Η1 Coordination Mode Research Articles

Allyl Calcium Compounds: Synthesis and Structure of Bis(η3-1-alkenyl)calcium

Allyl calcium compounds of different chain lengths [Ca(R)2(THF)x] (x = 0.15−0.25 (1-Ca, 3-Ca), 0.25−0.75 (2-Ca)) were synthesized by salt metathesis of CaI2 with allylpotassium reagents [K(R)] (R = n-butenyl (1-K), isobutenyl (2-K), n-hexenyl (3-K)), prepared from the corresponding α-olefin and Schlosser base. The new calcium derivatives were obtained in nearly quantitative yields. 1-Ca and 2-Ca could be crystallized as triglyme adducts (triglyme: tris(ethylene glycol)dimethyl ether) and structurally characterized by single-crystal X-ray diffraction. All potassium precursors [K(R)] were also isolated and characterized by 1H and 13C NMR spectroscopy. The solution properties in THF are in agreement with an η3-coordination mode of the allyl moiety for all isolated compounds. For the potassium reagents 1-K and 3-K, endo/exo equilibrium distributions of >99:<1 and 85:15 were observed, whereas for the calcium compounds 1-Ca and 3-Ca, distributions of 60:40 and 42:58 were found at 25 °C, respectively. This distr...

Bis(di-2-pyridylmethanediol-κ3N,O,N′)nickel(II) dibenzoate

The title compound, [Ni(C11H10N2O2)2](C7H5O2)2, consists of an NiII ion coordinated by two tridentate chelating (2-py)2C(OH)2 ligands (py is pyrid­yl) and two benzoate anions. The NiII ion is located on a twofold rotation axis, and its geometry is distorted octa­hedral. The gem-diol ligand (2-py)2C(OH)2 adopts an η1:η1:η1 coordination mode. There are O—H⋯O hydrogen bonds between the gem-diol ligands and benzoate anions.

Synthesis, structural characterization, and thermal properties of alkaline (earth) compounds derived from 2,4-dinitroimidazole

Eight alkaline and alkaline-earth compounds derived from 2,4-dinitroimidazole (2,4-HDNI) were synthesized and characterized by elemental analysis, FT-IR, and TG–DSC, of which K(2,4-DNI) (1), Rb(2,4-DNI)(2,4-HDNI)(H2O)2 (2), and Ba(2,4-DNI)2(H2O)4 (3) were characterized by single-crystal X-ray diffraction analysis. All the three compounds were crystallized from water, but 1 was an anhydrate. The coordination number in 1 and 3 is 10, but in 2 is 9. The 2,4-DNI adopts either η3, η2, or η1 coordination modes depending on the metal cation. In 3, there is an inversion center located on the metal. Only in 2 does water play an important role for the construction of the structure; in 3 it is a hydrogen bonding participant. TG–DSC analyses of 1 were also performed, and non-isothermal decomposition reaction kinetics were obtained.

Isolation and Characterization of a Chiral η1-Allyl Palladium DIPPAM Complex: Application to the Enantioselective Pd-Catalyzed Allylic Alkylation

In the presence of [Cl(C3H5)Pd]2, diphenylphosphinoazomethinylate salt (DIPPAM) 1a forms an original chiral η1-allyl palladium complex, 2. Precatalyst 2/MgBr2 is an efficient catalyst for asymmetric allylic alkylation, giving good yields and ee’s in the reactions of rac-4-acetoxy-2-pentene or rac-3-acetoxy-1,3-diphenyl-1-propene and dimethyl malonate (respectively 77% and 96% yield; 66% and 96% ee). Preliminary mechanistic studies have highlighted the key role of the η1-coordination mode of the allyl fragment.

Octa- and Nonamethylfluorenyl Complexes of Zirconium(IV): Reactive Hydride Derivatives and Reversible Hydrogen Migration between the Metal and the Fluorenyl Ligand

Reaction of the zirconocene dichloride Cp′′Flu*ZrCl2 (Cp′′ = 1,3-(SiMe3)2C5H3, Flu* = C13Me9) with iBuLi (iBuLi = LiCH2CHMe2) resulted in elimination of isobutylene and formation of Cp′′(η5:η3-C13Me9H)ZrH (1-syn-1,2-DHF*D), possessing an η5:η3-dihydrofluorenediyl ligand derived from a metal-to-benzo ring hydride transfer. This species undergoes reversible hydride transfer and exists in equilibrium with only one of its three other possible isomers (1-syn-3,4-DHF*D). Compound 1-syn-1,2-DHF*D catalyzes the cyclization of 1,5-hexadiene to methylenecyclopentane, and its reaction with excess isobutylene leads to the elimination of isobutane and formation of the cyclometalated zirconocene isobutyl species (η5:η1-C5H3-1-SiMe2CH2-3-SiMe3)(η5-C13Me9)ZriBu (2). Reaction of Cp′′Flu′′ZrCl2 with iBuLi directly generated the cyclometalated zirconocene species (η5:η1-C5H3-1-SiMe2CH2-3-SiMe3)(η5-C13Me8H)ZriBu (3); however, reaction of the dichloride Cp′′Flu′′ZrCl2 with iBuLi in the presence of hydrogen generated the dihydrofluorenediyl monohydride derivative Cp′′(η5:η3-C13Me8H2)ZrH (4). Treatment of the cyclometalated isobutyl species 3 with H2 led to partial hydrogenation of the Flu′′ ligand and formation of the monohydride Cp′′(η5:η3-C13Me8H6)ZrH (5), which contains a hexahydrofluorenediyl ligand. Partial hydrogenation of the Flu′′ ligand proceeded exclusively via an intramolecular pathway, as evidenced by the all-exo configuration of the methyl groups on the saturated benzo ring. Structural characterization of 1-syn-1,2-DHF*D, 2, 3, and 5 revealed a highly strained η5:η3-coordination mode for the dihydro- and hexahydrofluorenediyl ligands.

Volatility Enhancement in Calcium, Strontium, and Barium Complexes Containing β-Diketiminate Ligands with Dimethylamino Groups on the Ligand Core Nitrogen Atoms

Treatment of M(N(SiMe3)2)2(THF)2 with 2 equiv of 4-(2,2-dimethylhydrazino)dimethylhydrazone-3-penten-2-one (LNMe2H) in toluene at ambient temperature afforded Ca(η2-LNMe2)2 (88%), [Sr(η5-LNMe2)(μ-η1:η5-LNMe2)]2 (85%), and [Ba(η5-LNMe2)(μ-η2:η3-LNMe2)]2 (83%) as colorless or pale yellow crystalline solids. The formulations of the new complexes were assigned from spectral and analytical data and by X-ray crystal structure determinations. In the solid state, Ca(η2-LNMe2)2 exists as a tetrahedral monomer. [Sr(η5-LNMe2)(μ-η1:η5-LNMe2)]2 is a dimer that contains a terminal η5-LNMe2 ligand on each strontium ion. The dimer is held together by two μ-η1:η5-LNMe2 ligands, in which one dimethylamino moiety per LNMe2 ligand acts as a donor ligand to the adjacent strontium ion. [Ba(η5-LNMe2)(μ-η2:η3-LNMe2)]2 crystallizes as a dimer that contains a terminal η5-LNMe2 ligand on each barium ion. The two bridging LNMe2 ligands adopt a μ-η2:η3-coordination mode, where each LNMe2 ligand is bonded to one barium ion through the...

Reductive Reactivity of the Tetravalent Uranium Complex [(η5-C5Me5)(η8-C8H8)U]2(μ-η3:η3-C8H8)

The reductive reactivity of the cyclooctatetraenide ligands in [(η5-C5Me5)(η8-C8H8)U]2(μ-η3:η3-C8H8), 1, was examined with polycyclic hydrocarbons, phenazine, and the diphenyldichalcogenide compounds PhEEPh (E = S, Se, Te). Complex 1 does not reduce anthracene, acenaphthylene, or benzanthracene, but it acts as a two-electron reductant with phenazine to form 1 equiv of C8H8 and the bimetallic complex [(η5-C5Me5)(η8-C8H8)U]2(μ-η1:η1-C12H8N2), 2. X-ray crystallography showed that the heteroleptic metallocene unit [(C5Me5)(C8H8)U]1+ adopted an η1-coordination mode with the phenazine dianion rather than the η3-coordination previously found with the homoleptic f element metallocene cations [(C5Me5)2M]1+. Complex 1 also reacts as a two-electron reductant with PhEEPh (E = S, Se, Te) to form C8H8 and the heteroleptic complexes [(η5-C5Me5)(η8-C8H8)U]2(μ-EPh)2 (E = S, 3; Se, 4; Te, 5).

Ferromagnetism in CuII4 and CoII4 Complexes Derived from Metal‐Assisted Solvolysis of Di‐2,6‐(2‐pyridylcarbonyl)pyridine: Syntheses, Structures, and Magnetic Properties

AbstractMetal‐assisted solvolysis of di‐2,6‐(2‐pyridylcarbonyl)pyridine (pyCOpyCOpy, dpcp) by M(O2CMe)2·xH2O (MII = CuII, CoII) led to complex [Cu4{pyC(O)2pyC(O)(OEt)py}(O2CMe)5(EtOH)2] (1), when the reaction was carried out in EtOH, and to complex [Co4{pyC(O)(OMe)pyC(O)(OMe)py}2(O2CMe)2(N3)2] (2), when the reaction was carried out in MeOH in the presence of azide anions. Complex 1 consists of four CuII ions bridged by the hemiacetal‐gem‐diol form of the ligand, which is found in a μ4‐η2:η2:η2:η1:η1:η1 coordination mode. It exhibits ferromagnetic couplings among all nearest neighbors and antiferromagnetic next‐nearest‐neighbor interactions (J12 = J1 = 48.0 cm–1, J23 = J2 = 20.4 cm–1, J34 = J3 = 16.9 cm–1, J24 = J4 = –10.0 cm–1, H = –2ΣJiJj spin Hamiltonian formalism), which stabilize an S = 1 ground state and an S = 2 state lying closely above it. Complex 2 consists of four CoII ions bridged by the bis(hemiacetal) form of the ligand, which is found in a μ3‐η2:η2:η1:η1:η1 coordination mode, and by μ3‐azido ligands. It also exhibits ferromagnetic interactions due to the μ3–1,1,1 bridging mode of the azido ligands, which is known to promote ferromagnetic interactions. (© Wiley‐VCH Verlag GmbH &amp; Co. KGaA, 69451 Weinheim, Germany, 2008)

Synthesis of Rhenium Carbonyl Complexes Bearing Substituted Pyrrolyl Ligands

The formation of rhenium carbonyl complexes incorporating substituted pyrrolyl ligands was studied: the η5 coordination mode of the pyrrolyl motif was not favored, while several bidentate monosubstituted pyrrolyl rhenium complexes were synthesized. It was shown that these species easily lose one carbonyl in refluxing THF or in the presence of triphenylphosphine.

Synthesis and structures of new metallocene derivatives of lanthanides. Molecular structures of the complexes (C13H9)2Eu(THF)2 and (C5Me4H)2YbI(THF)

The divalent europium bis-fluorenyl complex (C13H9)2Eu(THF)2 was synthesized by the metathesis reaction of EuI2(THF)2 with two equivalents of fluorenylpotassium and by the protolytic substitution of the naphthalene ligand in the (C10H8)Eu(THF)2 complex using the reaction with fluorene. According to X-ray diffraction data, the complex displays a skewed sandwich structure, in which one fluorenyl ligand is η5-coordinated to the metal atom, whereas the η3-coordination mode makes a great contribution to the coordination of another ligand. The (C5Me4H)2YbI(THF) complex was synthesized by the reaction of YbI3(THF)2 with two equivalents of (C5Me4H)K. The structure of the complex was established by X-ray diffraction.

Synthesis and Structural Characterization of β‐Diketiminato Yttrium Complexes and their Application in Epoxide/CO2‐Copolymerization

AbstractThe β‐diketiminato yttrium complexes [(BDIPh)2Y{N(SiHMe2)2}] (1, BDIPh = [PhNC(Me)CHC(Me)NPh]−), [(BDIPh)3Y] (2), and [(C5Me5)(BDIPh)Y{N(SiHMe2)2}] (4) are available via amine elimination starting from (BDIPh)H and either [Y{N(SiHMe2)2}3(THF)2] or [(C5Me5)Y{N(SiHMe2)2}2(THF)] (3). X‐ray crystallographic analysis of complexes 1 and 4 revealed a η5 coordination mode for the β‐diketiminato ligand, whereas the distorted octahedral complex 2 displayed pure κ2 coordination. Complex 3 was also structurally characterized. 1, 3, and 4 are moderately active catalysts in the copolymerization of cyclohexene oxide and CO2. Complex 3 was the most active system (TOF up to 33 h−1 at 75 °C, 8.5 atm CO2) and gave the highest molecular weight and narrowest polydispersity (Mn = 12600 g mol−1, Mw/Mn = 1.6).

New Reactivity of 4‐Amino‐3,5‐bis(pyridin‐2‐yl)‐1,2,4‐triazole: Synthesis and Structure of a Mononuclear Species, a Dinuclear Species, and a Novel Tetranuclear Nickel(II) Rectangle Box, and Magnetic Properties of the Dinuclear and Tetranuclear Complexes

AbstractReactions of Ni(O2CMe)2·4H2O or NiCl2·6H2O, 4‐amino‐3,5‐bis(pyridin‐2‐yl)‐1,2,4‐triazole (abpt) and NaN3 or KSCN in different molar ratios heated under reflux or hydrothermal conditions generate a mononuclear species with dimorphous phases, a dinuclear species incorporating an in situ deaminated [bpt‐H]– ligand and a tetranuclear rectangle box incorporating an unprecedented μ:η1:η2:η1 coordination mode of the deprotonated [abpt‐H]– ligand. Structural analysis reveals that a pair of [Ni2(μ1,1‐N3)(μ‐OAc)] motifs in [Ni4(abpt)2(abpt‐H)(N3)5(O2CMe)2]·5H2O (1) are bridged by two abpt and one [abpt‐H]– units into a rectangle box. [Ni2(bpt‐H)2(SCN)2(H2O)2]·2H2O (2) is a neutral centrosymmetric dinuclear NiII complex doubly bridged by abpt ligands. The complex [Ni(abpt)2(N3)2] (3) is a neutral centrosymmetric mononuclear NiII complex and crystallizes in polymorphous phases, showing an interesting example of temperature‐induced polymorphism. Variable‐temperature magnetic susceptibility measurements reveal that the ferromagnetic interaction via the (μ1,1‐N3)2(μ‐OAc) and (μ1,1‐N3)(μ1,1‐NHabpt–H)(μ‐OAc) bridges slightly dominates over the antiferromagnetic interaction via the abpt bridges, therefore indicative of an overall ferromagnetic coupling between NiII centers in 1, and a moderate antiferromagnetic interaction occurs in 2. (© Wiley‐VCH Verlag GmbH &amp; Co. KGaA, 69451 Weinheim, Germany, 2007)

Chlorido(η6-p-cymene)[6-(2-hydroxyphenyl)-2,2′-bipyridine]ruthenium(II) chloride chloroform solvate

The title compound, [RuCl(C10H14)(C16H12N2O)]Cl·CHCl3, has been synthesized by the reaction of [RuCl2(p-cymene)]2 with 6-(2-hydroxy­phen­yl)-2,2′-bipyridine in acetonitrile. The RuII cation is in a pseudo-octa­hedral environment formed by a chloride anion, a cymene mol­ecule (with an η6 coordination mode) and a chelating 6-(2-hydroxy­phen­yl)-2,2′-bipyridine ligand. The other chloride anion is uncoordinated but links with the complex via O—H⋯Cl hydrogen bonding. The two methyl groups of the isopropyl group are disordered over two positions in approximately a 0.7:0.3 ratio.

Zinc, Cadmium, and Mercury Metallocenes Incorporating 1,2-Diaza-3,5-diborolyl Ligands

Sandwich compounds incorporating 1,2-diaza-3,5-diborolidine ligands have been prepared by metathesis reactions between zinc, cadmium, and mercury dihalides and M[cyclo-MeC(BR)2(NiPr)2] (M = Li, K; R = Me, Ph). The metallocenes M[cyclo-MeC(BR)2(NiPr)2)]2 (M = Zn, R = Me (2a), Ph (2b); M = Cd, R = Me (3a), Ph (3b); M = Hg, R = Me (4a)) have been isolated and characterized by multinuclear NMR and mass spectrometry. The molecular structures of complexes 2a,b, 3a·BrLi(THF)3, 3b, and 4a were determined by single-crystal X-ray diffraction and displayed strong similarities to the structures of their cyclopentadienyl analogues. All molecules are monomeric in the solid state, containing nearly parallel ligands featuring an η3 coordination mode in 2a and η1 coordination modes in the remaining complexes. Spectroscopic evidence indicates that the solid-state structure is maintained in solution and that Lewis basic solvents have the ability to coordinate reversibly to the metal centers. For comparison, the σ-bonded ana...

(η5-1-n-Butyl-2,3,4,5-tetramethylcyclopentadienyl)trichloridotitanium(IV)

In the title compound, [Ti(C13H21)Cl3], the titanium metal centre exhibits distorted tetra­hedral coordination, with the substituted cyclo­penta­dienyl ring bound to the TiCl3 group in an η5-coordination mode.

Synthesis and Characterization of New Diiron and Diruthenium μ-Aminocarbyne Complexes Containing Terminal S-, P- and C-Ligands

The diiron aminocarbyne complexes [Fe2{μ-CN(Me)(R)}(μ-CO)(CO)(NCMe)(Cp)2][SO3CF3] (R = Xy1, 1a; R = Me, 1b; R = CH2Ph, 1c; Xy1 = 2,6-Me2C6H3) undergo replacement of the coordinated nitrile by halides, diethyldithiocarbamate, and dicyanomethanide to give [Fe2{μ-CN(Me) (R)}(μ-CO)(CO)(X)(Cp)2] complexes (R = Me, X = Br, 4a; R = Me, X = I, 4b; R = CH2Ph, X = Cl, 4c; R = CH2Ph, X = Br, 4d; R = CH2Ph, X = I, 4e; R = Xy1, X = SC(S)NEt2, 5a; R = Me, X = SC(S)NEt2, 5b; R = Xy1, X = CH(CN)2, 7), in good yields. The molecular structure of 5a shows an unusual η1 coordination mode of the dithiocarbamate ligand. Similarly, treatment of [M2{μ-CN(Me) (R)}(μ-CO)(CO)(NCMe)(Cp)2][SO3CF3] (M = Fe, R = Xy1, 1a; M = Fe, R = Me, 1b; M = Ru, R = Xy1, 2a; M = Ru, R = Me, 2b) with a series of phosphanes generates the cationic complexes [M2{μ- CN(Me)(R)}(μ-CO)(CO)(P)(Cp)2][SO3CF3] (M = Fe, R = Xy1, P = PPh2H, 6a; M = Fe, R = Xy1, P = PPh3, 6b; M = Fe, R = Xy1, P = PMe3, 6c; M = Fe, R = Me, P = PMe2Ph, 6d; M = Fe, R = Me, P = PPh3, 6e; M = Fe, R = Me, P = PMePh2, 6f; M = Ru, R = Xy1, P = PPh2H, 6g; M = Ru, R = Me, P = PPh2H, 6h), in high yields. The molecular structure of 6a has been elucidated by an X-ray diffraction study. The reactions of [Fe2{μ-CN(Me)(Xyl)}(μ-CO)(CO)(NCR′)(Cp)2][SO3CF3] [R′ = Me, 1a; R′ = tBu, 3] with PhLi and PPh2Li yield [Fe2{μ-CN(Me)(Xy1)}(μ-CO)(CO)(Ph)(Cp)2] (8) and [Fe2{μ-CN(Me)(Xy1)}(μ-CO)(CO)(PPh2)(Cp)2] (9), respectively. The molecular structure of 8 has been ascertained by X-ray diffraction. Conversely, the reaction of 1a with MeLi generates the aminoalkylidene compound [Fe2{C(Me)N(Me)(Xy1)}(μ-CO)2(CO)(Cp)2] (10). Finally, the acetone complex [Fe2{μ-CN(Me)(Xy1)}(μ-CO)(CO)(OCMe2)(Cp)2][SO3CF3] (12) reacts with lithium acetylides to give complexes [Fe2{μ-CN(Me)(Xy1)}(μ-CO)(CO)(C≡CR)(Cp)2] (R = p-C6H4Me, 11a; R = Ph, 11b; R = SiMe3, 11c), in high yields. Filtration through alumina of a solution of 11a in CH2Cl2 results in hydration of the acetylide group and C-Si bond cleavage, affording [Fe2{μ-CN(Me)(Xy1)}(μ-CO)(CO){C(O)Me}(Cp)2] (12).

Implementation of Ln(AlMe4)3 as Precursors in Postlanthanidocene Chemistry

cis-2,5-Bis[N,N-((2,6-diisopropylphenyl)amino)methyl]tetrahydrofuran (H2BDPPthf) was obtained from LiNH(2,6-iPr2C6H3) and cis-2,5-bis((tosyloxy)methyl)tetrahydrofuran in high yield and employed as a new [NON]2- ancillary ligand for rare-earth metal centers. The reaction of H2BDPPthf with homoleptic tetramethylaluminates Ln(AlMe4)3 (Ln = Y, Nd, La) quantitatively yielded heterobimetallic complexes (BDPPthf)Ln(AlMe4)(AlMe3) via alkane elimination. X-ray structure analysis of (BDPPthf)Ln(AlMe4)(AlMe3) (Ln = Y, La) revealed different coordination modes of BDPPthf, AlMe4-, and AlMe3. The yttrium derivative displays an η2-coordination of BDPPthf and insertion of AlMe3 into one of the Ln−N anilido bonds to form a novel [LnIII(μ-Me)2AlMe(NR2)] moiety. In contrast, BDPPthf coordinates the larger lanthanum center in an η3 fashion involving a heterobridging [La(μ-NR2)(μ-Me)AlMe2] moiety. The AlMe4- ligand adopts an unusual distorted μ:η3- (La) and a routine μ:η2-coordination mode (Y) depending on the size of the metal center. The intrinsic [NON]2- ligand functionality for the first time implied the formation and structural identification of a kinetically favored aluminate/HR protonolysis product (Y), whereas the thermodynamically favored Ln−amido contact is found for the lanthanum derivative. All organolanthanide complexes were fully characterized by NMR and FTIR spectroscopy and elemental analysis.

Zinc(II) η1- and η2-Toluene Complexes: Structure and Bonding in Zn(C6F5)2·(toluene) and Zn(C6F4-2-C6F5)2·(toluene)

The first structural characterization of toluene complexes of zinc is reported. The (perfluoroaryl)zinc compounds Zn(C6F5)2·(toluene) and Zn(C6F4-2-C6F5)2·(toluene) show toluene in η2 and η1 coordination modes, respectively. On the other hand, charge distribution calculations, Mulliken overlap population analysis, and bonding energy data suggest that the interactions between the Zn and the toluene ring are rather similar in both cases.

The Versatility of Pentalene Coordination to Transition Metals: A Density Functional Theory Investigation

DFT calculations with full geometry optimization have been carried out on a series of real and hypothetical compounds of the type [CpM(C8H6)], [(CO)3M(C8H6)], [M(C8H6)2], [(CpM)2(C8H6)], [[(CO)3M]2(C8H6)], and [M2(C8H6)2] (M = transition metal). The bonding in all the currently known compounds is rationalized, as well as in the (so far) hypothetical stable complexes. Depending on the electron count and the nature of the metal(s), eta2 (predicted), eta3, eta5, eta8, or intermediate coordination modes can be adopted. In the case of the mononuclear species, the most favored closed-shell electron counts are 18 and 16 metal valence electrons (MVE). In the case of the dinuclear species, an electron count of 34 MVEs is most favored. However, other electron counts can be stabilized, especially in the case of dinuclear complexes. Coordinated pentalene should most often be considered as formally being a dianion, but sometimes as a neutral ligand. In the former case it can behave as an aromatic species made of two equivalent fused rings, as a C5 aromatic ring connected to an allylic anion, or even as two allylic anions bridged by a C7=C8 double bond. In the latter case, it can behave as a bond-alternating cyclic polyene or as a C5 aromatic ring connected to an allylic cation.

Oxidatively-induced μ-η1→ μ-η1:η1rearrangement of {NN} ligands at a {Mo2(μ-SMe)3} site and protonation of the oxidized diazenido complex

The electrochemical oxidation of [Mo2(cp)2(μ-SMe)3(μ-N2Ph)] and [Mo2(cp)2(μ-SMe)3(μ-N2HPh)]+ complexes where the diazo bridge adopts either an η1 or an η1:η1 coordination mode has been studied by cyclic voltammetry and controlled-potential electrolysis in THF– and CH2Cl2–[NBu4][PF6]. The electrochemical oxidation of [Mo2(cp)2(μ-SMe)3(μ-η1-N2Ph)] 1 and of [Mo2(cp)2(μ-SMe)3(μ-η1-N2HPh)]+1-H+++ triggers the isomerization of the diazo bridge to the η1:η1 mode found in 2+++ and 2-H2+2+2+ respectively. The electrochemical oxidation of [Mo2(cp)2(μ-SMe)3(μ-η1:η1-N2Ph)] 3 and of [Mo2(cp)2(μ-SMe)3(μ-η1:η1-HN2Ph)]+3-H+++ with a syn (“up–up”) arrangement of the Me substituents of the equatorial sulfur bridges is also followed by an isomerization to 2+++ and 2-H2+2+2+, respectively, with an anti (“up–down”) configuration of the equatorial Me groups. The rates of the isomerization 1++ → 2+++, 1-H2+2+2+ → 2-H2+2+2+, and 3-H2+2+ → 2-H2+2+2+ were studied by cyclic voltammetry at different scan rates and at different temperatures. The isomerization of the protonated complexes with either a hydrazido(2−) or a diazene bridge (respectively 1-H2+2+2+ and 3-H2+2+) is faster than that of the diazenido precursors (respectively 1++ and 3++). The diazenido complex 2+++ protonates readily, affording 2-H2+2+2+, while 2-H3+3+ undergoes proton loss.