Carolina Manzur

Bonding analysis of transition metal NNR end-on complexes and comparison with isoelectronic NNR2 species

DFT calculations have been carried out on various NNR and NNR2 transition metal complexes. The theoretical results have been analyzed together with a collection of structural data obtained through a Cambridge Data Base search covering ca. 140 compounds. When linearly coordinated in mono-substituted complexes and assuming the respective formal charges of −3 and −2, both hydrazide(−3) (NNR3−) and hydrazide(−2) (NNR22−) ligands act as 6-electron donors through their 3 occupied FMOs (one σ-type FMO and two non-equivalent π-type FMOs). Hydrazide(−3) is found to be a weaker π-donor ligand, in agreement with most of the reported X-ray structures. Calculations of the FMO occupations suggest that the ligand formal oxidation state of an NNR ligand is close to −1 and that of NNR2 is intermediate between 0 and −1. In the case of the cis-di-substituted complexes, and still assuming the NNR3− and NNR22− formal ligand charges, either the d0 or the d−2 metal configuration is always found. In the former case, both cis ligands act together as a 10-electron system leading to the 18-electron count. In the latter case, the d−2 value is meaningless. Calculations show that the 2-electron oxidation of the d0 species involves a ligand-based MO that is metal–ligand non-bonding, leaving the metal oxidation state unchanged, as well as the 18-electron count of the complex. Such an oxidation is associated with a 90° rotation of the cis ligands. A similar situation is computed for the 2-electron oxidation of d2 18-MVE trans-dihydrazide(−2) models, in which the NNR2 formal charge varies from −2 to −1, whereas the hydrazide system acts as an 8-electron donor in both the reduced and oxidized states. The trans-di(NNR3−) compounds behave somewhat differently since their oxidized form is better described as a d0 hydrazide(−3) 16-MVE system.

Organometallic iron (II) hydrazines and hydrazones — syntheses, characterisations and the X-ray crystal structures of [Fe(η5-Cp)(η6-C6H5NHNH2)]+PF6− and [Fe(η5-Cp)(η6-p-MeC6H4NHNCMe2)]+PF6−

The three new organometallic hydrazines [Fe(η 5 -Cp)(η 6 -RC 6 H 4 NHNH 2 )] + PF 6 − , CpC 5 H 5 , RH, [ 1 ] + PF 6 − ; m -Me, [ 2 ] + PF 6 − ; p -MeO, [ 3 ] + PF 6 − , were synthesised and characterised. They were obtained in CH 2 Cl 2 by reaction of the hydrazine monohydrate, NH 2 NH 2 ·H 2 O, with the corresponding precursors [Fe(η 5 -Cp)(η 6 -RC 6 H 4 Cl)] + PF 6 − . Similarly to free conventional organic hydrazines, the organometallic hydrazines [ 1 ] + PF 6 − and [ 3 ] + PF 6 − react with acetone affording hydrazones formulated as [Fe(η 5 -Cp)(η 6 -RC 6 H 4 NHNCMe 2 )] + PF 6 − , RH, [ 6 ] + PF 6 − ; p -MeO, [ 7 ] + PF 6 − . Likewise, the two other organometallic hydrazones containing the substituent groups R o -Cl, [ 8 ] + PF 6 − and p -Me, [ 9 ] + PF 6 − were also obtained from their parent hydrazine precursors [ 4 ] + PF 6 − and [ 5 ] + PF 6 − , respectively. All the new compounds were characterised by elemental analysis and IR, UV–vis, 1 H- and 13 C-NMR spectroscopy. The crystalline and molecular structures of [ 1 ] + PF 6 − and [ 9 ] + PF 6 − were determined by single crystal X-ray crystallographic analysis. Both structures show a cyclohexadienyl-like character at the coordinated C 6 ring of the phenylhydrazine and the p -methylphenylhydrazone with a folding angle of 6.0(5) and 7.1(6)°, respectively.

[MoO(NNPh2)(acac)2], a precursor of novel binuclear hydrazido(2−)molybdenum(VI) complexes containing bridging alkoxo ligands: [{MoO(NNPh2)(acac)(μ-OR)}2]. Syntheses, characterization, reactivity and electrochemical studies. Crystal structure of [{MoO (NNPh2) (acac) (μ-OEt)}2]

Abstract 1,1-Diphenylhydrazine reacts with [MoO 2 (acac) 2 ] in methanol to yield either the mononuclear complex [MoO(NNPh 2 )(acac) 2 ] ( I ) or the binuclear complex [{MoO(NNPh 2 )(acac)(μ-OMe)} 2 ] (II) depending on the temperature. In refluxing ROH, complex I transforms into [{MoO(NNPh 2 )(acac)(μ-OR)}]. (R=Me: II ; R=Et: III ; R=n-Pr: IV .) The crystal structure of III is reported. Crystals are triclinic, space group P 1 , with unit cell dimensions a =9.211(1), b =10.375(2), c =12.107(3) A, α=72.98(2), β=64.55(1), γ=70.10(1)° and Z =1. The structure was solved using 5034 unique observed reflections; the refinement of 304 variables gave R and R w values of 0.024 and 0.026, respectively. The lattice is made of discrete centrosymmetrical dinuclear molecules. The geometry of the hydrazido(2−) ligand (MoN = 1.784(1), NN = 1.298(2) A, MoNN = 169.5(1)°) indicates extensive delocalization through the MoNN unit. II , III and IV are representative members of a new family of dinuclear complexes which display the [(Ph 2 NN)OMo(μ-OR) 2 MoO(NNPh 2 )] 2+ core.

An improved synthetic method and vibrational study of (pentamethylcyclopentadienyl) dicarbonylrhenium dihalides (η5-C5Me5)Re(CO)2X2 (X = C1, Br and I)

An improved synthetic method has been found for the preparation of the pentamethylcyclopentadienyl rhenium dicarbonyldihalide complexes. From the reaction of (η5-C5Me5)Re(CO)3 with Br2 or I2 in THF-H2O a mixture of cis and trans isomers of (η5-C5Me5)Re(CO)2X2 X = Br and I is formed. On the other hand, the reaction of [(η5-C5Me5)Re(CO)3C1][SbC16] in water gives the cis-(η5-C5Me5)Re(CO)2C12 complex. The solid IR spectra of the dicarbonyldihalide complexes are recorded and an assignment of the normal modes in terms of local symmetry is suggested by comparison with those observed in analogous molecules. A normal coordinate analysis performed using a modified general valence force field and considering simplified models, confirms most of the experimental assignments. The set of valence force constants reflects the structure of the isomers under study.

Homodimetallic iron(II) hydrazones: syntheses, spectroscopic, electrochemical, and theoretical investigations. X-Ray crystal structure of both syn- and anti- rotamers of [(η5-Cp)Fe(η6-C6H5)–NHNC(Me)–(η5-C5H4) Fe(η5-Cp)]+PF6−

Two homogeneous series of homodimetallic iron(II) hydrazone complexes of general formula [CpFe(η6-p-RC6H4)–NHNCH–(η5-C5H4)FeCp]+PF6− (Cp=η5-C5H5): R=H, [5]+PF6−; Me, [6]+PF6−; MeO, [7]+PF6−; Cl, [8]+PF6−; and [CpFe(η6-p-RC6H4)–NHNCMe–(η5-C5H4)FeCp]+PF6−: R=H, [9]+PF6−; Me, [10]+PF6−; MeO, [11]+PF6−, have been prepared. These hydrazones were stereoselectively obtained as their trans isomers about the NC double bond, by reaction of the corresponding organometallic hydrazines [CpFe(η6-p-RC6H4NHNH2)]+PF6−, R=H, [1]+PF6−; Me, [2]+PF6−; MeO, [3]+PF6−; and Cl, [4]+PF6−, with formylferrocene, CpFe(η5-C5H4–CHO), and acetylferrocene, CpFe(η5-C5H4–CO-Me), respectively. All the new compounds were characterized by elemental analysis and IR, UV-Vis and 1H NMR spectroscopies. For compound [9]+PF6−, the activation energy ΔG# for the hindered rotations of the mixed sandwich [CpFe(η6-C6H5–)]+ (41.8±0.9 and 41.2±3.7 kJ mol−1) and the ferrocenyl unit (40.0±3.2 kJ mol−1) about the –NH–NCMe– hydrazone backbone have been determined by variable temperature 1H NMR spectroscopic studies. The electrochemical behavior of the dinuclear hydrazones was explored by cyclic voltammetry, and features the role of the cationic [CpFe(η6-arene)]+ moiety as an electron acceptor. The crystalline and molecular structure of [9]+PF6− was determined by single crystal X-ray crystallographic analysis. The structure shows the presence of both syn and anti rotamers in the asymmetric unit. The analysis of the electronic structure of [9]+ through DFT calculations indicate a strong perturbation of the metal centers by the hydrazone bridge as well as some metal-metal interaction through the bridge.

Synthesis and characterization of mononuclear bis[organohydrazido(2−)]molybdenum(VI) complexes. Crystal structures of [Mo(NNMePh)2(acac)2] and [Mo(NNPh2)2(acac)7]

Abstract In the presence of Na2SO4, 1-methyl-1-phenylhydrazine and 1,1-diphenylhydrazine react with [MoO2(acac)2] to yield [Mo(NNMePh)2(acac)2] (1) and [Mo(NNPh2)3(acac)2] (2), respectively. Crystals of 1 are triclinic, space group P 1 , with unit cell dimensions a = 9.780(6), b = 11.134(11), c = 13.504(7) A , α = 110.69(6), β =95.71(5), γ = 11.70(7) c and Z = 2 . The structure was solved using 4317 unique observed reflections; the refinement of 299 variables gave R and Rw values of 0.059 and 0.067, respectively. Crystals are 2 are monoclinic, space group C2/c, with unit cell dimensions a = 21.151(3), b = 13.174(3), c = 13.477(2) A , β = 123.17(1)° and Z = 4. The structure was solved using 2760 unique observed reflection; the refinement of 195 variables gave R and Rw values of 0.039 and 0.040 respectively. In both complexes, the molybdenum atom display distorted octahedral geometry with nearly linear cis-hydrazido ligands.

Organodiiron(II)-complexes containing a long conjugated hydrazonato spacer. Synthesis, characterization, electrochemical and structural studies

Abstract Organometallic hydrazines of general formula [(η5-Cp)Fe(η6-p-RC6H4NHNH2)]+PF6− (Cp=C5H5; R=H, (1)+PF6−; Me, (2)+PF6−; MeO, (3)+PF6−; Cl, (4)+PF6−) react with equimolar quantities of (E)-4-(2-ferrocenylvinyl)-benzaldehyde, (E)-[(η5-Cp)Fe(η5-C5H4)CHCHC6H4CHO], to afford stereoselectively, the new homodimetallic hydrazones formulated as (E)-[(η5-Cp)Fe(η6-p-RC6H4)NHNCHC6H4CHCH(η5-C5H4)Fe(η5-Cp)]+PF6− (R=H, (5)+PF6−; Me, (6)+PF6−; MeO, (7)+PF6−; Cl, (8)+PF6−). These compounds were fully characterized by elemental analysis and spectroscopic techniques (1H- and 13C-NMR, IR and UV–vis) and, in the case of complex (6)+PF6−, by single crystal X-ray diffraction methods. The rotations of the ferrocenyl unit by 37.2° out of the NHNCHC6H4CHCH spacer and coordinated phenyl ring planes, may generate an unfavorable structure to allow π-electron delocalization along the entire hydrazonato backbone between the two metals separated through bonds by more than 1.8 nm, as confirmed by the electrochemical data.

FIRST X-RAY CRYSTAL STRUCTURE OF A BIMETALLIC COMPLEX CONTAINING A p -COORDINATED HYDRAZONE: [(h 5-Cp)Fe(h 6-p-MeOC6H4)-NHN=CH-(h 5-C5H4)Fe(h 5-Cp)]+PF6

La hidrazona organometalica dinuclear [(h 5-Cp)Fe(h 6-p-MeO-C6H4)-NHN=CH-(h 5-C5H4)Fe(h 5-Cp)]+PF6- es preparada estereoquimicamente como su isomero trans por reaccion de la hidracina organometalica precursora [(h 5-Cp)Fe(h 6-p-MeO-C6H4)-NHNH2)]+PF6- con ferrocencarboxaldehido. Se ha determinado su estructura cristalina y molecular que consiste en dos sanwiches de hierro(II) del tipo [(h 5-Cp)Fe(h 6-areno)]+ y [(h 5-C5H4)Fe(h 5-Cp)] en posicion anti uno respecto del otro, los que se encuentran enlazados por un espaciador hidrazonico en forma de zig-zag

Convenient access to new mono- and dinuclear organometallic hydrazones from [(η5-Cp)Fe(η6-arylhydrazine)]+

New mononuclear and dinuclear organometallic hydrazones [(η5-Cp)Fe(η6-R-C6H4NHNCR′R′′)]+PF6−, were synthesised by reacting the corresponding organometallic hydrazines [(η5-Cp)Fe(η6-R-C6H4NHNH2)]+PF6−, with acetone, R=H, 2-Cl, 4-Me, 4-MeO; R′=R′′=Me, and formylferrocene, R=H, 4-Me; R′=H; R′′=(η5-C5H4)FeCp, respectively.

Reactivity of molybdenum complexes containing mixed NHNPhR and NNPhR hydrazido ligands (R=Ph, Me) toward di-imines. X-ray crystal structures of [MoO(NNPh2)Cl2(bpy)]·CH2Cl2, [MoO(NNPh2)Cl2(phen)]·CH2Cl2 and [Mo(NNPh2)2Cl2(phen)]

Complexes of the type [Mo(NHNPhR)(NNPhR)(acac)Cl 2 ] (R=Ph ( I ); Me ( II )) react in dichloromethane with the di-imines 2,2′-bipyridine (bpy) and 1,10-phenanthroline (phen) to yield, after slow evaporation under air of the solvent, the species [MoO(NNPhR)Cl 2 (bpy)] (R=Ph ( III ); Me ( IV )) and [MoO(NNPhR)Cl 2 (phen)] (R=Ph ( V ); Me ( VI )). When these reactions are carried out in toluene under inert atmosphere, I and II give the bis-hydrazido(2−) complexes [Mo(NNPhR) 2 Cl 2 (bpy)] (R=Ph ( VII ); Me ( VIII )) and [Mo(NNPhR) 2 Cl 2 (phen)] (R=Ph ( IX ); Me ( X )). The crystal structures of III , V and IX are reported. Crystals of III are orthorhombic, space group Pbca , with cell parameters a =15.290(6), b =16.225(8), c =19.954(9) A, Z =8, R =0.036 and R w =0.044. Crystals of V are triclinic, space group P , with a =8.935(1), b =12.960(2), c =13.443(2) A, α=61.84(1), β=74.75(1), γ=86.96(1)°, Z =2, R =0.036 and R w =0.044. Crystals of IX are triclinic, space group P , with a =9.812(4), b =10.459(4), c =17.979(7) A, α=73.69(3), β=77.98(3), γ=66.30(3)°, Z =2, R =0.038 and R w =0.043. All complexes display similar pseudooctahedral geometries with the hydrazido(2−) ligands adopting the nearly linear coordination mode.