Nitrido and imido transition metal complexes of Groups 6–8

Eikey, Rebecca A.

doi:10.1016/s0010-8545(03)00048-1

Cited by 344 publications

(160 citation statements)

References 206 publications

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“…[15] Starting from (4) ), [13a] which is in the typical range found for other Mo nitrides. [18] Nitride 3-OTf was also prepared on an alternative route from MoCl 3 (THF) 3 , SiMe 3 N 3 , and HPNP followed by anion exchange with NaOTf in over 70 % isolated yield. [15] Figure 1.…”

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confidence: 99%

Dinitrogen Splitting Coupled to Protonation

et al. 2017

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The coupling of electron- and proton-transfer steps provides a general concept to control the driving force of redox reactions. N splitting of a molybdenum dinitrogen complex into nitrides coupled to a reaction with Brønsted acid is reported. Remarkably, our spectroscopic, kinetic, and computational mechanistic analysis attributes N-N bond cleavage to protonation in the periphery of an amide pincer ligands rather than the {Mo-N -Mo} core. The strong effect on electronic structure and ultimately the thermochemistry and kinetic barrier of N-N bond cleavage is an unusual case of a proton-coupled metal-to-ligand charge transfer process, highlighting the use of proton-responsive ligands for nitrogen fixation.

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confidence: 99%

Dinitrogen Splitting Coupled to Protonation

et al. 2017

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“…[6] The nitrido complex, [Ru 2 (dPhf) 4 N] (1) was detected in positive-ion mode MALDI-TOF experiments on 2. At low laser power, only one set of peaks with the characteristic distribution of natural Ru isotopes can be seen, centered at 984.1, which is assigned as [2ÀN 3 ]…”

mentioning

confidence: 99%

Delocalized Metal–Metal and Metal–Ligand Multiple Bonding in a Linear RuRuN Unit: Elongation of a Traditionally Short RuN Bond

2008

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Binuclear metal-metal bonded complexes such as [Rh 2 -(OAc) 4 ] (Scheme 1, A) are celebrated because of their unmatched ability to catalyze reactions that directly functionalize CÀH bonds.[1] These metal-metal bonded catalysts function by assisting the transfer of a carbene or nitrene group (CR 2 or NR, respectively) to an organic substrate. [1] The key intermediates in these C À H activation reactions are proposed to have structures such as B (Scheme 1) that feature both a metal-metal bond and a metal-ligand multiple bond. Despite many years of mechanistic study on these reactions, no multiply bonded species, such as B, has, to our knowledge, ever been isolated and characterized.[2] In order to synthesize an M À M = E metal-metal/metal-ligand multiply bonded system, we chose to target a RuÀRuN nitrido complex (Scheme 1, C) for which no structural precedents exist. This species could be synthesized from thermal or photolytic decomposition of the appropriate RuÀRuÀN 3 azido precursor.[3] This experimental strategy is attractive because synthetically useful [Ru 2 (L) 4 X] compounds (L = ligand) are well known [4] and also because Ru is known to stabilize mononuclear nitrido Ru VI complexes [5] that form a useful comparison to C.We used the previously reported azido compound [Ru 2 -(dPhf) 4 N 3 ] (2, dPhf = N,N'-diphenylformamidinate) [6] as a precursor for the photoreaction (Scheme 2), since it has intense absorption bands at 520 nm and 660 nm.[6] The nitrido complex, [Ru 2 (dPhf) 4 N] (1) was detected in positive-ion mode MALDI-TOF experiments on 2. At low laser power, only one set of peaks with the characteristic distribution of natural Ru isotopes can be seen, centered at 984.1, which is assigned as [2ÀN 3 ] + whereas, at higher laser power, a new set of peaks is detected at 14 mass units higher (998.1), that is ascribed unequivocally to 1 + , as is further supported by the calculated isotopic pattern. [7] Owing to its quartet ground state, the X-band EPR spectrum of 2 at 8 K features a distinct S = 3/2 signal at g eff = 4.22. Photolysis of 2 at À40 8C produces a new sharp axial S = 1/2 EPR signal, described below, that is unmistakably due to a highly reactive intermediate species because it decays rapidly at À40 8C.Photolysis of frozen samples of 2 in CH 2 Cl 2 at 77 K allowed us to maximize the yield of this new species, and to observe an accompanying color change from purple to pink upon its formation (UV/Vis spectroscopic data are given in the Supporting Information). The new axial EPR signal (Figure 1) clearly indicates an S = 1/2 species that we suggest is due to the photooxidation product [Ru 2 (dPhf) 4 N] (1), because photooxidation formally removes two electrons from the {Ru 2 } moiety, leaving only one unpaired electron located in an Ru 2 d* orbital (see below). Simulation of the EPR data yielded g tensor components, g ? = 2.189 and g k = 1.900, consistent with axial molecular symmetry. The g k value < 2.00 suggests spin-orbit coupling with vacant d-orbital-based molecular orbitals, that is, a higher ...

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“…NtM nþ2 dO þ ShNtM n þ SO 4 ] 2À , prepared by Weighardt and co-workers, has a d 2 configuration and is relatively stable. 49 We found that it is a very active and selective catalyst for alkene epoxidation and alcohol oxidation by H 2 O 2 , with yields >90% (Scheme 12).…”

Section: Nitrido Complexes As Oxidation Catalystsmentioning

confidence: 99%

“…1À6 Nitrido complexes (MtN) are believed to be one of the key intermediates in chemical and biological nitrogen fixation. 3,4 They are also useful reagents for nitrogenation of organic compounds. 7,8 Extensive work by Meyer, 9À14 Mayer, 15,16 and Brown 17,18 also demonstrates that osmium(VI) nitrido complexes bearing terpy, bpy, or Tp ligands are highly electrophilic, and they react with a variety of nucleophiles to generate novel osmium(IV)/(V) products.…”

Section: Introductionmentioning

confidence: 99%

Reactivity of Nitrido Complexes of Ruthenium(VI), Osmium(VI), and Manganese(V) Bearing Schiff Base and Simple Anionic Ligands

2013

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Nitrido complexes (M≡N) may be key intermediates in chemical and biological nitrogen fixation and serve as useful reagents for nitrogenation of organic compounds. Osmium(VI) nitrido complexes bearing 2,2':6',2″-terpyridine (terpy), 2,2'-bipyridine (bpy), or hydrotris(1-pyrazolyl)borate anion (Tp) ligands are highly electrophilic: they can react with a variety of nucleophiles to generate novel osmium(IV)/(V) complexes. This Account describes our recent results studying the reactivity of nitridocomplexes of ruthenium(VI), osmium(VI), and manganese(V) that bear Schiff bases and other simple anionic ligands. We demonstrate that these nitrido complexes exhibit rich chemical reactivity. They react with various nucleophiles, activate C-H bonds, undergo N···N coupling, catalyze the oxidation of organic compounds, and show anticancer activities. Ruthenium(VI) nitrido complexes bearing Schiff base ligands, such as [Ru(VI)(N)(salchda)(CH3OH)](+) (salchda = N,N'-bis(salicylidene)o-cyclohexyldiamine dianion), are highly electrophilic. This complex reacts readily at ambient conditions with a variety of nucleophiles at rates that are much faster than similar reactions using Os(VI)≡N. This complex also carries out unique reactions, including the direct aziridination of alkenes, C-H bond activation of alkanes and C-N bond cleavage of anilines. The addition of ligands such as pyridine can enhance the reactivity of [Ru(VI)(N)(salchda)(CH3OH)](+). Therefore researchers can tune the reactivity of Ru≡N by adding a ligand L trans to nitride: L-Ru≡N. Moreover, the addition of various nucleophiles (Nu) to Ru(VI)≡N initially generate the ruthenium(IV) imido species Ru(IV)-N(Nu), a new class of hydrogen-atom transfer (HAT) reagents. Nucleophiles also readily add to coordinated Schiff base ligands in Os(VI)≡N and Ru(VI)≡N complexes. These additions are often stereospecific, suggesting that the nitrido ligand has a directing effect on the incoming nucleophile. M≡N is also a potential platform for the design of new oxidation catalysts. For example, [Os(VI)(N)Cl4](-) catalyzes the oxidation of alkanes by a variety of oxidants, and the addition of Lewis acids greatly accelerates these reactions. [Mn(V)(N)(CN)4]2(-) is another highly efficient oxidation catalyst, which facilitates the epoxidation of alkenes and the oxidation of alcohols to carbonyl compounds using H2O2. Finally, M≡N can potentially bind to and exert various effects on biomolecules. For example, a number of Os(VI)≡N complexes exhibit novel anticancer properties, which may be related to their ability to bind to DNA or other biomolecules.

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Nitrido and imido transition metal complexes of Groups 6–8

Cited by 344 publications

References 206 publications

Dinitrogen Splitting Coupled to Protonation

Dinitrogen Splitting Coupled to Protonation

Delocalized Metal–Metal and Metal–Ligand Multiple Bonding in a Linear RuRuN Unit: Elongation of a Traditionally Short RuN Bond

Reactivity of Nitrido Complexes of Ruthenium(VI), Osmium(VI), and Manganese(V) Bearing Schiff Base and Simple Anionic Ligands

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