The crystal structure of a new ferrocenyl P,N ligand: 1-[(2,2-dimethylhydrazin-1-ylidene)methyl]-1′-(diphenylphosphorothioyl)ferrocene

The asymmetric unit of the title compound contains two independent molecules with very similar conformations. Each molecule is built up from a ferrocene unit substituted in the 1 and 1′ positions by a protected sulfur diphenylphosphine and by a dimethylhydrazine fragment.

1. Chemical context P,N ligands have proved to be of great interest in various fields of catalysis (Bö rner, 2005;Carroll & Guiry, 2014); we were thus interested in obtaining new ferrocenyl P,N ligands (Dwadnia et al., 2018) bearing both phosphine and hydrazine moieties. Starting from compound 1 (Iftime et al., 1996), we aimed to obtain target ligand 4 ( Fig. 1). To avoid phosphine oxidation during reactions, work-ups and purifications, the phosphine group was protected as a thiophosphine by reaction with S 8 (Routaboul et al., 2005). The aldehyde-thiophosphine 2 provided product 3, the title compound, in one step. A study of the coordination chemistry of the free phosphine 4 and its use in catalytic reactions is now in progress in our laboratory. The synthesis of the title compound, 3.  Table 1. The two molecules have very similar conformations, as shown in the MolFitView, Fig. 3 (Spek, 2009). Each molecule is built up from a ferrocene unit substituted in positions 1,1 0 by a protected sulfur diphenylphosphine and by a dimethylhydrazine -C(H) N-N(CH 3 ) 2 fragment. The two independent molecules are linked by a C-HÁ Á ÁN hydrogen bond (Table 2 and Fig. 2).

Structural commentary
In both molecules, the two Cp rings are between eclipsed and staggered conformations, with a twist angle of 5.2 (2) for molecule A and 9.4 (1) for molecule B. However, the Cp rings are roughly parallel to each other with a dihedral angle of 1.46 (12) for molecule A and 1.85 (12) for molecule B. The protected diphenylphosphine and the dimethylhydrazine units are approximately trans with respect to the ferrocenyl moiety: the torsion angle P1-C11-C16-C161 and P2-C21-C26-C261 are ca 140.4 and ca 141.0 , respectively.
The sulfur atom is displaced endo towards the Fe II ion, by À0.7330 (6) Å (molecule A) and 0.6986 (6) Å (molecule B) from the Cp ring plane, whereas the phosphorus atom lies in this plane, displaced by 0.0114 (5) and À0.0603 (4) Å for molecules A and B, respectively. This arrangement, with the protected sulfur atom endo towards the Fe II ion and the P atom roughly coplanar with the Cp ring, is quite common in related compounds (see Section 4, Database survey). The geometry within the hydrazine moiety (see Table 1) is in agreement with already reported structures (Cambridge Structural Database; Groom et al., 2016). The Cp ring and the substituents on the terminal nitrogen are in a trans position. A view of the molecular structures of the two independent molecules (A and B) of compound 3, with the atom labelling. Displacement ellipsoids are drawn at the 50% probability level. The C-HÁ Á ÁN hydrogen bond is shown as a blue dashed line (see Table 2).

Figure 3
Molecular fitting of the two independent molecules (molecule A black and molecule B red).

Supramolecular features
In the crystal, the A-B units are linked through a pair of C-HÁ Á ÁS hydrogen bonds (Table 2), forming a four-molecule centrosymmetric unit ( Fig. 4 and Table 2). These units are linked by C-HÁ Á Á interactions, involving the phenyl ring, C111-C116, and the Cp rings, C16-C20 and C26-C30, linking the four-molecule units to form a supramolecular threedimensional structure ( Fig. 5 and Table 2).  Toma et al., 2015), which crystallizes with two independent molecules in the asymmetric unit, and 1,1 0 -bis(diphenylthiophosphoryl)ferrocene, for which two polymorphs have been reported, viz. monoclinic C2/c (ZEQSOD; Fang et al., 1995) and monoclinic P2 1 /c (ZEQSOD02; Tan et al., 2015). In CUJDAO, the substituents are cis to one another and in the -C(H) N-N(CH 3 ) 2 fragments the C N bond lengths, which vary from 1.270 (5) to 1.287 (4) Å , and the N-N bond lengths, which vary from 1.367 (4) to 1.382 (5) Å , are similar to those in the title compound (see Table 1). In ZEQSOD and ZEQSOD02, the P atom is roughly in the Cp ring plane, with deviations from the mean plane ranging from 0.009 (1) to 0.035 (1) Å , whereas the S atom is endo towards the Fe II ion with distances ranging from 0.583 (1) to 0.952 (1) Å . The corresponding distances for compound 3 fall within these ranges (see Section 2, Structural commentary).

Synthesis and crystallization
The synthesis of the title compound, 3, is illustrated in Fig. 1. In a Schlenk tube, under argon, were added 66 mg (0.153 mmol) of (1 0 -diphenylthiophosphino)ferrocenecarboxaldehyde (2), 200 mg (1.66 mmol) of anhydrous magnesium sulfate MgSO 4 and 5 ml of anhydrous dichloromethane. To the red suspension, 100 ml of N,N-dimethylhydrazine (79 mg, 1.31 mmol) was added using a syringe. The reaction mixture was then stirred at room temperature overnight. The crude material obtained was purified by flash chromatography on silica gel to yield 41 mg of compound 3 as A view along the c axis of the crystal packing of compound 3. The C-HÁ Á ÁN, C-HÁ Á ÁS and C-HÁ Á Á interactions (see Table 2) are represented as dashed lines. The H atoms involved in the C-HÁ Á Á interactions are shown as grey balls, and only the H atoms involved in the various intermolecular interactions have been included. Table 2 Hydrogen-bond geometry (Å , ).

Figure 4
A view of the four-molecule hydrogen-bonded unit. Hydrogen bonds are shown as dashed lines (see Table 2; only H atoms H123 and H226 have been included). [Symmetry code: (i) Àx, Ày + 1, Àz + 1.] a brown solid (yield = 57%). Orange needle-like crystals of 3 were obtained by slow evaporation of a solution in pentane.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 3. The C-bound H atoms were included in calculated positions and refined as riding: C-H = 0.95-0.98 Å with U iso (H) = 1.5U eq (C-methyl) and 1.2U eq (C) for other H atoms.

Funding information
The CNRS is acknowledged for financial support and TNM acknowledges the Department of Chemistry and Biochemistry of the University Constantine 1 for funding her stay at the LCC.

1-[(2,2-Dimethylhydrazin-1-ylidene)methyl]-1′-(diphenylphosphorothioyl)ferrocene
Crystal data Hydrogen site location: inferred from neighbouring sites H-atom parameters constrained where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.001 Δρ max = 0.49 e Å −3 Δρ min = −0.23 e Å −3 Special details Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell esds are taken into account in the estimation of distances, angles and torsion angles 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 > 2sigma(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.