E−H Bond Activation Reactions (E = H, C, Si, Ge) at Ruthenium: Terminal Phosphides, Silylenes, and Germylenes

Abstract

The placement of a strongly trans-influencing ligand on a ruthenium center opposite an anchoring silyl group of the tetradentate tripodal tris(phosphino)silyl ligand, [SiP Ph 3 ] -([SiP Ph 3 ] -=tris(2-(diphenylphosphino)phenyl)silyl), has been explored. Installation of alkyl or terminal phosphide ligands trans to the anchoring silyl group affords the complexes [SiP Ph 3 ]RuR (R=Me (2), CH 2 Ph (4), PPh 2 (5), P i Pr 2 ( 6)). Complexes 2, 4, and 5 are thermally unstable. Complexes 2 and 4 decay to the cyclometalated complex [SiP Ph 2 P 0Ph ]Ru (3), whereas complex 5 decays to the cyclometalated phosphine adduct [SiP Ph 2 P 0Ph ]Ru-(PHPh 2 ) (7). Complex 3 is found to effect E-H (E=H, C, Si, Ge) bond activation of substrates such as secondary silanes and germanes to yield the structurally unusual silylene complexes [SiP Ph 3 ]Ru(H) (SiRR 0 ) (R=R 0 =Ph (10a), R=Ph R 0 =Me (10b)) and the germylene complex [SiP Ph 3 ]Ru(H)(GeR 2 ) (R = Ph) (11) via double E-H activation transformations. Both theory and experiments suggest electrophilic character at the silylene moiety. Reaction of 3 with catecholborane, in contrast to silanes and germanes, results in insertion of the B-H unit into the M-C bond of the cyclometalated species to yield the borate complex [SiP Ph 2 P Ph -B(cat)]Ru(μ-H) ( 14). Complex 3 also reacts with bis(catecholato) diboron to yield a similar complex, [SiP Ph 2 P C6H3B(cat) -B(cat)]Ru(μ-H) (15), with selective borylation of an ortho C-H bond.

[Ge(H)(2‐C6H4PPh2)3] as Ligand Precursor at Ruthenium: Formation and Reactivity of [Ru(Cl){Ge(2‐C6H4PPh2)3}]

“…However, it is similar to the Ge–Ru bond distance in the germylene complex [Ru{Ge(N(SiMe 3 ) 2 ) 2 } 2 (CO) 3 ] [2.37(1) Å],21 but longer than the corresponding separations in [Ru(GePh 2 )(H){Si(2‐C 6 H 4 PPh 2 ) 3 }] [2.2821(6) Å]22 or [Cp*Ru{Ge(H)(2,4,6‐C 6 H 2 i Pr 3 )}(H)(PMe i Pr 2 )] [2.3579(3) Å] 23. Treatment of complex 4 with a solution of HCl in Et 2 O resulted in a cleavage of one of the Ge–C bonds to give the ruthenium complex [Ru(Cl){Ge(Cl)(2‐C 6 H 4 PPh 2 ) 2 }(PPh 3 )] ( 5 ) (Scheme ).…”

A Proton-Switchable Bifunctional Ruthenium Complex That Catalyzes Nitrile Hydroboration

“…In contrast, catalysis was turned on using complex 2 (initial TOF = 2.7(3) × 10 −4 s −1 ), and the rate was further accelerated using complex 1 (initial TOF = 1. 19(2) × 10 −2 s −1 ). We note that single proton transfer events of the appended OH groups promote dramatic changes in reaction rate for 1−3, which serve to both gate and accelerate the nitrile hydroboration reaction.…”

Syntheses, Structures and Reactivity of Terminal Phosphido Complexes of Iron(II) Supported by a β‐Diketiminato Ligand

“…In this context, special attention should be given to terminal low‐coordinated phosphido complexes with pyramidal or planar geometry . In these cases, phosphorus atom is connected only to one metal center and can exhibit either pyramidal geometry with one lone pair or planar geometry with the lone pair participating in π bonding , . It should be noted that, among the high number of bridged phosphido complexes,, there are many reports of transition metal complexes featuring non‐bridging, terminal phosphido ligands,, including some supported by nacnac ligands .…”