Bis[(1,1′-biphenyl-2,2′-diyl)di-tert-butylphosphonium] di-μ-chlorido-bis[dichloridopalladate(II)]

In the title compound, (C20H26P)2[Pd2Cl6], the PdII atom within the hexachloridodipalladate(II) dianion has a square-planar geometry. It resides on a centre of inversion with the asymmetric unit containing half of the dianion and one phosphonium cation. Only weak C—H⋯π interactions are present in the crystal structure.

In the title compound, (C 20 H 26 P) 2 [Pd 2 Cl 6 ], the Pd II atom within the hexachloridodipalladate(II) dianion has a squareplanar geometry. It resides on a centre of inversion with the asymmetric unit containing half of the dianion and one phosphonium cation. Only weak C-HÁ Á Á interactions are present in the crystal structure.
The structure of the title compound (I), [C 20 H 26 P. 0.5(Cl 6 Pd 2 )] 2 shows a square planar geometry for the Pd II atom within the hexachlorodipalladium(II) anion. The palladium atom sits on a centre of inversion and therefore the asymmetric unit contains half of the trichloropalladium(II) anion and one phosphonium cation. Figure 1 shows a diagram of the molecular structure of the asymmetric unit of (I). Weak interactions were observed in this structure where C-H···Cl and C-H···π are evident only.

Experimental
A solution of hydrogen chloride (142 mg; 4 mmol) in 18 ml of methanol was slowly added to a stirred solution of the palladocycle precursor, namely acetato-(2′-di-t-butylphosphino-1,1′-diphenyl-2yl) palladium(II) (493 mg; 1 mmol) in 17 ml of dichloromethane over a period of 10 minutes. The reaction mixture changed from colourless to dark purple and then to dark brown. After completion of the addition, stirring was discontinued and the reaction mixture left exposed to the air at room temperature. A red crystalline precipitate started to form after 45 minutes. After 24 h, the supernatant solution was removed, the solid material was with ether and dried in vacuo. The solid material (376 mg; 74%) was taken up in 15 ml of 2:1 dichloromethane:methanol and the resulting solution was exposed to the vapours of diethyl ether in a closed system for 24 h. Well formed, dark red prisms of the title compound (I) crystallized from the solution and a suitable single-crystal was selected for the single-crystal X-ray diffraction analysis.

Refinement
The H-atoms were geometrically positioned and refined in the riding-model approximation, with C-H = 0.97 Å, N-H = 0.89 Å, and U iso (H) = 1.2Ueq(C) or 1.5Ueq(N). For (I), the highest peak in the final difference map is 0.60 Å from Cl4B and the deepest hole is 0.27 Å from Cl4B.

Bis[(1,1′-biphenyl-2,2′-diyl)di-tert-butylphosphonium] di-µ-chlorido-bis[dichloridopalladate(II)]
Crystal data (C 20 H 26 P) 2 [Pd 2 Cl 6 ] M r = 1020.26 Triclinic, P1 Hall symbol: -P 1 a = 8.3247 (2) Å b = 11.2697 (2) Å c = 11.7004 (3) Å α = 73.0982 (6) 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.