The interaction of hydrogen peroxide with a range of polycrystalline titanium oxide systems, including TiO 2 , TS-1, [Ti]-APO-5 and ion-exchanged Ti-ZSM-5, has been investigated using c.w. X-band EPR spectroscopy. Decomposition of the peroxide occurs immediately upon contact with all of the metal oxides investigated, resulting in the formation of a series of paramagnetic oxygen centred radicals. In the TiO 2 /H 2 O 2 system, intense signals assigned to adsorbed O 2 À anions were observed. Traces of physisorbed water was found to retard the motional characteritics of the adsorbed O 2 À anion, as manifested in the variable-temperature EPR spectra. In addition, covalently bound superoxo species were also identified on the TiO 2 /H 2 O 2 surface. In the TS-1/H 2 O 2 system, two different bound peroxo radicals were observed and identified firstly as (1) Ti(OSi) 4 /O 2 À /H 2 O or Ti(OSi) 4 /OO /H 2 O and secondly (2) as HOTi(OSi) 3 /OO /H 2 O. In both cases, the adsorbed radical interacts with an adjacent water molecule, while the two models differ by the presence or absence of a titanol function. An EPR signal of the weakly adsorbed hyperperoxy radicals (HO 2 ) was also observed in H 2 O 2 -treated TS-1. In the [Ti]-APO-5/H 2 O 2 and Ti-ZSM5/H 2 O 2 systems bound peroxo radicals are observed in both cases, but broader EPR resonances are observed in the latter case over ZSM5 due to the heterogeneity of extraframework Ti 4+ adsorption sites for stabilisation of the radical anions.y Electronic supplementary information (ESI) available: XRD patterns and further EPR spectra. See

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The reactions of the paramagnetic gallium(II) complex [{(Bu(t)-DAB)GaI}2] (Bu(t)-DAB = {(Bu(t))NC(H)}2) with the alkali metal pnictides [ME(SiMe3)2] (M = Li or Na; E = N, P, or As) have been carried out under a range of stoichiometries. The 1:2 reactions have led to a series of paramagnetic gallium(III)-pnictide complexes, [(Bu(t)-DAB)Ga{E(SiMe3)2}I] (E = N, P, or As), while two of the 1:4 reactions afforded [(Bu(t)-DAB)Ga{E(SiMe3)2}2] (E = P or As). In contrast, treatment of [{(Bu(t)-DAB)GaI}2] with 4 equiv of [NaN(SiMe3)2] resulted in a novel gallium heterocycle coupling reaction and the formation of the diradical species [(Bu(t)-DAB)Ga{N(SiMe3)2}{[CC(H)N2(Bu(t))2]Ga[N(SiMe3)2]CH3}]. The mechanism of this unusual reaction has been explored, and evidence suggests it involves an intramolecular transmethylation reaction. The X-ray crystal structures of all prepared complexes are reported, and all have been characterized by EPR and ENDOR spectroscopies. The observed spin Hamiltonian parameters provide a detailed picture of the distribution of the unpaired spin density over the molecular frameworks of the complexes.