(μ1-Methanolato-κ1 O)-μ1-methoxo-κ1 O-(μ2-2-amino-1-methyl-5H-imidazol-4-one-κ2 N:N′)-hexacarbonyldirhenium(I)

In the title compound, [Re2(CH3O)2(CO)6(C4H6N3O)], the two ReI atoms are linked by a methoxo and methanolato bridge, as well as by a creatinine ligand that coordinates in a bidentate fashion. Three fac-carbonyl ligands occupy the rest of the slightly distorted octahedral geometry around each ReI atom. The bridging methanolato and methoxo ligands are bent out of the Re2O2 plane by 49.2 (4) and 47.8 (3)° respectively. This is normally associated with a methanolato-bridging-type coordination rather that the more planar methoxo-type bridging. Furthermore, the creatinine bridging molecule is very slightly distorted from the Re2N2C plane, indicating that the pyrazolo N atom bonded to the RhI atom is not protonated. Charge balance can thus only be attained if one assumes a positional disorder for the methanolato/methoxo H atom. All attempts to locate disordered protons around these O atoms were unsuccessful. Four hydrogen bonds, one N—H⋯O and three C—H⋯O, are observed in the structure. The molecules pack in a head-to-head and tail-to-tail fashion when viewed along the c axis, in alternating columns.

In the title compound, [Re 2 (CH 3 O) 2 (CO) 6 (C 4 H 6 N 3 O)], the two Re I atoms are linked by a methoxo and methanolato bridge, as well as by a creatinine ligand that coordinates in a bidentate fashion. Three fac-carbonyl ligands occupy the rest of the slightly distorted octahedral geometry around each Re I atom. The bridging methanolato and methoxo ligands are bent out of the Re 2 O 2 plane by 49.2 (4) and 47.8 (3) respectively. This is normally associated with a methanolato-bridging-type coordination rather that the more planar methoxo-type bridging. Furthermore, the creatinine bridging molecule is very slightly distorted from the Re 2 N 2 C plane, indicating that the pyrazolo N atom bonded to the Rh I atom is not protonated. Charge balance can thus only be attained if one assumes a positional disorder for the methanolato/methoxo H atom. All attempts to locate disordered protons around these O atoms were unsuccessful. Four hydrogen bonds, one N-HÁ Á ÁO and three C-HÁ Á ÁO, are observed in the structure. The molecules pack in a head-to-head and tail-to-tail fashion when viewed along the c axis, in alternating columns.
Data collection: APEX2 (Bruker, 2008); cell refinement: SAINT-Plus (Bruker, 2008); data reduction: SAINT-Plus; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics:  (Canty et al. 1979, Mitewa et al. 2002, Matos Beja et al. 1991, Panfil et al. 1995 but no structure reports are found where creatinine is coordinated to a metal centre in a bidentate fashion. All bond distances and angles of creatinine in this structure compare well with that of the reported structures of the free ligand with the N-C-N angle the only exception with 121° (Bell et al., 1995) and 120° (du Pré & Mendel, 1955)  This ligand, creatinine, forms part of an ongoing study where different N,N′ bidentate and N,N′,N′′ tridentate ligands are synthesized and coordinated to the rhenium(I) metal centre (Schutte et al., 2011(Schutte et al., , 2012b(Schutte et al., , 2012c. Four intermolecular hydrogen bonds are observed in the structure, Table 2, i.e. one N-H···O and three C-H···O. When viewed along the c axis, the molecules pack in column-like structures in an alternating head-to-head and tail-to-tail fashion (Fig. 2).

Experimental
[NEt 4 ] 2 [Re(CO) 3 Br 3 ] (500 mg, 0.650 mmol), as prepared by Alberto et al. (1996), was dissolved in 10 ml of water at pH 2. The pH was increased to pH 6 and after a slight colour change, creatinine (37 mg, 0.325 mmol) was added to the mixture and stirred for 6 h at room temperature. The yellow cuboidal crystals were obtained from the filtrate of the solution.

Refinement
The methyl and methene H atoms were placed in geometrically idealized positions and constrained to ride on its parent atoms with U iso (H) = 1.5U eq (C) and U iso (H) = 1.2U eq (C) and at a distance of 0.96 Å and 0.97 Å respectively. The N-bound H atom was refined freely. A number of reflections were omitted from the final cycles of refinement owing to poor agreement. All attempts to locate disordered protons around O1 and O2 were unsuccessful.

Figure 1
Representation of the title compound, showing the numbering scheme and displacement ellipsoids (50% probability).  Packing and hydrogen interactions (dashed lines) of the title compound in the unit cell. Hydrogen atoms omitted for clarity.