Dibismuthates as Linking Units for Bis-Zwitterions and Coordination Polymers

Adducts of bismuth trihalides BiX3 (X = Cl, Br, I) and the PS3 ligand (PS3 = P(C6H4-o-CH2SCH3)3) react with HCl to form inorganic/organic hybrids with the general formula [HPS3BiX4]2. On the basis of their solid-state structures determined by single-crystal X-ray diffraction, these compounds exhibit discrete bis-zwitterionic assemblies consisting of two phosphonium units [HPS3]+ linked to a central dibismuthate core [Bi2X8]2– via S→Bi dative interactions. Remarkably, the phosphorus center of the PS3 ligand undergoes protonation with hydrochloric acid. This is in stark contrast to the protonation of phosphines commonly observed with hydrogen halides resulting in equilibrium. To understand the important factors in this protonation reaction, 31P NMR experiments and DFT computations have been performed. Furthermore, the dibismuthate linker was utilized to obtain the coordination polymer {[AgPS3BiCl3(OTf)]2(CH3CN)2}∞, in which dicationic [Ag(PS3)]22+ macrocycles containing five-coordinate silver centers connect the dianionic [Bi2Cl6(OTf)2]2– dibismuthate fragments. The bonding situation in these dibismuthates has been investigated by single-crystal X-ray diffraction and DFT calculations (NBO analysis, AIM analysis, charge distribution).


S13
At room temperature, complex 1A crystallizes in two different polymorphic forms (1A' and 1A''). Both have monoclinic space group P2 1 /n, with one-half of the centrosymmetric molecule per asymmetric unit. Form 1A' is enantiotropic: between 220 and 200 K it undergoes a phase transition to a triclinic (space group P ) form 1A''', which then persists down to 120 K, at which temperature the crystal 1 structure of 1A''' was determined. During the transition, a single crystal of 1A' converts into a twocomponent pseudo-merohedral twin; the twinning is by a 180° rotation around the former unique monoclinic axis [note that the reduced cell of 1A''' differs from that of 1A' by circular permutation of axes, so that the monoclinic axis y of 1A' becomes z in 1A''']. In 1A''', the asymmetric unit comprises two halves of crystallographically non-equivalent centrosymmetric molecules ( Figure S13). The transition is fully reversible: on warming the twin reverted to a single crystal of 1A', full structure determination of which was then carried out at 240 K. On the contrary, form 1A'' showed no phase transition on cooling from room temperature to 120 K (Table S2).
The triclinic crystal structure of 1B closely resembles 1A'''; with the asymmetric unit also comprising two halves of centrosymmetric molecules. 1B can be described as pseudo-monoclinic (and thus similar to 1A'): the structure can be solved and refined in space group P2 1 /n (with unique axis z), albeit with irreducibly higher R-factor (0.09 cf. 0.043). Also like 1A''', 1B shows pseudo-merohedral twinning by a 180° rotation around the pseudo-monoclinic axis (z). The positions of Cl and Br atoms could not be resolved, therefore they were refined as single atoms with mixed scattering factors; the relative occupancies were refined independently for each site.
The monoclinic structure of 1C resembled that of 1A'. In this case, Cl and I atoms at each site were resolved and refined separately, again with relative occupancies refined independently for each site, with Cl…I separations of 0.36 -0.45 Å. a After rewarming S14 Figure S13: ORTEP representation of 1A'''. Thermal ellipsoids are drawn at 50% probability. Carbonbonded hydrogen atoms have been omitted for clarity. Figure S14: ORTEP representation of 1B. Thermal ellipsoids are drawn at 50% probability. Carbonbonded hydrogen atoms have been omitted for clarity. S15 Figure S15: ORTEP representation of 1C. Thermal ellipsoids are drawn at 50% probability. Carbonbonded hydrogen atoms have been omitted for clarity. S16

Computational details
The computations were performed with the Gaussian 09 suite of programs. 5 All structures were optimised using the ωB97XD functionals. We employed the def2-SVP basis set implemented in Gaussian 09 or thee all valence cc-pVDZ basis set for H, C, P, S, Cl, O, and Br, while for Bi and I the cc-pVDZ-PP basis sets including pseudopotentials for the modelling of relativistic effects were used.
For the anionic species the aug-cc-pVDZ-(PP) basis sets were used. Similar levels of theory have been successfully employed for similar systems. Wiberg Bond Indices and NPA charges the NBO program version 3.1 was used. 9 The AIM analysis was obtained with the Multiwfn code. 10 The plotting of the orbitals was performed with the AVOGADRO program (www.avogadro.cc).