Reactions of terphenylbismuth dihalides with KSi(SiMe3)3, K2Si2(SiMe3)4 and Na2[Fe(CO)]4: reduction vs. metathesis.

The reactions of bulky terphenylylbismuth dihalides with various anionic reducing agents gave dibismuthine (Bi-Bi) and dibismuthene (Bi:Bi) dimeric compds., rather than the corresponding substitution products. Attempted substitution of chlorides in Ar'BiCl2 [Ar' = 2,6-(2,6-iPr2-C6H3)2-C6H3] with one equiv. of KSi(SiMe3)3 gave the 1,2-dichlorodibismuthine Ar'(Cl)Bi-Bi(Cl)Ar' (1) in 40% yield. The reaction of Ar'BiCl2 with the dianionic salt K2Si2(SiMe3)4 yielded the dibismuthene Ar'Bi:BiAr' (2) in 72% yield. The terphenylylbismuth dihalides ArBiCl2 [Ar = Ar', 2,6-(2,4,6-Me3C6H2)2-C6H3 (Ar#)] were treated with carbonylferrate Na2[Fe(CO)4] in THF to afford the iron dibismuthene complexes [Fe(CO)4(Bi2Ar'2)] (3) and [Fe(CO)4(Bi2Ar#2)] (4) in modest yields (25% and 15% resp.). The compds. 1-4 were characterized by x-ray crystallog. and by spectroscopic methods (1H and 13C NMR, IR, and UV/Vis spectroscopy). The results show that redn. of the bismuth center is strongly preferred over salt metathesis chem. due to the reducing power of the silanide and ferrate salts and the strength of the Bi:Bi bond. [on SciFinder(R)]