Structural Diversity of Iso-Maleonitrile Dithiolate d10s2 Metal Complexes of Lead and Bismuth

The synthesis and solid-state structures of four structurally diverse i-mnt-based anionic complexes and coordination polymers are described (i-mnt = iso-maleonitrile dithiolate). (ⁿPr₄N)₄[Pb₂(i-mnt)₄] is dimeric, containing a five-coordinate distorted square pyramidal Pb(II) center with a stereochemically active lone pair. The isoelectronic (ⁿPr₄N)[Bi(i-mnt)₂] is a distorted six-coordinate complex that crystallizes in the polar P2₁ space group and forms a 2D coordination polymer via intermolecular Bi–N interactions; the d¹⁰s² Bi(III) center also has a hemidirectional coordination sphere with a stereochemically active lone pair. Using the more compact (Me₄N)⁺ cation, (Me₄N)₂[Pb(i-mnt)₂] contains eight-coordinate holodirectional Pb(II) centers that form 1D chains via bridging Pb–S bonding. These anionic complexes could provide the foundation to incorporate stereochemically active lone pairs into heterometallic coordination polymers. As a comparison, (ⁿPr₄N)₃Cr(i-mnt)₃·H₂O was also prepared and has a propeller structure with a typical octahedral Cr(III) center.