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

Abstract

Rhodium and iridium complexes of the general formula (PP2)MX bearing the new triphosphine ligand iPr2P(CH2)3P(Ph)(CH2)3PiPr2 (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)2Si(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 152.5°. 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.

Dehydrogenative Coupling of a Tertiary Silane Using Wilkinson's Catalyst

“…The formation of 1 suggests an oxidative addition of the hydrosilane to [Rh(PPh 3 ) 3 Cl]. This type of silyl‐hydrido‐Rh III complexes synthetized by Si–H activation of a hydrosilane to a rhodium center are well known . Compound 1 could be synthesized in a good yield by the reaction of Wilkinson's catalyst with an equimolar amount of the tridentate proligand SiMeH( o ‐C 6 H 4 SMe) 2 ( L1 ) in CH 2 Cl 2 at room temperature (Scheme ).…”

Reactions of Hydrosilanes with Transition Metal Complexes and Characterization of the Products

“…246 Another ligand that contained a phosphine tether was PhP(CH 2 CH 2 CH 2 P i Pr 2 ) 2 , PP 2 . When (PP 2 )RhH was reacted with HSi(SEt) 3 , oxidative addition occurred to give a 6-coordinate complex, 3-196, 245 in which the two hydrides were cis and the tridentate phosphine occupied mer-sites. 245 In contrast, when (PP 2 )RhMe reacted with HSi(SEt) 3 , methane was eliminated to give 4-coordinate (PP 2 )RhSi(SEt) 3 (3-195), although (PP 2 )IrMe, the iridium analogue, simply added the hydrosilane to give 6-coordinate 3-239 (fac-isomer).…”

“…245 In contrast, when (PP 2 )RhMe reacted with HSi(SEt) 3 , methane was eliminated to give 4-coordinate (PP 2 )RhSi(SEt) 3 (3-195), although (PP 2 )IrMe, the iridium analogue, simply added the hydrosilane to give 6-coordinate 3-239 (fac-isomer). 245 The phosphine can influence the course of the reaction as illustrated in the reaction of (Et 3 P) 3 IrCl and (Et 2 PhP) 3 IrCl with the primary silane, H 3 SiAr (Ar ) C 6 H 3 -Mes 2 -2,6) as shown in eq 102 for formation of 1-57, although Cl migration from Ir to Si in this case must also occur. 58 Just changing one of the ethyl groups in the phosphine for a phenyl group resulted in cyclometallation (atIr)ofanortho-mesitylCHbond,togive( 59 The difference in reactivity was attributed to the more sterically hindered silane.…”

“…Additional product observed, (PP 2 )RhSEt (ratio 1:4 favoring Rh-Si product). 245 2 , each in 91% yield. Also prepared by reaction of (Me 3 P) 3 Rh[SiMe 2 (CH 2 ) 2 PPh 2 ] with 5 PhMe 2 SiH.…”

Stabilized Gallylene in a Pincer‐Type Ligand: Synthesis, Structure, and Reactivity of PGaIP‐Ir Complexes

“…TheI r ÀSi bond length (2.422(1) )i sc omparable to those of previously reported silyliridium complexes. [21,22] TheI r À Ga1 distance of 2.4616(6) is clearly longer than those of 3 and 4 owing to the strong trans influence of the silyl ligand on 7.I n 1 HNMR, hydrogen atoms on Ir and Si appeared at d = À11.6 (1 H, IrH), À8.9 (1 H, IrH), and 5.0 (2 H, SiH 2 )s eparately in [D 2 ]dichloromethane,a nd no…”