Janusz Zakrzewski

Activation of C-H bonds in saturated hydrocarbons. The catalytic functionalisation of cyclooctane by means of some soluble iridium and ruthenium polyhydride systems

Homogeneous catalytic dehydrogenation of cyclooctane into cyclooctene has been effected by means of a variety of iridium and ruthenium polyhydrides, at 150°C, in the presence of an olefin as the hydrogen acceptor; best results (45–70 catalytic turnovers) have been achieved with (iPr3P)2IrH5, [(p-F-C6H4)3P]2IrH5 and [(p-F-C6H4)3P]3RuH4.

An improved photochemical synthesis of azaferrocene

Abstract A new synthesis of azaferrocene, (η5-C4H4N)(η5-C5H5)Fe, involving photo-substitution of iodide in (η5-C5H5)Fe(CO)2I by the η1-pyrrolyl ligand, followed by decarbonylation of the resulting dicarbonyl η1-pyrrolyl complex, is described. The mechanism of the former reaction is discussed in terms of the photo-induced SRN1-type chain process.

Activation of C-H bonds in saturated hydrocarbons. The formation of bis(triphenylphospine)(η-alkadiene)rhenium trihydrides from n-Alkanes, and their selective conversion into the corresponding 1-alkenes

Abstract n-Alkanes (C 6 ue5f8C 8 ) react at 70°C with bis(triphenylphosphine)-rhenium heptahydride and 3,3-dimethylbutene to afford equilibrium mixtures of the corresponding bis(triphenylphosphine) (η-conjugated-diene)-rhenium trihydrides; treatment of these mixtures with trimethylphosphite at 60°C converts them, in >95% yield and with >98% selectivity, into the corresponding 1-alkenes.

Axial coordination of azaferrocene and dioxygen to cobalt(II) porphyrins. Photochemistry of six-coordinated adducts

Abstract The coordination of azaferrocene to cobalt(II) porphyrins (CoP) and the photochemistry of the resulting five- and six-coordinated complexes were studied by electron spin resonance spectroscopy. The five-coordinated complexes CoP(B) (B = azaferrocene) are photostable, whereas the six-coordinated complexes CoP(B)(L) (L ue5fc O 2 or B) eject L on irradation with visible light. Two alternative mechanisms for the photoejection of O 2 are proposed. The first involves a photoinduced electron transfer between the cobalt(III) and iron(II) centres in the six-coordinated dioxygen complex and the second is based on the photoejection of azaferrocene ( 4 ) from this complex.

The structure and dynamic behaviour in solution of the trihydridodienerhenium complexes (Ph3P)2(η-1,3-diene)ReH3

Abstract The structure and fluxionality of the trihydridodiene complexes (Ph 3 P) 2 (η-1,3- 3 have been studied by NMR spectroscopy (η-1-3-diene = buta-1,3-diene, 2-methylbuta-1,3-diene, 2,3-dimethylbuta-1,3-diene, cyclohexa-1,3-diene, penta-1,3-diene, hexa-1,3-diene and hexa-2,4-diene). Several rearrangement processes have been observed; they are, in order of increasing temperature: (a) ligand interchange; (b) reversible migration of a hydride ligand on to the diene ligand, leading to η-allyl species and, in the case of the cyclohexadiene trihydride, degenerate isomerisation of the cyclohexadiene moiety; and (c), in the case of the pentadiene and hexadiene derivatives, isomerisation of the diene ligand.

Photoinduced electron transfer between nitroxide radicals and W10O324

Abstract Irradiation (900 W xenon lamp, λ > 280 nm) of deaerated acetonitrile solutions of nitroxide radicals and (Bu 4 N) 4 W 10 O 32 directly in the cavity of an electron spin resonance (ESR) spectrometer produces a gradual decrease in the ESR signal of these radicals. Simultaneously, the reduced blue species W 10 O 32 5− (λ max = 784 nm) and the nitrosonium salt are formed. The rate constants of the photoinduced electron transfer from nitroxide radical to W 10 O 32 4− ( k 1 ) and the reverse process ( k −1 ) are reported.

The disruption of furan by bis(triphenylphosphine)rhenium heptahydride: synthesis and crystal structure of the 1-oxapentadienyl complex Re(η5-C4H5O)(PPh3)2(CO)

Reaction of furan with (Ph3P)2ReH7 and 3,3-dimethylbutene yields the 1-oxapentadienyl complex Re(η5-C4H5O)(PPh3)2(CO), the X-ray crystal structure of which has been determined.

Photo-oxygenation of 1,8-cineole by molecular oxygen catalysed by (Bu4N)4W10O32

Abstract The irradiation (λ > 280 nm) of oxygen-saturated solutions of 1,8-cineole containing catalytic amounts of (Bu4N)4W10O32 leads to the oxygenation of this natural product. After subsequent treatment with pyridinium chlorochromate, 5- and 6-keto derivatives of 1,8-cineole are obtained in the ratio of 2.5:1. This regioselectivity is compared with that observed in the oxidation of 1,8-cineole by chemical oxidants and microorganisms.

Axial coordination of azaferrocene to a cobalt(II) porphyrin and alkylcobaloximes

A study of axial coordination of azaferrocene to tetra-p-tolylporphinatocobalt(II) and alkylcobaloximes is reported. The ESR and O2 binding data show that N-ligating properties of this organometallic nitrogen base are similar to those of pyridine.

The selective conversion of n-pentane into pent-1-ene via trihydrido(trans-penta-1,3-diene)bis(triarylphosphine)rhenium

Treatment of n-pentane with heptahydridobis(triarylphosphine)rhenium and 3,3-dimethylbutene gives trihydrido(trans-penta-1,3-diene)bis(triarylphosphine)rhenium; trimethyl phosphite converts this, with high selectivity, into pent-1-ene.