Bis[O-propyl (4-ethoxyphenyl)dithiophosphonato-κ2 S,S′]nickel(II)

The title compound, [Ni(C11H16O2PS2)2], contains a four-coordinate NiII cation with an idealized square-planar geometry. The metal atom is surrounded by two chelating isobidentate dithiophosphonate ligands in a trans or anti configuration, binding through the S-donor atoms.

The title compound, [Ni(C 11 H 16 O 2 PS 2 ) 2 ], contains a fourcoordinate Ni II cation with an idealized square-planar geometry. The metal atom is surrounded by two chelating isobidentate dithiophosphonate ligands in a trans or anti configuration, binding through the S-donor atoms.

Shirveen Sewpersad, Bernard Omondi and Werner E. Van Zyl Comment
The phosphor-1,1,-dithiolate class of compounds is the heavier and softer congener of the more popular phosphonate derivatives (Van Zyl, 2010). It contains the S 2 P functionality as a common feature and several sub-categories are known which include the dithiophosphato [S 2 P(OR) 2 ]¯, (R = typically alkyl), dithiophosphinato [S 2 PR 2 ]¯ (R = alkyl or aryl), and dithiophosphonato [S 2 PR(OR′)]¯, (R = typically aryl or ferrocenyl, R′ = alkyl) monoanionic ligands. The latter may be described as a hybrid of the former two, and are also much less developed.
Amongst all metals involved in the coordination chemistry of dithiophosphonato ligands, however, nickel(II) is by far the best represented [Liu et al. (2004); Gray et al. (2004); Aragoni et al. (2007); Arca et al. (1997); Van Zyl & Woollins, (2012)] with the first X-ray structural report of a nickel(II) dithiophosphonate complex reported more than 4 decades ago (Hartung, 1967). The structure of the title complex does not differ significantly from related Ni II complexes previously reported (see related literature). The Ni-S bond length is 2.2254 (2) and 2.2264 (2) Å, which is an insignificantly small difference to be considered anisobidentate. The Ni-P bond length is 2.8310 (3) Å, and the S-P bond length is 2.0081 (3) and 2.0026 (4) Å, respectively.
The complex in the present study was formed from the reaction between NiCl 2 .6H 2 0 and the ammonium salt of [S 2 P(OPr)(4-C 6 H 4 OEt)] (molar ratio 1:2) in an aqueous/methanolic solution, the NH 4 Cl by-product was dissolved and the precipitated product filtered off and washed with water. General and convenient methods to prepare dithiophosphonate salt derivatives have been reported (Van Zyl & Fackler, 2000).

Experimental
A colorless methanol (40 ml) solution of NH 4 [S 2 P(OPr)(4-C 6 H 4 OEt)] (997 mg, 3.398 mmol) was prepared. A second green solution of NiCl 2 .6H 2 0 (424 mg, 1.699 mmol) in deionized water (20 ml) was prepared, and added to the colorless solution with stirring over a period of 5 min. This resulted in a purple precipitate indicating the formation of the title complex. The precipitate was collected by vacuum filtration, washed with water (3 x 10 ml) and allowed to dry under vacuum for a period of 3 hrs, yielding a dry, free-flowing purple powder. Purple crystals suitable for X-ray analysis were grown by the slow diffusion of hexane into a dichloromethane solution of the title complex. Yield: 740 mg, 30%. M.p.

Refinement
All hydrogen atoms were found in the difference electron density maps and were placed in idealized positions and refined with geometrical constraints, with C-H bond lengths in the range 0.95-1.00 Å. The structure was refined to R factor of 0.0193.

Figure 1
The ORTEP molecular structure of the title complex, shown with 50% probability.

Bis[O-propyl (4-ethoxyphenyl)dithiophosphonato-κ 2 S,S′]nickel(II)
Crystal data 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 > σ(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.