Karl Wilhelm Törnroos

The synthesis of alkali-metal-free compounds [LnMe3]n is scrutinized using two distinct protocols. The donor-promoted cleavage of homoleptic tetramethylaluminate complexes Ln(AlMe4)3 proves rare-earth metal (Ln) size-dependent and gives access to [LnMe3]n (small to midsized Ln(III)) and [LnMe3-x(AlMe4)x(OEt2)y] (large Ln(III)). Both compounds can be converted to homoleptic tetramethylgallates Ln(GaMe4)3 by addition of trimethylgallium. Crystallization attempts of [LnMe3-x(AlMe4)x(OEt2)y] via extended donor-solvent treatment produced structural snapshots of a diverse set of clusters featuring different stages of methyl group degradation. New homometallic coordination motifs are detected for carbides [(C4−)(Ln3+)4] (Ln = La, Nd) and [(C4−)(Gd3+)6] as well as methylidyne [(CH3−)(Nd3+)5]. Applying the salt-metathesis protocol (Me3TACN)LnCl3(THF)x (x = 0, 1)/MeLi the discrete monomeric 6-coordinate (Me3TACN)LnMe3 (Ln = Dy, Er, Tm) and 7-coordinate (Me3TACN)LnMe3(THF) (Ln = La, Ce) can be obtained (Me3TACN = 1,4,7-trimethyl-1,4,7-triazacyclononane). Incomplete Cl/CH3 exchange to afford mixed methyl/chloride complexes (Me3TACN)LnMe3-xClx was observed for praseodymium, neodymium, and samarium. Crystal structures of most of the new complexes have been obtained and are discussed along with the findings from NMR studies.

The development of hybrid organic–inorganic polyoxometalate compounds with well-characterized structures remains an important goal in the design of functional materials. Herein, we report the synthesis of a Zn–salen-type complex covalently tethered to the lacunary Keggin polyoxometalate {SiW₁₁O₃₉} via silico-functionalization, representing the first Zn-containing example within this class of metallosalen-{SiW₁₁} hybrids. The corresponding amine- and imine-functionalized intermediates were also isolated, and single-crystal X-ray diffraction analyses of the amine precursor provide structural validation of the organo-functionalization. Formation of the Zn-salen-{SiW₁₁} hybrid is supported by NMR, FTIR, EDX, and ESI/MS analyses, with the observed isotopic distributions and accurate masses showing that the hybrid structure are present in the solution state. Comparative experiments with the previously reported Ni analogue afforded corresponding hybrid species that exhibited analogous ESI/MS results, supporting the structural assignments of the metallated hybrids. These results establish the first Zn-salen-{SiW₁₁} system and provide structural and solution-state characterization for this class of materials.

A series of bis-phenolate saturated N-heterocyclic carbene (NHC) group 4 complexes ([κ³-O,C,O]-NHC)­M­(OiPr)­Cl­(THF) (M = Ti, 1; Zr, 2; Hf, 3) in the presence of [PPN]Cl as cocatalyst were investigated and showed high activity in the tandem terpolymerization of phthalic anhydride (PA), cyclohexene oxide (CHO) with CO₂. The resultant terpolymers revealed a diblock pattern leading selectively to poly­(ester-b-carbonate). Subsequently, other titanium complexes ([κ³-O,C,O]-NHC)­TiX₂ bearing various coligands (X = Cl, 4; OiPr, 5; OAc, 6; OAc^F, 7) also displayed high activity with a turnover frequency (TOF) up to 460 h^–1 that is comparable to 1. Using the same tandem approach, the nature of terpolymers was modulated with other mono- and tricyclic anhydrides alongside CHO with CO₂. Intrigued by the high rates of PA conversion observed experimentally in terpolymerization, complexes 1–3 as well as benzannulated and unsaturated NHC analogues of complex 1 were investigated as a stand-alone reaction for the copolymerization of PA and CHO. Complex 1/[PPN]Cl displayed excellent catalytic activity (TOF ∼ 1600 h^–1) and high selectivity (≥99%) toward polyesters comparable to other highly active heteronuclear (Al/K and Fe/K) catalysts and binary (salen)­MX systems. Kinetic studies performed on complexes 1 and 3 determined activation barriers (E _a) consistent with the observed catalytic trend, i.e., E _a: Ti < Hf.

We report the use of DOTA as a chelator for titanium. The resulting complex is fully characterised and in vitro stability studies reveal its high kinetic inertness against transmetallation and transchelation. The radiolabeling of DOTA with ⁴⁵Ti, via a guaiacol-based liquid–liquid extraction method, leads to a high radiochemical conversion up to 98%.

We report the first use of DOTA as a chelator for titanium. The resulting complex is fully characterized and extended to the radiolabelling of DOTA with titanium-45.

Homoleptic tetramethylaluminates Ln(AlMe4)(3) react with KTp(tBu,Me) (Tp(tBu,Me) = tris(3-tBu-5-Me-pyrazolyl)borato) to yield rare-earth-metal methylidene complexes (Tp(tBu,Me))Ln(mu(3)-CH2)[(mu-Me)AlMe2](2) (Ln = La, Ce, Nd). The lanthanum reaction is prone to additional C-H- and B-N-bond activation, affording coproducts La[HB(pz(Me,tBu))(pz(CMe2,Me))(2)][(mu-CH2)(mu-Me)AlMe2](2) and [La(mu-pz(tBu,Me))(AlMe4)(2)](2) (pz(tBu,Me) = 3-tBu-5-Me-pyrazolato). The protonolysis reaction of Ln(AlMe4)(3) and Hpz(tBu,Me) provides more efficient access to [Ln(mu-pz(tBu,Me))(AlMe4)(2)](2) (Ln = La, Nd). Treatment of Ln(AlMe4)(3) with KTp(Me,Me) led to methylidene complexes (Tp(Me,Me))Ln(mu(3)-CH2)[(mu-Me)AlMe2](2) (Ln = Nd, Sm) or bis(tetramethylaluminate) complexes (Tp(Me,Me))Ln(AlMe4)(2) (Ln = Y, Lu). The neodymium reaction generated methine derivative (Tp(Me,Me))Nd[(mu(4)-CH)(AlMe2)(2)(mu-pz(,Me,Me))][(mu-Me)AlMe2] as a minor coproduct. The reaction of Ln(GaMe4)(3) (Ln = Y, La, Ce, Nd, Sm, Ho) with HTp(tBu,Me) gave methylidene complexes (Tp(tBu,Me))Ln(mu(3)-CH2)[(mu-Me)GaMe2](2) (Ln = La, Ce, Nd, Sm) and alkyl complexes (Tp(tBu,Me))LnMe[(mu-Me)GaMe3] (Ln = Y, Ho), while competing B-N bond activation reactions produced GaMe2[BH(Me)(mu-pz(tBu,Me))(2)] and (Tp(tBu,Me))Ln(eta(2)-pz(tBu,Me))[(mu-Me)GaMe3] (Ln = Y, Ho). The steric impact of the Tp(R,Me) ligands was examined by cone angle calculations. Rare-earth-metal methylidene complexes (Tp(tBu,Me))Ln(mu(3)-CH2)[(mu-Me)EMe2](2) (E = Al, Ga) successfully promote carbonyl methylenation reactions upon addition of ketone.

We present the synthesis of a new type of an expanded porphyrinoid macrocycle with a saddle-shaped morphology and its complexation of C60 guest molecules. The new macrocycle contains four carbazole and four triazole moieties and can be readily synthesized via a copper-catalyzed click reaction. It shows specific photo-physical properties including fluorescence with a high quantum yield of 60 %. The combination of the saddle-shaped geometry with the expanded -system allows for host-guest interactions with C60 in a stacked polymer fashion. Evidence for the presence of a host-guest complex is provided both in solution by NMR spectroscopy and in the solid state by X-ray structure analysis.

Intense synchrotron radiation makes time-resolved structural experiments with increasingly finer time sampling possible. On the other hand, radiation heating, radiation-induced volume change and structural disorder become more frequent. Temperature, volume change and disorder are known to be coupled with equilibrium in molecular spin complexes, balancing between two or more spin state configurations. Combining single-crystal diffraction and synchrotron radiation it is illustrated how the radiation damage and associated effects can affect the spin crossover process and may serve as yet another tool to further manipulate the spin crossover properties.