Tetra-n-butylammonium bis(1,1-dicyanoethylene-2,2-dithiolato)platinum(II)

In the title compound, (C16H36N)2[Pt(C4N2S2)2], the PtII center adopts a distorted square-planar geometry due to the 4-membered chelate rings formed by coordination to the S atoms of the 1,1-dicyanoethylene-2,2-dithiolate (i-mnt) ligands [bite angle 74.35 (4)°]. The bond distances in the coordinated i-mnt ligands indicate some delocalization of the π-system.

In the title compound, (C 16 H 36 N) 2 [Pt(C 4 N 2 S 2 ) 2 ], the Pt II center adopts a distorted square-planar geometry due to the 4-membered chelate rings formed by coordination to the S atoms of the 1,1-dicyanoethylene-2,2-dithiolate (i-mnt) ligands [bite angle 74.35 (4) ]. The bond distances in the coordinated i-mnt ligands indicate some delocalization of the -system.
This work was supported by funding from the NSF through a Research Site for Educators in Chemistry grant. The authors acknowledge Victor G. Young, Jr and the X-ray Crystallographic Laboratory in the Department of Chemistry at the University of Minnesota.
The structure of the anion in the title compound (C 16 H 36 N) 2 [Pt(S 2 C 4 N 2 ) 2 ] shows significant distortions from a square planar environment as forced by the four-membered chelate rings of the i-mnt ligands, with the i-mnt bite angle S(2)-Pt(1)-S(1) = 74.35 (4)°. As the Pt sits on the special position (1/2, 1/2, 1/2) in the space group P2 1 /n, Z′ = 0.5, the anion is quite planar, with a calculated r.m.s. deviation from a least-squares plane formed by all atoms of the complex anion of 0.042 (3) Å. The bond lengths within coordinated i-mnt ligand, in particular the bonds C(1)-C(2) 1.361 (6) Å, C(2)-C(3) 1.429 (6) Å, and C(2)-C(4) 1.430 (6)Å are very similar to those observed in the tetraethylammonium salt, showing significant π-delocalization. No columnar stacking is observed amongst the complex anions. As expected, upon comparison of the structure of the title compound and the tetraethylammonium salt, little effect was observed on the intramolecular features of the complex anion.

S2. Experimental
The title compound (C 16 H 36 N) 2 [Pt(S 2 C 4 N 2 ) 2 ] was prepared using a procedure similar to that described by Fackler and Coucouvanis (1966) subsituting the use of tetra-n-propylammonium iodide with tetra-n-butylammonium bromide. The title compound has been previously characterized by Werden et al.(1966). Spectroscopic analysis of the present sample obtained by this procedure was consistent with the data previously reported. Crystals were obtained by diffusion of diethyl ether into a concentrated solution of the title compound dissolved in dichloromethane.
Only the crystallographically independent atoms are labelled.

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. 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.