Phosphorus-Bismuth Peri-Substituted Acenaphthenes: A Synthetic, Structural, and Computational Study

A series of acenaphthene species with a diisopropylphosphino group and a variety of bismuth functionalities in the peri 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(PiPr₂)(BiPh₂) (2; Acenap = acenaphthene-5,6-diyl), which was subjected to a fluorodearylation reaction to produce Acenap(PiPr₂)(BiPhX) (5-8 and 10; X = BF₄^-_, Cl, Br, I, SPh), displaying varying degrees of ionicity. The geminally bis(acenaphthyl)-substituted [Acenap(PiPr₂)]₂BiPh (3) shows a large through-space coupling of 17.8 Hz, formally ^8TSJ_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(PiPr₂)(BiI₂) (9) have been investigated; however, the purity of this, surprisingly thermally stable potential synthon, remains poor.