Reaction of 1-(Dimethylsilyl)-2-silylbenzene with Platinum(0) Phosphine Complexes

Reaction of 1,2-C 6 H 4 (SiMe 2 H)(SiH 3 ) ( 8 ) with Pt(dmpe)(PEt 3 ) 2 (dmpe = Me 2 PCH 2 CH 2 PMe 2 ) or Pt(dmpe) 2 in 1:1 ratio at room temperature gave {1,2-C 6 H 4 (SiMe 2 )(SiH 2 )}Pt II (dmpe) ( 11a ) as a major product in solution. Complex 11a can easily dimerize to form [(dmpe)Pt IV (H){1,2-C 6 H 4 (SiMe 2 )(μ-SiH)}] 2 ( 12a ), and 11a and 12a are in equilibrium in solution. Although monomer 11a is a major species in solution, only dimer 12a crystallized out from toluene, THF, or DMF solution. Addition of excess dmpe to a toluene solution of 11a / 12a trapped the Pt II species as a pentacoordinated dimer [{1,2-C 6 H 4 (SiMe 2 )(SiH 2 )}Pt II (dmpe)] 2 (μ-dmpe) ( 13 ). A similar reaction took place between 8 and Pt(depe)(PEt 3 ) 2 (depe = Et 2 PCH 2 CH 2 PEt 2 ) or Pt(depe) 2 to give {1,2-C 6 H 4 (SiMe 2 )(SiH 2 )}Pt II (depe) ( 11b ) and [(depe)Pt IV (H){1,2-C 6 H 4 (SiMe 2 )(μ-SiH)}] 2 ( 12b ), and 11b and 12b are in equilibrium in solution. Two equivalents of 8 reacted with Pt(dmpe)(PEt 3 ) 2 in toluene at room temperature to afford two isomeric {1,2-C 6 H 4 (SiMe 2 H)(SiH 2 )}{1,2-C 6 H 4 (SiMe 2 )(SiH 2 )}(H)Pt IV (dmpe) complexes 16 and 17 in 5:3 ratio among eight possible isomers. Heating the mixture of 16 and 17 at 100 °C in toluene resulted in slow intramolecular dehydrogenative cyclization to afford a mixture of isomeric {1,2-C 6 H 4 (SiMe 2 )(SiH 2 )} 2 Pt IV (dmpe) 18 and 19 . The structures of complexes 12a, 12b, 13, 17, 18, and 19 were unambiguously determined by single-crystal X-ray analysis.