1-(Diphenylphosphinothioyl)-2-[(4-methylphenyl)methoxymethyl]ferrocene

Following our continuing interest in developing new chiral phosphine-containing ferrocenyl ligands, we synthesized the title compound, [Fe(C5H5)(C26H24OPS)], in which there are two nearly identical molecules in the asymmetric unit. The conformation of the cyclopentadienyl (Cp) rings in each ferrocenyl group are intermediate between eclipsed and staggered, with twist angles of 16.6 (2) and 8.9 (2)°. The protecting S atom is located endo with respect to the substituted Cp ring. In the crystal, molecules are connected through intermolecular C—H⋯π interactions.

Following our continuing interest in developing new chiral phosphine-containing ferrocenyl ligands, we synthesized the title compound, [Fe(C 5 H 5 )(C 26 H 24 OPS)], in which there are two nearly identical molecules in the asymmetric unit. The conformation of the cyclopentadienyl (Cp) rings in each ferrocenyl group are intermediate between eclipsed and staggered, with twist angles of 16.6 (2) and 8.9 (2) . The protecting S atom is located endo with respect to the substituted Cp ring. In the crystal, molecules are connected through intermolecular C-HÁ Á Á interactions.
Cg1 and Cg2 are the centroids of the C111-C116 and C211-C216 rings, respectively.   Homogenous asymmetric catalysis by transition metals has received considerable attention over the last few decades, and numerous chiral ligands and complexes allowing high efficiency reactions have been reported (Jacobsen et al., 1999;Börner, 2008). In this field, chiral phosphines have played a significant role. The possibility to easily modify their electronic and steric properties by a judicious choice of their substituents has proven extremely useful to successfully optimized catalytic reactions. However, only few examples have been transferred to industrial processes (Collins et al., 1992;Hawkins & Watson, 2004;Blaser et al., 2007) in many cases because of the expenses associated to ligand and catalyst loss.

D-HÁ
The efficient separation of expensive catalysts and ligands to enable reuse in subsequent cycles is a main challenge that meets both industrial economical needs and new stricter environmental regulations. We have long been interested in the design and the synthesis of new chiral catalysts for exploring new asymmetric catalytic reactions or for improving existing ones (Manoury et al., 2000;Mourgues et al., 2003;Routaboul et al., 2005;Lopez Cortes et al., 2006;Mateus et al., 2006;Routaboul et al., 2007;Le Roux et al., 2007;Labande et al., 2007;Diab et al., 2008). Among the numerous phosphine ligands reported to date, ferrocenyl phosphines functionalized by an oxygen atom (PO ferrocenyl phosphines) constitute a distinct class of hemilabile ligands attracting increasing interest (Breit & Breuniger, 2004;Atkinson et al., 2004;Breit & Breuniger, 2005;Teo et al., 2006;Yu et al., 2007;Mateus et al., 2006). We have recently developed promising PO ferrocenyl ligands (Mateus et al., 2006;Audin et al., 2009). In addition, we recently took interest in improving catalyst recycling using ionic liquid, water or PEG as catalyst "liquid carriers" and in investigating the influence of these media on both the catalytic reaction and the recycling efficiency. To reach this goal, we have prepared a new family of PO ferrocenyl phosphine-ethers, bearing charged (imidazolium) or neutral (monomethylether PEG 750, tetraethylbisphosphonate) polar tags (Audin et al., 2009) to increase their solubility in non conventional media. The simplest member of this new family is compound 2 b (Scheme 1) which efficiency in the Suzuki-Miyaura reaction has been demonstrated (Yoshida & Itami, 2002).
The title molecule 2a is built up from a ferrocenyl moiety in which one Cp ring is substituted by a sulfur protected phosphine and a ((4-methylphenyl)-methoxy)methyl group resulting in a planar chirality. As the space group is centrosymmetric the two enantiomers R/S are present in the crystal (Fig. 1). There are two molecules with the same configuration within the asymmetric unit. As shown by molecular fitting (Spek, 2009), the two molecules have very closely related geometry (Fig. 2).
The Cp rings within the ferrocene moiety have intermediate conformation between eclipsed and staggered with a twist angle of 16.6 (2)° and 8.9 (2)° respectively. These Cp rings are slightly bent wit respect to each other making dihedral angles of 2.16 (24)° and 4.06 (21)° respectively. The S atom is endo with respect to the Cp ring by 0.884 (7)Å and 0.992 (6)Å respectively.
supplementary materials sup-2 There are weak intra and intermolecular C-H···π interactions involving H atoms of phenyl rings and related phenyl rings either to the same molecule or to a symmetry related one (Table 1, Cg1 is the centroid of the C111-C116 ring whereas Cg2 is the centroid of the C211-C216 ring).

Experimental
In a Schlenk tube, 0.75 g of the racemic 2-thiodiphenylphosphino(hydroxymethyl)ferrocene (1.74 mmol) was dissolved in 8 ml of dry dichloromethane. A 54% solution of tetrafluoroboric acid in ether (0.73 ml, 5.30 mmol) was then added. After 1 min stirring, a solution of 2.5 g of 4-methylbenzylalcohol (20.5 mmol) in 8 mL of dry dichloromethane was added. After 1 min of stirring, the crude material was filtered on silica gel with ether as eluent. After evaporation of the solvent, 0.