Sterically Encumbered Tin and Phosphorus <i>peri-</i>Substituted Acenaphthenes

A group of sterically encumbered <i>peri</i>-substituted acenaphthenes have been prepared, containing tin moieties at the 5,6-positions in <b>1</b>–<b>3</b> ([Acenap­(SnR₃)₂], Acenap = acenaphthene-5,6-diyl; R₃ = Ph₃ (<b>1</b>), Me₃ (<b>2</b>); [(Acenap)₂(SnMe₂)₂] (<b>3</b>)) and phosphorus functional groups at the proximal <i>peri</i>-positions in <b>4</b> and <b>5</b> ([Acenap­(PR₂)­(P^<i>i</i>Pr₂)] R₂ = Ph₂ (<b>4</b>), Ph­(^<i>i</i>Pr) (<b>5</b>)). Bis­(stannane) structures <b>1</b>–<b>3</b> are dominated by repulsive interactions between the bulky tin groups, leading to <i>peri</i>-distances approaching the sum of van der Waals radii. Conversely, the <i>quasi</i>-linear C_Ph-P···P three-body fragments found in bis­(phosphine) <b>4</b> suggest the presence of a lp­(P)−σ*­(P–C) donor–acceptor 3c-4e type interaction, supported by a notably short intramolecular P···P distance and notably large <i>J</i>_PP through-space coupling (180 Hz). Severely strained bis­(sulfides) <b>4-S</b> and <b>5-S</b>, experiencing pronounced in-plane and out-of-plane displacements of the exocyclic <i>peri</i>-bonds, have also been isolated following treatment of <b>4</b> and <b>5</b> with sulfur. The resulting nonbonded intramolecular P···P distances, ∼4.05 Å and ∼12% longer than twice the van der Waals radii of P (3.60 Å), are among the largest ever reported <i>peri</i>-separations, independent of the heteroatoms involved, and comparable to the distance found in <b>1</b> containing the larger Sn atoms (4.07 Å). In addition we report two metal complexes with square planar [(<b>4</b>)­PtCl₂] (<b>4-Pt</b>) and octahedral <i>cis</i>-[(<b>4</b>)­Mo­(CO)₄] (<b>4-Mo</b>) geometries. In both complexes the bis­(phosphine) backbone is distorted, but notably less so than in bis­(sulfide) <b>4-S</b>. All compounds were fully characterized, and except for bis­(phosphine) <b>5</b>, crystal structures were determined