High molar weight polyphosphinoboranes represent materials with auspicious properties, but their preparation requires transition metal-based catalysts. Here, calix[4]pyrrolato aluminate is shown to induce the dehydropolymerization of phosphine boranes to high molar mass polyphosphinoboranes (up to M n = 43 000 Da). Combined GPC and 31 P DOSY NMR spectroscopic analyses, quantum chemical computations, and stoichiometric reactions disclose a PÀ H bond activation by the cooperative action of the square-planar aluminate and the electron-rich ligand framework. This first transition metal-free catalyst for PÀ B dehydrocoupling overcomes the problem of residual d-block metal impurities in the resulting polymers that might interfere with the reproducibility of the properties for this emerging class of inorganic materials.
The coordination chemistry of two selenourea ligands (SeIMes and SeIPr) towards silver(i) triflate and silver(i) nitrate was investigated. Two aggregation modes were observed in the solid state, strongly influenced by the size of the aromatic substituents on the ligand. With mesityl groups, selenium-bridged bimetallic motifs [AgX(SeIMes)] were obtained, while for the bulkier diisopropylphenyl groups ion-separated species of formulae [Ag(SeIPr)][X] were obtained. Recrystallization of [Ag(NO)(SeIMes)] from hot methanol resulted in the formation of a unique coordination polymer featuring three silver environments. Characterization of the complexes by NMR spectroscopy and mass spectrometry suggested all complexes adopt the ionic aggregation mode in methanol solution.
The synthesis and reactivity of the first series of monoanionic bidentate ligands containing an N-heterocyclic carbene−phosphinidene adduct and their corresponding half-metallocene titanium complexes were investigated. The structural characterization of 5a confirmed bidentate coordination through the phosphorus and oxygen atoms of the ligand, with evidence of significant electron delocalization over the ligand structure. The new titanium complexes produced polyethylene at room temperature and under 1 atm of ethylene at a rate of up to 9.2 kg PE mol Ti −1 h −1 .
Stoichiometric reaction of phosphine–borane adducts RR'PH⋅BH3 (R=Ph, R’=H, Ph, Et, and R=R’=tBu) with the strong acid HNTf2 (Tf=SO2CF3) leads to H2 elimination and the formation of the triflimido derivatives, RR'PH⋅BH2(NTf2). Subsequent deprotonation by using bases, such as diisopropylethylamine or the carbene IPr (IPr=N,N’‐bis(2,6‐diisopropylphenyl)imidazol‐2‐ylidene), led to the formation of P‐mono‐ or ‐disubstituted polyphosphinoboranes [RR'P‐BH2]n. Evidence for the intermediacy of transient phosphinoborane monomers, RR'PBH2, was provided by trapping reactions.
An amphiphilic block copolymer of polyphosphinoborane has been prepared by a mechanism-led strategy of the sequential catalytic dehydropolymerization of precursor monomers, H 3 B • PRH 2 (R = Ph, nhexyl), using the simple pre-catalyst [Rh-(Ph 2 PCH 2 CH 2 PPh 2 ) 2 ]Cl. Speciation, mechanism and polymer chain growth studies support a step-growth process where reversible chain transfer occurs, i.e. H 3 B • PRH 2 / oligomer/polymer can all coordinate with, and be activated by, the catalyst. Block copolymer [H 2 BPPhH] 110 -b-[H 2 BP(n-hexyl)H] 11 can be synthesized and self-assembles in solution to form either rod-like micelles or vesicles depending on solvent polarity.
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