No abstract

Half-sandwich Cp*RhIII complexes (Cp* = η5-1,2,3,4,5-pentamethylcyclopentadienyl) supported by 2,2′-bipyridine or 4,4′-di-tert-butyl-2,2′-bipyridine catalyze dehydrogenation of dimethylamine–borane (Me2NH·BH3) to produce H2 and dimethylamino–borane dimer (Me2NBH2)2 with turnovers of 2200. The IrIII analogues, on the other hand, display dramatically poorer catalytic activity. Mechanistic inferences drawn from stoichiometric reactions and DFT calculations suggest noninnocent involvement of the Cp* moiety as a proton shuttle.

The selective formation of heterobimetallic PtII/CuI complexes demonstrates how facile bond activation processes can be achieved by altering the reactivity of common organoplatinum compounds through their interaction with another metal center.

Abstract:Single-walled carbon nanotubes (SWNTs) have been coated with gold and platinum nanoparticles either by microwave treatment or by the click reaction and the Raman spectra of these SWNT-metal nanoparticle composites have been investigated. Analysis of the G bands in the Raman spectra shows an increase in the proportion of metallic SWNTs on attachment with metal nanoparticles. This conclusion is also supported by the changes observed in the RBM bands. Ab-initio calculations reveal that semiconductor-metal transition occurs in SWNTs due to Columbic charge transfer between the metal nanoparticles and the semiconducting SWNTs.

Selective reductive elimination of ethane (Csp(3)-Csp(3) RE) was observed following bromide abstraction and subsequent thermolysis of a Pt(IV) complex bearing both Csp(3)- and Csp(2)-hybridized hydrocarbyl ligands. Through a comparative experimental and theoretical study with two other Pt(IV) complexes featuring greater conformational flexibility of the ligand scaffold, we show that the rigidity of a meridionally coordinating ligand raises the barrier for Csp(2)-Csp(3) RE, resulting in unprecedented reactivity.

Dimethyl- and diphenylplatinum(II) fragments Pt(II)R2 (R = Me, Ph) enable facile and efficient oxidative C(sp(3))-H bond cleavage and stepwise C-C and C=C coupling at the boron atom of a coordinated 1,5-cyclooctanediyldi(2-pyridyl)borato ligand with O2 as the sole oxidant.

Unambiguous catalytic homogeneous alkane transfer dehydrogenation was observed with a group 10 metal complex catalyst, LPt(II)(cyclo-C6H10)H, supported by a lipophilic dimethyl-di(4-tert-butyl-2-pyridyl)borate anionic ligand and tert-butylethene as the sacrificial hydrogen acceptor.

Carbon homologation reactions occur within the well-known Fischer-Tropsch process, usually mediated by transition metal catalysts at high temperature. Here we report the low-temperature, heavy metal-free homologation of a carbon chain using CO as a C1-source showing for the first time that transition-metal catalysts are not required for Fischer-Tropsch-type reactivity. Reaction of an alkylborane in the presence of either LiHBEt3 or LiAlH4 resulted in multiple CO insertion/reduction events to afford elongated chains by more than two methylene (-CH2-) units, affording aldehyde products upon oxidative aqueous work-up. Theoretical and experimental mechanistic studies indicate that the boron-terminus is responsible for CO incorporation as well as sequential hydride delivery leading to reduction of acylborane intermediates to alkylboranes.