Crystal structures of three complexes of zinc chloride with tri-tert-butylphosphane

The crystal structures of three complexes of zinc chloride with tri-tert-butylphosphane are reported.


Figure 2
The molecular structure of (2), showing 50% probability ellipsoids for non-H atoms and spheres of arbitrary size for H atoms.

Figure 3
The molecular structure of (3), showing one of the three molecules of the asymmetric unit (Z 0 = 3) showing 50% probability ellipsoids for non-H atoms and spheres of arbitrary size for H atoms.

Supramolecular features
Supramolecular features of (1) form from weak C1-H3CÁ Á ÁCl1 i interactions ( Fig. 4 and Table 1), which creates layers in the ab plane that stack along the c axis. The supramolecular features of (2) are also based on weak interactions. There are weak C15-H15AÁ Á ÁCl1 ii interactions as well as weak C12-H12AÁ Á ÁCl2 1 interactions ( Fig. 5 and Table 2). Together the weak interactions, where each Cl atom is an acceptor, create a three-dimensional packing structure.

Figure 5
The weak HÁ Á ÁCl interactions in (2) with short contacts shown in cyan. The left molecule is related to the middle one by the symmetry operation (2 À x, Ày, 1 2 + z), and the right molecule is related to the middle one by the symmetry operation ( 3 2 À x, À 1 2 + y, 1 2 + z).

Figure 6
Chains of the three [(H 2 O)ZnCl 3 ] À ions formed from the hydrogen bonds between Zn-Cl and water ligands in (3) ion is optimized for steric interactions; that is, the P-H hydrogen atom is oriented toward the center of the Zn tetrahedron surrounded by three Cl atoms, suggesting a nucleophilic-type protonation of the phosphane, with the water ligand pointing away from the P-H bond. Each tertbutyl group is staggered slightly relative to the positions of the Cl atoms. In this arrangement, there are no hydrogen-bonding interactions involving the phosphonium hydrogen. This arrangement also optimizes the ion contact between the phosphonium cations and [(H 2 O)ZnCl 3 ] À anions. The disorder of the solvent molecules suggests no or at best weak interactions between the solvent and hosts; indeed, none can be found.
Besides Goel's report on the hydrolysis of [(PtBu 3 )(ZnI 2 )], there are no other reports on the hydrolysis of zinc-phosphane complexes to form phosphonium salts. The [(H 2 O)ZnCl 3 ] À ion is relatively uncommon in the CSD: there are 19 entries containing such an ion. However, there is one report of the hydrolysis of a triphenylphosphinomethyl-ZnCl 2 dimer (CORRAD; Pattacini et al., 2009)

Synthesis and crystallization
The synthesis of (1) has been reported (Goel & Ogini, 1977); the methods reported here are modified from the original report. Crystals of (1) were grown from slow diffusion of pentane into an equimolar solution of ZnCl 2 and PtBu 3 in (CH 2 Cl) 2 at 243 K under an atmosphere of Ar gas. Crystals of (2) were grown from slow diffusion of pentane into an equimolar solution of ZnCl 2 and PtBu 3 in THF at 243 K under an atmosphere of Ar gas. Crystals of (3) were grown from slow diffusion of pentane into an equimolar solution of ZnCl 2 and PtBu 3 in 1,2-dichloroethane (1,2-DCE) at room temperature under ambient conditions.

Refinement
Compound (1): A structural model consisting of one-half of (1) was developed. Methyl H atom positions, R-CH 3 , were optimized by rotation about R--C bonds with idealized C-H, R-H and HÁ Á ÁH distances. For all H atoms, U iso (H) = 1.5U eq (carrier).
Compound (2): A structural model consisting of the host molecule was developed. The coordinating Cl atoms had elongated anisotropic displacement parameters in one direction; however, splitting the Cl positions did not significantly improve the model so it was removed from the final model. Methyl H atom positions, R-CH 3 , were optimized by rotation about R-C bonds with idealized C-H, R-H and HÁ Á ÁH distances. Remaining H atoms were included as riding idealized contributors. U iso (H) = 1.5U eq (C) for methyl atoms and 1.2U eq (carrier) for remaining H atoms. On the basis of 1704 unmerged Friedel opposites, the minor component occupancy of the inversion twin was 0.206 (13) (Flack & Bernardinelli, 2000).

Special details
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.

Special details
Experimental. One distinct cell was identified using APEX2 (Bruker, 2004). Six frame series were integrated and filtered for statistical outliers using SAINT (Bruker, 2005) then corrected for absorption by integration using SHELXTL/XPREP V2005/2 (Bruker, 2005) before using SAINT/SADABS (Bruker, 2005) to sort, merge, and scale the combined data. No decay correction was applied. 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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq

Special details
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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq Occ. (