant solution was then added to a solution of GeCl2·dioxane
(0.397 g, 1.72 mmol) in THF (5 mL) at –80 °C. The resultant solution
was warmed to room temperature over 16 h, whereupon volatiles
were removed in vacuo. The residue was extracted with warm
toluene (20 mL), the extract filtered, and volatiles removed in
vacuo to give a yellow-brown oil. The residue was washed with
hexane (5 mL) and dried in vacuo to give 4 as a bright yellow
powder (970 mg, 82%); mp 96–108 °C (melt), mp 242–248 °C
(decomp.). IR (ATR, cm−1) ␯: 1598 (w), 1164 (w), 1032 (w), 881 (w),
Acknowledgements
This research was supported by the Australian Research Council
and the US Air Force Asian Office of Aerospace Research and De-
velopment (grant FA2386-11-1-4110). The EPSRC is also thanked for
access to the UK National Mass Spectrometry Facility. Part of this
research was undertaken on the MX1 beamline at the Australian
Synchrotron, Victoria, Australia.
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[L*GeI] (5)
To a solution of [L*GeGeL*] (0.10 g, 0.09 mmol) in toluene (15 mL)
at –80 °C was added solid iodine (0.02 g, 0.086 mmol). The resul-
tant solution was warmed to room temperature and stirred over-
night. Volatiles were then removed in vacuo and the residue was
dissolved in toluene (5 mL). Hexane (15 mL) was subsequently
layered onto the solution, from which grew colorless crystals of 5
(0.04 g, 34%); mp 230–234 °C (decomp.). 1H NMR (400 MHz, C6D6,
298 K) ␦: 0.82 (s, 9H, Si(CH3)3), 1.87 (s, 3H, ArCH3), 5.89 (s, 2H,
CHPh2), 6.81–7.33 (m, 22H, Ar-H). 13C{1H} NMR (126 MHz, C6D6) ␦:
5.3 (Si(CH3)3), 21.2 (ArCH3), 53.6 (CHPh2), 126.9, 127.1, 128.8, 129.7,
129.8, 130.0, 130.24, 130.7, 134.9, 142.6, 142.9, 143.0 (Ar-C). 29Si{1H}
NMR (80 MHz, CD2Cl2) ␦: 0.07. IR (ATR, cm−1) ␯: 1092 (w), 1020 (w)
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Published by NRC Research Press