cis-Dichlorido[2,3-dimethyl-3-(4,4,5,5-tetramethyl-1,3,2λ5-dioxaphospholan-2-yloxy)butan-2-olato-κ2 O,P]oxido(triphenylphosphane-κP)rhenium(V)

The title compound, cis-[Re(C12H24O4P)Cl2O(C18H15P)], was prepared from the analogous trans isomer [Głowiak et al. (2000 ▶). Polyhedron, 19, 2667–2672] by a trans–cis isomerization reaction. The ReV atom adopts a distorted octahedral coordination geometry. Besides being coordinated by the oxide and the butanolate O atoms, the ReV atom is coordinated by a pair of chloride ligands and two P atoms in cis positions with respect to each other. In the crystal, adjacent molecules are linked by weak C—H⋯Cl interactions, forming a three-dimensional network.

The title compound, cis-[Re(C 12 H 24 O 4 P)Cl 2 O(C 18 H 15 P)], was prepared from the analogous trans isomer [Głowiak et al. (2000). Polyhedron, 19, 2667-2672] by a trans-cis isomerization reaction. The Re V atom adopts a distorted octahedral coordination geometry. Besides being coordinated by the oxide and the butanolate O atoms, the Re V atom is coordinated by a pair of chloride ligands and two P atoms in cis positions with respect to each other. In the crystal, adjacent molecules are linked by weak C-HÁ Á ÁCl interactions, forming a three-dimensional network.
This work was supported with European funds in the frame of the Human Capital Operational Programme, through project POKL.04.01.01-00-054/10-00 "Development of the potential and educational offer of the University of Wrocławthe chance to enhance the competitiveness of the University".  (Rybak et al., 2005). In this paper we report the synthesis and crystal structure of the title oxidorhenium(V) complex, obtained starting from an analogous trans complex (Głowiak et al. 2000). As a result of the trans-cis isomerization reaction single crystals of the cis isomer were obtained.
The coordination environment around the metal center, Re1, is a distorted octahedron with three sets of donor atoms: two O atoms in a trans arrangement and two chlorides and both phosphorus located in cis positions to each other (Fig. 1).
The Re-ligand bond distances (Table 1) are generally similar to those reported for other rhenium complexes, nevertheless some disparities are observed. The distortions of the angles in the coordination sphere of the Re1 atom are significant, for example the O1-Re1-O2 angle of 168.36 (10) ° that differs from the expected value of 180°. The rhenium atom is located 0.06 Å out of the P1/P2/Cl1/Cl2 plane, towards the terminal oxo ligand. The Re1-P2 (phosphane) bond length of 2.4883 (12) Å is within the range 2.42-2.57 Å reported for analogous PR 3 derivatives, however the Re1-P1 (phosphite) distance of 2.3659 (12) Å is quite short. This shortening may be explained by the strong π-acceptor character of the phosphite moiety and is consistent with the Re-P distances observed for other phosphite derivatives (Głowiak et al. 1998). The Re1-Cl bond lengths [2.4461 (10) and 2.4339 (10) Å] appear long compared with the expected values of 2.36-2.41 Å (Orpen et al., 1989). This is a result of the high trans influence of the phosphorus ligands.
The crystal structure of the title compound is stabilized by a number of weak hydrogen bonds of the C-H···Cl type (Desiraju & Steiner, 1999). Consequently, a three-dimensional network is formed (Table 2). Even though the observed H···Cl distances may first appear to be fairly long compared with the expected values (Aullón et al., 1998), the presence of C-H···Cl hydrogen bonds was confirmed spectroscopically for complexes with H···Cl spacings even above 3 Å (Fábry et al., 2004).

Experimental
The title compound, cis-[ReOCl 2 {P(OCMe 2 CMe 2 O)OCMe 2 CMe 2 O}PPh 3 ], was prepared from an analogous trans isomer, which had been synthesized according to a previously reported procedure (Głowiak et al. 2000). The trans complex (0.1 g, 0.12 mmol) was dissolved in acetonitrile and refluxed for 6 h. Single crystals of the cis isomer suitable for the X-ray analysis were obtained after continuous, slow evaporation of the solvent at ambient temperature.

Refinement
The C-bonded H atoms were positioned geometrically and refined using a riding model: C-H = 0.95 and 0.98 Å for CH and CH 3 H atoms, respectively, with U iso (H) = k × U eq (C), where k = 1.5 for CH 3 H atoms, and = 1.2 for other H atoms. In the final difference electron density map the highest residual peak and the deepest hole are located 1.27 and 1.36 Å, respectively, from atom P2.

Figure 1
The molecular structure of the title compound, with atom numbering. Displacement ellipsoids are drawn at the 30% probability level.

cis-Dichlorido[2,3-dimethyl-3-(4,4,5,5-tetramethyl-1,3,2λ 5 -dioxaphospholan-2-yloxy)butan-2-olatoκ 2 O,P]oxido(triphenylphosphane-κP)rhenium(V)
Crystal data  (Cosier & Glazer, 1986) operating at 100 K. An analytical numeric absorption correction was carried out with CrysAlis RED (Oxford Diffraction, 2010) using a multifaceted crystal model (Clark & Reid, 1995). Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > 2σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F and R-factors based on ALL data will be even larger.