[Ge(H)(2-C6H4PPh2)3] as ligand precursor at ruthenium: Formation and reactivity of [Ru(Cl){Ge(2-C6H4PPh2)3}]

Article abstract of DOI:10.1002/ejic.201402256

The germane [Ge(H)(2-C₆H₄PPh₂)₃] (2) was synthesized by reaction of Li[Ge(2-C₆H₄PPh₂)₃] (1) with water. The presence of nBuBr led to the formation of [Ge(nBu)(2-C

Full text of DOI:10.1002/ejic.201402256

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DOI:10.1002/ejic.201402256
[Ge(H)(2-C6H4PPh2)3] as Ligand Precursor at Ruthenium:
Formation and Reactivity of [Ru(Cl){Ge(2-C6H4PPh2)3}]
Roy Herrmann,[a] Thomas Braun,*[a] and Stefan Mebs[a]
Keywords: Ligand design / Podand-type ligands / Ruthenium / Germanium / Hydrazine / Ammonia
The germane [Ge(H)(2-C6H4PPh2)3] (2) was synthesized by
reaction of Li[Ge(2-C6H4PPh2)3] (1) with water. The presence
of nBuBr led to the formation of [Ge(nBu)(2-C6H4PPh2)3] (3).
The complex [Ru(Cl){Ge(2-C6H4PPh2)3}] (4) was obtained by
reaction of 2 with [Ru(Cl)2(PPh3)3] and NEt3. The ruthenium-
bound Ge(2-C6H4PPh2)3 moiety in 4 can be converted into
a Ge(Cl)(2-C6H4PPh2)2 fragment on treatment of 4 with a
solution of HCl in diethyl ether to yield [Ru(Cl){Ge(Cl)-
(2-C6H4PPh2)2}(PPh3)] (5). The reaction of complex 4 with
potassium hydride in an atmosphere of dihydrogen led to
[Ru{Ge(2-C6H4PPh2)3}(H)(H2)] (6). Complex 6 reacted with
hydrazine to give [Ru{Ge(2-C6H4PPh2)3}(H)(N2H4)] (7). With
an excess of hydrazine, complex 6 catalyzed the dispropor-
tionation of hydrazine to produce ammonia and the ruth-
enium complex [Ru{Ge(2-C6H4PPh2)3}(H)(NH3)] (8).
taining ligands (L = N2, N2H4, and NH3) can be ob-
tained.[8] Field et al. investigated the different reactivity of
ruthenium complexes bearing bidentate or tripodal phos-
phine ligands towards hydrazine. The reaction of a ruth-
enium complex bearing the bidentate ligand depe [= 1,2-
bis(diethylphosphanyl)ethane] with hydrazine gave the di-
azene complex [Ru(μ2-NH=NH)(depe)2].[9] In contrast to
that, the ruthenium complex [Ru(Cl)2{P(CH2CH2PR2)3}]
(R = Ph and iPr) bearing a tripodal ligand reacts with
hydrazine and potassium butoxide to give the dinitrogen
complex [Ru(N2){P(CH2CH2PR2)3}] and the dihydrido
complex [Ru(H)2{P(CH2CH2PR2)3}] by disproportionation
of hydrazine.[10]
Examples for heavier group 14 elements in the backbone
of tetradentate tripodal podand-type ligands are rare,[11]
whereas tetradentante tripodal ligands with group 13 and
15 elements as the backbone atoms are well estab-
lished.[2a–2g,2j–2m] Notably, Nakazawa et al. reported on the
synthesis of [E(H)(2-C6H4PPh2)3] (E = Ge, Sn), which serve
as a precursor for the generation of the rhodium and irid-
ium complexes [M{E(2-C6H4PPh2)3}(CO)] (M = Rh, Ir; E
= Ge, Sn).[11] The ligand precursor [Ge(H)(2-C6H4PPh2)3]
(2) was prepared by treatment of [Ge(OMe)(2-C6H4PPh2)3]
with LiAlH4. [Ge(OMe)(2-C6H4PPh2)3] was obtained by
the reaction of 3 equiv. of [2-C6H4PPh2]Li·Et2O with Ge-
(OMe)4 in the presence of tetramethylethylenediamine.[11a]
In this paper we report on an alternative route to access
[Ge(H)(2-C6H4PPh2)3] (2) via Li[Ge(2-C6H4PPh2)3] (1) as
well as on the molecular structure of 2 in the solid state.
Moreover, the ruthenium complexes [Ru(Cl){Ge-
(2-C6H4PPh2)3}] (4) and [Ru(Cl){Ge(Cl)(2-C6H4PPh2)2}-
(PPh3)] (5) were synthesized, in which the Ge(Cl)-
(2-C6H4PPh2)2 unit represents a rare example of germa-
nium-based pincer-type entities.[12] The structural analysis
Introduction
Studies on transition metal complexes with pincer-type[1]
or podand-type[2] ligands were the subject of intense re-
search over the last decades. The design of the ligand back-
bone often allows an adjustment of the steric and electronic
properties of the metal center. Moreover, sophisticated li-
gands can even participate in catalytic conversions as coop-
erative ligands.[3] Metal complexes with tridentate pincer-
type ligands are efficient catalysts for a variety of organic
reactions[4] and play a key role in the activation of small
molecules such as ammonia or dihydrogen.[5] However, po-
dand-type ligands can also offer a high flexibility and versa-
tility of the ligand backbone. The formally anionic anchor
atom in the backbone of some tetradentate derivatives can
lead to a strong labilizing electronic influence on the bind-
ing of a ligand in the trans position, and therefore influ-
ences its reactivity. This was demonstrated by Stobart et
al. by their studies on “anchoring” the silicon atom of the
formally anionic ligand [Si(CH2CH2PPh2)3]– onto a rho-
dium metal center.[6] In an extension of this work, Peters et
al. reported on the formation and reactivity of a variety of
transition metal complexes, which are characterized by
[Si(2-C6H4PR2)3]– (R = Ph and iPr) as ligands.[7] For in-
stance, the reduction of [Fe(Cl){Si(2-C6H4PiPr2)3}] led to
the dinitrogen complex [Fe{Si(2-C6H4PiPr2)3}(N2)], which
exhibits a strong trans labilization of the N2 ligand due to
the silyl donor moiety.[7a] Furthermore, complexes with a
Fe{Si(2-C6H4PiPr2)3}(L) scaffold and various nitrogen-con-
[a] Humboldt-Universität zu Berlin, Department of Chemistry,
Brook-Taylor-Str. 2, 12489 Berlin, Germany
E-mail: thomas.braun@chemie.hu-berlin.de
https://www2.hu-berlin.de/chemie/braun/
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.201402256.
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of the complexes 4 and 5 is supported by density functional in the formation of [Ph3Ge]Li, which can be converted into
theory (DFT) calculations. The reactivity of [Ru{Ge- [Ph3GeH] after treatment with water.[14] [2-C6H4PPh2]Li
(2-C6H4PPh2)3}(H)(H2)] (6) towards hydrazine was ex- can also be generated, together with nBuBr, by in situ lithi-
plored,whichledtotheformationof[Ru{Ge(2-C6H4PPh2)3}- ation of 2-Ph2PC6H4Br with nBuLi. However, subsequent
(H)(N2H4)] (7). With an excess of hydrazine its catalytic dis- treatment of the reaction mixture with GeCl2·dioxane gave
proportionation into ammonia and the formation of [Ge(nBu)(2-C6H4PPh2)3] (3), because 1 reacted with nBuBr
[Ru{Ge(2-C6H4PPh2)3}(H)(NH3)] (8) was observed.
(Scheme 2).
Results and Discussion
The germane [Ge(H)(2-C6H4PPh2)3] (2) was prepared by
the reaction of 3 equiv. of [2-C6H4PPh2]Li·Et2O with
GeCl2·dioxane, followed by treatment of the reaction mix-
ture with water (Scheme 1). On using D2O instead of H2O
the conversion resulted in the formation of the correspond-
ing germane [Ge(D)(2-C6H4PPh2)3] (2D). The reaction of
[2-C6H4PPh2]Li·Et2O with GeCl2·dioxane involves the ini-
tial formation of the lithium salt Li[Ge(2-C6H4PPh2)3] (1)
before hydrolysis (Scheme 1).
Scheme 2. Synthesis of the germane 3.
1
The H NMR spectrum of 2 in C6D6 shows a signal at δ
= 7.60 ppm, which can be assigned to three magnetically
equivalent hydrogen atoms at the three C6H4 groups. A
quartet at δ = 7.19 ppm was found for the germanium-
bound hydrogen, whereas in CD2Cl2 the quartet appears at
δ = 6.74 ppm. The latter exhibits a coupling to the phos-
phorus atoms of JHP = 5.5 Hz. This resonance is not pres-
1
ent in the H NMR spectrum of 2D, though a broad signal
2
was found in the H NMR spectrum at δ = 6.80 ppm. The
31P{1H} NMR spectrum of 2 shows a singlet at δ =
–8.97 ppm. For 3 a signal at δ = –8.91 ppm appears in the
31P{1H} NMR spectrum. The infrared spectrum of 2 re-
veals an absorption band at 2092 cm–1. This band is not
present in the spectrum of isotopologue 2D, but a new band
can be found at 1506 cm–1 instead. We therefore assign
these absorption bands to the Ge–H and Ge–D stretching
vibrations. The band for 2 appears at a slightly higher fre-
quency than the band for the Ge–H stretching vibration in
[Ph3GeH] (2037 cm–1).[15]
The molecular structure of 2 in the solid state is depicted
in Figure 2. Selected distances and angles are summarized
in Table 1. The hydrogen atom H1 was located in the differ-
ence Fourier map and refined isotropically. Compound 2
reveals a distorted C3 symmetry. The three phosphine moie-
Scheme 1. Synthesis of the germanes 2 and 2D.
Compound 1 can be detected by 31P{1H} NMR spec-
troscopy and features a signal at δ = –6.86 ppm with cou-
7
pling to the Li nucleus of JLiP = 25.7 Hz, as is depicted in
Figure 1. For comparison, McFarlane et al. reported that
7
Li[C(H)(PPh2)2] exhibits a Li coupling to the phosphorus
atoms of JLiP = 54 Hz.[13]
Figure 1. 31P{1H} NMR spectrum (162 MHz) of 1 at room tem-
perature.
Mechanistically, we presume that the germylene [Ge-
(2-C6H4PPh2)2] is generated initially and reacts further with
[2-C6H4PPh2]Li·Et2O to give 1. We were not able to detect
[Ge(2-C6H4PPh2)2], even when only 2 equiv. of [2-
C6H4PPh2]Li·Et2O were used. Note that Glockling and
Figure 2. Molecular structure of 2 in the solid state (ORTEP dia-
gram, ellipsoids at 50% probability). Hydrogen atoms, except for
Hooton showed that a reaction of GeI2 with PhLi results the germanium-bound hydrogen H1, are omitted for clarity.
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ties adopt a propeller-like structure, in which the lone pairs
of the phosphorus atoms encapsulate the Ge1–H1 entity.
The Ge1–H1 bond distance of 1.39(3) Å is shorter than the
Ge–H bond distance in [Ph3GeH] [1.45(4) and
1.50(5) Å].[16] Note that the Ge–P separations of 3.05, 3.13,
and 3.31 Å are below the sum of the van der Waals radii
(3.91 Å).[17] The molecular structure of 3 was also investi-
gated by X-ray crystallography (Figure 3, Table 1). In con-
trast to compound 2, the phosphine moieties do not encap-
sulate the butyl chain as is the case in 2 for the GeH moiety.
The Ge–P separations are 3.41 and 3.36 Å.
Table 1. Selected bond lengths [Å] and angles [°] in the germanes 2
and 3.
Scheme 3. Synthesis of ruthenium complexes 4 and 5.
2
3
to be close to zero for square-pyramidal structures and is
equal to unity for a trigonal-bipyramidal geometry.[18] The
Ge1–Ru1 bond length of 2.3695(3) Å is at the shorter end
ofGe–Rudistances,whicharereportedintheliterature,suchas
in [Ru(Cl)(GeMe3)(CO)(PPh3)2] [2.4455(4) Å][19] or in
[Ru(Cl){Ge(4-C6H4CH3)3}(CO)(PPh3)2] [2.4591(3) Å].[20]
Ge1–H1
Ge1–C1
Ge1–C19
Ge1–C37
H1–Ge1–C1
H1–Ge1–C19 111.7(11)
H1–Ge1–C37 109.0(11)
1.39(3)
Ge1–C4
Ge1–C8
Ge1–C12
Ge1–C55
C55–Ge1–C4
C55–Ge1–C8
C55–Ge1–C12
1.990(3)
1.969(3)
1.976(3)
1.968(3)
108.42(14)
113.47(14)
107.67(14)
1.966(3)
1.957(2)
1.967(3)
115.5(11)
Figure 4. Molecular structure of 4 in the solid state (ORTEP dia-
gram, ellipsoids at 50% probability). The hydrogen atoms are omit-
ted for clarity.
Figure 3. Molecular structure of 3 in the solid state (ORTEP dia-
gram, ellipsoids the 50% probability). Hydrogen atoms are omitted
for clarity.
Table 2. Selected bond lengths [Å] and angles [°] in 4 and 5.
4
5
Ge1–Ru1
Cl1–Ru1
Ru1–P1
Ru1–P2
Ru1–P3
2.3695(3)
2.4598(6)
2.3234(6)
2.2150(6)
2.3269(6)
Ge1–Ru1
Cl1–Ru1
Cl2–Ge1
Ru1–P1
Ru1–P2
2.3906(5)
2.4584(10)
2.2334(11)
2.2075(10)
2.3407(12)
2.3387(11)
167.66(3)
106.29(4)
152.93(4)
99.76(4)
Treatment of 2 with [Ru(Cl)2(PPh3)3] in the presence of
an excess of NEt3 yielded the ruthenium complex
1
[Ru(Cl){Ge(2-C6H4PPh2)3}] (4) (Scheme 3). The H NMR
spectrum of 4 reveals a prominent signal at δ = 8.48 ppm,
which corresponds to three equivalent aromatic hydrogen
atoms, one at each of the three C6H4 groups. The resonance
is shifted downfield compared with the corresponding sig-
nal for 2. A singlet at δ = 72.96 ppm in the 31P{1H} NMR
spectrum indicates three equivalent phosphine moieties.
The molecular structure of 4 in the solid state was deter-
mined by X-ray crystallography (Figure 4, Table 2).
Ge1–Ru1–Cl1 176.249(17)
Ru1–P3
P1–Ru1–P2
P2–Ru1–P3
P1–Ru1–P3
103.10(2)
104.81(2)
145.14(2)
Ge1–Ru1–Cl1
P1–Ru1–P2
P2–Ru1–P3
P1–Ru1–P3
Cl2–Ge1–Ru1
129.21(4)
However, it is similar to the Ge–Ru bond distance in
Complex 4 exhibits a structure that is between a trigonal the germylene complex [Ru{Ge(N(SiMe3)2)2}2(CO)3]
bipyramid and square pyramid with a Ge1–Ru1–Cl1 angle [2.37(1) Å],[21] but longer than the corresponding separa-
of 176.249(17)° with τ = 0.52. The parameter τ is defined tions in [Ru(GePh2)(H){Si(2-C6H4PPh2)3}] [2.2821(6) Å][22]
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or
[Cp*Ru{Ge(H)(2,4,6-C6H2iPr3)}(H)(PMeiPr2)]
[2.3579(3) Å].[23] Treatment of complex 4 with a solution of
HCl in Et2O resulted in a cleavage of one of the Ge–C
bonds to give the ruthenium complex [Ru(Cl){Ge(Cl)-
(2-C6H4PPh2)2}(PPh3)] (5) (Scheme 3). The 31P{1H} NMR
spectrum of 5 in [D8]toluene at room temperature features
a very broad signal at δ = 60–120 ppm and a signal at δ =
28.1–25.4 ppm, indicating the exchange of the phosphorus
atoms in solution (Figure 5). Cooling of the NMR sample
to –50 °C (122 MHz) led, after decoalescence, to the ap-
pearance of doublets of doublets at δ = 105.00, 67.58, and
25.75 ppm in a ratio of 1:1:1. The NMR spectroscopic data
are in accordance with the presence of three nonequivalent
phosphorus atoms. One Ge(2-C6H4PPh2) moiety is charac-
terized by the signal at δ = 67.58 ppm, which shows a trans-
coupling to the phosphorus atom in the PPh3 ligand of 2JPP
= 276.4 Hz. The signal at δ = 105.00 ppm for the second
2
Ge(2-C6H4PPh2) moiety reveals cis-couplings of JPP
=
Figure 6. Molecular structure of 5 in the solid state (ORTEP dia-
gram, ellipsoids at 50% probability). Hydrogen atoms are omitted
for clarity.
2
29.6 Hz and JPP = 24.2 Hz. Mechanistically, we suggest
that the dynamic behavior involves a migration of the PPh3
ligand to the vacant coordination site at the square-pyrami-
dal coordinated ruthenium center, which renders the germa-
nium-bound 2-C6H4PPh2 moieties equivalent on the NMR
time-scale at higher temperatures.
homopolar bonds the RJI is 50%). The electronic analysis
focused on the Ru–X (X = Ge, Cl, P) and Ge–X (X = Cl,
C) bonds and the involved atoms. The relevant topological
and integrated bond properties and atomic charges are
summarized in Table 3. The AIM bond-path motifs of 4
and 5 as well as iso-surface representations of the ELI-D
are shown in Figure 7.
Table 3. Topological and integrated bond properties and atomic
charges for the Ge–Ru and Ru–Cl bond of complexes 4 and 5.
Model:
Bond:
4
5
Ge–Ru
Ru–Cl
Ge–Ru
Ru–Cl
d [Å]
2.370
0.64
0.7
0.52
0.04
0.54
–0.47
2.00
8.2
1.21
0.661
64.5
0.07
1.14
2.459
0.44
4.6
0.48
0.14
0.96
–0.23
0.59
0.9
2.390
0.61
1.1
2.458
0.44
4.5
0.48
0.03
0.94
–0.23
0.66
1.0
ρ(r)bcp [eÅ–3]
Δρ(r)bcp [eÅ–5]
d1/d [%]
Figure 5. 31P{1H} NMR spectra (122 MHz) of 4 at room tempera-
ture (top), –15 °C (middle), and –50 °C (bottom).
0.51
0.06
0.57
–0.44
2.18
10.5
1.30
0.808
69.3
0.13
1.18
ε
G/ρ(r)bcp [he–1]
H/ρ(r)bcp [he–1]
The molecular structure of 5 in the solid state is shown
in Figure 6. Selected distances and angles are summarized
in Table 2. The molecule reveals a slightly distorted square-
pyramidal structure (τ = 0.25)[18] with P–Ru–P angles of
99.76(4)°, 106.29(4)°, and 152.93(4)°. The Ge1–Ru1–Cl1
angle is 167.66(3)°. The Ge1–Ru1 bond length of
2.3906(5) Å is slightly longer than the corresponding dis-
tance in 4.
ELI
N(001)
V(001)
Ymax
ΔELI [Å]
RJI [%]
Q(001) [e]
Q(001)
[Å3]
[e]
ELI
1.49
0.052
90.2
1.49
0.093
89.6
left
right
[e]
–0.66
–0.68
The structural analysis of the ruthenium complexes 4 and
For all bonds, ρ(r)bcp is the electron density at the bond
5 is supported by density functional theory (DFT) calcula- critical point, Δρ(r)bcp is the corresponding Laplacian, d1 is
tions (Gaussian 09[24]). These calculations were performed the distance from the first listed atom to the bond critical
on the basis of the X-ray data and subsequent determi- point, ε is the bond ellipticity (ε = λ1/λ2 – 1; λ1/2: curvatures
nation of real-space bonding indicators (RSBIs) derived perpendicular to the bond path), G/ρ(r)bcp and H/ρ(r)bcp are
from the electron and pair densities according to the atoms the kinetic and total energy density over ρ(r)bcp ratios.
ELI
in molecules (AIM[25]) and electron localizability indicator Results were obtained with AIM2000.[28] N(001)
and
ELI
(ELI-D[26]) space partitioning schemes. The recently intro- V(001)
are the electron populations and corresponding
duced Raub–Jansen index (RJI[27]) is the percental electron volumes of the ELI-D disynaptic valence basins, respec-
population overlap of the ELI-D basin under consideration tively, Ymax is the ELI-D value at the attractor position,
in the AIM atom with the higher electronegativity (for ΔELI is the perpendicular distance of the attractor position
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higher. Although the slightly more positive AIM atomic
charges of the Ru and Ge atoms in 5 compared with 4 indi-
cate an electron-withdrawing effect of the additional Cl
atom, the electron population within the V2(Ru,Ge) basin
is 0.18 e larger in 5. Taking into account the different types
of space-partitioning into atoms (AIM) and paired elec-
trons (ELI-D) this is not a contradiction. The bond charac-
ter of all other bonds remains unchanged.
The ruthenium complex [Ru(Cl){Ge(2-C6H4PPh2)3}] (4)
can be transformed into the hydrido dihydrogen complex
[Ru{Ge(2-C6H4PPh2)3}(H)(H2)] (6) by addition of potas-
sium hydride in a dihydrogen atmosphere (Scheme 4). The
1H NMR spectrum of 6 in C6D6 features a signal at δ =
8.54 ppm for three aromatic hydrogen atoms of the three
C6H4 groups that integrates in a ratio of 3:3 with a broad
resonance at δ = –5.03 ppm for the metal-bound hydrogen
atoms. The T1 value of 23 ms at 253 K ([D8]THF, 300 MHz)
is in accordance with the presence of a hydrido dihydrogen
complex.[31] The 31P{1H} NMR spectrum shows only one
singlet at δ = 77.11 ppm ([D8]THF). The latter resonance
1
and the signal at δ = –5.03 ppm in the H NMR spectrum
show no decoalescence in [D8]THF, even at –60 °C.
Figure 7. AIM bond topology of 4 (a) and 5 (b) (AIM2000 repre-
sentation[28]) and iso-surface representations of the ELI-D localiza-
tion domains (Y = 1.2) of 4 (c) and 5 (d) (MolIso representa-
tion[30]). The ELI-D surfaces are color-coded according to the ba-
sin size transforming from green (small) to blue (large). For clarity,
only domains connected to the Ru and/or the Ge atom are solid;
all others are given in transparent mode.
to the atom–atom axis, RJI is the Raub–Jansen index.
Q(001)left and Q(001)right are the AIM atomic charges. Results
were obtained with DGRID.[29]
Scheme 4. Synthesis of hydrido dihydrogen complex 6.
All but the Ru–Cl bonds show the typical characteristics
of polar-covalent interactions with appreciable ionic contri-
butions such as an electron density value at the bcp (bond
critical point) below 1.0 eÅ–3, a positive Laplacian (but
close to zero), a significantly positive kinetic density over
rho ratio [G/ρ(r)bcp], a potential density over rho ratio
[H/ρ(r)bcp] that is significantly negative, and finally a RJI
between 65% and 85%. However, the Ru–Cl bonds are
mainly ionic, which is reflected in the smallest ρ(r)bcp values
of 0.44 eÅ–3, large G/ρ(r)bcp values above 0.9 he–1, less
negative H/ρ(r)bcp values of –0.23 he–1, and small electron
populations [N(001)ELI] below 1 e. At ca. 90% the RJI is
at the border between polar-covalent and purely ionic. In
contrast, the Ru–Ge bond polarity is quite small with a RJI
of below 70%. Interestingly, the Ru–Ge bonds show quite
large distances of the ELI-D attractor of the disynaptic Ru–
Ge valence basins [V2(Ru,Ge)] to the Ru–Ge axes (Ͼ0.6 Å)
in 4 and 5 as shown in Figure 7c and 7d. Large ΔELI values
are a sign of bond strain in covalent single bonds and typi-
cal for non-directed ionic bonds in solids, but obviously
may also appear in multi-nuclear metal–organic com-
pounds.
The molecular structure of 6 in the solid state is shown
in Figure 8. Selected distances and angles are summarized
in Table 4. Complex 6 exhibits a distorted octahedral struc-
ture, if the dihydrogen ligand is treated as occupying a sin-
gle coordination site. The Ge1–Ru1 bond length of
The electronic impact of the Ge–Cl bond formation on
all bonds and atoms in the central Ru–Ge regime is quite
small as only the Ru–Ge bond is affected. In 5 the Ru–
Ge bond polarity is slightly increased as ionic contributions
Figure 8. Molecular structure of 6 in the solid state (ORTEP dia-
gram, ellipsoids at 50% probability). Hydrogen atoms (except for
the ruthenium-bound hydrogen atoms) and solvent molecules are
become more relevant and also the ΔELI value is slightly omitted for clarity.
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2.3724(4) Å is comparable to that of the chlorido complex hydrogen atoms H2a, H2b, H3a, and H3b were semi-freely
4 [2.3695(3) Å]. The ruthenium-bound hydrogen atom H1 refined. The Ge1–Ru1 distance of 2.3547(3) in complex 7 is
[Ru1–H1 distance of 1.55(4) Å] was located in the difference slightly shorter than in [Ru(Cl){Ge(2-C6H4PPh2)3}] (4) with
Fourier map and refined isotropically, whereas the di- a Ge–Ru distance of 2.3695(3) Å. The Ru1–H1 distance is
hydrogen atoms H2a and H2b were fixed with a Ru–H 1.68(3) Å and therefore longer than the Ru–H distance of
bond distance of 1.75 Å and an H2a–H2b bond distance of the hydrido dihydrogen complex 7 [1.55(4) Å]. The Ru1–N1
0.9 Å. These values are in accordance with the mean di- bond distance [2.2718(16) Å] and the N1–N2 bond distance
hydrogen distances in the complex [RuH2(H2)2(PCyp3)2] [1.468(2) Å] are in the expected range. For instance, the
(Cyp = cyclopentyl, Ru–H 1.75 Å and H–H 0.83 Å), which N–N bond lengths in [Ru(Cl)(μ1-N2H4)2{μ3-P(CH2CH2-
was characterized by single-crystal X-ray diffraction and PPh2)3}]+Cl– are 1.382(8) Å and 1.484(6) Å, whereas the
single-crystal neutron diffraction.[32] The Ru1–P1 bond dis- Ru–N distances are 2.219(5) Å and 2.239(4) Å.[10]
tance is presumably longer than the Ru1–P2 and Ru1–P3
distance due to the trans-influence of the hydrido ligand.[33]
Table 4. Selected bond lengths [Å] and angles [°] in 6.
Ge1–Ru1
Ru1–H1
Ru1–H2a
Ru1–H2b
Ru1–P1
Ru1–P2
Ru1–P3
2.3724(4)
1.55(4)
1.757(5)
1.758(5)
2.3591(7)
2.2993(7)
2.3107(7)
Ge1–Ru1–H1 76.7(16)
P1–Ru1–P2
P2–Ru1–P3
P1–Ru1–P3
P3–Ru1–H1
P2–Ru1–H1
105.91(3)
140.38(3)
109.37(3)
73.2(16)
67.4(16)
We also explored the reaction of complex 6 with hydraz-
ine, which yielded the hydrido hydrazine complex
[Ru{Ge(2-C6H4PPh2)3}(H)(μ1-N2H4)] (7) by replacement of
the dihydrogen ligand with hydrazine (Scheme 5).
Figure 9. Molecular structure of 7 in the solid state (ORTEP dia-
gram, ellipsoids at 50% probability). Hydrogen atoms (except for
the ruthenium-bound and nitrogen-bound hydrogen atoms) and
solvent molecules are omitted for clarity.
Table 5. Selected bond lengths [Å] and angles [°] in 7 and 8.
7
8
Scheme 5. Synthesis of hydrazine complex 7, amine complex 8, and
dinitrogen complex 9.
Ge1–Ru1
Ru1–H1
Ru1–N1
N1–N2
Ru1–P1
Ru1–P2
Ru1–P3
Ge1–Ru1–H1 88.6(12)
Ge1–Ru1–N1 177.83(4)
P1–Ru1–H1
P2–Ru1–H1
2.3547(3)
1.68(3)
2.2718(16)
1.468(2)
2.3123(5)
2.3558(5)
2.3155(5)
Ge1–Ru1
Ru1–H1
Ru1–N1
Ru1–P1
Ru1–P2
Ru1–P3
Ge1–Ru1–H1 82.6(17)
Ge1–Ru1–N1 172.61(10)
P2–Ru1–H1
P3–Ru1–H1
2.3469(5)
1.58(5)
2.258(4)
2.3444(9)
2.2902(9)
2.2860(9)
1
The hydrido ligand of complex 7 gives, in the H NMR
spectrum in C6D6, a resonance at δ = –8.81 ppm with a
doublet of triplet splitting, indicating a planar coordination
of the phosphorus entities and the hydrido ligand (2JP,H,trans
2
= 67.7, JP,H,cis = 30.2 Hz).[33] This corresponds to an
69.9(17)
72.5(17)
end-on coordination of the hydrazine ligand trans to the
germanium anchor atom. The signals for the hydrazine li-
gand appear in the 1H NMR spectrum at δ = 4.06 ppm and
δ = 2.58 ppm. Complex 7 is not stable in solution and
showed disproportionation of hydrazine to give the di-
74.4(12)
77.0(12)
Treatment of 6 with an excess of hydrazine (THF solu-
hydrogen complex [Ru{Ge(2-C6H4PPh2)3}(H)(H2)] (6) and tion) resulted in the catalytic disproportionation at room
amine complex [Ru{Ge(2-C6H4PPh2)3}(H)(NH3)] (8). temperature, to produce ammonia, dihydrogen, and pre-
Complex 7 was crystallized in the presence of a large excess sumably dinitrogen (2 N2H4 ǞN2 + H2 + 2 NH3). The for-
of hydrazine in THF. The molecular structure of 7 in the mation of N2H2 was not observed (2 N2H4 ǞN2H2
+
solid state is shown in Figure 9. Selected distances and 2 NH3), because of its fast disproportionation into dinitro-
angles are summarized in Table 5. Complex 7 exhibits a dis- gen and dihydrogen. We also could not identify any com-
torted octahedral structure. The ruthenium-bound plex with a N2H2 moiety bound at the ruthenium center.
hydrogen atom H1 was located in the difference Fourier We were not able to detect the dinitrogen complex
map and refined isotropically, whereas the hydrazine-bound [Ru{Ge(2-C6H4PPh2)3}(H)(N2)] (9), presumably because of
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a favored coordination of ammonia and dihydrogen at the refined. The Ru1–N1 bond distance of 2.258(4) Å is the
metal center. same as the corresponding separation in the hydrido ammo-
The catalytic disproportionation of hydrazine was ex- nia complex trans-[Ru(H)(dmpe)2(NH3)][C13H9] [dmpe =
plored by treatment of complex 7 with an excess of hydraz- 1,2-bis(dimethylphosphanyl)ethane; 2.252(7) Å].[35]
ine (5 equiv., 1 m in THF) at 50 °C for 2 d in benzene. Am-
monia was produced in 88% yield based on the amount of
hydrazine. The amount of ammonia was quantified by the
indophenol test.[34] It has to be taken into account that an
additional 10% of the formed ammonia is bound to
[Ru{Ge(2-C6H4PPh2)3}(H)(NH3)] (8), which is formed to-
gether with [Ru{Ge(2-C6H4PPh2)3}(H)(H2)] (6) in a 1:1 ra-
tio.
Conclusions
We reported on the synthesis of the germane [Ge(H)-
(2-C6H4PPh2)3] (2) by hydrolysis of the lithium compound
Li[Ge(2-C6H4PPh2)3] (1). The ruthenium complex [Ru(Cl)-
{Ge(2-C6H4PPh2)3}] (4) bears the Ge(2-C6H4PPh2)3 entity
as a tetradentate tripodal ligand. Reactivity studies of 4
show that this podand-type ligand can be transformed into
a pincer-type ligand to give [Ru(Cl){Ge(Cl)(2-C6H4PPh2)2}-
(PPh3)] (5), which exhibits a facial coordination of
the Ge(2-C6H4PPh2)3 unit. The binding of Ge(Cl)-
(2-C6H4PPh2)2 represents a rare example for pincer-type li-
gands with germanium in the backbone, whereas other
pincer-type ligands with heavier group 13 to 15 elements as
backbone atoms are well known.[2a,12b,36] In both complexes
4 and 5 the Ge–Ru bond is a polar-covalent bond. More-
over, the hydrido dihydrogen complex [Ru{Ge(2-C6H4-
PPh2)3}(H)(H2)] (6) reacts with hydrazine to give [Ru{Ge-
(2-C6H4PPh2)3}(H)(N2H4)] (7). Adding an excess of
hydrazine results in the catalytic formation of ammonia by
disproportionation of hydrazine, giving access to the
ammonia complex [Ru{Ge(2-C6H4PPh2)3}(H)(NH3)] (8).
The complexes [Ru{Ge(2-C6H4PPh2)3}(H)(NH3)] (8)
and [Ru{Ge(2-C6H4PPh2)3}(H)(N2)] (9) can be prepared in-
dependently by the treatment of [Ru{Ge(2-C6H4PPh2)3}-
(H)(H2)] (6) with ammonia or dinitrogen, respectively
(Scheme 5). The signal for the ammonia ligand of complex
1
8 appears in the H NMR spectrum at δ = 1.21 ppm and
the hydrido ligand gives a doublet of triplets at δ =
2
–8.64 ppm (2JP,H,trans = 68.7, JP,H,cis = 30.2 Hz). In the
31P{1H} NMR spectrum there is a doublet at δ = 73.85 ppm
and a triplet at δ = 63.71 ppm. The ruthenium complex 9
shows the expected splitting pattern of a doublet of triplets
2
at δ = –8.57 ppm (2JP,H,trans = 66.1, JP,H,cis = 28.1 Hz) in
1
the H NMR spectrum in C6D6 and in the 31P NMR spec-
trum a doublet at δ = 72.86 ppm and a triplet at δ =
64.61 ppm.
Moreover, the molecular structure of 8 in the solid state
was determined by X-ray crystallography (Figure 10,
Table 5). The ruthenium-bound hydrogen atom H1 [Ru1–
H1 distance of 1.58(5) Å] was located in the difference Fou-
rier map and refined isotropically, whereas the nitrogen-
bound hydrogen atoms H2a, H2b, and H2c were semi-freely
Experimental Section
General: All manipulations were carried out under an atmosphere
of argon using standard Schlenk techniques or in an Argon-filled
glovebox (MBRAUN). Tetrahydrofuran and benzene were dried by
conventional methods and distilled under argon before use. Diethyl
ether, dichloromethane, pentane, and toluene were purified using a
two-column solid-state purification system (MBRAUN). [D6]Benz-
ene, [D8]tetrahydrofuran, and [D8]toluene were dried by stirring
over Na/K and then distilled. [D2]Dichloromethane was dried with
CaH2 and then distilled. GeCl2·dioxane was purchased from
ABCR, nBuLi (1.6 m in hexanes), hydrazine (1 m in THF), and HCl
(1 m in Et2O) were purchased from Sigma–Aldrich and used with-
out further purification. Potassium hydride (Sigma–Aldrich) was
washed with hexane and dried under vacuum. NEt3 (Sigma–Ald-
rich) was dried with CaH2 and then distilled. Celite and Silica were
dried under vacuum overnight before use. 2-Ph2PC6H4Br[37] and
[Ru(Cl)2(PPh3)3][38] were prepared according to literature pro-
cedures. The NMR spectra were recorded with a Bruker AV 400
NMR or a Bruker DPX 300 spectrometer at 25 °C, if not men-
1
tioned otherwise. The H NMR chemical shifts were referenced to
residual C6D5H at δ = 7.15 ppm, [D7]toluene at δ = 7.09 ppm, and
CDHCl2 at δ = 5.33 ppm. The 31P{1H} NMR spectra were refer-
enced externally to H3PO4 at δ = 0.00 ppm. The 2H NMR chemical
shifts were referenced to [D3]acetonitrile at δ = 1.97 ppm in
CH2Cl2. Microanalyses were performed with a HEKAtech Euro
EA Elemental Analyzer. Infrared spectra were recorded with a
Bruker Vertex 70 spectrometer that was equipped with an ATR
unit (diamond).
Figure 10. Molecular structure of 8 in the solid state (ORTEP dia-
gram, ellipsoids at 50% probability). Hydrogen atoms (except for
the ruthenium-bound and nitrogen-bound hydrogen atoms) and
solvent molecules are omitted for clarity.
[Ge(H)(2-C6H4PPh2)3] (2): 2-Ph2PC6H4Br (1.50 g, 4.40 mmol) was
dissolved in Et2O (40 mL) and the solution was cooled to –78 °C.
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nBuLi (1.6 m in hexanes, 2.85 mL, 4.56 mmol) was slowly added,
which caused the precipitation of a colorless solid. After 1 h the
solution darkened and a precipitate was formed. The solution was
separated and the residue was dissolved in CH2Cl2 and filtered
mixture was warmed gradually to room temperature and stirred for through a pad of Celite. Evaporation of the solvent under vacuum
1 h. The volatiles were removed under vacuum. The residue was
washed with pentane (3ϫ 20 mL) and dried under vacuum to af-
ford [2-C6H4PPh2]Li·Et2O as a colorless solid, yield 1.35 g (90%).
afforded a purple powder, yield 0.37 g (55%). Volatiles were re-
moved from the filtrate under vacuum and the residue was washed
with pentane (3ϫ 20 mL), dried under vacuum, redissolved in
[2-C6H4PPh2]Li·Et2O (1.24 g, 3.62 mmol) and GeCl2·dioxane CH2Cl2, and purified by silica column chromatography (7 cm). Elu-
(0.28 g, 1.20 mmol) were then placed in a Schlenk tube and Et2O
(40 mL) was added at –78 °C. The mixture was warmed to room
temperature and stirred overnight. A 31P{1H} NMR spectrum of
tion with CH2Cl2 afforded [Ru(Cl){Ge(Cl)(2-C6H4PPh2)2}(PPh3)]
(5) in traces and subsequent elution with THF gave a purple pow-
der after evaporation of the solvent under vacuum, yield 0.17 g
the yellow solution indicated the formation of Li[Ge(2-C6H4PPh2)3] (25%). C54H42ClGeP3Ru·CH2Cl2 (1077.93): calcd. C 61.28, H 4.11;
1
(1). Adding an excess of water (0.10 mL) to the solution caused the
precipitation of a colorless solid. The mixture was stirred for
30 min at room temperature and the volatiles were removed under
vacuum. The residue was dissolved in toluene (75 mL) and the
solution was filtered through a pad of Celite. The volatiles were
removed from the filtrate under vacuum and the residue was
washed with pentane (3ϫ 20 mL). Lyophilization yielded a color-
less solid, yield 0.85 g (83%, based on the amount of
GeCl2·dioxane). An analogous procedure was used to prepare
[Ge(D)(2-C6H4PPh2)3] (2D) by using D2O instead of H2O. Analyti-
cal data for 2: C54H43GeP3 (857.48): calcd. C 75.64, H 5.05; found
found C 61.20, H 4.02. H NMR (400 MHz, C6D6): δ = 8.48 (d,
JH,H = 7.3 Hz, 3 H, Ar), 7.42–7.34 (m, 12 H, Ar), 7.30–7.24 (m, 3
H, Ar), 7.21–7.17 (m, 3 H, Ar), 6.92–6.86 (m, 3 H, Ar), 6.77–6.71
(m, 6 H, Ar), 6.66–6.59 (m, 12 H, Ar) ppm. 31P{1H} NMR
(162 MHz, C6D6): δ = 72.75 (s) ppm.
[Ru(Cl){Ge(Cl)(2-C6H4PPh2)2}(PPh3)] (5): A solution of HCl (1 m
in Et2O, 0.13 mL, 0.13 mmol) was slowly added to a solution of
[Ru(Cl){Ge(2-C6H4PPh2)3}] (4) (0.12 g, 0.12 mmol) in CH2Cl2
(15 mL) and the reaction mixture was stirred for 48 h. The volatiles
were removed under vacuum and the crude product was redissolved
in CH2Cl2 and purified by chromatography using a silica column
(7 cm). Elution with CH2Cl2 and evaporation of the solvent under
1
C 75.61, H 5.04. H NMR (400 MHz, C6D6): δ = 7.60 [dm, JH,H
= 7.4 Hz, 3 H, Ar], 7.31 (ddd, JH,H = 7.6, 3.3, 1.2 Hz, 3 H, Ar),
7.26–7.20 (m, 12 H, Ar), 7.19 (partially obscured by the signal of
C6D5H, q, JP,H = 5.8 Hz, 1 H, GeH), 7.05–6.92 (m, 24 H, Ar) ppm.
1H NMR (400 MHz, CD2Cl2): δ = 7.38–7.02 (m, 42 H, Ar), 6.74 (q,
JP,H = 5.5 Hz, 1 H, GeH) ppm. 31P{1H} NMR (162 MHz, C6D6): δ
= –8.97 (s) ppm. 31P{1H} NMR (162 MHz, CD2Cl2): δ = –9.57
vacuum afforded
a
purple powder, yield 0.10 g (83%).
C54H43Cl2GeP3Ru (1029.46): calcd. C 63.00, H 4.21; found C
1
63.12, H 4.59. H NMR (300 MHz, [D8]toluene): δ = 8.25 (d, JH,H
= 7.3 Hz, 2 H, Ar), 8.04–7.88 (br. s, 3 H, Ar), 7.32–7.13 (m, 8 H,
Ar), 6.98–6.59 (m, 30 H, Ar) ppm. 31P{1H} NMR (122 MHz, [D8]-
2
2
toluene, –50 °C): δ = 105.0 (dd, JPP = 29.6, JPP = 24.2 Hz,
(s) ppm. IR (ATR): ν = 2092 (Ge–H) cm–1. Analytical data for 2D:
2
2
˜
C6H4PPh2), 67.58 (dd, JPP = 276.4, JPP = 24.2 Hz, C6H4PPh2),
C54H42DGeP3 (858.49): 1H NMR (400 MHz, C6D6): δ = 7.60 (dm,
JH,H = 7.4 Hz, 3 H, Ar), 7.31 (ddd, JH,H = 7.6, 3.3, 1.2 Hz, 3 H,
Ar), 7.26–7.20 (m, 12 H, Ar), 7.05–6.92 (m, 24 H, Ar) ppm. 1H
NMR (400 MHz, CD2Cl2): δ = 7.38–7.02 (m, 42 H, Ar) ppm.
31P{1H} NMR (162 MHz, C6D6): δ = –8.97 (s) ppm. 31P{1H}
NMR (162 MHz, CD2Cl2): δ = –9.57 (s) ppm. 2H NMR (300 MHz,
2
2
25.75 (dd, JPP = 276.4, JPP = 29.6 Hz, PPh3) ppm.
[Ru{Ge(2-C6H4PPh2)3}(H)(H2)] (6): [Ru(Cl){Ge(2-C6H4PPh2)3}]
(4) (350 mg, 0.35 mmol) and potassium hydride (15 mg, 0.38 mmol)
were placed in a Schlenk tube and THF (30 mL) was added. Using
a freeze-pump-thaw cycle an atmosphere of dihydrogen was placed
in the Schlenk tube and the reaction mixture was stirred overnight
at room temperature. The solvent was removed, and the residue was
dissolved in toluene followed by filtration of the solution through a
pad of Celite. The solvent was then removed from the filtrate under
vacuum and the residue dried under vacuum to afford a dark yel-
low powder, yield 265 mg (79%). C54H45GeP3Ru (960.57): calcd. C
67.52, H 4.72; found C 67.31, H 4.91. 1H NMR (300 MHz, C6D6):
δ = 8.54 (d, JH,H = 7.3 Hz, 3 H, Ar), 7.31–7.24 (m, 6 H, Ar), 7.24–
7.16 (m, 9 H, Ar), 7.08–6.98 (m, 3 H, Ar), 6.98–6.89 (m, 3 H, Ar),
6.78–6.71 (m, 6 H, Ar), 6.65–6.57 (m, 12 H, Ar), –5.03 (br. s, 3 H,
Ru-H and Ru-H2) ppm. 31P{1H} NMR (162 MHz, C6D6): δ =
CD Cl ): δ = 6.80 (br. s, GeD) ppm. IR (ATR): ν = 1506 (Ge–
˜
2
2
D) cm–1.
[Ge(nBu)(2-C6H4PPh2)3] (3): 2-Ph2PC6H4Br (1.12 g, 3.28 mmol)
was dissolved in THF (15 mL) and the solution was cooled to
–78 °C. At this temperature nBuLi (1.6 m in hexanes, 2.05 mL,
3.28 mmol) was added dropwise to give a brown reaction mixture
and the precipitation of a solid was observed. After 1 h the slurry
was brought to room temperature and stirred for another hour.
The reaction mixture was then cooled to –78 °C and a suspension
of GeCl2·dioxane (0.23 g, 0.99 mmol) in THF (5 mL) was added.
The mixture was brought to room temperature and stirred over-
night. Evaporation of the solvent under vacuum yielded a colorless
solid. The solid was dissolved in benzene (15 mL) and filtered
through a pad of Celite. The solvent was removed from the filtrate
under vacuum. The residue was washed with pentane (3ϫ 20 mL)
and dried under vacuum to afford a colorless powder, yield 0.61 g
77.11 (s) ppm. 1H NMR (300 MHz, [D8]THF): δ = 8.47 (d, JH,H
7.3 Hz, 3 H, Ar), 7.42–7.31 (m, 3 H, Ar), 7.23–6.92 (m, 24 H, Ar),
6.84–6.72 (m, 12 H, Ar), –5.37 (br. s, 3 H, RuH and RuH2) ppm.
31P{1H} NMR (162 MHz, [D8]THF): δ = 74.92 (s) ppm.
=
[Ru{Ge(2-C6H4PPh2)3}(H)(NH3)] (8): [Ru{Ge(2-C6H4PPh2)3}(H)-
(H2)] (6) (50 mg, 0.05 mmol) was dissolved in benzene (5 mL). Am-
monia was bubbled through the solution for 2 min. The solvent
was then evaporated under vacuum to give a dark yellow powder,
yield quant. C54H46GeNP3Ru (975.58): calcd. C 66.48, H 4.75, N
(68%). C58H51GeP3 (913.59): calcd. C 76.25, H 5.63; found C
1
75.87, H 5.43. H NMR (400 MHz, C6D6): δ = 8.07 (dm, JH,H
=
7.1 Hz, 3 H, Ar), 7.44 (ddd, JH,H = 7.6, 3.6, 1.3 Hz, 3 H, Ar), 7.27–
7.19 (m, 12 H, Ar), 7.03–6.92 (m, 24 H, Ar), 2.28–2.20 (m, 2 H,
CH2), 1.59–1.48 (m, 2 H, CH2), 1.04–0.91 (m, 2 H, CH2), 0.59 (t,
3JHH = 7.3 Hz, 3 H, CH3) ppm. 31P{1H} NMR (162 MHz, C6D6):
δ = –8.91 (s) ppm.
1
1.44; found C 66.13, H 4.91, N 1.03. H NMR (300 MHz, C6D6):
δ = 8.61 (d, JH,H = 7.2 Hz, 2 H, Ar), 8.39 (d, JH,H = 7.2 Hz, 1 H,
Ar), 7.79–7.69 (m, 4 H, Ar), 7.44–7.37 (m, 2 H, Ar), 7.33–7.22 (m,
4 H, Ar), 7.05–6.95 (m, 9 H, Ar), 6.90–6.80 (m, 5 H, Ar), 6.79–
[Ru(Cl){Ge(2-C6H4PPh2)3}] (4): [Ge(H)(2-C6H4PPh2)3] (2) (0.58 g, 6.67 (m, 7 H, Ar), 6.60–6.48 (m, 8 H, Ar), 1.21 (s, 3 H, RuNH3),
2
2
0.68 mmol) was dissolved in toluene (30 mL). NEt3 (0.95 mL, –8.64 (dt, JP,H,trans = 68.7, JP,H,cis = 30.2 Hz, 1 H, RuH) ppm.
2
6.85 mmol) and a solution of [Ru(Cl)2(PPh3)3] (0.65 g, 0.68 mmol)
in toluene (20 mL) were then added. Upon overnight stirring the
31P{1H} NMR (162 MHz, C6D6): δ = 73.85 (d, JP,P = 12.7 Hz, 2
P), 63.71 (t, JP,P = 12.7 Hz, 1 P) ppm.
2
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FULL PAPER
[Ru{Ge(2-C6H4PPh2)3}(H)(N2)] (9): [Ru{Ge(2-C6H4PPh2)3}(H)- Data Centre via wwww.ccdc.cam.ac.uk/data_request/cif. Crystallo-
(H2)] (6) was dissolved in C6D6 and placed into an NMR tube. graphic data are summarized in Table S1 in the Supporting Infor-
Dinitrogen was bubbled through the solution for 5 min. The NMR
mation.
analysis indicated a complete conversion into 9. C54H46GeNP3Ru
(986.65): H NMR (300 MHz, C6D6): δ = 8.53 (d, JH,H = 7.2 Hz,
Supporting Information (see footnote on the first page of this arti-
cle): Crystallographic data and details on structural analysis of the
ruthenium complexes 4 and 5 by DFT.
1
2 H, Ar), 8.31 (d, JH,H = 7.2 Hz, 1 H, Ar), 7.88–7.78 (m, 4 H, Ar),
7.47–7.39 (m, 2 H, Ar), 7.34–7.26 (m, 2 H, Ar), 7.07–6.85 (m, 17
H, Ar), 6.85–6.78 (m, 1 H, Ar), 6.75–6.57 (m, 5 H, Ar), 6.54–6.42
2
2
Acknowledgments
(m, 8 H, Ar), –8.57 (dt, JP,H,trans = 66.1, JP,H,cis = 28.1 Hz, 1 H,
RuH) ppm. 31P{1H} NMR (162 MHz, C6D6): δ = 72.86 (d, JP,P
11.8 Hz, 2 P), 64.61 (t, JP,P = 11.8 Hz, 1 P) ppm.
=
2
2
The authors thank Dr. Gregor Meier, Dr. Battist Rábay, Anna
Lena Raza, and Dr. Beatrice Braun for help with NMR spec-
troscopy and crystallography.
Reaction of [Ru{Ge(2-C6H4PPh2)3}(H)(H2)] (6) with Hydrazine:
[Ru{Ge(2-C6H4PPh2)3}(H)(H2)] (6) (50 mg, 0.05 mmol) was dis-
solved in benzene (2 mL). An excess N2H4 solution in THF
(0.2 mL, 0.2 mmol) was added and the mixture was stirred for
10 min at room temperature. The solvent was then evaporated un-
der vacuum to give a dark yellow powder. The NMR spectra re-
vealed the formation of [Ru{Ge(2-C6H4PPh2)3}(H)(N2H4)] (7),
which slowly disproportionates in solution. C54H47GeN2P3Ru
(990.60): calcd. C 65.47, H 4.78, N 2.83; found C 65.31, H 5.15, N
2.20. 1H NMR (300 MHz, C6D6): δ = 8.58 (d, JH,H = 7.2 Hz, 2 H,
Ar), 8.37 (d, JH,H = 7.2 Hz, 1 H, Ar), 7.36–7.16 (m, 4 H, Ar), 7.14–
6.78 (m, 17 H, Ar), 6.78–6.62 (m, 6 H, Ar), 6.61–6.50 (m, 8 H, Ar),
4.06 (br. s, 2 H, RuNH2NH2), 2.58 (br. s, 2 H, RuNH2NH2), –8.81
[1] a) H. D. Empsall, E. M. Hyde, R. Markham, W. S. McDonald,
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2
2
(dt, JP,H,trans = 67.7, JP,H,cis = 30.2 Hz, 1 H, RuH) ppm. 31P{1H}
2
NMR (162 MHz, C6D6): δ = 72.42 (d, JP,P = 12.1 Hz, 2 P), 63.86
(t, JP,P = 11.7 Hz, 1 P) ppm.
2
Catalytic Reaction of [Ru{Ge(2-C6H4PPh2)3}(H)(H2)] (6) with
Hydrazine: [Ru{Ge(2-C6H4PPh2)3}(H)(H2)] (6) (20 mg, 0.02 mmol)
was dissolved in benzene (2 mL) and placed in a Schlenk tube (vol-
ume 30 mL). A N2H4 solution in THF (0.1 mL, 0.1 mmol) was
added and the mixture was stirred for 2 d at 50 °C. For three sepa-
rate runs, the gas phase and all volatile materials were condensed
in 5 mL of 1 m H2SO4. The collected ammonia was quantified by
the indophenol method[34] and gave an average yield of 88% (three
runs 86%, 88%, and 90%; based on hydrazine). In a separate
1
fourth run in C6D6 the H NMR spectrum of the reaction mixture
revealed the formation of complex 6 and 8 in a 1:1 ratio that corre-
sponds to 10% formed ammonia bound in complex 8.
Structure Determination for the Compounds 2–8: Colorless crystals
suitable for X-ray crystal structure determination of 2 and 3 were
grown from a solution in benzene by slow evaporation. Purple crys-
tals of 4 suitable for X-ray crystal structure determination were
obtained by vapor diffusion of pentane into a concentrated CH2Cl2
solution. Purple crystals of 5 were obtained by vapor diffusion of
pentane into a concentrated benzene solution. Yellow crystals of 6
were grown from a concentrated THF solution by slow evapora-
tion. Yellow crystals of 7 were obtained by slow evaporation of a
concentrated benzene solution with an excess of hydrazine (1 m in
THF). Yellow crystals of 8 were obtained by slow evaporation of
a concentrated benzene/THF solution. The diffraction data were
collected on a Bruker D8 Venture diffractometer at –173 °C using
Mo-Kα (λ = 0.71073 Å) or Cu-Kα (λ = 1.54178 Å) radiation. The
structures were solved by direct methods and refined with the full-
matrix least-squares method on F2 (SHELXL-97).[39] The hydrogen
atoms were placed at calculated positions and refined by using a
riding model.
CCDC for 885951 (for 2), 885952 (for 3), 885953 (for 4), 885954
(for 5), 994094 (for 6), 994095 (for 7), 994096 (for 8) contain the
supplementary crystallographic data for this paper. These data can
be obtained free of charge from the Cambridge Crystallographic
Eur. J. Inorg. Chem. 2014, 4826–4835
4834
© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.eurjic.org
FULL PAPER
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Received: April 1, 2014
Published Online: August 6, 2014
Eur. J. Inorg. Chem. 2014, 4826–4835
4835
© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim