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Monocationic complexes of yttrium with various bis-alkyl and bis-allyl ligands Y(CH2SiMe2Ph)2(THF)4][B(C6F5)4], [Y(CH2C6H4NMe2)2(THF)2][B(C6F5)4], and [Y[1,3-(SiMe3)2C3H3]2(THF)2][B(C6F5)4] have been prepared by protonolysis of the corresponding homoleptic tris-alkyl or -allyl complexes using the anilinium borate salt [PhNMe2H][B(C6F5)4]. The resulting ion-pair complexes have been isolated and characterized by different techniques such as elemental analysis, 1H, 13C, and 89Y NMR, and EXAFS for the allyl cationic complex [Y[1,3-(SiMe3)2C3H3]2(THF)2][B(C6F5)4]. More specifically, a 1H-coupled 89Y INEPT sequence has been developed in order to quantify the metal/alkyl ligand stoichiometry of both synthesized neutral tris-alkyl and cationic bis-alkyl yttrium complexes. The activity of the cationic complexes toward ethylene and isoprene homopolymerization has been assessed. In presence of TiBA, polyethylene was produced with activities ranging from 6 to 26 kgPEmolY–1h–1bar–1. The molar mass of the yielded polymers shows a bimodal distribution. Under similar conditions, polyisoprene was produced up to full conversion of the monomer. The microstructure of the yielded polyisoprene displayed mainly cis-1,4-units (ca. 60–70%) and 3,4-units (ca. 20–30%). Only a few percent of trans-1,4 units was revealed.

A range of dialkenylmagnesium compounds ([CH2═CH(CH2)n]2Mg; n= 1–6) were synthesized and used as chain transfer agents (CTA) with either (C5Me5)2NdCl2Li(OEt2)2(1) or [Me2Si(C13H8)2Nd(BH4)2Li(thf)]2(2) neodymium precursors for the polymerization of ethylene. In all cases, the systems followed a controlled coordinative chain transfer polymerization mechanism. The intramolecular insertion of the vinyl group on the CTA in growing chains is possible and led to the formation of cyclopentyl, cyclohexyl, and possibly cycloheptyl chain ends. While the production of cyclopentyl- or cyclohexyl-capped polyethylene chains can be quantitative (n= 2–5), the integrity of this double bond can also be kept if nis higher than 6. In comparison to 1/CTA catalytic systems, 2/CTA catalytic systems showed a higher propensity to produce cycloalkyl chain ends. This was ascribed to the lower steric demand around the active site, as shown by DFT calculations. In addition, the formation of bis(cyclopentylmethyl)magnesium from dipentenylmagnesium using a catalytic amount of 2was shown.

All the pathways leading to bis-stannane and regeneration of the catalyst Cp2LaH (Cp 5-C5H5) for the stannane SnH4have been computed using the DFT (B3PW91) method. In all cases, the reaction is at least a two-step process with a common first step, which is the Sn−H activation of the stannane, leading to the hydrostannyl complex Cp2LaSnH3. From a pure thermodynamic point of view, the overall process is found to be exergonic by 9.3 kcal·mol-1. Since the most stable product of the energy profile is the intermediary hydrostannyl complex, the second step, which corresponds to Sn−Sn coupling, is endergonic. This explains the relatively low turnover, found experimentally, for the homocoupling of stannane into bis-stannane. This overall process is in agreement with the experiment made on hafnium complexes, where the intermediary hydrostannyl compounds have been isolated and characterized. From a kinetic point of view, the second reaction step is proposed to occur through a direct SnH3transfer of the hydrostannyl to the incoming stannane rather than stannylene or stannylenoide insertion into the incoming stannane.

We report a mass spectrometry study of the interaction between three representative Au(I) catalysts containing the ligands L= JohnPhos (2-biphenylyl[bis(2-methyl-2-propanyl)]phosphine), TPP (PPh3, triphenylphosphine), the N-heterocyclic carbene IPr (carbene form of 1,3-bis(2,6-diisopropylphenyl)-2,3-dihydro-1H-imidazole), and 27 organic molecules S(substrates) bearing organic functionalities often present in reactants (alkenes, alkynes, allenes, enol ethers, aldehydes, ketones, and epoxides). An experimental scale of gas-phase relative binding energy between three L(Au+) ions and the organic substrates was established by energy-resolved experiments of the 81 cationic two-coordinate gold adducts L(Au+)Susing a quadrupole ion trap mass spectrometer. The experimental scale is expressed in units of normalized collision energy for 50% dissociation (NCE50) of the precursor ion. In parallel, the gas-phase bond dissociation energetics and the structure of adducts were probed by DFT calculations. The experimental affinity order of each substrate for the three cationic gold complexes L(Au+), IPr(Au+) > TPP(Au+) > JohnPhos(Au+) is well reproduced by the calculated bond dissociation energies ΔE. At the computational level used in this study, the agreement between the calculated ΔEand the experimental NCE50values is limited to series of substrates with the same functionality, and reasonable correlations NCE50vsΔEare observed within series. The DFT-optimized structures are discussed and compared with available X-ray crystal structures. Although no general trend can be observed between bond lengths or their changes upon coordination with the L(Au+) cations and dissociation energies, a significant correlation between the Au–O distance (S= O-bases) and ΔEis observed.

A family of L2Ni(ORF)2(L2: (Cy3PO)24, dcpmS 5, dppf 9, bipyMe210; RF= C(CF3)3) complexes is synthesized via selective substitution of 2 equiv of (DME)NaORFfrom homoleptic [Ni(ORF)4][Na(DME)]2complex 1, all characterized by 19F and 1H NMR and SCXRD analyses as well as elemental analyses. These L2Ni(ORF)2precursors, activated by 2 equiv of PhF → Al(ORF)3, were active in ethylene oligomerization with selectivity toward butenes up to 97% and activities ranging from 10 to 50 kgC2H4·gNi·h–1. Mechanistic investigations, involving experiments with C2H4/C2D4(1/1) coupled with GC-MS analysis, revealed the formation of a Ni–H fragment in the catalytic process. The L2Ni(ORF)2/2PhF → Al(ORF)3catalytic system thus dimerizes ethylene through a Cossee–Arlman mechanism.