A carbazole-based azaphosphole (compound 3) has been prepared by acid-catalyzed dehydrocyclization of 1-phosphino-9H-carbazole (2) with benzoyl chloride. Unlike other benzazaphospholes having σ 2 ,λ 3 -multiply bonded phosphorus atoms, compound 3 displays significant fluorescence in solution, as does primary phosphine 2. Compound 3, as well as the materials on route to its synthesis, were characterized by

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Under conditions typically effective to achieve a catalytic aryl–aryl bond during palladium Suzuki–Miyaura (SM) coupling reactions of ArB­(OH)2 and ArBr, reactions of p-tolylboronic acid and 2-(BrC6H4)-1,3-benzoxaphosphole (BrC6H4-BOP, 1) failed to provide the anticipated product of CC bond coupling, 2-(p-CH3C6H4-C6H4)-1,3-benzoxaphosphole. An analysis of reaction mixtures by 1H and 31P­{1H} NMR spectroscopic methods showed the presence of numerous broad resonances, suggesting the formation of labile metal complexes with 1. This possibility was confirmed by determinations of the solid-state structures of [(tBu3P)­(Ph-BOP)­M]2 (M = Pt, 5; M = Pd, 6) from the reaction of Ph-BOP and [M­(tBu3P)2] (M = Pt, Pd). The structures of 5 and 6 are isomorphous and reveal unusual bridging μ2-P-BOP bonding modes. Computational studies have explored the structures and relative energies and indicate that dimeric complexes of this form can dissociate easily. Surprisingly, even when PC double bonds of Ar-BOPs are sheltered by coordination to tungsten pentacarbonyl, the Ar-BOP units resist yielding products of CC coupling under similar SM conditions but instead yield unusual products whereby CsOH adds across the PC bonds in [(CO)5W­{2-Ar-BOP}]. Computational studies are consistent with ready addition of hydroxide to the tungsten-protected PC bond.

Synthesis of a Luminescent Azaphosphole. -A carbazole-based azaphosphole (VI) is prepared by acid-catalyzed dehydrocyclization of 1-phosphino-9H-carbazole (IV) with toluyl chloride (V). Compound (VI) displays significant fluorescence in solution. -(WU, S.; RHEINGOLD, A. L.; GOLEN, J. A.; GRIMM, A. B.; PROTASIEWICZ*, J. D.; Eur. J. Inorg. Chem. 2016, 5, 768-773, http://dx.doi.org/10.1002/ejic.201501279 ; Dep. Chem., Case West. Reserve Univ., Cleveland, OH 44106, USA; Eng.) -R. Langenstrassen 27-208