catena-Poly[[(6,7,9,10,17,18,20,21-octahydro-5,8,11,16,19,22-hexaoxadibenzo[a,j]cyclooctadecene)barium]-di-μ-thiocyanato-[thiocyanatodiaurate(I)(Au—Au)]-μ-thiocyanato]

In the title compound, [Au2Ba(NCS)4(C20H24O6)]n, the dithiocyanatoaurate(I) anion adopts a dimeric structure with an Au⋯Au distance of 3.1109 (10) Å; both AuI atoms are also bonded to two S atoms. The BaII ion adopts an irregular BaN3O6 geometry, arising from the crown ether and three adjacent thiocyanate N atoms; the extended structure of the complex can be described as a one-dimensional coordination polymer generated by the Ba⋯N interactions (two on the endo side and one on the exo side of the crown ether) running parallel to the b axis, with an antiparallel arrangement of ribbons in the unit cell.

In the title compound, [Au 2 Ba(NCS) 4 (C 20 H 24 O 6 )] n , the dithiocyanatoaurate(I) anion adopts a dimeric structure with an AuÁ Á ÁAu distance of 3.1109 (10) Å ; both Au I atoms are also bonded to two S atoms. The Ba II ion adopts an irregular BaN 3 O 6 geometry, arising from the crown ether and three adjacent thiocyanate N atoms; the extended structure of the complex can be described as a one-dimensional coordination polymer generated by the BaÁ Á ÁN interactions (two on the endo side and one on the exo side of the crown ether) running parallel to the b axis, with an antiparallel arrangement of ribbons in the unit cell.
To further explore the influence of the cation on the motif adopted by the bis(thiocyanato)aurate(I) anion, we synthesized and characterized the (1,4,7,10,13,16-hexaoxacyclooctadecane)-potassium dithiocyanatoaurate(I) [1,4,7,10,13,16-hexaoxacyclooctadecane = 18-crown-6] (Coker et al., 2004b) and (18-crown-6)-caesium dithiocyanatoaurate(I) (Coker, 2003) complexes. The geometry of the [Au(SCN) 2 ]anion in these complexes is monomeric and analogous to the Ph 4 P + and Ph 4 As + salts. The extended structure can be described as a zigzag polymeric chain formed by the coordination of the N atoms of the thiocyanate via a single intermolecular interaction to the vacant coordination site on the K or Cs atoms.
This characteristic makes them useful in applications where coordination-flexible ligating agents are a necessity (e.g. sequestration) (Bradshaw & Izatt, 1997). The nine-coordinate Ba atom in (I) is bound to the six oxygen atoms of the dbz-18crown-6 (Ba-O distances range: 2.940 (9)-2.988 (10) Å) and sits 0.769 (5) Å out of the plane generated by these atoms.
The remainder of the coordination sites consists of two endo side and one exo side Ba···N interaction (2.774 (14)-2.877 (13) Å). The fourth thiocyanate moiety (N4) remains uncoordinated, the nearest nonbonded distance to Ba is 4.728 (15) Å. Thus the extended structure of (I) (Fig. 2) can be described as a one-dimensional coordination polymer generated by Ba···N intermolecular interactions running parallel to the b axis, with an overall antiparallel arrangement of ribbons in the unit cell.

Experimental
Reaction of barium hydroxide (1 equiv) with ammonium thiocyanate (2 eqiv) in water results in the formation of barium thiocyanate with the release of ammonia gas.

Refinement
The H-atoms were placed in calculated positions (C aromatic -H = 0.95 Å, C methylene -H = 0.99 Å). The isotropic displacement parameters for all hydrogen atoms were defined as 1.2U eq of the adjacent atom. The maximum residual electron-density peaks are located approximately 1 Å from the Au atoms.  catena-Poly [[(6,7,9,10,17,18,20,21-octahydro-5,8,11,16,19,22-hexaoxadibenzo[a,j]  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 Rfactors(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.
The anisotropic displacement parameters for C7 and C20 were constrained to be equivalent to C6 and C5, respectively.