Bis(cyclopentadienyl)zirconium(IV) or hafnium-(IV) Compounds with Si-, Ge-, Sn-, N-, P-, As-, Sb-, O-, S-, Se-, Te-, or Transition Metal-Centered Anionic Ligands

Expanding Bismuth Trihalide Coordination Chemistry with Trimethyltriazacyclohexane and Trimethyltriazacyclononane

1,3,5-Trimethyltriazacyclohexane, Me₃tach, readily adds to bismuth triiodide to form a variety of new coordination compounds depending on the stoichiometry, solvent, and crystallization conditions. X-ray crystallographic evidence has been obtained for both 2:1 and 1:1 Me₃tach:Bi complexes with formulas of [(Me₃tach)₂BiI₂][(Me₃tach)BiI₄], [(Me₃tach)₂BiI₂]₃[Bi₂I₉][I][HMe₃tach]·THF, and (Me₃tach)BiI₃(py)₂. The related chloride structure (Me₃tach)BiCl₃(py)₂ forms from BiCl₃. The structure of (Me₃tacn)BiI₃ with the larger chelate, 1,4,7-trimethyltriazacyclononane, Me₃tacn, was obtained for comparison, and the polymeric structure of BiI₃ in THF was defined as [BiI(THF)(μ-I)₂]_n.

CO2 activation by permethylpentalene amido zirconium complexes

We report the synthesis and characterisation of new permethylpentalene zirconium bis(amido) and permethylpentalene zirconium cyclopentadienyl mono(amido) complexes, and their reactivity with carbon dioxide.

Mechanistic insights into dehydrocoupling of amine boranes using dinuclear zirconocene complexes

Catalytic dehydrocoupling of H₃B·NMe₂H using Cp₂Zr(Cl)(μ-Me₃SiC₃SiMe₃)Zr(Cl)Cp₂ (1)/MeLi was studied. Spectroscopic monitoring and stoichiometric experiments show the formation and interconversion of several catalytically active Zr species.

The Taming of Redox-Labile Phosphidotitanocene Cations

Tame d⁰ phosphidotitanocene cations stabilized with a pendant tertiary phosphane arm are reported. These compounds were obtained by one-electron oxidation of d¹ precursors with [Cp₂ Fe][BPh₄ ]. The electronic structure of these compounds was studied experimentally (EPR, UV/Vis, and NMR spectroscopy, X-ray diffraction analysis) and through DFT calculations. The theoretical analysis of the bonding situation by using the electron localization function (ELF) shows the presence of π-interactions between the phosphido ligand and Ti in the d⁰ complexes, whereas dπ-pπ repulsion prevents such interactions in the d¹ complexes. In addition, CH-π interactions were observed in several complexes, both in solution and in the solid state, between the phosphido ligand and the phosphane arm. The d⁰ complexes were found to be light sensitive, and decompose through Ti-P bond homolysis to give Ti^III species. A naked d⁰ phosphidotitanocene cation has been trapped by reaction with diphenylacetylene, yielding a Ti/P frustrated Lewis pair (FLP), which was found to be less reactive than a previously reported Zr analog.

Metal-phosphido and -phosphinidene complexes in P-E bond-forming reactions

Metal complexes bearing terminal phosphido or phosphinidene ligands have become versatile tools in the stoichiometric and catalytic preparation of phosphorus-element bonds. This Perspective describes a selection of recent advances in this field, and certain emphasis has been placed on reactions that vary from what has been previously observed. Some of the general reactivity trends and mechanistic understanding in these metal-mediated reactions that has emerged are also described. Much of what is chronicled herein comes from a flux of reports over the last decade describing unique metal-mediated phosphorus-element bond formation reactions that are likely to stimulate further discoveries.

Zirconium-catalyzed heterodehydrocoupling of primary phosphines with silanes and germanes

Triamidoamine-supported zirconium complexes catalyze the heterodehydrocoupling of primary phosphines with silane and germanes. In this catalysis, P-Si or P-Ge products are observed exclusively with no competitive P-P bond formation. Phosphido complexes (N3N)ZrPHR (N3N = N(CH2CH2NSiMe3)33-, R = Ph, 2; Cy, 3) were observed to be the catalyst resting state, and complex 2 was structurally characterized.

Five-membered metallacycles of titanium and zirconium--attractive compounds for organometallic chemistry and catalysis

In these days a renaissance of metallacycles as an increasingly important class of organometallic compounds for synthetic and catalytic applications is evident, making such very attractive for a plethora of investigations. Titanocene and zirconocene bis(trimethylsilyl)acetylene complexes, regarded as three-membered metallacycles (1-metallacyclopropenes), present a rich chemistry towards unsaturated molecules. By elimination of the alkyne these complexes form by reaction with unsaturated compounds five-membered titana- and zirconacycles, all of which are relevant to stoichiometric and catalytic C-C coupling and cleavage reactions of unsaturated molecules.

Activation of a CNXylyl ancillary ligand in the reaction of electron-deficient alkynes with a phosphido niobocene complex

The niobium phosphido complex [Nb(eta5-C5H4SiMe3)2-(CNXylyl)(PPh2)] (2) undergoes an unusual cycloaddition reaction with electron-deficient alkynes to give the novel five-membered heteroniobacycles [Nb(eta5-C5H4SiMe3)2(kappaC-C(=N(Xylyl))C(CO2Me)=C(R)PPh2-kappaP)] (R = H 3 and R = Me 4).

Reactions of Cp2MCl2 (M=Ti or Zr) with imine-oxime ligands. Formation of metallacycles

The reactions of bis(cyclopentadienyl)titanium(IV)/zirconium(IV) dichloride with a series of imine-oxime ligands (LH2), derived by condensing benzil-alpha-monoxime and 2-phenylenediamine, 4-phenylenediamine, 4-methyl-2-phenylenediamine, 2,6-diamino-pyridine, have been studied in anhydrous tetrahydrofuran in the presence of base and metallocycles of the [Cp2M(L)] (M=Ti or Zr) type have been isolated. Tentative structures have been proposed for the products based on elemental analysis, electrical conductance and spectral (electronic, IR and (1)H-NMR) data. Proton NMR spectra indicate that on the NMR time scale there is rapid rotation of the cyclopentadienyl ring around the metal-ring axis at 25 degrees C. Studies were conducted to assess the growth inhibiting potential of the complexes synthesized and the ligands against various bacterial strains.

A new synthetic entry to phosphinophosphinidene complexes. Synthesis and structural characterisation of the first side-on bonded and the first terminally bonded phosphinophosphinidene zirconium complexes [mu-(1,2:2-eta-tBu2P=P)[Zr(Cl)Cp2]2] and [[Zr(PPhMe2)Cp2](eta1)-P-PtBu2)]

The reactions of lithiated diphosphanes with transition metal chlorides constitute a new general entry to phosphinophosphinidene complexes: the reaction of Cp2ZrCl2(Cp = C5H5) with tBu2P-P(SiMe3)Li (molar ratio approximately 1:1) yields [mu-(1,2:2-eta-tBu2P=P)[Zr(Cl)Cp2]2]; the reaction of Cp2ZrCl2 with tBu2P-P(SiMe3)Li (molar ratio approximately 1:2) and an excess of PPhMe2 in DME yields the first terminally bonded phosphinophosphinidene complex, [[Zr(PPhMe2)Cp2](eta1-P-PtBu2)].