Extending the Toolbox for the Modular Arrangement of Functions at Xanthene/Dibenzofuran Platforms: Introduction of Directly Linked Transition Metals beside Bismuthanes

Abstract

XanI2 (4,5‐diiodo‐2,7‐di‐tert‐butyl‐9,9‐dimethylxanthene) and DBFI2 (4,6‐diiododibenzofuran) have been functionalized first with Ph2Bi units through reaction with PhLi and then with Ph2BiCl. The remaining C–I bonds were shown to undergo oxidative additions to M(PPh3)2 species (M = Pd, Ni; generated from employed [M(PPh3)4]), thus giving rise to heterometallic systems [Xan(BiPh2)Pd(PPh3)2I] (2), [Xan(BiPh2)Ni(PPh3)2I] (3), and [DBF(BiPh2)Pd(PPh3)2I] (6), where the bismuthane moieties are positioned vis‐à‐vis a d8‐MII center; treatment of 2 with AgOTf led to an exchange of the iodide ligand at the central nickel atom by a more weakly bound triflate ligand. The developed synthetic strategy can be envisioned to also provide access to combinations of such transition metal moieties with other main group entities for cooperative substrate activation.

NMR spectroscopic investigations on the successive implementation of nickel and zinc ions to a NacNac‐dibenzofuran‐Br ligand precursor

“…We had shown previously that a xanthenyl iodide unit reacts with Ni(COD) 2 and PPh 3 to give xanthene-Ni(PPh 3 ) 2 I entities. [23] To decrease the steric bulk in this case we used TMEDA (tetramethylethylendiamine) instead of phosphane co-ligands and thus reacted LH with Ni(COD) 2 in the presence of TMEDA to generate HNacNac-DBF-Ni(TMEDA)Br. This complex should feature a nickel center in a square planar coordination environment (see also below), and thus a diamagnetic behavior should be expected.…”

“…Subsequently, we targeted the introduction of metal centers, starting by addressing the C−Br unit. We had shown previously that a xanthenyl iodide unit reacts with Ni(COD) 2 and PPh 3 to give xanthene‐Ni(PPh 3 ) 2 I entities [23] . To decrease the steric bulk in this case we used TMEDA (tetramethylethylendiamine) instead of phosphane co‐ligands and thus reacted LH with Ni(COD) 2 in the presence of TMEDA to generate HNacNac‐DBF‐Ni(TMEDA)Br.…”