metal-organic compounds
Acta Crystallographica Section C
Crystal Structure
Communications
N-donor ligand has m symmetry and is therefore completely
planar. Due to the mm site symmetry of the molecule as a
whole, the N-donor ligand plane bisects the angles of one pair
of opposite CeqÐWÐCeq angles. Table 1 shows that the
endocyclic angles at N, C5, C6 and C9 are all less than the ideal
value of 120ꢀ, which is consistent with elongation of the ligand
in the direction from N to C9, although the discrepancy
decreases from atom to atom in the series, in the order given
above. Similar discrepancies, but fewer in number and with no
real regularity, are found in the pyridine ligands of (II) (at N
and C7; Table 2) and (III) [116.6 (6) and 115.9 (7)ꢀ at the
donor and free pyridine N, respectively].
ISSN 0108-2701
Pentacarbonyl(4-phenylpyridine)-
tungsten(0) and pentacarbonyl-
(2-phenylpyridine)chromium(0)
Bernadette S. Creaven,a² R. Alan Howieb* and Conor
Longa
aThe School of Chemical Sciences, Dublin City University, Dublin 9, Ireland, and
bDepartment of Chemistry, University of Aberdeen, Meston Walk, Aberdeen
AB24 3UE, Scotland
Correspondence e-mail: r.a.howie@abdn.ac.uk
In (I), the pyridine ligand is attached to the M(CO)5 frag-
ment in an end-on manner. In (II) and (III), the mode of
attachment is sideways on, brought about by the presence in
each case of a substituent species in the 2-position. Despite
this, the pyridine ligand in (III), although not constrained by
symmetry, is still essentially planar and is oriented with respect
to the equatorial carbonyl groups in much the same way as the
corresponding ligand in (I).
The situation is very different in the case of (II). Here, in the
absence of the bridging amine link present in (III), the phenyl
and pyridine rings are twisted through 67.7 (3)ꢀ [estimated
from the dihedral angles in Table 2; this angle is calculated as
67.44 (15)ꢀ by MPLA in SHELXL97 (Sheldrick, 1997)] in
order to avoid impossibly short non-bonding intramolecular
contacts.
Received 26 October 2000
Accepted 8 January 2001
In pentacarbonyl(4-phenylpyridine)tungsten(0), [W(C11H9N)-
(CO)5], the molecules have mm site symmetry and the
pyridine ligand, with m symmetry, is completely planar. In
pentacarbonyl(2-phenylpyridine)chromium(0), [Cr(C11H9N)-
(CO)5], the molecules are in general positions and the phenyl
and pyridine rings of the ligand are twisted by 67.7 (3)ꢀ with
respect to one another by rotation about the CÐC bond
joining them. In both compounds, the axial MÐCcarbonyl bond
trans to the MÐNligand bond is signi®cantly shorter than the
equatorial MÐCcarbonyl bonds.
The planarity of the pyridine ligands in (I) and (III) is
re¯ected in the manner in which the molecules are packed in
the unit cells. In (I), the molecules are ®rst of all arranged
linearly, head to tail, in the b direction. These rows, with the
orientation of the molecules alternating from row to row, form
layers parallel to [100], with the pyridine ligands face to face
Comment
The molecular structures of pentacarbonyl(4-phenylpyri-
dine)tungsten(0), (I) (Fig. 1), and pentacarbonyl(2-phenyl-
pyridine)chromium(0), (II) (Fig. 2), along with that previously
reported by Creaven et al. (2000) for pentacarbonyl(di-2-
pyridylamine)tungsten(0), (III), are formally all very similar.
Thus, in all three cases, the metal atom M (M is Wor Cr) is six-
coordinate in a distorted octahedral environment comprising
®ve carbonyl ligands and the monodentate N-donor ligand. In
every case, the MÐCcarbonyl bond axial and trans to the MÐ
Nligand bond is signi®cantly shorter than the equatorial MÐC
bonds [see Tables 1 and 2 for (I) and (II), respectively; in (III),
Ê
and completely superimposed, and c/2 [3.933 (2) A] apart. In
(III), the pyridine ligands are again face to face but in columns,
with coordinates of the form (0,y,0) and (12,y,21), related pair-
Ê
Ê
the axial bond is 1.967 (7) A versus 2.020 (7)±2.063 (8) A for
the equatorial bonds]. In addition, in all three cases, because
the CaxÐMÐCeq angles are all less than 90ꢀ [Tables 1 and 2
for (I) and (II), respectively; 84.9 (3)±89.2 (3)ꢀ for (III)], the
MÐC bonds are distributed in an umbrella-like manner, with
MÐCax as the handle and MÐCeq as the spokes.
The variously substituted N-donor pyridine ligands are, of
course, totally different throughout the series. In (I), the
Figure 1
The molecular structure of (I) showing the atom-labelling scheme.
Displacement ellipsoids are drawn at the 50% probability level and H
atoms are shown as small spheres of arbitrary radii [symmetry codes:
² Present address: School of Science, Institute of Technology, Tallaght, Dublin
24, Ireland.
1
2
1
2
(i) 1 x, y,
z; (ii) x, y,
z; (iii) 1 x, y, z].
ꢁ
Acta Cryst. (2001). C57, 385±387
# 2001 International Union of Crystallography
Printed in Great Britain ± all rights reserved 385
Creaven, Bernadette S.
