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Rh(ii)-catalyzed unusual branch-selective ortho-C-H alkylation of aryl sulfonamides with vinylsilanes was achieved using an 8-aminoquinoline directing group., Rhodium(ii)-catalyzed unusual branch-selective ortho-C–H alkylation of aryl sulfonamides with vinylsilanes was achieved using an 8-aminoquinoline directing group. Notably, the para-substituted aryl sulfonamides gave mono-(branched)alkylated products exclusively without the formation of any double C–H alkylated byproducts. The results of deuterium labeling experiments suggest that both hydrometalation and carbometalation pathways are involved in this conversion.

Tetrafluoroallene (1) and 1,1-difluoroallene (2) react under mild conditions with group 6 and 7 transition metal hydride complexes Cp(CO)3MoH (4), CO5MnH (5), Cp2WH2 (9), and Cp2MoH2 (10) to give the new fluoropropenyl complexes 6a, 7a, 11, 12, 15a–c, and 16a–c, which were characterized by single crystal X-ray diffraction. Complexes 6a and 7a undergo thermally induced 1,3-fluorine migration, whereas 11 and 12 show hindered rotation around the carbon metal single bond.

We report on the synthesis and reactivity of rhodium complexes featuring bulky, neutral pincer ligands with a “POP” coordinating motif, tBuxanPOP, iPrxanPOP, and tBufurPOP (tBuxanPOP = 4,5-bis(di-tert-butylphosphino)-9,9-dimethyl-9H-xanthene; iPrxanPOP = 4,5-bis(diisopropylphosphino)-9,9-dimethyl-9H-xanthene; tBufurPOP = 2,5-bis((di-tert-butylphosphino)methyl)furan). The (POP)Rh complexes described in this work are, in general, more reactive than their (PNP)Rh and (PCP)Rh analogues, which allows for the generation of several new species under relatively mild conditions. Thus, monomeric (POP)RhCl complexes oxidatively add H2 to form (POP)Rh(H)2Cl, from which the coordinatively unsaturated hydride complexes (POP)Rh(H)2+ and (tBuxanPOP)Rh(H) can be obtained. In the case of the new ligand tBufurPOP, a major kinetic product of the reaction with H2 is, surprisingly, the trans dihydride, i.e. trans-(tBufurPOP)Rh(H)2Cl; this is most likely attributable to reversible decoordination of one of the pincer coordinating groups, followed by addition of H2 to a highly reactive three-coordinate species. Ethylene is hydrogenated by (tBuxanPOP)Rh(H)2+ at 25 °C, but propylene is not, even at elevated temperatures. Ethylene undergoes insertion into the Rh–H bond of (tBuxanPOP)RhH; this reaction is reversible, allowing for an experimental determination of the equilibrium constant for this hydrometalation. The less bulky iPrxanPOP ligand affords a dihydride complex which functions as a modestly active alkane dehydrogenation catalyst, the first such example for a cationic pincer complex of any metal.

Regioselective (1,4-) hydrocobaltation of myrcene (1) leads to a 2 : 1 mixture of (E)- and (Z)-allylcobaloximes (2) which can be converted via the corresponding hydroxylamines (5) to geraniol (6a) and nerol (6b); by contrast, in the presence of molecular oxygen, (2) is converted into the peroxyallylcobalt complex (7), a precursor to linalool (8) and to linalool oxide (10).

Addition of bis(η-cyclopentadienyi)zirconium hydride (Cp2ZrHCl) to phospha-alkenes and phosphaimines leads either to a functionalized bis(η-cyclopentadienyl)zirconium phosphirane and azaphosphirane or to a protonated dico-ordinated phosphorus species.

Cross-coupling reactions between two alkenes, leading to new functionalised alkenes, can be brought about via‘hydrocobaltation’ of one of the alkenes followed by irradiation of the resulting organocobalt reagent in the presence of the second alkene substrate.

Two-step hydrolithiation of 3,4,6-tri-O-benzyl-D-glucal (hydrochlorination and lithium naphthalenide reductive lithiation) gives a reactive glycosyl-lithium derivative which is shown to be a precursor of C-glycosides.

Copper(I) hydride species, prepared in situ in tetrahydrofuran using NaBH4–MgBr2–Et3N–CuCl or NaH–MgBr2–CuCl reagent systems, convert terminal alkynes into (E,E)-1,3-dienes in good yields.

Irradiation of methyl methacrylate (MMA) in the presence of acyl- and alkyl-cobalt ‘salophen’ reagents leads to good yields of oligomers [(11)–(13)] by way of a novel catalytic ‘hydrocobaltation–dehydrocobaltation’ sequence; hydrocobaltation of the dimer (11)[to (14)] followed by conversion of the latter into (15) in the presence of styrene demonstrates the possibilities for ‘reactivation’ of oligomers of MMA for further chemical studies.