Gabriela Nemes

Chalcogeno[bis(phosphaalkenyl)] germanium and tin compounds.

The first diphosphaalkenylstannylene stabilized through complexation with a carbene NHC-Sn[C(Cl)═PMes*](2)1 (Mes* = 2,4,6-tri-tert-butylphenyl; NHC = :C{N(iPr)C(Me)}(2)) was isolated and fully characterized including single crystal X-ray diffraction analysis. Its reaction with elemental sulfur rapidly gives the cyclic Sn(2)S(2) (dithiadistannetanne) derivative 3, presumably formed by dimerization of a stannathione intermediate. By contrast, its germanium analogue NHC-Ge[C(Cl)═PMes*](2)7 leads to the corresponding monomeric germathione 4 and germaselenone 5. The germaselenone was more stable than the germathione and could be structurally characterized. An unusual thermal cyclization reaction of the last one occurs with an excess of selenium to give the Ge(2)Se(3) (triselenadigermolane) ring derivative 6.

Bridging a Knowledge Gap from Siloxanes to Germoxanes and Stannoxanes. A Theoretical Natural Bond Orbital Study

Explaining the nature of the E-O chemical bond (E = Si, Ge, Sn) has been a great challenge for theoretical chemists during the last decades. Among the large number of models used for this purpose, the one based on hyperconjugative interactions sheds more light on the nature of chemical bonding in siloxanes. Starting from this concept, this study aimed to evaluate the impact of siloxane type hyperconjugative effects on the structural features of germoxanic and stannoxanic species and in addition to assess if p-d-like back-bonding interactions can also play important roles in determining the particular structures of these heavier analogues of ethers. Natural bond orbital deletion (NBO DEL) optimizations, carried out at the DFT level of theory, revealed that hyperconjugative effects dictate to a large extent the structural behavior of these species. Furthermore, this study points out that p-d back-bonding interactions also influence the equilibrium geometry of these species, although acting as a secondary electronic effect within the E-O-E moieties (E = Si, Ge, Sn).

Bis‐Sulfonyl O,C,O‐Chelated Metallylenes (Ge, Sn) as Adjustable Ligands for Iron and Tungsten Complexes

The synthesis and characterization of an E2 CE2 bis-sulfonyl aryl pincer ligand and its efficiency for the stabilization of compounds containing low-valent Group 14 elements (Ge and Sn) are reported. Complexation reaction of these metallylenes with iron or tungsten complexes resulted in the modulation of the oxygen atoms of the sulfonyl groups implicated in the stabilization of the Group 14 elements, demonstrating the original adjustable character of the bis-sulfonyl O2 S-C-SO2 aryl pincer.

An insight into the structure of model germaphosphaallenes

The geometries of all possible isomers of the model compound H2Ge=C=PH were optimized at the B3LYP/6-31G(d,p) level of the theory. The calculation were repeated at higher correlated methods with similar results and for the the isomers of the methyl-substituted phosphagermaallene MeP=C=GeMe2. As another way to stabilise the P=C=Ge unit consists in the use electronic effects, a NBO study was carried out in order to identify the influence that the nature (electropositive or electronegative) of several substituents would have on the strength of the C=Ge bond. Model compounds HP=C=GeR2 and HP=C=GeRR′ were investigated (R = BH2, CH3, SiH3, NH2, OMe, F; R′ = H). It was found that the main interaction contributing to the weakening of the C=Ge bond is a transfer of electron density from the lone pair of the phosphorus atom to the molecular antibonding orbital localized on the Ge–C bond.

Theoretical Investigation on the PCP(O) Linear Moiety: How to Stabilize Diphosphaallenic Derivatives

Abstract Density functional theory calculations on phosphavinylidene(oxo)phosphorane RP˭C˭P(˭O)R′ I are reported, where the R and R′ groups represent substituents with various electron-donor or electron-acceptor properties and different steric hindrance: H, F, Cl, OMe, SiH3, SiMe3, Me, Ph, Mes (2,4,6-trimethylphenyl), and Mes* (2,4,6-tri-tert-butylphenyl) and RF 2,4,6-tris(trifluoromethyl)-phenyl. The investigations provide information about the groups that seem to be the best choice for the stabilization of such systems. The influence of the substituents’ nature on the geometrical parameters and Wiberg bond orders for the P‒C bonds are discussed. Two isomers of I with a PCPO linkage (P≡C‒P(˭O)RR′ II and O˭P‒C≡PRR′ III) have also been studied. GRAPHICAL ABSTRACT