2‐Triorgano‐silyl, ‐germyl, ‐stannyl and ‐plumbyl derivatives of 1,3‐diisopropyl‐benzo‐1,3,2‐diazaborolidine and related compounds and their reactions with (η 2 ‐C 2 H 4 )Pt(PPh 3 ) 2

A series of 1,3‐diisopropyl‐benzo‐1,3,2‐diazaborolidines 1–6 carrying ER 3 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 BE bond length increases along this series. Moreover, the orientation of the isopropyl groups relative to the ER 3 substituent is influenced by the steric demand of these substituents. The 11 B NMR data show a deshielding of the boron nucleus as the atomic weight of E increases. Oxidative addition reactions with (η 2 ‐C 2 H 4 )Pt(PPh 3 ) 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 (η 2 ‐C 2 H 4 )Pt(PPh 3 ) 2 to give cis ‐ and trans ‐diphenyl‐bis(triphenylphosphane)platinum besides Ph(Ph 3 Pb)Pt(PPh 3 ) 2 . Obviously, the PbC bond is more reactive than the PbB bond. Cis ‐Platinum–boryl complexes were also obtained from (Me 2 N) 2 BSnMe 3 and (Me 2 N) 2 BGeMe 3 while the boranes tmpB(SnMe 3 ) 2 and i Pr 2 NB(SnMe 3 ) 2 were unreactive. Copyright © 2003 John Wiley & Sons, Ltd.