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

Reaction of 1,2-C6H4(SiMe2H)(SiH3) (8) with Pt(dmpe)(PEt3)2 (dmpe = Me2PCH2CH2PMe2)
or Pt(dmpe)2 in 1:1 ratio at room temperature gave {1,2-C6H4(SiMe2)(SiH2)}PtII(dmpe) (11a)
as a major product in solution. Complex 11a can easily dimerize to form [(dmpe)PtIV(H){1,2-C6H4(SiMe2)(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 PtII species as a pentacoordinated dimer [{1,2-C6H4(SiMe2)(SiH2)}PtII(dmpe)]2(μ-dmpe)
(13). A similar reaction took place between 8 and Pt(depe)(PEt3)2 (depe = Et2PCH2CH2PEt2) or Pt(depe)2 to give {1,2-C6H4(SiMe2)(SiH2)}PtII(depe) (11b) and [(depe)PtIV(H){1,2-C6H4(SiMe2)(μ-SiH)}]2 (12b), and 11b and 12b are in equilibrium in solution. Two equivalents
of 8 reacted with Pt(dmpe)(PEt3)2 in toluene at room temperature to afford two isomeric
{1,2-C6H4(SiMe2H)(SiH2)}{1,2-C6H4(SiMe2)(SiH2)}(H)PtIV(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-C6H4(SiMe2)(SiH2)}2PtIV(dmpe) 18 and 19. The structures of complexes 12a, 12b, 13,
17, 18, and 19 were unambiguously determined by single-crystal X-ray analysis.