The first example of a [P,S]-ligated metal perfluorocyclopentane is reported. The new metallacycle undergoes Cα–F activation in the presence of a Lewis acid, followed by chemoselective ligand migration, affording a fused metallabicyclic product. Reactivity of this product includes an unprecedented nucleophile-induced ring-opening reaction, involving loss of a β-fluoride. Additionally, hydrolysis of the metallabicyclic product affords a single isomer of hexafluoro-1-butene.

Treatment of Ni(0) complexes 1a-e with sub-atmospheric pressures of trifluoroethylene (TrFE) affords hydrofluoronickelacyclopentanes LNi(CFH) 2a-e (L = PPh, P(O-o-tol), PPhMe, PPhMe, PMe). Fluorine NMR analysis of 2a-e demonstrates predominant formation of three (of the possible six) isomers upon oxidative cycloaddition of TrFE: the cis and trans head-tail isomers and the trans head-head isomer, where the CHF group is defined as the TrFE "head". The respective ratios of LNi(CFH) isomers are influenced by the nature of L, with smaller phosphines favoring the thermodynamically preferred (from DFT calculations) trans head-head isomer (cf. 50% with PMe) and the largest affording small amounts of the tail-tail isomers. Lewis and Brønsted acids induce a surprising double C-F bond activation in 2c-d, affording small functionalized hydrofluoroalkenes. Interestingly, varying the acid employed dictates the organic product obtained from the head-tail isomers: BF·OEt is selective for 1,1,2,3-tetrafluorocyclobutene, whereas MeSiOTf and N,N-dimethylanilinium bromide yield (Z,E)-1,1,3,4-tetrafluorobutadiene as the major fluorinated product. Reaction intermediates were isolated, and possible pathways are discussed.

Treatment of L2Ni(CF2)44a-c (L = PPh3, PPh2Me, pyridine) with an external Lewis acid (trimethylsilyl triflate) gives new L-functionalized fluoronickelacyclopentanes 5a-c. Complexes L2Ni(CF2)44a,b react with the thiol form of the bidentate ligand 1,2,4-(HS)(Ph2P)Me(C6H3) [P,SH] through a unique Brønsted acid-promoted Cα-F bond activation mechanism, affording phosphine-functionalized nickelacycles bearing a phosphinothiolate ligand 6a-b. Furthermore, substituting monodentate ligands in L2Ni(CF2)44a-c with the deprotonated form of the bidentate ligand [P,S(-)] leads to the first anionic perfluoronickelacycle 7. The anionic metallacyle reacts with phosphonium salts [PHPh3](Br) and [PHPh2Me](Br) to yield HF and phosphine-functionalized nickelacycles 6a,b that still contain the terminal thiolate moiety.

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Ansa-zirconocene complexes are widely employed as precatalysts for olefin polymerization. Their synthesis generally leads to mixtures of their rac and meso isomers, whose separation is often problematic. In this contribution, we report on the synthesis of a novel silyl-bridged bis(indenyl)-based metallocene, and on the separation of its rac and meso isomers by simple recrystallization from toluene. The two complexes, activated by methylaluminoxane (MAO), have been used as precatalysts in ethylene/1-hexene copolymerization. Regardless of the reaction conditions, the meso complex outperformed its rac congener. A similar trend was observed by performing the process in the presence of the silica-supported versions of the complexes. This is remarkable, since meso metallocenes generally display lower activities than their rac analogues. Furthermore, the meso isomer generates polymer products that are more in line with the targets for the preparation of a bimodal PE grade made of a lower-MW high-density (HDPE) fraction and a higher-MW linear low-density (LLDPE) fraction.