High Oxidation State Rhodium and Iridium Bis(silyl)dihydride Complexes Supported by a Chelating Pyridyl-Pyrrolide Ligand

Abstract

New rhodium and iridium complexes containing the bidentate ligand 3,5-diphenyl-2-(2-pyridyl)pyrrolide (PyPyr) were prepared. The bis(ethylene) complex (PyPyr)Rh(C(2)H(4))(2) (3) reacted with HSiEt(3), HSiPh(3), and HSi(t)BuPh(2) to produce the 16-electron Rh(V) bis(silyl)dihydrides (PyPyr)Rh(H)(2)(SiEt(3))(2) (8), (PyPyr)Rh(H)(2)(SiPh(3))(2) (9), and (PyPyr)Rh(H)(2)(Si(t)BuPh(2))(2) (10), respectively. The analogous Ir(V) bis(silyl)dihyride (PyPyr)Ir(H)(2)(SiPh(3))(2) (11) has also been synthesized. X-ray crystallography reveals that 9-11 adopt a coordination geometry best described as a bicapped tetrahedron. Silane elimination from 9 and 10 occurred in the presence of either HSiEt(3) or PPh(3). Mechanistic studies of the silane exchange process involving 10 and free HSiEt(3) (to give 8) indicate that this process occurs by rate-limiting reductive elimination of HSi(t)BuPh(2) from 10 to generate a 14-electron Rh(III) intermediate of the type (PyPyr)Rh(H)(Si(t)BuPh(2)).

Synthesis and Structures of Fluorinated (β‐Diketiminato)rhodium Complexes: Si–H Activation of Silanes at a Carbonyl Complex

“…They revealed that the isomer of [Rh{κ 2 -(N,N)-(C 6 F 5 )NC(Me)CHC(Me)N(C 6 F 5 )}(H)-(SiMe 3 )(CO)] (10a), which exhibits a mutual cis orientation of the hydrido and the carbonyl ligands and in which the silyl ligand occupies the apical position in a square-pyramidal complex, is the only isomer that converged to a stable structure (Figure 8; see the Supporting Information). Such a geometry with the silyl ligand in the apical position can also be found for [Rh{κ 2 -(N,N)-3,5-diphenyl-2-(2-pyridyl)-pyrrolido}(H)(SiPh 3 )(PPh 3 )] [35] and trans-[Os(SiR 3 )(Cl)-(CO)(PPh 3 ) 2 ]…”

“…[11,31] The NMR spectroscopic data are in accordance with those found for other bis(silyl)-rhodium(V) complexes, in which the silyl ligands are in a mutual trans orientation. [35] DFT calculations were performed to model conceivable configurations of 10a and 16. They revealed that the isomer of [Rh{κ 2 -(N,N)-(C 6 F 5 )NC(Me)CHC(Me)N(C 6 F 5 )}(H)-(SiMe 3 )(CO)] (10a), which exhibits a mutual cis orientation of the hydrido and the carbonyl ligands and in which the silyl ligand occupies the apical position in a square-pyramidal complex, is the only isomer that converged to a stable structure (Figure 8; see the Supporting Information).…”

“…There is no indication of the pres- ence of a non-classical structure (i.e., an interaction between a silyl and a hydrido ligand). [37] Note that often bis(silyl) complexes show a mutual cis orientation of the SiR 3 ligands, [36,38] but trans arrangements are also known [31,35] . [11] Such a degradation reaction can be avoided by the use of the highly fluorinated β-diketimine 17.…”

Traceless Chelation‐Controlled Rhodium‐Catalyzed Intermolecular Alkene and Alkyne Hydroacylation

“…The cycle A is completed by addition of HSi(OEt) 3 to 10 , which shows the elimination of 4 a (i.e., 11 is formed) and MeSSi(OEt) 3 . This process presumably occurs either by sigma‐bond metathesis through an η 2 ‐silane,22 for example, F , or oxidative addition to give a Rh V species 23. Intermediates, such as F , have recently been invoked in reactivity of CS bonds with silanes 13a.…”

An iridium–pyridylpyrrolide complex exhibiting reversible binding of H2

“…13,14 Although there are only a few metal complexes of pyridylpyrrolide in literature, it has been shown that this ligand can stabilize high-valent, polyhydride iridium complexes. [15][16][17][18][19][20][21][22][23] The pyridylpyrrolide derivative that will be implemented in this work is the ligand 3,5-bis(trifluoromethyl)-2-(2′-pyridyl)pyrrole [(X)(L)] (X = H + or K + ). 14 The choice of the electron withdrawing trifluoromethyl groups originates from the idea of diminishing the basicity of the pyrrolide amine, thus lessening the chance of L − experiencing protonation and subsequent demetallation in the presence of acid or adventitious H + sources.…”