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Two different dinitrogen‐derived molybdenum nitrido complexes varying by their geometry, ligand spheres and oxidations states were shown to engage their N ligand in dative bonding with the strong Lewis acid B(C6F5)3. The stable adducts were assessed for frustrated Lewis pair‐type heterolytic E−H bond splitting of hydrosilanes (E=Si) and HB(C6F5)2. Whereas Si−H bond activation was achieved, HB(C6F5)2 was shown to substitute B(C6F5)3 in a quantitative or equilibrated fashion, depending on the nature of the nitrido complex. No B−H bond splitting was observed. Thermodynamics of these reactions, computed by DFT, are in agreement with the experimental outcomes. [ABSTRACT FROM AUTHOR]

The cyclometalated monobenzyl complexes [(CbzdiphosR-CH)ZrBnX] 1 i Pr Cl and 1 Ph I reacted with dihydrogen (10 bar) to yield the η6-toluene complexes [(CbzdiphosR)Zr(η6-tol)X] 2 i Pr Cl and 2 Ph I (cbzdiphos=1,8-bis(phosphino)-3,6-di- tert-butyl-9 H-carbazole). The arene complexes were also found to be directly accessible from the triiodide [(CbzdiphosPh)ZrI3] through an in situ reaction with a dibenzylmagnesium reagent and subsequent hydrogenolysis, as exemplified for the η6-mesitylene complex [(CbzdiphosPh)Zr(η6-mes)I] ( 3 Ph I). The tolyl-ring in 2 i Pr Cl adopts a puckered arrangement (fold angle 23.3°) indicating significant arene-1,4-diido character. Deuterium labeling experiments were consistent with an intramolecular reaction sequence after the initial hydrogenolysis of a Zr−C bond by a σ-bond metathesis. A DFT study of the reaction sequence indicates that hydrogenolysis by σ-bond metathesis first occurs at the cyclometalated ancillary ligand giving a hydrido-benzyl intermediate, which subsequently reductively eliminates toluene that then coordinates to the Zr atom as the reduced arene ligand. Complex 2 Ph I was reacted with 2,6-diisopropylphenyl isocyanide giving the deep blue, diamagnetic ZrII-diisocyanide complex [(CbzdiphosPh)Zr(CNDipp)2I] ( 4 Ph I). DFT modeling of 4 Ph I demonstrated that the HOMO of the complex is primarily located as a 'lone pair on zirconium', with some degree of back-bonding into the C≡N π* bond, and the complex is thus most appropriately described as a zirconium(II) species. Reaction of 2 Ph I with trimethylsilylazide (N3TMS) and 2 i Pr Cl with 1-azidoadamantane (N3Ad) resulted in the formation of the imido complexes [(CbzdiphosR)Zr=NR′(X)] 5 i Pr Cl-NAd and 5 Ph I-NTMS, respectively. Reaction of 2 i Pr Cl with azobenzene led to N−N bond scission giving 6 i Pr Cl, in which one of the NPh-fragments is coupled with the carbazole nitrogen to form a central η2-bonded hydrazide(−1), whereas the other NPh-fragment binds to zirconium acting as an imido-ligand. Finally, addition of pyridine to 2 i Pr Cl yielded the dark purple complex [(Cbzdiphos iPr)Zr(bpy)Cl] ( 7 i Pr Cl) through a combination of CH-activation and C−C-coupling. The structural data and UV/Vis spectroscopic properties of 7 i Pr Cl indicate that the bpy (bipyridine) may be regarded as a (dianionic) diamido-type ligand. [ABSTRACT FROM AUTHOR]

The catalytic cycle for the Murai reaction at room temperature between ethylene and acetophenone catalyzed by [Ru(H)2(H2)2(PMe3)2] has been studied computationally at the B3PW91 level. The active species is the ruthenium dihydride complex [Ru(H)2(PMe3)2]. Coordination of the ketone group to Ru induces very easy CH bond cleavage. Coordination of ethylene after ketone de-coordination, followed by ethylene insertion into a RuH bond, creates the Ruethyl bond. Isomerization of the complex to a RuIV intermediate creates the geometry adapted to CC bond formation. Re-coordination of the ketone before the CC coupling lowers the energy of the corresponding TS. The highest point on the potential energy surface (PES) is the TS for the isomerization to the RuIV intermediate, which prepares the catalyst geometry for the CC coupling step. Inclusion of dispersion corrections significantly lowers the height of the overall activation barrier. The actual bond cleavage and bond forming processes are associated to low activation barriers because of the presence of hydrogen atoms around the Ru center. They act as redox buffers through formation and breaking of HH bonds in the coordination sphere. This flexibility allows optimal repartition of the various ligands according to the change in stereoelectronic demands along the catalytic cycle. [ABSTRACT FROM AUTHOR]