Phosphorus–Bismuth <i>Peri</i>-Substituted Acenaphthenes: A Synthetic, Structural, and Computational Study

Abstract

A series of acenaphthene species with a diisopropylphosphino group and a variety of bismuth functionalities in the <i>peri</i> positions were synthesized and fully characterized, including single-crystal X-ray diffraction. The majority of the reported species feature a relatively rare interpnictogen P-Bi bond. The series includes the phosphine-bismuthine Acenap(P<i>i</i>Pr₂)(BiPh₂) (<b>2</b>; Acenap = acenaphthene-5,6-diyl), which was subjected to a fluorodearylation reaction to produce Acenap(P<i>i</i>Pr₂)(BiPhX) (<b>5</b>-<b>8</b> and <b>10</b>; X = BF₄^-_, Cl, Br, I, SPh), displaying varying degrees of ionicity. The geminally bis(acenaphthyl)-substituted [Acenap(P<i>i</i>Pr₂)]₂BiPh (<b>3</b>) shows a large through-space coupling of 17.8 Hz, formally ^8TS<i>J</i>_PP. Coupling deformation density calculations confirm the double through-space coupling pathway, in which the P and Bi lone pairs mediate communication between the two ³¹P nuclei. Several synthetic routes toward the phosphine-diiodobismuthine Acenap(P<i>i</i>Pr₂)(BiI₂) (<b>9</b>) have been investigated; however, the purity of this, surprisingly thermally stable potential synthon, remains poor.