604783-60-0

Upstream product

• 7789-20-0 water-d2 
• 100-58-3 phenylmagnesium bromide 
• 100-59-4 phenylmagnesium chloride 
• 2206-26-0 [D₃]acetonitrile 
• 666-52-4 [⁽²⁾H₆]acetone 
• 62-53-3 aniline 

Relevant academic research and scientific papers

Protonation and deprotonation of TpOs(NHPh)Cl2: An unusually inert amido ligand

Protonation of the Os(IV) amido complex TpOs(NHPh)Cl2 (1) to give the aniline complex [TpOs(NH2Ph)Cl2]-OTf (2) requires excess triflic acid (HOTf). Complex 1 is unreactive with HCl and other moderately strong acids. Consistent with the low basicity of 1, the aniline complex 2 is extremely acidic and is deprotonated by stoichiometric addition of weak bases such as Cl- or H2O. No reaction is observed between 1 and methyl triflate (CH3OTf) at ambient temperatures. Upon heating, CH3OTf removes the chloride ligands from 1 to give CH3Cl and the amidobis-(triflate) complex TpOs(NHPh)(OTf)2 (3). Attack at the amido nitrogen is not observed. Complex 1 is thus very inert to protonation and electrophilic attack at nitrogen. A deprotonated form of 1, TpOs[NPh(MgBr)]Cl2 (4), is generated on reaction of PhMgBr with TpOs(N)Cl2. Complex 4 is extremely basic and will protonate to 1 with weak acids such as CH3CN, DMSO, and acetic anhydride. Thus, 1 has a low acidity as well as a low basicity; it is both less acidic and less basic than aniline. The inertness of 1 is ascribed to partial Os-N π bonding and to the oxidizing nature of the Os(IV) center.

Slow hydrogen atom self-exchange between Os(IV) anilide and Os(III) aniline complexes: Relationships with electron and proton transfer self-exchange

Abstract: Hydrogen atom, proton and electron transfer self-exchange and cross-reaction rates have been determined for reactions of Os(IV) and Os(III) aniline and anilide complexes. Addition of an H-atom to the Os(IV) anilide TpOs(NHPh)Cl2 (OsIVNHPh) TpOs(NHPh)Cl2 (Os IVNHPh) gives the Os(III) aniline complex TpOs(NH 2Ph)Cl2 (OsIIINH2Ph) with a new 66 kcal mol-1 N-H bond. Concerted transfer of H* between Os IVNHPh and OsIIINH2Ph is remarkably slow in MeCN-d3, with kexH* = (3 ± 2) x 10 -3 M-1 s-1 at 298 K. This hydrogen atom transfer (HAT) reaction could also be termed proton-coupled electron transfer (PCET). Related to this HAT process are two proton transfer (PT) and two electron transfer (ET) self-exchange reactions, for instance, the ET reactions OsIVNHPh + OsIIINHPh- and OsIVNH2Ph+ + Os IIINH2Ph. All four of these PT and ET reactions are much faster (k = 103-105 M-1 s-1) than HAT self-exchange. This is the first system where all five relevant self-exchange rates related to an HAT or PCET reaction have been measured. The slowness of concerted transfer of H* between OsIVNHPh and Os IIINH2Ph is suggested to result not from a large intrinsic barrier but rather from a large work term for formation of the precursor complex to H* transfer and/or from significantly nonadiabatic reaction dynamics. The energetics for precursor complex formation is related to the strength of the hydrogen bond between reactants. To probe this effect further, HAT cross-reactions have been performed with sterically hindered aniline/anilide complexes and nitroxyl radical species. Positioning steric bulk near the active site retards both H* and H+ transfer. Net H* transfer is catalyzed by trace acids and bases in both self-exchange and cross reactions, by stepwise mechanisms utilizing the fast ET and PT reactions.

C-N bond formation on addition of aryl carbanions to the electrophilic nitrido ligand in TpOs(N)Cl2

The osmium (VI) nitrido complex TpOs(N)Cl2 (1) has been prepared from K[Os(N)O3] and KTp in aqueous ethanolic HCl. It reacts rapidly with PhMgCl and related reagents with transfer of a phenyl group to the nitrido ligand. This forms Os(IV) metalla-analido complexes, which are readily protonated to give the analido complex TpOs(NHPh)Cl2 (4). The nitrido-phenyl derivatives TpOs(N)PhCl and TpOs(N)Ph2 react more slowly with PhMgCl and are not competent intermediates for the reaction of 1 with PhMgCl. Reactions of 1 with alkyl- and arylboranes similarly result in transfer of one organic group to nitrogen, leading to isolable borylamido complexes such as TpOs[N(Ph)(BPh2)]Cl2 (11). This is an unprecedented insertion of a nitrido ligand into a boron - carbon bond. Hydrolysis of 11 gives 4. Mechanistic studies suggest that both the Grignard and borane reactions proceed by initial weak coordination of Mg or B to the nitrido ligand, followed by migration of the carbanion to nitrogen. The hydrocarbyl group does not go to osmium and then move to nitrogen - there is no change in the atoms bound to the osmium during the reactions. It is suggested that there may be a general preference for nucleophiles to add directly to the metal - ligand multiple bond rather than binding to the metal first and migrating. Ab initio calculations show that the unusual reactivity of 1 results from its accessible LUMO and LUMO + 1, which are the Os≡N π* orbitals. The bonding in 1 and its reactivity with organoboranes are reminiscent of CO.