Several families of heteroleptic tetrelenes of general formulae M(E^R^NMe2)[N(SiMe₃)₂] and M(O^E^R^NMe2)[N(SiMe₃)₂] (where E = S, Se; M = Ge, Sn, Pb; R^NMe2 = 2-(Me₂NCH₂)C₆H₄] supported by organochalcogenolato ligands have been prepared and fully characterised. The coordination chemistry of these ligands containing both hard (N, O) and soft (S, Se) atoms onto metals of varying size, polarisability, electropositivity and electrostatic surface potential has been explored. In the molecular solid-state, the complexes M(E^R^NMe2)[N(SiMe₃)₂] are monomeric, although an occurrence of weak Pb⋯Se intermolecular interactions yielding a bimolecular species has been identified in the case of the plumbylene Pb[SeC₆H₄(CH₂NMe₂)-2][N(SiMe₃)₂]. On the other hand, all complexes M(O^E^R^NMe2)[N(SiMe₃)₂] form centro-symmetric bimetallic dimers with O-bridging atoms. Multinuclear (²⁹Si, ⁷⁷Se, ¹¹⁹Sn, ²⁰⁷Pb) NMR spectroscopy and crystallographic studies reveal that the metal preferably remains 3-coordinated in all these heteroleptic complexes with absence of coordination of N and S/Se atoms, unless severe depletion of electronic density onto the metal is enforced. Coordination of these heteroelements can thus be achieved either through replacement of α-CH₃ substituents (as in the ligand 2-(Me₂NCH₂)C₆H₄SeCH₂C(Me)₂O⁻) by electron-withdrawing α-CF₃ moieties (as in the ligand 2-(Me₂NCH₂)C₆H₄SeCH₂C(CF₃)₂O⁻), or else with recourse to the use of a cationizing agent leading to the formation of the ion pair [{2-(Me₂NCH₂)C₆H₄SeCH₂C(Me)₂O}Pb]⁺·[H₂N{B(C₆F₅)₃}₂]⁻ where the cationic metal complex is associated to a weakly-coordinating anion. The data collated herein provide compelling evidence that the coordination chemistry of divalent tetrel elements with ligands featuring both hard and soft donors cannot be reliably anticipated by sole use of general concepts such as the HSAB theory. The related metal complexes containing the rigid 8-(NMe₂)naphthalen-1-yl group are also discussed.

The hypervalent diorganobismuth( iii ) halides of type [RCH ₂ N(CH ₂ C ₆ H ₄ ) ₂ ]BiX, (R = Ph, Bz, and MeO) show a strong tendency to associate either by Bi⋯X or by Bi⋯π arene secondary interactions.

New organoselenium(II) halides of the type [RSe]⁺X⁻ [R = 2,6-(Me₂NCH₂)₂C₆H₃; X = Cl (2), Br (3), I (4)] were prepared by cleavage of the Se–Se bond in R₂Se₂ (1) with SO₂Cl₂ followed by halogen exchange when organoselenium chloride was treated with NaBr or KI. The reaction between 2 and R′₂MCl_n resulted in new ionic [RSe]⁺[R′₂MCl_n+1]⁻ [R′ = 2-(Me₂NCH₂)C₆H₄, n = 1, M = Sb (5), Bi (6); R′ = Ph, M = Sb, n = 1 (7) or n = 3 (8)] species. All new compounds were investigated in solution by multinuclear NMR spectroscopy (¹H, ¹³C, ⁷⁷Se, 2D experiments) and mass spectrometry. The ionic nature of 2 and the antimonates species was confirmed by conductivity studies. The molecular structures of [{2,6-(Me₂NCH₂)₂C₆H₃}Se]⁺Cl⁻·nH₂O (2·H₂O and 2·2H₂O) and [{2,6-(Me₂NCH₂)₂C₆H₃}Se]⁺[Ph₂SbCl₄]⁻ (8), respectively, were established by single-crystal X-ray diffraction, pointing out that the ionic nature of these compounds is also preserved in the solid state, with both nitrogen atoms strongly trans coordinated to the selenium atom of the cation. Theoretical calculations carried out at the DFT level were exploited to investigate the nature of the bonding in compounds 2–4 and the free cation [RSe]⁺ (2a). A topological analysis based on the theory of Atoms-In-Molecules (AIM) and Electron Localization Function (ELF) jointly to a Natural Bond Orbital (NBO) approach was used to shed light on the effect of the nature of the halogen species X on the bonding within the 3c-4e N–Se–N moiety.

Different Pd-complexes containing orthometallated push–pull oxazolones were inserted by supramolecular Pd-amino acid coordination on two genetically engineered modified variants of the thermoalkalophilic Geobacillus thermocatenolatus lipase (GTL). Pd-lipase conjugation was performed on the solid phase in the previously immobilized form of GTL under mild conditions, and soluble conjugated Pd-GTL complexes were obtained by simply desorbing by washing with an acetonitrile aqueous solution. Three different Pd complexes were incorporated into two different genetically modified enzyme variants, one containing all the natural cysteine residues changed to serine residues, and another variant including an additional Cys mutation directly in the catalytic serine (Ser114Cys). The new Pd–enzyme conjugates were fluorescent even at ppm concentrations, while under the same conditions free Pd complexes did not show fluorescence at all. The Pd conjugation with the enzyme extremely increases the catalytic profile of the corresponding Pd complex from 200 to almost 1000-fold in the hydrogenation of arenes in aqueous media, achieving in the case of GTL conjugated with orthopalladated 4a an outstanding TOF value of 27 428 min⁻¹. Also the applicability of GTL-C114 conjugated with orthopalladated 4b in a site-selective C–H activation reaction under mild conditions has been demonstrated. Therefore, the Pd incorporation into the enzyme produces a highly stable conjugate, and improves remarkably the catalytic activity and selectivity, as well as the fluorescence intensity, of the Pd complexes.

Reactions between methyldiphenylphosphane selenide, SePPh₂Me, and different group 11 metal starting materials {CuCl, [CuNO₃(PPh₃)₂], AgOTf, [AgOTf(PPh₃)] (OTf = OSO₂CF₃), [AuCl(tht)], [Au(C₆F₅)(tht)] and [Au(C₆F₅)₃(tht)] (tht = tetrahydrothiophene)} were performed in order to obtain several new species with metal–selenium bonds. The new complexes [CuCl(SePPh₂Me)] (1), [AgOTf(SePPh₂Me)] (2), [AuCl(SePPh₂Me)] (5), [Au(C₆F₅)(SePPh₂Me)] (6) and [Au(C₆F₅)₃(SePPh₂Me)] (7) were isolated and structurally characterized in solution by multinuclear NMR spectroscopy (¹H, ³¹P, ⁷⁷Se and ¹⁹F where appropriate). Solid products were isolated also from the reactions between SePPh₂Me and [CuNO₃(PPh₃)₂] or [AgOTf(PPh₃)], respectively. NMR experiments, including low temperature ¹H and ³¹P NMR, revealed for them a dynamic behaviour in solution, involving the transfer of selenium from PPh₂Me to PPh₃. In case of the isolated silver(I) containing solid an equilibrium between, respectively, monomeric [AgOTf(PPh₃)(SePPh₂Me)] (3) and [AgOTf(PPh₂Me)(SePPh₃)] (4), and dimeric [Ag(PPh₃)(μ-SePPh₂Me)]₂(OTf)₂ (3a) and [Ag(PPh₂Me)(μ-SePPh₃)]₂(OTf)₂ (4a) species was observed in solution. In case of the isolated copper(I) containing solid the NMR studies brought no clear evidence for a similar behaviour, but it can not be excluded in a first stage of the reaction. However the transfer of selenium between the two triorganophosphanes takes place also in this case, but the NMR spectra suggest that the final reaction mixture contains the free triorganophospane selenides SePPh₂Me and SePPh₃ as well as the complex species [CuNO₃(PPh₃)₂], [CuNO₃(PPh₂Me)₂] and [CuNO₃(PPh₃)(PPh₂Me)] in equilibrium. Single-crystal X-ray diffraction studies revealed monomeric structures for the gold(I) 6 and gold(III) 7 complexes. In case of compound 6 weak aurophilic gold(I)gold(I) contacts were also observed in the crystal. DFT calculations were performed in order to understand the solution behaviour of the silver(I) and copper(I) species containing both P(III) and P(V) ligands, to verify the stability of possible dimeric species and to account for the aurophilic interactions found for 6. In addition, the nature of the electronic transitions involved in the absorption/emission processes observed for 6 and 7 in the solid state were also investigated by means of TD-DFT calculations.