Stiba-, Arsa- and Phosphastannenes: Syntheses and Reactivities

A facile synthesis for unprecedented stibastannene ( 10 ) featuring a Sn=Sb-double bond together with the homologous arsa- ( 9 ) and phosphastannenes ( 8 ) is presented. Chloride abstraction from respective stannyl pnictinidenes E=P ( 5 ), As ( 6 ), Sb ( 7 )], which were made accessible by reduction of ECl₃ addition products at an intramolecular phosphine-stabilized stannylene, gave the pnictastannenes in moderate yields. The pnictastannenes coordinate Pd(PPh₃)₂ fragments ( 12 – 14 ) and the phosphastannene forms also a nickel coordination compound with the Ni(PPh₃)₂-fragment ( 11 ). 2,3-Dimethylbutadiene shows a 2+4]-cycloaddition ( 15 – 17 ) in reaction with the pnictastannenes ( 8 – 10 ). Products of a 2+2]-addition ( 18 , 19 ) were isolated as the phosphaalkyne reaction products for 8 and 9 . Addition of an O?H bond at the Sn=P-bond was found in reaction of water with phosphastannene 8 . Reaction with ammonia afforded the NH₃-adducts ( 21 – 23 ) at the tin atom for pnictastannenes 8 – 10 . Only in the case of the arsastannene an azide reaction product featuring a three membered Sn?As?N-ring was obtained.