Synthesis of electronically and coordinatively unsaturated complexes [Ru2(CO)4(μ-H)(μ-PtBu2)(μ- L2)] (L2 = biphosphanes)

Article abstract of DOI:10.1016/j.jorganchem.2011.07.033

A convenient synthesis and the characterization of six new electronically and coordinatively unsaturated complexes of the formula [Ru₂(CO) ₄(μ-H)(μ-P^tBu₂)(μ-L₂)] (2b-g) (RuRu) is described exhibiting a close relation to the known [Ru ₂(CO)₄(μ-H)(μ-P^tBu₂)(μ- dppm)] (2a). The complexes 2b-g were obtained in a kind of one-pot synthesis starting from [Ru₃(CO)₁₂] and P^tBu₂H in the first step followed by the reaction with the bidentate bridging ligand in the second step. The method was developed for the following bridging ligands (μ-L₂): dmpm (2b, dmpm = Me₂PCH₂PMe ₂), dcypm (2c, dcypm = Cy₂PCH₂PCy₂), dppen (2d, dppen = Ph₂PC(=CH₂)PPh₂), dpppha (2e, dpppha = Ph₂PN(Ph)PPh₂), dpppra (2f, dpppra = Ph ₂PN(Pr)PPh₂), and dppbza (2g, dppbza = Ph ₂PN(CH₂Ph)PPh₂). The molecular structures of all new complexes 2b-g were determined by X-ray diffraction.

Full text of DOI:10.1016/j.jorganchem.2011.07.033

Journal of Organometallic Chemistry 696 (2011) 3415e3420
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Synthesis of electronically and coordinatively unsaturated complexes
[Ru2(CO)4(
m
-H)(
m
-PtBu2)(
m
-L2)] (L2 ¼ biphosphanes)
*
Tobias Mayer, Edris Parsa, Hans-Christian Böttcher
Department Chemie, Ludwig-Maximilians-Universität München, Butenandtstrasse 5-13, 81377 München, Germany
a r t i c l e i n f o
a b s t r a c t
Article history:
A convenient synthesis and the characterization of six new electronically and coordinatively unsaturated
complexes of the formula [Ru2(CO)4(
m
-H)(
m
m m-L2)] (2beg) (Ru]Ru) is described exhibiting a close
-PtBu2)(
Received 5 April 2011
Received in revised form
3 July 2011
relation to the known [Ru2(CO)4(
m
-H)( m-dppm)] (2a). The complexes 2beg were obtained in
-PtBu2)(
a kind of one-pot synthesis starting from [Ru3(CO)12] and PtBu2H in the first step followed by the reaction
Accepted 25 July 2011
with the bidentate bridging ligand in the second step. The method was developed for the following
bridging ligands (
m
-L2): dmpm (2b, dmpm ¼ Me2PCH2PMe2), dcypm (2c, dcypm ¼ Cy2PCH2PCy2), dppen
Dedicated to Prof. Dirk Steinborn on the
occasion of his 65th birthday.
(2d, dppen ¼ Ph2PC(¼CH2)PPh2), dpppha (2e, dpppha ¼ Ph2PN(Ph)PPh2), dpppra (2f, dpppra ¼ Ph2PN
(Pr)PPh2), and dppbza (2g, dppbza ¼ Ph2PN(CH2Ph)PPh2). The molecular structures of all new complexes
2bꢀg were determined by X-ray diffraction.
Keywords:
Ruthenium
Carbonyl
Ó 2011 Elsevier B.V. All rights reserved.
Coordinative Unsaturation
Phosphanido-bridged
Crystal structure
1. Introduction
complexes to explore the influence of the ligand sphere on the
course of the unusual reaction behavior towards NO. As a first step in
Some years ago we described the synthesis and crystal structure
of the electronically and coordinatively unsaturated complex
this direction, herein we describe investigations on the synthesis
and the structural characterization of some new electronically and
[Ru2(CO)4(
PPh2) [1]. The latter compound was obtained in a kind of one-pot
synthesis from [Ru3(CO)12
and PtBu2H affording the 32 VE
complex [Ru2(CO)4( -H)(
-PtBu2)(PtBu2H)2] (1) in situ [2], followed
by the substitution of both secondary phosphanes towards dppm.
Because of the unsaturated nature of the central Ru2( -H) moiety
m-H)(
m
-PtBu2)(
m-dppm)] (Ru]Ru) (2a, dppm ¼ Ph2PCH2
coordinatively unsaturated complexes of the formula [Ru2(CO)4(
m-
H)(m
-PtBu2)(
m-L2)] (L2 ¼ biphosphane).
]
m
m
2. Experimental
m
2.1. General considerations
compound 2a showed an enhanced reactivity towards a great
variety of small molecules under mild conditions. Thus reactions
were obtained with molecules like CO and CH2, respectively [1], CCl4,
S8, NOþ, and CS2 [3], phosphanes as well as phenylethyne [4]. The
reaction with HBF4 resulted in the protonation of the metalemetal
All manipulations were performed under an atmosphere of dry
argon using conventional Schlenk techniques. Solvents were dried
over sodium-benzophenone ketyl or molecular sieves and were
distilled under argon prior to use. Chemicals were purchased
commercially from Aldrich, the ligands dmpm, dcypm, and dppen
from ABCR. The amino ligands dpppha, dpppra, and dppbza were
prepared by a modified literature procedure [9]. IR spectra were
recorded as solid with a JASCO FT/IR-460 plus spectrometer. NMR
spectra were obtained using Jeol Eclipse 270 and 400 instruments
operating at 270 and 400 (1H) and at 109 MHz and 161 MHz (31P),
respectively. Chemical shifts are given in ppm from SiMe4 (1H) or
bond [5], SO2 added to the corresponding m-SO2 complex [6], and
P^CtBu resulted in the hydrodimetalation of the phosphaethyne [7].
Nitric oxide afforded in an unexpected reaction with the reductive
dimerization of the latter, the hyponitrite species [Ru2(CO)4(
m-H)(m-
PtBu2)( h2eONNO)] [8]. Especially in light of this reaction we are
m-
currently interested in some new similarly constituted diruthenium
85% H3PO4 (
31P{1H}). Microanalyses (C, H, N) were performed by
the Microanalytical Laboratory of the Department of Chemistry,
LMU Munich, using a Heraeus Elementar Vario EI instrument.
* Corresponding author. Tel.: þ49 89218077422; fax: þ49 89218077407.
E-mail address: hans.boettcher@cup.uni-muenchen.de (H.-C. Böttcher).
0022-328X/$ e see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2011.07.033

3416
T. Mayer et al. / Journal of Organometallic Chemistry 696 (2011) 3415e3420
2.2. Synthesis of [Ru2(CO)4(
dcypm, 2c; dppen, 2d)
m
-H)(
m
-PtBu2)(
m
-L2)] (L2 ¼ dmpm, 2b;
3JPH ¼ 7.3 Hz, CH2), 1.39 (d, 18H, 3JPH ¼ 14.5 Hz, t-C4H9), ꢀ14.72 (dt,
2
2
1H, JPH ¼ 22.1 Hz, JPH ¼ 16.2 Hz,
m
-H). 31P{1H} NMR (CD2Cl2):
2
2
d
279.4 (t, JPP ¼ 144.4 Hz,
m
-PtBu2), 111.6 (d, JPP ¼ 144.4 Hz,
m-
A mixture of [Ru3(CO)12] (640 mg, 1.0 mmol) and PBut2H (1 mL,
6.8 mmol) in THF (30 mL) was refluxed with stirring for 4 h. During
this time the color of the solution changed from orange to deep red.
After cooling to room temperature, the solvent was removed in
vacuo and the excess phosphane was pumped off for about 30 min.
The remaining residue was dissolved in 20 mL of toluene, the
corresponding ligand L2 (1.0 mmol) was added and the mixture
refluxed with stirring for 5 h. After cooling to room temperature,
the solvent was removed to dryness in vacuo. The remaining
residue was crystallized from diethyl ether/ethanol and diethyl
ether/hexane, respectively, affording deep violet crystals of 2bed.
2b: Yield: 418 mg (70%). Anal. Calcd for C17H33O4P3Ru2 (596.51): C,
dppbza).
2.4. X-ray structural determination
Suitable single crystals for X-ray diffraction were selected by
means of a polarization microscope, mounted on the tip of a glass
fiber, and investigated on an Oxford XCalibur and a Bruker Nonius-
Kappa CCD diffractometer, respectively, using Mo-K
a radiation
(
l
¼ 0.71073 Å). The structures were solved by direct methods
(SHELXS) [10] and refined by full-matrix least-squares calculations
on F2 (SHELXL-97) [11]. Details of the crystal data, data collection,
structure solution, and refinement parameters of compounds 2beg
are summarized in Table 1 and Table 2 respectively.
34.23; H, 5.58. Found: C, 34.45; H, 5.72. IR (solid): n(CO): 1951s,
1897vs, 1877vs, 1864s. 1H NMR (CD2Cl2):
d
3.43 (t, 2H, 2JPH ¼ 9.8 Hz,
CH2), 1.37 (d, 18H, 3JPH ¼ 13.8 Hz, t-C4H9), 1.21 (d, 12H, 2JPH ¼ 4.3 Hz,
-H). 31P{1H} NMR (CD2Cl2):
d
279.9
3. Results and discussion
PCH3), ꢀ9.40 (m, 1H,
m
2
(t, JPP ¼ 137.9 Hz,
m
-PtBu2), 6.7 (d, 2JPP ¼ 137.9 Hz,
m-dmpm).
3.1. Synthesis and characterization of compounds
2c: Yield: 539 mg (62%). Anal. Calcd for C37H65O4P3Ru2 (868.98):
C, 51.14; H, 7.54. Found: C, 51.01; H, 7.68%. IR (solid):
1964vs, 1918vs. 1H NMR (CD2Cl2):
1.81e1.14 (m, br, 46H, C6H11
overlapped with PꢀCH2ꢀP), 1.34 (d, 18H, JPH
n(CO): 1994s,
Some time ago we investigated the reaction of [Ru3(CO)12] with
PtBu2H resulting in the electronically and coordinatively unsatu-
d
3
¼
13.9 Hz,
rated complex [Ru2(CO)4(m-H)(m
-PtBu2)(PtBu2H)2] (Ru]Ru) (1) [2].
t-C4H9), ꢀ9.10 (m, 1H,
m d 290.6 (t,
-H). 31P{1H} NMR (CD2Cl2):
2
2JPP ¼ 134.4 Hz,
m
-PtBu2), 34.4 (d, JPP ¼ 134.4 Hz,
m-dcypm). 2d:
An interesting feature of 1 affects its molecular fluxionality during
the change from the solution into the solid state. Thus 1 exhibits in
solution a symmetrical structure with exclusively terminal CO
groups whereas 1 adopts in the crystal an asymmetrical framework
containing a semibridging carbonyl ligand. Compound 1 reacted
with dppm (dppm ¼ Ph2PCH2PPh2) in refluxing toluene with the
substitution of both terminal phosphane ligands towards the
Yield: 574 mg (67%). Anal. Calcd for C38H41O4P3Ru2 (856.80): C,
53.27; H, 4.82. Found: C, 53.01; H, 4.69%. IR (solid): n(CO): 1966s,
1942vs, 1932vs, 1913s. 1H NMR (CD2Cl2):
d 7.41e7.17 (m, 20H, C6H5),
6.04 (t, 2H, ¼ CH2, 3JPH ¼ 20.3 Hz), 1.49 (d, 9H, 3JPH ¼ 14.4 Hz), 1.36
(d, 9H, 3JPH ¼ 14.4 Hz), ꢀ14.24 (dt, 1H, 2JPH ¼ 22.3 Hz, 2JPH ¼ 16.3 Hz,
2
m
-H). 31P{1H} NMR (CD2Cl2):
d
279.9 (t, JPP ¼ 133.3 Hz,
m
-PtBu2),
bridging bidentate dppm resulting in [Ru2(CO)4(m-H)(m m-
-PtBu2)(
dppm)] (2a) [1]. It should be noted here that the most important
prerequisite for the isolation of 1 and the latter species 2a is only
44.3 (d, 2JPP ¼ 133.3 Hz,
m
-dppen).
-PtBu2)(
2.3. Synthesis of [Ru2(CO)4(
dpppra, 2f; dppbza, 2g)
m-H)(
m
m
-L2)] (L2 ¼ dpppha, 2e;
Table 1
A mixture of [Ru3(CO)12] (640 mg, 1.0 mmol) and PBut2H (1 mL,
6.8 mmol) in THF (30 mL) was refluxed with stirring for 4 h. After
cooling to room temperature, the solvent was removed in vacuo.
The remaining residue was dissolved in 20 mL of acetone, the
corresponding ligand L2 (1.0 mmol) was added and the mixture
refluxed with stirring for 3 h. After cooling to room temperature,
the solvent was removed to dryness in vacuo. The remaining
residue was crystallized from dichloromethane/ethanol affording
deep violet crystals of 2eeg. 2e: Yield: 673 mg (73%). Anal. Calcd for
C42H44NO4P3Ru2 (921.88): C, 54.72; H, 4.81; N,1.52. Found: C, 54.51;
Crystal data and structure refinement details for compounds 2bed.
Compound
2b
2c
2d
Empirical formula
Formula weight
Temperature (K)
Crystal system
Space group
a (Å)
C17H33O4P3Ru2
596.48
200 (2)
monoclinic
P21/c
16.436 (2)
8.9509 (9)
22.199 (4)
90
131.323 (11)
90
2456.7 (7)
4
1.613
1.442
3.79e26.32
C37H65O4P3Ru2
868.94
C38H41O4P3Ru2
856.76
173 (2)
monoclinic
P21/c
17.0748 (19)
16.2508 (15)
13.8819 (7)
90
104.291 (6)
90
3732.7 (6)
4
1.525
0.975
200 (2)
orthorhombic
P212121
11.4469 (5)
18.6483 (10)
19.1508 (9)
90
b (Å)
c (Å)
a
b
g
(ꢁ)
(ꢁ)
(ꢁ)
H, 4.69; N, 1.47%. IR (solid):
n
(CO): 1994s, 1972vs, 1932vs, 1922s. 1H
90
90
NMR (CD2Cl2): 7.57e7.29 (m, 20H, C6H5), 6.88e5.89 (m, 5H,
d
Volume (Å3)
Z
4088.0 (3)
4
1.412
0.891
3.71e26.31
3
NC6H5), 1.37 (d, 9H, JPH
¼
14.1 Hz, t-C4H9), 1.32 (d, 9H,
3JPH ¼ 14.1 Hz, t-C4H9), ꢀ14.45 (dt, 1H, 2JPH ¼ 21.8 Hz, 2JPH ¼ 16.2 Hz,
rcalcd (g cmꢀ3
)
2
/mmꢀ1
m
-H). 31P{1H} NMR (CD2Cl2):
d
286.3 (t, JPP ¼ 144.7 Hz,
m
-PtBu2),
m
2
q
range for
data collection (ꢁ)
4.33e26.32
110.9 (d, JPP ¼ 144.7 Hz,
m-dpppha).
2f: Yield: 506 mg (57%). Anal. Calcd for C39H46NO4P3Ru2
Reflections measured
Rint
Observed reflections
Reflections
in refinement
Parameters/restraints
14196
0.0322
3761
31969
0.0631
6189
16024
0.0242
5341
(887.86): C, 52.76; H, 5.22; N,1.58. Found: C, 53.01; H, 4.95; N,1.40%.
IR (solid):
7.67e7.37 (m, 20H, C6H5), 3.63 (m, 2H, NCH2), 2.78 (m,
n
(CO): 1994s, 1971vs, 1928vs, 1916s. 1H NMR (CD2Cl2):
d
4971
8311
7537
3
2H, ꢀCH2CH3), 1.31 (d, 9H, JPH ¼ 14.1 Hz, t-C4H9), 1.26 (d, 9H,
249/0
0.0385
0.1012
1.121
425/0
0.0338
0.0554
0.848
434/0
0.0303
0.0686
0.914
3JPH ¼ 14.1 Hz, t-C4H9), 0.13 (t, 3H, JHH ¼ 7.3 Hz, CH2CH3), ꢀ14.79
3
R (Fobs
)
(dt, 1H, 2JPH ¼ 22.0 Hz, 2JPH ¼ 16.5 Hz,
m
-H). 31P{1H} NMR (CD2Cl2):
Rw (F2)
2
2
d
283.5 (t, JPP ¼ 142.2 Hz,
m
-PtBu2), 108.1 (d, JPP ¼ 142.2 Hz,
m-
S
Max electron
density (e$Åꢀ3
Min electron
density (e$Åꢀ3
2.089
0.598
0.778
dpppra). 2g: Yield: 608 mg (65%). Anal. Calcd for C43H46NO4P3Ru2
)
)
(935.90): C, 55.18; H, 4.95; N,1.50. Found: C, 54.91; H, 4.93; N,1.38%.
ꢀ1.391
ꢀ0.432
ꢀ1.137
IR (solid):
7.68e7.30 (m, 20H, C6H5), 7.33e6.66 (m, 5H, CH2C6H5), 4.34 (t, 2H,
n
(CO): 1988s, 1971vs, 1926vs, 1893s. 1H NMR (CD2Cl2):
d

T. Mayer et al. / Journal of Organometallic Chemistry 696 (2011) 3415e3420
3417
Table 2
Crystal data and structure refinement details for compounds 2eeg.
t
P Bu2
THF
t
(CO)2Ru
Compound
2e
2f
2g
[Ru3(CO)12] + 3 P Bu2H
Ru(CO)2
4h, reflux
Empirical formula
Formula weight
Temperature (K)
Crystal system
Space group
a (Å)
C42H44NO4P3Ru2 C39H46NO4P3Ru2 C43H46NO4P3Ru2
H
t
t
921.83
887.82
935.86
H Bu2P
P Bu2H
173 (2)
monoclinic
P21/c
173 (2)
monoclinic
P21/c
173 (2)
monoclinic
P21/c
1
+ biphosphane
t
- 2 P Bu2H
toluene, 5h,
reflux
9.8265 (2)
18.7030 (4)
22.8079 (4)
90
9.6511 (18)
34.279 (4)
12.3799 (8)
90
18.7391
11.9867 (2)
18.7391 (2)
90
b (Å)
t
c (Å)
P Bu2
a
b
g
(ꢁ)
(ꢁ)
(ꢁ)
103.3440 (10)
90
103.882 (10)
90
94.417 (2)
90
(CO)2Ru
R2P
Ru(CO)2
Volume (Å3)
Z
4078.58 (14)
4
3976.0 (9)
4
4196.67 (9)
4
H
PR2
rcalcd (g cmꢀ3
m
)
1.501
1.483
1.481
/mmꢀ1
0.899
0.919
0.875
2
R = Me, 2b; R = Cy, 2c
q
range for
data collection (ꢁ)
3.26e27.51
4.17e26.25
4.22e26.02
Scheme.
Reflections measured 32955
17170
0.0293
5841
27772
0.0456
6390
Rint
0.0797
6870
Observed reflections
Reflections
9361
7995
8100
in refinement
Parameters/restraints 480/2
Therefore the use of acetone as the reaction medium was preferred,
resulting in comparable yields as obtained during the synthesis of
compounds 2bed. The reactions were conducted under similar
conditions as applied to the preparation of compounds 2aed and
the sequence of this one-pot synthesis was similar to that outlined
in the Scheme.
Suitable crystals of all compounds 2beg for X-ray diffraction
studies were obtained and their molecular structures could be
determined (see below). Furthermore, the compounds 2beg were
characterized by analytical and spectroscopic methods. The IR
spectra (as solids) of all compounds show in each case four
absorption bands that are characteristic of terminal carbonyl ligands
(see Experimental). The 1H NMR spectra of all new complexes
453/0
0.0296
0.0607
0.902
0.759
488/0
0.0294
0.0727
0.953
0.881
R (Fobs
)
0.0430
0.1076
1.075
Rw (F2)
S
Max electron
density (e$Åꢀ3
Min electron
density (e$Åꢀ3
1.280
)
)
ꢀ0.890
ꢀ0.470
ꢀ0.670
given in the presence of the bulky m
-PtBu2 group. This essential
circumstance affects even all the other complexes described in this
work. Some efforts to obtain analogously constituted complexes
with less bulky substituents at the bridging phosphorus (e.g. Cy or
Ph) failed. We assume that the peculiar sterical and electronical
properties of the Bu groups could be the reasonable explanation
for this.
By using the same synthetic protocol as developed for the
preparation of 2a, now we were successful in the synthesis of the
new compounds 2bed. Thus the in situ-prepared complex 1 reac-
ted with the corresponding biphosphanes in refluxing toluene
include
a characteristic resonance in the high field region
t
(ca. ꢀ9 ppm, 2b and 2c; ca. ꢀ14 ppm, 2deg) as a doublet of triplets
(or multiplet) with corresponding couplings to the bridging phos-
phorus nuclei. These signals can be attributed to the bridging
hydrido ligands. The compounds 2b and 2c show the hydride
resonance shifted to lower field values because of the higher elec-
tron density at the ruthenium atoms caused by the þI effect of the
alkyl groups of the biphosphane ligands. Some remarks should be
given concerning the signals of the tert-butyl groups of the bridging
phosphanido ligands. By our long experience, in the room temper-
ature 1H NMR spectra these signals were observed as a set of two
affording the unsaturated complexes [Ru2(CO)4(
m
m
-H)(
-H)(
m
m
-PtBu2)(
-PtBu2)(
m-
m-
m-
dmpm)] (2b; dmpm ¼ Me2PCH2PMe2), [Ru2(CO)4(
dcypm)] (2c; dcypm ¼ Cy2PCH2PCy2), and [Ru2(CO)4(
m-H)(
PtBu2)(
m
-dppen)] (2d; dppen ¼ Ph2PC(]CH2)PPh2) in good yields.
The first step of the one-pot synthesis occurs with a loss of carbon
monoxide and an accompanying redox process including the
oxidation of the formally zerovalent ruthenium with simultaneous
formation of the hydrido ligand. The reaction sequence for the
preparation of 2b and 2c, respectively, is illustrated in the Scheme.
As a side product in the degradation reaction of the trinuclear
ruthenium carbonyl the compound [Ru(CO)3(PtBu2H)2] [2] could be
identified which was omitted in the Scheme.
doublets in the case where three bridging ligands (
and a third ligand
m m-dppm,
-PtBu2,
-X) are present in the molecule, e.g [1,3ꢀ7]. An
m
exception in this light represent the compounds 2b, 2c, and 2g
which show in the room temperature 1H NMR spectra only one
doublet (18H) corresponding to the protons of the tert-butyl groups
of the phosphanido bridge. The same observation was also made for
the closely related compound [Fe2(CO)4(m-H)(m m-dppm)]
-PtBu2)(
[12], whereas for the closely related diruthenium complex 2a
however, the more frequently observed case of two doublets (each
9H) was found at room temperature. To bright more insight into this
The complexes 2bed were obtained by this procedure as deep
violet crystals in yields of about 70%. The crystalline compounds are
moderately stable in air. Their solutions, however, are very sensitive
towards atmospheric oxygen, i.e., they decompose within seconds
while decolorizing the solutions. Unfortunately we have no
evidence of what happens during this spontaneous decomposition
reaction because no defined products could be identified by spec-
troscopic means in many attempts.
A small variation in the synthetic protocol was necessary for the
synthesis of the compounds 2eeg containing the aminophosphane
ligands. In these cases the use of toluene as the solvent was not
possible because decomposition to some extent was observed.
phenomenon, a dynamic NMR (DNMR) investigation of [Fe2(CO)4(m-
H)(
m
-PtBu2)(
m
-dppm)] in the range from 25 ꢁC to ꢀ80 ꢁC was carried
out in toluene as the solvent. Interestingly, this study afforded
significant changes in the 1H NMR spectra concerning the shape of
the doublet belonging to the tert-butyl groups. Thus the 1H NMR
spectrum of the latter diiron complex showed at 25 ꢁC a sharp
doublet at
d
1.59 (3JPH ¼ 14.4 Hz). In the range from ꢀ20 to ꢀ40 ꢁC
these two signals broadened with a shoulder. At ꢀ50 ꢁC the signal
appeared only as one very broad signal with a shoulder which
separated between ꢀ60 to ꢀ70 ꢁC into two broad signal groups.

3418
T. Mayer et al. / Journal of Organometallic Chemistry 696 (2011) 3415e3420
Finally at ꢀ80 ꢁC, two broad signals (with some shoulder structure)
were observed exhibiting chemical shifts at 1.79 and 1.53 ppm,
respectively. These results hint to a stereodynamic behavior with
respect to the rotation of the tert-butyl substituents about Pꢀ(t-
C4H9) bonds on the one side and the rotation of the phosphanido
ligand about the PꢀM bonds on the other side. At the moment we
have no determined explanation which kind of stereodynamic
processes are really responsible for this observation. In this light we
have planned a broad DNMR investigation of a great number of our
Table 3
Selected bond lengths (Å) and angles (ꢁ) for compounds 2bꢀ2d.
2b
2c
2d
2.692 (1)
1.90 (3)
1.88 (3)
Ru(1)ꢀRu(2)
Ru(1)ꢀH(1)
Ru(2)ꢀH(1)
Ru(1)ꢀC(1)
2.683 (1)
1.94 (4)
1.92 (4)
1.836 (6)
1.886 (6)
1.871 (6)
1.852 (7)
2.334 (2)
2.341 (1)
2.324 (2)
2.339 (2)
e
2.703 (1)
1.83 (3)
1.88 (3)
1.856 (4)
1.873 (4)
1.880 (4)
1.852 (5)
2.331 (1)
2.331 (1)
2.355 (1)
2.387 (1)
e
1.872 (3)
1.880 (3)
1.883 (3)
1.856 (4)
2.316 (1)
2.323 (1)
2.346 (1)
2.360 (1)
1.324 (4)
91.1 (16)
70.92 (2)
111.35 (14)
Ru(1)ꢀC(2)
Ru(2)ꢀC(3)
Ru(2)ꢀC(4)
compounds containing the M(m
-PtBu2)-M moiety. The 31P{1H} NMR
Ru(1)ꢀP(1)
Ru(2)ꢀP(1)
solution spectra of compounds 2bef indicate in each case the
chemical equivalence of the two phosphorus nuclei of the bridging
biphosphanes and aminobiphosphanes, respectively. This is
confirmed by the observed triplet/doublet pattern in the spectra of
all compounds (see Experimental).
Ru(1)ꢀP(2)
Ru(2)ꢀP(3)
C(5)ꢀC(6)
Ru(1)ꢀH(1)ꢀRu(2)
Ru(1)ꢀP(1)ꢀRu(2)
P(2)ꢀC(5)ꢀP(3)
88.1 (23)
70.07 (4)
114.4 (4)
93.6 (16)
70.88 (3)
113.7 (2)
In the case where the hydrido ligand is taken into account, by
electron counting, 32 valence electrons (VE) result for these
complexes. Therefore they are electronically unsaturated in the
sense of the 18e rule. Moreover they are also coordinatively
unsaturated because addition reactions of further ligands are
possible. To obey the 18e rule, a dinuclear complex should exhibit
an overall electron count of 34 VE. Therefore a formally Ru-Ru
double bond can be assumed in all new complexes 2beg. The
short Ru-Ru bond distances found in each case of all these new
compounds (shorter than 2.7 Å) confirm this assumption.
Furthermore, in light of the isolobal relationship between CH2 and
a fragment d8ꢀML4, these complexes can be formally considered as
isolobal to ethylene.
bridged by a phosphanido ligand, a dppm group and a hydrido
ligand. Both complexes 2a and 2b constitute complexes with 32 VE
and, in the sense of the 18e rule, they should possess metalemetal
double bonds as discussed before. The found short RueRu distances
are in good agreement with this. Thus for comparison purposes, for
2a the Ru(1)eRu(2) bond was found to be 2.6974(4) Å [1]. The short
Ru(1)eRu(2) separation in the molecule of 2b confirms the
reasonable assumption of a double bond between the ruthenium
atoms.
The compound 2c crystallized in the orthorhombic space group
P212121 with four molecules in the unit cell. The molecular struc-
ture of 2c (not depicted, selected bonding parameters see Table 3) is
also closely related to those of 2a and 2b. The compound 2c exhibits
the longest RueRu separation in this series of compounds 2aeg
adopting this similar arrangement of ligands. We assume that this
is caused by steric effects of the bulky cyclohexyl groups. However,
in comparison with the RueRu single bond lengths of the related
3.2. Crystal and molecular structures of 2beg
Suitable single crystals for the X-ray diffraction study of 2b and
2c, respectively, were grown from acetonitrile at 4 ꢁC. Violet crys-
tals of 2b belonging to the monoclinic space group P21/c were
obtained. Fig. 1 shows a selected ORTEP view of the molecule of 2b,
selected bond lengths and angles are listed in Table 3. The molec-
molecules
2.768(1) Å) and [Ru2(CO)4(
[Ru2(
m
-CO)(CO)4(
m
-H)(
m
-PtBu2)(
-PtBu2)(
m
-dppm)]
(RueRu,
m
-CH2)(
m-H)(
m
m-dppm)] (RueRu,
ular structure of 2b is closely related to that of [Ru2(CO)4(
m-H)(m-
PtBu2)(
m-dppm)] (2a). The molecule consists of a diruthenium core
2.784(1) Å) [1], which are electronically and coordinatively satu-
rated complexes, the metalemetal bond in 2c is short enough to be
considered as a RueRu double bond. The molecular structure of 2d
in the crystal is shown in Fig. 2, selected bond lengths are listed in
Table 3. The compound crystallized from dichloromethane/meth-
anol at room temperature in the monoclinic space group wit P21/c
Fig. 1. ORTEP diagram and atom labeling scheme of compound 2b with ellipsoids
Fig. 2. ORTEP diagram and atom labeling scheme for 2d with ellipsoids drawn at the
drawn at the 50% probability level.
50% probability level. Hydrogen atoms (except hydride) were omitted for clarity.

T. Mayer et al. / Journal of Organometallic Chemistry 696 (2011) 3415e3420
3419
Table 4
Selected bond lengths (Å) and angles (ꢁ) for compounds 2ee2 g.
2e
2.660 (1)
1.83 (2)
1.87 (2)
2f
2.668 (1)
1.79 (3)
1.84 (3)
2g
2.652 (1)
1.80 (3)
1.80 (3)
Ru(1)ꢀRu(2)
Ru(1)ꢀH(1)
Ru(2)ꢀH(1)
Ru(1)ꢀC(1)
Ru(1)ꢀC(2)
Ru(2)ꢀC(3)
Ru(2)ꢀC(4)
Ru(1)ꢀP(1)
Ru(2)ꢀP(1)
Ru(1)ꢀP(2)
Ru(2)ꢀP(3)
NꢀC(5)
1.859 (4)
1.891 (5)
1.890 (4)
1.852 (4)
2.328 (1)
2.326 (1)
2.341 (1)
2.334 (1)
1.450 (4)
91.7 (15)
69.73 (4)
120.08 (16)
1.875 (3)
1.885 (3)
1.884 (4)
1.866 (3)
2.328 (1)
2.334 (1)
2.344 (1)
2.340 (1)
1.500 (3)
94.6 (17)
69.83 (2)
119.36 (13)
1.870 (3)
1.890 (3)
1.893 (3)
1.873 (3)
2.333 (1)
2.336 (1)
2.339 (1)
2.322 (1)
1.494 (3)
95.2 (20)
69.21 (2)
118.27 (11)
Ru(1)ꢀH(1)ꢀRu(2)
Ru(1)ꢀP(1)ꢀRu(2)
P(2)ꢀNꢀP(3)
respectively, selected bond lengths and angles of the compounds
2eeg are summarized in the Table 4. The compounds 2eeg crys-
tallized all in the monoclinic space group P21/c with four molecules
in the unit cell. Their molecular structures are closely related to
those of 2bed. Also in these molecules short RueRu distances were
found confirming the double bonding character as discussed above.
With the observed values in the range from 2.652(1) to 2.668(1) Å
they are shorter than the RueRu separation found in the electroni-
cally and coordinatively unsaturated parent compound 2a (RueRu,
2.6974(4) Å [1]).
Fig. 3. ORTEP diagram and atom labeling scheme for 2e with ellipsoids drawn at the
50% probability level. Hydrogen atoms (except hydride) were omitted for clarity.
with four molecules in the unit cell. As discussed before, the Ru(1)ꢀ
Ru(2) bond in 2d could even be considered as a double bond
between both ruthenium atoms.
Good quality single crystals of the compounds 2eeg containing
the aminophosphane ligands were obtained from dichloromethane/
ethanol at room temperature. Selected views of the molecular
structures in the crystal of 2e and 2f are shown in the Figs. 3 and 4,
4. Conclusions
Herein we described the synthesis and the X-ray crystal
structures of six new electronically and coordinatively unsatu-
rated complexes of the formula [Ru2(CO)4(m-H)(m m-L2)]
-PtBu2)(
(Ru]Ru) (2bLg) (L2 ¼ biphosphanes and aminobiphosphanes
respectively). The molecular structures of 2beg are closely related
to that of the known parent compound [Ru2(CO)4(
m-H)(m-
PtBu2)(
m
-dppm)] (2a). Furthermore, we have first evidences that
these compounds show an unusual stereodynamic behavior con-
cerning the signals of the tert.-butyl groups in the dynamic 1H
NMR spectra. For the near future, we have planned a broad DNMR
investigation of a great number of compounds containing the M(m-
PtBu2)-M moiety to bring more insight into understanding of these
phenomena.
Acknowledgments
The authors are grateful to the Department of Chemistry of the
Ludwig Maximilian University Munich for supporting these inves-
tigations and the Johnson Matthey plc, Reading, UK, for a generous
loan of hydrated RuCl3. T. M. is thankful to Prof. P. Klüfers for
financial support. Furthermore we thank P. Mayer for collecting the
X-ray crystal data.
Appendix A. Supplementary material
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.jorganchem.2011.07.033.
References
[1] H.-C. Böttcher, C. Bruhn, K. Merzweiler, Z. Anorg. Allg. Chem. 625 (1999) 586.
[2] H.-C. Böttcher, G. Rheinwald, H. Stoeckli-Evans, G. Süss-Fink, B. Walther,
J. Organomet. Chem. 469 (1994) 163.
[3] H.-C. Böttcher, M. Graf, K. Merzweiler, C. Wagner, Z. Anorg. Allg. Chem. 626
(2000) 597.
Fig. 4. ORTEP diagram and atom labeling scheme for 2f with ellipsoids drawn at the
50% probability level. Hydrogen atoms (except hydride) were omitted for clarity.

3420
T. Mayer et al. / Journal of Organometallic Chemistry 696 (2011) 3415e3420
[4] H.-C. Böttcher, M. Graf, K. Merzweiler, C. Wagner, Z. Anorg. Allg. Chem. 626
[8] H.-C. Böttcher, M. Graf, K. Mereiter, K. Kirchner, Organometallics 23 (2004) 1269.
[9] Y. Wang, Z. Li, X. Zeng, X. Wang, C. Zhan, Y. Liu, X. Zeng, Q. Luo, X. Liu, Y. Zhan,
X. Liu, New J. Chem. 33 (2009) 1780.
(2000) 1335.
[5] H.-C. Böttcher, M. Graf, K. Merzweiler, C. Wagner, J. Organomet. Chem. 628
(2001) 144.
[10] G.M. Sheldrick, SHELXS, Program for Crystal Structure Solution. University of
Göttingen, Germany, 1997.
[6] H.-C. Böttcher, M. Graf, K. Merzweiler, C. Wagner, Inorg. Chim. Acta 350 (2003)
399.
[11] G.M. Sheldrick, Acta Crystallogr. Sect. A 62 (2008) 112.
[12] H.-C. Böttcher, K. Merzweiler, C. Wagner, Z. Anorg. Allg. Chem. 625 (1999) 857.
[7] H.-C. Böttcher, D. Himmel, M. Scheer, Organometallics 23 (2004) 5314.