This journal is © The Royal Society of Chemistry 2000
X-Ray crystal structure of the bis(dihydrogen) complex RuH2(H2)2(PCy3)2
Andrzej F. Borowski, Bruno Donnadieu, Jean-Claude Daran, Sylviane Sabo-Etienne
and Bruno Chaudret
Following the publication of this paper, the attention of the authors was drawn by a number of
colleagues to the likely centrosymmetry of this structure. Although all the statistical tests indicate a noncentrosymmetric system, it is obvious from the examination of the structure that it is very close to
centrosymmetry, if not really centrosymmetrical. The resolution and refinement of the structure in space
group P1 had been previously carried out but not discussed in the published paper. So, the authors wish
to present here the results concerning the refinement in the centrosymmetric space group P1.†
In this case, the Ru atom is located on an inversion center and only half of the molecule has to
be refined. The heavy atoms were located with the help of SIR97 and refined by full matrix least
squares using SHELXL97. After including, using a riding model, the hydrogen of the cyclohexyl
groups, a difference Fourier map in the equatorial plane of the Ru atom showed two large peaks (four
by reason of symmetry) with an electron density of ca. 1.5 e Å-3. These two positions could be
refined as H atoms without any restraints leading to the results showed in Table 1.
Table 1 Comparison of refinement between the non-disordered model and the disordered one
Model with no disorder
Disordered model
Data/restraints/parameters
Goodness-of-fit on F2
3084/0/187
3084/12/197
1.045
1.045
Final R indices [I>2σ(I)]
R1 = 0.0321, wR2 = 0.0709
R1 = 0.0314, wR2 = 0.0676
R indices (all data)
R1 = 0.0373, wR2 = 0.0730
R1 = 0.0366, wR2 = 0.0696
Largest diff. peak and hole/e Å-3
0.491 and -0.362
0.372 and -0.355
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The Ru-H distances are 1.52(2) and 1.60(3) Å, respectively, and the H-Ru-H angle is
98.2(1.4)°. However, owing to the fact that there is good evidence that this compound contains
hydride and dihydrogen ligands, it was attempted to resolve these large electron density peaks.
Introducing only one half of hydrogen on each site and calculating a new Fourier difference map
resulted in the appearance of two residual densities around each site. This result led us to consider a
disordered distribution of hydride and dihydrogen ligands on the two sites. The refinement of this
new model was carried out with the help of soft restraints (Ru-H and H-H distances) to maintain, as
far as possible, a reasonable geometry. The result of the refinement is given in Table 1 and a view of
the molecule is shown in Fig. 1. It is obvious that the model shown in this figure does not lead to an
unambiguous attribution for the structure of RuH2(H2)2(PCy3)2, but is in agreement with the proposed
structure established on a spectroscopic basis.1
Fig. 1
In conclusion, the main question remains, is the structure centrosymmetric or noncentrosymmetric? Owing to the statistical test, we were inclined to consider the possibility of a twin by
This journal is © The Royal Society of Chemistry 2000
inversion (racemic twin) and to refine the structure in the P1 space group to eliminate the disordered
model. It is clear that from a pure crystallographic approach, the refinement in P1 is more satisfactory
with a better set of C-C distances within the cyclohexyl groups. A comparison of the Ru-P, Ru-H and HH distances between the two hypotheses is given in Table 2. Finally note that the structure of the very
similar complex RuH2(H2)2(PPri3)2 has recently been reported.2
Table 2 Comparison of bond distances (Å) and bond angles (º) between the P1 and the disordered P1
refinement
Ru(1) - P(1)
Ru(1) – P(2)
Ru(1) - H(5)
Ru(1) - H(6)
Ru(1) - H(1)
Ru(1) - H(2)
Ru(1) - H(3)
Ru(1) - H(4)
H(1) - H(2)
H(3) - H(4)
H(2) - H(3)
H(1) - Ru(1) - H(2)
H(2) - Ru(1) - H(3)
H(3) - Ru(1) - H(4)
H(4) - Ru(1) - H(5)
H(5) - Ru(1) - H(6)'
H(6) - Ru(1) - H(1)'
P1
2.330(2)
2.347(2)
1.71(4)
1.69(4)
1.54(3)
1.55(3)
1.52(3)
1.53(3)
0.85(4)
0.86(4)
1.41(7)
31.8(1.4)
54.6(2.5)
33.0(1.5)
79.8(2.3)
78.9(2.4)
83.5(2.5)
P1
2.3384(7)
1.73(4)
1.74(5)
1.48(3)
1.49(3)
1.49(3)
1.49(3)
0.87(4)
0.86(4)
1.48(6)
34.1(1.7)
59.7(2.8)
33.3(1.7)
68.6(2.4)
83.1(2.3)
68.7(2.5)
The authors wish to acknowledge Professors G. Parkin and A. Rheingold for interesting comments on
the reported structure.
Notes and references
†Crystal data for C 1 8 H 3 6 PRu 0 . 5 , M = 333.97, triclinic, space group P1, a =
8.1781(13), b = 9.9339(17), c = 11.7055(19) Å,  = 76.18(2),  = 84.45(2),  =
69.39(2)°, Z = 2, V = 864.2(2) Å 3 , D c = 1.283 gcm - 3 , Mo-K radiation (  = 71073
Å),  = 5.69 cm - 1 , crystal dimensions 0.5 x 0.2 x 0.1 mm, F(000) = 362. Stoe IPDS
diffractometer, T = 160(2) K. Numerical absorption corrections were applied. From
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8239 reflections, 3084 were unique ( R i n t = 0.0447). Data/restraints/parameters ratio
3084/12/197, R = 0.0314, wR2 = 0.676 [2735 reflections with F > 4(Fo)], R = 0.0366, wR2 = 0.0696
(all data), S = 1.030. CCDC 182/1678. See http://www.rsc.org/suppdata/cc/a9/a908567j/addition.htm
for revised crystallographic files in .cif format.
1 V. Rodriguez, S. Sabo-Etienne, B. Chaudret, J. Thoburn, S. Ulrich, H.-H. Limbach, J. Eckert, J.-C.
Barthelat, K. Hussein and C. J. Marsden, Inorg. Chem., 1998, 37, 3475.
2 K. Abdur-Rashid, D. G. Gusev, A. J. Lough and R. H. Morris Organometallics, 2000, 19, 1652.