Dicarbon­yl[2-hydr­oxy-3,5,7-tris­(mor­pho­linomethyl)cyclo­hepta-2,4,6-trien­onato(1–)-κ2O1,O2]rhodium(I)

Tania N Hill; G Steyl

doi:10.1107/S160053680803780X

. 2008 Nov 20;64(Pt 12):m1580–m1581. doi: 10.1107/S160053680803780X

Dicarbonyl[2-hydroxy-3,5,7-tris(morpholinomethyl)cyclohepta-2,4,6-trienonato(1–)-κ²O¹,O²]rhodium(I)

Tania N Hill ^a,^*, G Steyl ^a

PMCID: PMC2960118 PMID: 21581182

Abstract

In the title compound, [Rh(C₂₂H₃₂N₃O₅)(CO)₂], the Rh^I atom is coordinated by two carbonyl ligands and two tropolonate O atoms in a distorted square-planar geometry. It is an example of a new type of tropolone derivative that has not been characterized via solid-state methods. Weak intramolecular C—H⋯N and intermolecular C—H⋯O hydrogen bonds, and π–π stacking interactions between the tropolone rings [centroid–centroid distance = 3.590 (8) Å] are observed in the crystal structure.

Related literature

For general background, see: Banwell et al. (1992 ▶); Boguszewska-Chachulska et al. (2006 ▶); Burgstein et al. (1998 ▶); Crous et al. (2005 ▶); Dewar (1945 ▶); Kierst et al. (1982 ▶). For a related structure, see: Steyl et al. (2004 ▶).

Experimental

Crystal data

[Rh(C₂₂H₃₂N₃O₅)(CO)₂]
M _r = 577.44
Monoclinic,
a = 17.7889 (6) Å
b = 16.6106 (5) Å
c = 17.7279 (4) Å
β = 105.772 (1)°
V = 5041.1 (3) Å³
Z = 8
Mo Kα radiation
μ = 0.73 mm⁻¹
T = 100 (2) K
0.15 × 0.06 × 0.05 mm

Data collection

Bruker X8 APEXII Kappa CCD diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2001 ▶) T _min = 0.901, T _max = 0.966
36747 measured reflections
5450 independent reflections
4616 reflections with I > 2σ(I)
R _int = 0.06

Refinement

R[F ² > 2σ(F ²)] = 0.034
wR(F ²) = 0.070
S = 1.01
5450 reflections
316 parameters
H-atom parameters constrained
Δρ_max = 0.58 e Å⁻³
Δρ_min = −0.55 e Å⁻³

Data collection: APEX2 (Bruker, 2007 ▶); cell refinement: SAINT-Plus (Bruker, 2007 ▶); data reduction: SAINT-Plus; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: DIAMOND (Brandenburg & Putz, 1999 ▶); software used to prepare material for publication: WinGX (Farrugia, 1999 ▶).

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S160053680803780X/hy2163sup1.cif

e-64-m1580-sup1.cif^{(23.6KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S160053680803780X/hy2163Isup2.hkl

e-64-m1580-Isup2.hkl^{(261.6KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Selected bond lengths (Å).

Rh1—C01	1.835 (3)
Rh1—C02	1.840 (2)
Rh1—O1	2.0209 (16)
Rh1—O2	2.0212 (15)

Open in a new tab

Table 2. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C4—H4⋯N32	0.95	2.28	2.760 (3)	110
C6—H6⋯N72	0.95	2.31	2.785 (3)	110
C36—H36A⋯O01ⁱ	0.99	2.59	3.497 (3)	153
C53—H53A⋯O55ⁱⁱ	0.99	2.56	3.509 (4)	161

Open in a new tab

Symmetry codes: (i) Inline graphic ; (ii) .

Acknowledgments

Financial assistance from the University of the Free State and Professor A. Roodt is gratefully acknowledged. Mr L. Kirsten is acknowledged for the data collection. Part of this research is based on work supported by the South African National Research Foundation (NRF) (grant No. GUN 2068915). Opinions, findings, conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the NRF.

supplementary crystallographic information

Comment

Tropolone type compounds have been of interest since its first discovery in the early 1940's (Dewar, 1945), with applications in pharmacology (Banwell et al., 1992; Kierst et al., 1982) and catalysis (Burgstein et al., 1998; Crous et al., 2005). A recent report on the anti-viral activity of morpholine derivatives of tropolone (Doering Knox) indicated moderate to strong activity against the hepatitis C virus strain (Boguszewska-Chachulska et al., 2006). The addition of morpholine groups to a compound increases its water solubilty properties and thus simplifying the method of dosage, i.e., pallative. Although this compound has been extensively studied, the preferred orientation of the morpholine groups are unknown, as well as the geometrical properties of the tropolone ring system. In this regard, we present a dicarbonyl rhodium(I) complex of a 3,5,7-tris(methylmorpholine)tropolonate ligand (Fig. 1; Table 1).

The molecular packing of the title compound is strongly influenced by the morpholine moieties as these form extensive hydrogen bonding networks (Table 2). A close Rh1···Rh1ⁱ contact [3.2826 (3)Å; symmetry code: (i) 1-x, y, 0.5-z] exists between associated metal centres. This short contact is stabilized by π–π stacking between the corresponding cycloheptatriene rings, with a centroid–centroid distance of 3.590 (8)Å and an interplanar angle of 3.99 (5)°. The slight twist of the two cycloheptatriene ring systems can be attributed to the methylmorpholine functional groups creating a sterically crowded environment.

The crystal packing of diketonate dicarbonyl rhodium(I) complexes tends to favour a head-to-tail packing mode. The [Rh(tropolonate)(CO)₂] complex (Steyl et al., 2004) was deemed to be a singular occurance of the head-to-head packing mode of these molecular systems. The title compound exhibits a slightly distorted orientation as defined by the O1—Rh1—Rh1ⁱ—O2ⁱ torsion angle of 37.09 (3)°. This observation is surprising since the addition of bulky groups on the 3,7-positions was expected to force the molecular system in the head-to-tail packing mode. The π–π stacking and hydrogen bonding interactions stabilize the crystal structure.

Experimental

The title compound was synthesized by the addition of 3,5,7-tris(methylmorpholine)tropolone (0.083 g, 0.32 mmol) to an acetone solution of [Rh(µ-Cl)(CO)₂]₂ (0.100 g, 0.29 mmol). On slow evaporation of the solvent, crystals suitable for X-ray analysis was obtained (yield 30%, 0.045 g).