Cationic Vanadium(IV) Methyl Complexes [Cp₂VMe(CH₃CN)][B(C₆H₅)₄] and [Cp₂VMe(THF)][MeB(C₆F₅)₃]

The cationic vanadocene alkyl complex [Cp2VMe(CH3CN)]+ with [BPh4]- counteranion was structurally established. The reaction of Cp2VMe2 in THF in the presence of B(C6F5)3 is also described:  EPR evidence of the intermediate formation of the [Cp2VMe(THF)]+ species, which gives, via a disproportionation redox reaction, the VIII species [Cp2V(THF)][Me B(C6F5)3], is demonstrated

The α-Iminophospholide Ligands

The reaction of phospholide ions with imidoyl chlorides in the presence of tBuOK gives the α-iminophospholides that are isolated as their trimethylstannyl derivatives. These derivatives in turn react with metal chlorides to give complexes of the title ligands. A DFT study shows that substantial electronic delocalization takes place between the imino group and the phospholyl ring in these anions. The X-ray crystal structure of one stannylphosphole shows a highly pyramidal phosphorus atom (sum of angles = ca. 280°). A tetrameric copper complex has also been structurally characterized

Stable Planar Six-π-Electron Six-Membered N-Heterocyclic Carbenes with Tunable Electronic Properties

Carbene analogues of borazines are highly thermally stable. Keeping quasi-identical steric demands, the electronic properties of the carbene can be precisely tuned by varying the nature of the substituents at the boron centers

Generation and Trapping of a Superelectrophilic Terminal Fluorophosphinidene Complex

Comparative DFT calculations on terminal phosphinidene complexes [MeP-Cr(CO)5] and [FP-Cr(CO)5] show a huge increase of the positive charge at P when replacing the methyl by the fluorine substituent (NBO charges +0.60 and +0.94). The electrophilic fluorination of the (3,4-dimethylphospholyl)pentacarbonylmolybdenum anion by Selectfluor gives a straightforward access to the corresponding 1-fluoro-3,4-dimethylphosphole molybdenum complex. This complex reacts as a conjugated diene with dimethyl acetylenedicarboxylate to give the corresponding 7-fluoro-7-phosphanorbornadiene complex. This bicyclic species is a precursor of [FP-Mo(CO)5] at 120 °C in xylene, as shown by trapping reactions with diphenylacetylene and 2,3-dimethylbutadiene

Synthesis and Crystal Structure of Unprecedented Phosphine Adducts of d¹-Aryl Imido−Vanadium(IV) Complexes

The reaction of the imido precursor [V(NAr)Cl2]n (1) (Ar = 2,6-i-Pr2C6H3) with 3 equiv of PMe2Ph yields the monomeric complex [V(NAr)Cl2(PMe2Ph)2] (2). Reacting 1 with 1.5 equiv of dmpe or 1 equiv of dppm affords the dimeric complexes [V(NAr)Cl2(dmpe)]2(μ-P,P‘-dmpe) (3) and [V(NAr)Cl2(dppm)]2 (4), respectively. Complexes 2−4 have been fully characterized by spectroscopic methods, magnetism studies, and X-ray crystallography

Synthesis and Structure of Group 4 and 5 Metal Complexes with an Ancillary Sterically Demanding Diamido Ligand

Reaction of tetrachlorides of group 4 and 5 transition metals with the chelating diamide [Me2C(CH2N(Li)(SiButPh2))2] (LLi2) leads to LMCl2 (M = Ti, Zr, Hf, V) complexes, which were characterized by X-ray diffraction. The reactivity of LMCl2 toward ethylene polymerization was tested with MAO as cocatalyst

Synthesis and Structure of a Series of New d¹-Aryl Imido−Vanadium(IV) Complexes Stabilized by N-Donor Ligands

A family of new coordination vanadium(IV) compounds supported by a terminal or bridged aryl imido ligand are reported. Reaction of V(NMe2)4 with anilines ArNH2, where Ar = 2,6-i-Pr2-C6H3, 2,6-Me2-C6H3, Ph, 2,6-Cl2-C6H3, and C6F5, afforded the diamagnetic imido-bridged complexes [V(NAr)(NMe2)2]2 (1a−e). Chlorination of 1a−e with trimethylchlorosilane afforded complexes 2a−e formulated as [V(NAr)Cl2(NHMe2)x]n. One-pot reaction of V(NMe2)4 with ArNH2 in the presence of an excess of trimethylchlorosilane gave the five-coordinate compound [V(NAr)Cl2(NHMe2)2] (3a−e). Reaction of 3a−e with pyridine, bipyridine (bipy), or N,N,N‘,N‘-tetramethylethylenediamine (tmeda) gave respectively the six-coordinate tris- or bis(pyridine) adducts [V(NAr)Cl2(Py)3] (4a−e) or [V(NAr)Cl2(Py)2(NHMe2)] (5a), bipyridine complexes [V(NAr)Cl2(bipy)(NHMe2)] (5a−e) and [V(NAr)Cl2(bipy)(Py)] (9a), and tmeda adduct [V(NAr)Cl2(tmeda)(NHMe2)] (10a). Moreover, five-coordinate complexes free of NHMe2 ligands, such as [V(NAr)Cl2(Py)2] (5a), [V(NAr)Cl2(bipy)] (8a), and [V(NAr)Cl2(tmeda)] (11a), were directly prepared starting from precursors 2a−e. All compounds were totally characterized by spectroscopic methods (IR, 1H NMR for diamagnetic complexes, and EPR for paramagnetic complexes), elemental analysis, magnetism, and single-crystal X-ray diffraction studies for 1b, 3a, 3d, 4b, 4d, 7c, 10a, and 11a

Zwitterionic, Ring-Borylated Vanadium(III) Complexes from [Cp₂VCO] and B(C₆F₅)₃

The reaction of the vanadium(II) carbonyl [Cp2V(CO)] and B(C6F5)3 resulted in formation of zwitterionic, ring-borylated vanadium(III) complexes [(Cp)(C5H4B(C6F5)3)V] (3) and [(Cp)(C5H4B(C6F5)3)V(CO)2] (4) and of the salt [Cp2V(CO)2][HB(C6F5)3] (5). All were characterized by crystallography. Formation of a hydride vanadium(IV) [(Cp)(C5H4B(C6F5)3)VH(CO)] obtained by the electrophilic addition of the borane at the Cp-ring followed by redox and disproportionation reaction is suggested to account for these results

Synthesis and Structure of a Series of New d¹-Aryl Imido−Vanadium(IV) Complexes Stabilized by N-Donor Ligands

A family of new coordination vanadium(IV) compounds supported by a terminal or bridged aryl imido ligand are reported. Reaction of V(NMe2)4 with anilines ArNH2, where Ar = 2,6-i-Pr2-C6H3, 2,6-Me2-C6H3, Ph, 2,6-Cl2-C6H3, and C6F5, afforded the diamagnetic imido-bridged complexes [V(NAr)(NMe2)2]2 (1a−e). Chlorination of 1a−e with trimethylchlorosilane afforded complexes 2a−e formulated as [V(NAr)Cl2(NHMe2)x]n. One-pot reaction of V(NMe2)4 with ArNH2 in the presence of an excess of trimethylchlorosilane gave the five-coordinate compound [V(NAr)Cl2(NHMe2)2] (3a−e). Reaction of 3a−e with pyridine, bipyridine (bipy), or N,N,N‘,N‘-tetramethylethylenediamine (tmeda) gave respectively the six-coordinate tris- or bis(pyridine) adducts [V(NAr)Cl2(Py)3] (4a−e) or [V(NAr)Cl2(Py)2(NHMe2)] (5a), bipyridine complexes [V(NAr)Cl2(bipy)(NHMe2)] (5a−e) and [V(NAr)Cl2(bipy)(Py)] (9a), and tmeda adduct [V(NAr)Cl2(tmeda)(NHMe2)] (10a). Moreover, five-coordinate complexes free of NHMe2 ligands, such as [V(NAr)Cl2(Py)2] (5a), [V(NAr)Cl2(bipy)] (8a), and [V(NAr)Cl2(tmeda)] (11a), were directly prepared starting from precursors 2a−e. All compounds were totally characterized by spectroscopic methods (IR, 1H NMR for diamagnetic complexes, and EPR for paramagnetic complexes), elemental analysis, magnetism, and single-crystal X-ray diffraction studies for 1b, 3a, 3d, 4b, 4d, 7c, 10a, and 11a

Preparation of the New Bis(phenanthroline) Ligand “Clip-Phen” and Evaluation of the Nuclease Activity of the Corresponding Copper Complex

The best nuclease activities of 1,10-phenanthroline−copper complexes have been observed for a chelate/metal stoichiometry of 2/1. To favor this stoichiometry, the “Clip-Phen” ligand was synthesized with two 1,10-phenanthroline units linked via their C2-carbons by a short flexible arm. An exogenous amine function was present to allow future vectorization of this new chelating ligand. X-ray analysis of monocrystals of Clip-Phen confirmed its structure. An EPR study of (Clip-Phen)CuCl2 showed that the cupric ion was pentacoordinated with a water molecule as the possible fifth ligand. The Cu(I/II) redox couple was found to be near 85 mV vs SCE, close to the redox couple of (Phen)2CuCl2. A comparison of the nuclease activity of copper complexes of Clip-Phen and 1,10-phenanthroline indicated that (Clip-Phen)Cu was the more active