Novel Weakly-Bonded Complexes Constructed With Tellurium Or First Subgroup Metal Compounds

In this thesis,by menas of theoretical calculations,novel weakly-bonded complexes constructed with tellurium/first subgroup metal compounds have been studied.There are four parts,where the structures,strengthes,properties,and nature of these complexes are highlighted.The main contents areas follows:The halogen-bonded complexes between H₂Te/Me₂Te and the dihalogen molecules XY(XY=F₂,Cl₂,Br₂,I₂,Cl F,Cl Br,Br F,Br Cl,Br I,IF,ICl,IBr)have been studied to investigate the dependence of its strength and nature on the halogen donor X and its adjoining atom Y,as well as the methyl groups in the electron donor.The interaction energy varies between-1.7 and-43.5 kcal/mol,indicating that the Te atom in H₂Te/Me₂Te has a strong affinity for the dihalogen molecules.For the H₂Te-XY complex,the halogen bond is stronger for the heavier halogen donor X atom and the strong electron-withdrawing group Y.However,for Me₂Te-XY,the halogen bond is stronger for the lighter halogen donor X atom.The H₂Te/Me₂Te-F₂complex has the largest interaction energy,although the?-hole on F₂is the smallest in magnitude.In most of the complexes,the electrostatic and polarization contributions to the binding strength are similar in magnitude.However,for H₂Te/Me₂Te-F₂,the polarization contribution is much larger than the electrostatic contribution,with a significant contribution from charge transfer.The triel bond between the?-hole on the triel atom of TrR₃(Tr=B,Al,Ga;R=H,F,Cl,Br)and a lone pair on the Te atom of H₂Te is examined using ab initio methods.For Tr=B,the triel bond is weakened as the R substituent becomes more electronegative,while the opposite pattern is noted for Al and Ga.The weakest triel bond of all occurs in H₂Te-BF₃(-2.9 kcal/mol)but is much stronger for all the other complexes(>-11 kcal/mol).The placement of electron-releasing OH,NH₂,and CH₃R'substituents on the R'₂Te base strengthens the triel bond,whereas the opposite occurs for the electron-withdrawing CN.Despite its high electronegativity,the F substituent causes a strengthening of the interaction,which is due in large part to the formation of secondary chalcogen bonds that involve the?-holes on Te in F₂Te.However,the F atom on Tr F₃is unable to act as an electron donorin thesechalcogen bonds,leading toweakened F₂Te···Tr F₃interactions.A regium bond has been predicted and characterized in the complexes of[1.1.1]propellane(P)and M₂/MCl/MCH₃(M=Cu,Ag,and Au).The interaction energy varies between-16 and-47kcal/mol,indicating that the bridgehead carbon atom of P has a good affinity for the regium atom.The regium bond becomes stronger in the Ag<Cu<Au sequence.Relative to M₂,both MCl and MCH₃engage in a stronger regium bond,both-Cl and-CH₃groups showing an electron-withdrawing property.The formation of regium bonding is mainly attributed to the donation orbital interactions from the occupied C-C orbital into the empty metal orbitals and a back-donation from the occupied d orbital of metal into the empty C-C anti-bonding orbital.In most complexes,the regium bond is dominated by electrostatic interaction,with moderate contribution of polarization.When P binds simultaneously with two regium donors,negative cooperativity is found.Moreover,this cooperativity is prominent for thestronger regiumbond.The various sorts of complexes in which HArF and AuX(X=F,Cl,Br,I)can engage are probed by MP2/aug-cc-p VTZ calculations.The most weakly bound are those containing a halogen bond(XB)of the AuX···FAr H sort,with binding energies less than-8 kcal/mol.H-bonded dimers FAr H···XAu are a little stronger,held together by some-12 kcal/mol.Being the most strongly bound places the F atom of HArF roughly midway between Ar and Au in an F shaped structure,bound by some-43?-54 kcal/mol.The last sort of product involves atomic rearrangements wherein the H atom migrates from Ar to Au,followed by formation of a covalent H-Au bond.The resulting molecular unit is stabilized by-30?-40 kcal/mol relative to the original HArF and AuX reactants.The H-bonded dimers are held together by an unusually large polarization component,surpassing electrostatic attraction,while dispersion predominates for the halogen bonds.Perturbations of the geometries and stretching frequencies offer a ready means of distinguishing the different types of complexes by spectroscopic techniques.