metal-organic compounds
Acta Crystallographica Section C
Crystal Structure
Communications
In both phases of (I), [Ru(PhCO2)(CO)2(py)]2, one binuc-
lear molecule, devoid of crystallographic symmetry, comprises
the asymmetric unit of the structure. The geometric para-
meters of the present phase (Table 1 and Fig. 1) are generally
similar to those of the other phase insofar as bond lengths and
angles are concerned. There is a signi®cant difference,
however, in the dihedral angle between the pair of C2O2
carboxylate planes, the present value of 78.20 (7)ꢀ being more
nearly comparable to the values of 67.5 (1), 71 (1)/76 (1),
73.1 (4) and 70.8 (1)ꢀ reported previously for the analogues in
which R/L is Me/py, Me/mpy (two molecules), Et/py and tBu/
py, all of which are very much less than the value found for the
C2/c Ph/py phase [84.9 (2)ꢀ]. The molecule of the present
phase has quasi-mm symmetry, the pyridine ligands lying in
one putative mirror plane (`upright'), the other plane
containing the CÐC bonds of the carboxylates and the RuÐ
Ru bisector; this symmetry is also compatible with the pyri-
dine ligands lying normal to the ®rst mirror plane (`¯at'), as
reported for the Me/py adduct. The previous Ph/py (C2/c)
molecule is unusual in that the pyridine ligands have a one-
upright/one-¯at combination, reducing the putative molecular
symmetry to m. It seems unlikely that this conformation
(rather than, for example, `packing forces') is responsible for
the considerably greater splaying of the carboxylate ligands in
the less symmetrical form; the disparity in, for example, the
angles about the two Ru atoms is less than that in the present,
more symmetric, array. The C6/CO2 interplanar dihedral
angles of the carboxylate ligands of the C2/c form are 15.7 (2)
and 10.2 (1)ꢀ [cf. the present values of 4.62 (7) and 6.55 (6)ꢀ];
the Ru-atom deviations from the CCO2 planes are 0.148 (6)
ISSN 0108-2701
Di-l-benzoato-bis[dicarbonyl(pyri-
dine)ruthenium(I)] (new polymorph)
and di-l-trifluoroacetato-bis[di-
carbonyl(pyridine)ruthenium(I)]
Glen B. Deacon,a Pauline Pearson,a Brian W. Skelton,b*
Leone Spicciaa and Allan H. Whiteb
aDepartment of Chemistry, Monash University, Victoria 3800, Australia, and
bChemistry, University of Western Australia, 35 Stirling Highway, Crawley,
WA 6009, Australia
Correspondence e-mail: bws@crystal.uwa.edu.au
Received 8 August 2003
Accepted 17 October 2003
Online 14 November 2003
The syntheses and crystal structure determinations of a pair of
`sawhorse' dimers are reported, viz. [Ru2(C6H5CO2)2-
(C5H5N)2(CO)4] [a new polymorph, cf. Kepert, Deacon,
Spiccia, Fallon, Skelton & White (2000). J. Chem. Soc. Dalton
Trans. pp. 2867±2874] and [Ru2(CF3CO2)2(C5H5N)2(CO)4].
Ê
The RuÁ Á ÁRu distances are 2.6724 (2) and 2.7122 (5) A,
Ê
Ê
and 0.131 (6) A for atom Ru1, and 0.228 (6) and 0.254 (5) A
for atom Ru2.
respectively.
Comment
An earlier report (Kepert et al., 2000) records the syntheses
and chemical and structural characterizations of a number of
binuclear ruthenium(I) `sawhorse' complexes, viz. [Ru(RCO2)-
t
(CO)2L]2 [R = Me, Et, Bu and Ph; L is pyridine (py) or
3-methylpyridine (mpy)]. Despite the diversity of the
carboxylate substituents, the core geometry of the binuclear
array proved remarkably resistant to any form of systematic
substituent variation across the array. A counterpart complex,
with an electronically more signi®cantly varied substituent
(R = CF3 and L = py), (II), has since been crystallized and
examined structurally as an extension of the series, and is
reported here; also reported is the structure of a second
monoclinic polymorph, (I), this time in space group P21/c
rather than C2/c, of the previously studied Ph/py complex.
Both (I) and (II) were obtained as unsolvated crystals; a
further phase of the Ph/py complex is a toluene hemisolvate
(triclinic, P1, Z = 2; Xu & Sasaki, 1999). There are no coor-
dinates in the Cambridge Structural Database (Allen, 2002)
deposition for this form; the limited data in that report, in
In the tri¯uoroacetate/pyridine counterpart, [Ru(F3CCO2)-
(CO)2(py)]2, (II), one complete binuclear neutral molecule
again composes the asymmetric unit of the structure; the
putative symmetry is again quasi-mm, with a pair of `upright'
pyridine ligands. That symmetry is broken, however, by the
pair of CF3 substituents, whose mutual orientations are
`geared'. Again, much of the geometry of the core of the dimer
(Table 2 and Fig. 2) is similar to that found in the related
complexes. Worthy of note as being different, however, are the
Ê
particular, the RuÐRu distance of 2.6809 (7) A and the mean
Ê
Ê
RuÐO distance of 2.121 (4) A, agree with the following
comments.
RuÐO distances, with a mean value of 2.144 (8) A [cf. the
Ê
mean value of 2.13 (1) A for the C2/c and P21/c benzoates], in
Acta Cryst. (2003). C59, m537±m539
DOI: 10.1107/S0108270103023709
# 2003 International Union of Crystallography m537
Deacon, Glen B.
