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DFT calculations with the BP86, OPBE and hybrid B3LYP* functionals have been performed on a series of homo- and heterobimetallic compounds of the type [(RuCp)2(Ind)]+, [(CoCb)2(Ind)]+ and [(RuCp)(CoCb)(Ind)]+ (Ind = indenyl, Cp = cyclopentadienyl and Cb = cyclobutadiene) of 34-TNE (Total number of electrons), their oxidized 32- and 33-TNEs and their reduced 35- and 36-TNEs species. Depending on the ancillary Cp or Cb ligand to the metal, the electronic and molecular structures and the metal–metal bonding of this family of compounds have been analyzed. The syn and anti-configurations are possible for the studied binuclear complexes, which are related to the metal nature, where mostly steric constraints of the Cp or the Cb ligand appear to control its spatial disposition favouring the anti configuration, despite its electronic deficiency for the 32- and 33-TNEs species. The flexibility of the indenyl ligand, which is related to the metal hapticity, favors the possibility of existence of several syn and anti isomers of close energies. This study showed quite similar behaviours of the (RuCp)+ and (CoCb)+ fragments of 12-electrons regarding their change or their permutation. The current study shows the ease of reduction with regard to oxidation, particularly that by the loss of two electrons. The used three functionals gave comparable tendencies of the stability sequences between isomers, favouring the low-spin structures, and provided comparable findings regarding the low-spin/high-spin energy splittings.

DFT calculations at the B3LYP/Def2-SVP level have been conducted on the half-sandwich cycloheptatrienyl molybdenum complexes [Mo(CO)(3)(eta-C7H7)(+), [1](+) and [MoBrL2(eta-C7H7)](n+) (L-2= 2 CO, n = 0, 2; L-2= bpy, n = 0, 3; L-2 = bpy, n = 1, [3](+); bpy = 2,2'-bipyridyl). In all cases, strong delta-bonding interactions operate between the e(2) level of the C7F7 ring and metal d(xy), and d(x2-y2) orbitals resulting in a metal-centred HOMO with substantial d(z2), character in the 18-electron, closed shell systems. The experimental electronic UV-Vis spectra of [1](+), 2 and 3 are accurately reproduced by TD-DFT methods, For complexes 2 and 3, assignments made with the assistance of calculated spectra indicate that absorptions in the region 390-770 nm originate from a series of MLCT (metal-ligand charge transfer) or ILCT (inter-ligand charge transfer) transitions in which carbonyl, C7H7 and 2,2'-bipyridyl ligands act as acceptor systems from the metal or mixed metal and bromide donor groups. The metal-centred, one-electron oxidation of 3 to 3[PF6] results in almost complete quenching of the visible region MLCT/ILCT absorptions of 3 and replacement with weak transitions probably arising from bromide to metal LMCT (ligand to metal charge transfer) processes. (C) 2014 Elsevier Ltd. All rights reserved.

Previous theoretical studies have predicted structural differences between the tris(cyclopentadienyl) zirconium and hafnium complexes Cp3MX (Cp = C5H5; M = Zr, Hf). Cp3ZrCl can be isolated via the stoichiometric reaction of Cp2ZrCl2 and NaCp, but forming the analogous Hf complex is complicated by ligand redistribution. Partial crystallographic analysis of these two complexes indicates likely structural differences wherein the Zr complex has three η5 Cp ligands (“3-5” structure) while the Hf complex has two η5 Cp ligands and one η1 Cp ligand (“2-5,1-1” structure). The use of C5H4CH3 (MeCp) simplifies both the syntheses and the procurement of suitable crystals. The preparation of a number of MeCp complexes of Zr and Hf is reported along with crystallographic characterization of (MeCp)3HfCl, which has a 2-5,1-1 structure and (MeCp)4Zr, which has a 3-5,1-1 structure.

The oligomeric potassium complex [(Me2pzH)(Me2pz)2(18-crown-6)(THF)K2]2 (1) and the lithium dimer [(tBu2pz)(THF)Li]2 (2) were synthesized. Both complexes were fully characterized by spectroscopic methods and single crystal X-ray diffraction. Complex 1 crystallized in the triclinic space group P 1 ¯ , the structure shows an oligomer capped with 18-crown-6 and THF in both ends. This oligomer may be thought as the result of exscind an infinite single ladder structure in which η2-coordinated pyrazolate ligands to potassium ions are the steps of the stair, and the crown ether acting as a scissor. The potassium ions that form the truncated stair are coordinated in a η5-fashion to one pyrazolate ligand and in a η1-fashion to one pyrazolate and one pyrazolyl ligand, respectively. The potassium ions in the cavity of the 18-crown-6 ligand complete their coordination spheres with η5-coordination to one pyrazolate ligand and one THF molecule. Complex 2 is formed from the nucleophilic addition of THF to the lithium pyrazolate tetramer, [(tBu2pz)Li]4. Complex 2 crystallized in the monoclinic space group C2/c. The molecular structure shows a dimer in which the pyrazolate ligands are coordinated in a μ-η1:η 1 fashion to two Li ions. These ions complete their respective coordination spheres with THF.

The octamethyloctahydrodibenzofluorenyl (Oct) ligand has been incorporated into twelve ansa -Oct-amido complexes having the general structures Me 2 Si(η 1 -C 29 H 36 )(η 1 -N- t Bu)MX 2 · L or Me 2 Si(η 5 -C 29 H 36 )(η 1 -N- t Bu)MX 2 (M = Zr or Hf): 2 (X = Cl, L = Et 2 O); 3 (X = Br, L = Et 2 O); 4 (X = Me, L = Et 2 O); 5 (X = Me, L = THF); 6 (X = CH 2 Ph); and 7 (X = CH 2 SiMe 3 ). The solid-state structures have been determined for seven of these complexes by X-ray crystallography, revealing η 5 -C 29 H 36 coordination for the ether-free, pseudotetrahedral species 6-Zr , 6-Hf , and 7-Zr , but η 1 -C 29 H 36 coordination for the ether-bound, trigonal bipyramidal species 2-Zr , 3-Zr , 3-Hf , and 5-Zr . The unusual η 1 -C 29 H 36 coordination was assigned because only one metal–carbon bond in each structure was in the range of 2.281–2.330 A; a second metal–carbon distance was found between 2.731 and 2.847 A; the remaining metal–carbon distances were found between 3.130 and 4.029 A. An increase in the hapticity of these and other Oct- and fluorenyl-containing compounds was correlated to a convergence in the carbon–carbon bond lengths within the relevant five-membered rings.

The reaction of Ru(η2-RL)(PPh3)2(CO)Cl (1) with sodium pyridine-2-thiolate (Napyt) has afforded the complexes of the type Ru(η1-RL)(PPh3)2(CO)(pyt) (3) in excellent yield (η2-RL is C6H2O-2-CHNC6H4R(p)-3-Me-5, η1-RL is C6H2OH-2-CHNC6H4R(p)-3-Me-5 and R is Me, MeO, Cl). The reaction is irreversible and is believed to proceed via cis attack by pyt− on an octahedral face. The type 3 species are thermodynamically more stable than the corresponding carboxylates, nitrites and nitrates. Structure determination of the solvate, 3(R=Cl)·C6H6·0.5C6H14 has revealed a distorted octahedral RuC2P2NS coordination sphere with the pairs (P, P), (C(aryl), N) and (C(carbonyl), S) defining the three trans directions. The η1-ClL ligand metallated ortho to the phenolic oxygen occurs in the imine–phenol tautomeric form (N⋯O, 2.639(8) A) which is consistent with IR and 1H NMR data. The transformation 1→3 is associated with changes in tautomeric form, hapticity and conformation (in relation to CO) of RL. The Ru(η1-ClL) fragment excluding the pendant C6H4Cl(p) group is nearly coplanar (dihedral angle 6.1°) with the Ru(pyt) plane. The RuS distance, 2.524(1) A, is longer than usual due to steric reasons. The type 3 complexes display a quasi-reversible Ru(III)/Ru(II) couple near 0.6 V versus SCE.

Reaction of the seven-coordinate [Mo(I)2(CO)3(CH3CN)2] with an equivalent amount of the hydrotris(3, 5-dimethylpyrazol-1-yl)borate (TpMe2) ligand has been studied. The reaction course and the isolated products depend on the solvent and the initial concentration of the starting compound. Degradation of the TpMe2 ligand to produce derivatives containing 3, 5-dimethylpyrazole (HpzMe2) has been observed in all the experimental conditions used. So, in acetonitrile the reactions yield [Mo4O8(OH)2(HpzMe2)6]I2·4CH3CN and, only if a concentration of the starting complex greater than 0.01 M is used, the compound [Mo(I)( k 3-TpMe2)(CO)2]·2CH3CN is isolated together the above oxo-tetramer. When a less coordinating solvent like dichloromethane is used the complex [Mo(μ-I) (CO)2(HpzMe2)2]2I2·2CH3CN is always obtained independent of the initial concentration. Intermediate compounds in which the TpMe2 ligand is implicated with different hapticity are proposed to explain the different results. The molecular structure of [Mo4O4(μ3-O)2(μ2-O)2 (μ2-OH)2(HpzMe2)6]I2·4CH3CN has been crystallographically determined. The complex can be described as having a tetrametallic framework with a skeleton of edge-linked MoL6 (L = HpzMe2, O, OH) octahedra, which makes a compact closed structure. In each dimeric unit the Mov centres participate in a metal-metal single bond with an average Mo-Mo bond length of 2.568(1)A˚. This complex is the first structurally characterized cationic polyoxo tetrametallic Mov-containing the cluster described.