ABSTRACT
The photophysical properties of a series of T-shaped coinage d10 metal complexes, supported by a bis(mesoionic carbene)carbazolide (CNC) pincer ligand, are explored. The series includes a rare new example of a tridentate T-shaped AgI complex. Post-complexation modification of the AuI complex provides access to a linear cationic AuI complex following ligand alkylation, or the first example of a cationic square planar AuIII -F complex from electrophilic attack on the metal centre. Emissions ranging from blue (CuI ) to orange (AgI ) are obtained, with variable contributions of thermally-dependent fluorescence and phosphorescence to the observed photoluminescence. Green emissions are observed for all three gold complexes (neutral T-shaped AuI , cationic linear AuI and square planar cationic AuIII ). The higher quantum yield and longer decay lifetime of the linear gold(I) complex are indicative of increased phosphorescence contribution.
ABSTRACT
The synthesis of 4f n Ln3+ complexes of the tris(aryloxide) mesitylene ligand, ((Ad,MeArO)3mes)3-, with Ln = La, Ce, Pr, Sm, and Yb, and their reduction with potassium have revealed that this ligand system can be redox active with some metals. Protonolysis of [Ln(N(SiMe3)2)3] (Ln = La, Ce, Pr, Sm, Yb) with the tris(phenol) (Ad,MeArOH)3mes yielded the Ln3+ complexes [((Ad,MeArO)3mes)Ln] (Ln = La, Ce, Pr, Sm, Yb), 1-Ln. Single electron reduction of each 4f n complex, 1-Ln, using potassium yielded the reduced products, [K(2.2.2-cryptand)][((Ad,MeArO)3mes)Ln] (Ln = La, Ce, Pr, Sm, Yb), 2-Ln. The Sm and Yb complexes have properties consistent with the presence of Ln2+ ions with traditional 4f n+1 electron configurations. However, the La, Ce, and Pr complexes appear to formally contain Ln3+ ions and ((Ad,MeArO)3mes)4- ligands. Structural comparisons of the [((Ad,MeArO)3mes)Ln] and [((Ad,MeOAr)3mes)Ln]1- complexes along with UV-vis absorption and EPR spectroscopy as well as density functional theory calculations support these ground state assignments.
ABSTRACT
The Th3+ complex, (C5Me5)3Th, has been isolated despite the fact that tris(pentamethylcyclopentadienyl) complexes are highly reactive due to steric crowding and few crystallographically characterizable Th3+ complexes are known due to their highly reducing nature. Reaction of (C5Me5)2ThMe2 with [Et3NH][BPh4] produces the cationic thorium complex [(C5Me5)2ThMe][BPh4] that can be treated with KC5Me5 to generate (C5Me5)3ThMe, 1. The methyl group on (C5Me5)3ThMe can be removed with [Et3NH][BPh4] to form [(C5Me5)3Th][BPh4], 2, the first cationic tris(pentamethylcyclopentadienyl) metal complex, which can be reduced with KC8 to yield (C5Me5)3Th, 3. Complexes 1-3 have metrical parameters consistent with the extreme steric crowding that previously has given unusual (C5Me5)- reactivity to (C5Me5)3M complexes in reactions that form less crowded (C5Me5)2M-containing products. However, neither sterically induced reduction nor (η1-C5Me5)- reactivity is observed for these complexes. (C5Me5)3Th, which has a characteristic EPR spectrum consistent with a d1 ground state, has the capacity for two-electron reduction via Th3+ and sterically induced reduction. However, it reacts with MeI to make two sterically more crowded complexes, (C5Me5)3ThI, 4, and (C5Me5)3ThMe, 1, rather than (C5Me5)2Th(Me)I. Complex 3 also forms more crowded complexes in reactions with I2, PhCl, and Al2Me6, which generate (C5Me5)3ThI, (C5Me5)3ThCl, and (C5Me5)3ThMe, 1, respectively. The reaction of (C5Me5)3Th, 3, with H2 forms the known (C5Me5)3ThH as the sole thorium-containing product. Surprisingly, (C5Me5)3ThH is also observed when (C5Me5)3Th is combined with 1,3,5,7-cyclooctatetraene. [(C5Me5)3Th][BPh4] reacts with tetrahydrofuran (THF) to make [(C5Me5)3Th(THF)][BPh4], 2-THF, which is the first (C5Me5)3M of any kind that does not have a trigonal planar arrangement of the (C5Me5)- rings. It is also the first (C5Me5)3M complex that does not ring-open THF. [(C5Me5)3Th][BPh4], 2, reacts with CO to generate a product characterized as [(C5Me5)3Th(CO)][BPh4], 5, the first example of a molecular thorium carbonyl isolable at room temperature. These results have been analyzed using density functional theory calculations.
