2-Triorgano-silyl, -germyl, -stannyl and -plumbyl derivatives of 1,3-diisopropyl-benzo-1,3,2-diazaborolidine and related compounds and their reactions with (η2-C2H4)Pt(PPh3)2

A series of 1,3‐diisopropyl‐benzo‐1,3,2‐diazaborolidines 1–6 carrying ER3 substituents of Group 14 at the boron atom (E = C, Si, Ge, Sn, Pb; R = Me, Ph) have been prepared. Their molecular structures have been determined. As expected, the BE bond length increases along this series. Moreover, the orientation of the isopropyl groups relative to the ER3 substituent is influenced by the steric demand of these substituents. The 11B NMR data show a deshielding of the boron nucleus as the atomic weight of E increases. Oxidative addition reactions with (η2‐C2H4)Pt(PPh3)2 were successful only for the bromo derivative 1 and the trimethylstannyl derivative 5a; they failed for the triphenylsilyl, triphenylgermyl and triphenylstannyl compounds, indicating that steric effects play an important role in the successful oxidative addition to boryl‐substituted bis(triphenylphosphane)platinum(II) complexes. The triphenylplumbyl derivative 6 reacted with (η2‐C2H4)Pt(PPh3)2 to give cis‐ and trans‐diphenyl‐bis(triphenylphosphane)platinum besides Ph(Ph3Pb)Pt(PPh3)2. Obviously, the PbC bond is more reactive than the PbB bond. Cis‐Platinum–boryl complexes were also obtained from (Me2N)2BSnMe3 and (Me2N)2BGeMe3 while the boranes tmpB(SnMe3)2 and iPr2NB(SnMe3)2 were unreactive. Copyright © 2003 John Wiley & Sons, Ltd.