New tridentate phosphine rhodium and iridium complexes, including a stable rhodium(I) silyl. Si-S activation and a strong effect of X in (PP2)M-X (X = H, Cl, Me) on Si-H activation

摘要

Rhodium and iridium complexes of the general formula (PP2)MX bearing the new triphosphine ligand (Pr2P)-Pr-i(CH2)(3)P(Ph)(CH2)(3)(PPr2)-Pr-i (PP2) have been synthesized. Reactivity of the PP2MX complexes toward HSi(SEt)(3) was studied. Whereas (PP2)RhCl and (PP2)IrCl do not react with HSi(SEt)(3), (PP2)RhH gives rise to the Rh(III) adduct [(PP2)Rh(H)(2)Si(SEt)(3)], and (PP2)RhMe (3) activates both the Si-H and the Si-S bonds of HSi(SEt)(3), affording the Rh(I) complexes (PP2)RhSi(SEt)(3) (5) and (PP2)RhSEt (6). Only a few stable Rh(I) silyl complexes are known, and SI-S bond activation by transition-metal complexes has been rarely observed. The X-ray crystal structure of 5 exhibits a considerable distortion from square-planar geometry, the average angle between the trans-disposed ligands being 152.5degrees. In contrast to 3, (PP2)IrMe (8) forms a stable Ir(III) adduct with HSi(SEt)(3), fac-[(PP2)Ir(Me)(H)(Si(SEt)(3))] (9). No Si-S activation was observed with 8. Thus, the reactivity Of (PP2)-MX complexes toward HSi(SEt)(3) strongly depends on the nature of M and X. [References: 26]