Bidentate Phosphanyl- and Arsanylboranes.

A new class of neutral bidentate ligands with pnictogenyl-functional sites has been obtained. The reaction of tmeda⋅(BH2 I)2 (1, tmeda=tetramethylethylendiamine) with different phosphanides yields the corresponding bidentate phosphanylboranes tmeda⋅(BH2 PH2 )2 (2 a), tmeda⋅(BH2 PPh2 )2 (2 b), and tmeda⋅(BH2 tBuPH)2 (2 c). This reaction strategy could be further extended to synthesize the first bidentate arsanylborane tmeda⋅(BH2 AsPh2 )2 (3). Depending on the substituents on the phosphorus, these compounds form different AuI complexes, to build either polymeric tmeda⋅(BH2 PH2 AuCl)2 (4 a), or monomeric tmeda⋅(BH2 PPh2 AuCl)2 (4 b) products. These compounds form also neutral oligomeric group 13/15 chain-like molecules by coordination to a boron moiety such as tmeda⋅(BH2 PH2 BH3 )2 (5 a) and tmeda⋅(BH2 AsPh2 BH3 )2 (5 b). DFT calculations provide insight into the differences between the syntheses of mono- and bidentate pnictogenylboranes.