Structure and properties of halogeno(hydrido)(triorganosilyl)rhodium(III) complexes, RhX(H)(SiR_n¹R_3-n²)(PPh₃) ₂ (X = Cl, I; R¹ = OSiMe₃, OEt, R² = Me). Influence of the alkoxy groups and halo ligand on stability and reactivity of the complexes

Silylrhodium(III) complexes RhX(H)(SiR_n¹R_3-n²)(PPh₃) ₂ (1: X = I, R¹ = OSiMe₃, R² = Me, n = 1; 2: X = I, R¹ = OEt, n = 3; 3: X = I, R¹ = OEt, R² = Me, n = 2; 4: X = I, R¹ = OEt, R² = Me, n = 1; 5: X = Cl, R¹ = OSiMe₃, R² = Me, n = 1; 6: X = Cl, R¹ = OEt, n = 3; 7: X = Cl, R¹ = OEt, R² = Me, n = 2; 8: X = Cl, R¹ = OEt, R² = Me, n = 1) were prepared by oxidative addition of HSiR_n¹R_3-n² to RhX(PPh₃)₃ and characterized by means of NMR (¹H, ¹³C{¹H}, ³¹P{¹H}, and ²⁹Si{¹H}) and IR spectroscopy as well as elemental analyses. X-ray crystallography of 1, 2, and 6 showed a distorted square-pyramidal coordination around the Rh center that is bonded to the silyl ligand at the apical position and to halo and hydrido ligands in trans positions in the basal plane. The Rh-Si bonds in 2 and 6 are the shortest among Rh-Si bonds of the silylrhodium complexes reported to date. ²⁹Si{¹H} NMR spectra of 1-8 show that the J(RhSi) value increases with an increase in the number of alkoxy substituents on the Si atom. Complex 2 reacted with HSiMe₂(OSiMe₃), HSi(OEt)₂Me, and HSi(OEt)Me₂, respectively, to cause exchange of the silyl group between the Rh complex and the organosilane, forming an equilibrium mixture. Complexes 5-8 undergo thermally induced coupling of their chloro and triorganosilyl ligands at 60 °C to liberate the respective chloro(triorgano)silane. The reaction obeys first-order kinetics in the Rh complex with the observed rate constants in the order 5 ≅ 8 > 7 > 6. The OEt groups at the Si retard the coupling of chloro and triorganosilyl ligands significantly. Formation of ISiMe₂(OEt)₂ from 4 takes place at a slightly slower rate than the reaction of 6, while complexes 2 and 3 do not undergo coupling of their iodo and silyl ligands at 60 °C.