Design And Synthesis Of Novel Boron?Germanium Complexes

Many main-group element ?-diketiminate complexes with novel structural features are one of the research hot topic of p-block synthetic field.Our group have synthesized a constitutionally stable ?-diketiminato ligand 4,[PhC(PhCNDip)2H;Dip=2,6-Pr2C6H3],where the carbon skeleton does not contain active hydrogen,and synthesized a ?-diketiminato germylene chloride 6,[PhC(PhCNDip)2GeCl],based on ligand 4.In the latest research,by different reaction paths on 6,a new germanium(?)radical 7[PhC·(PhCNDip)2Ge],?-diketiminato germylene 8[PhCH(PhCNDip)2Ge],?-diketiminato germylene azide 9[PhC(PhCNDip)2GeN3]have been synthesized.Their molecular structures were characterized by X-ray single crystal diffraction and nuclear magnetic resonance.The six-membered C3N2Ge ring in 7 is not perfectly planar.DFT calculations were performed on compound 7 for the explanation of frontier molecular orbitals and their electron occupation.The SOMO(singly occupied molecular orbital)of 7,corresponding to the LUMO,mainly consists of ?-antibonding orbital between the N and C atoms.Ge(II)atom bonds with two nitrogen atoms,much like the feature of a N-heterocyclic carbene.The slightly positive NICS value illustrates that the six-membered C3N2Ge ring containing 7? unsaturated electrons is nonaromatic.The six-membered C3N2Ge ring of compound 8 is approximate to the plane.That of compound 9 is not plane,in which the Ge atom is apparently folded to the outer ring,and the three nitrogen atoms connected to the Ge are in a linear structure.Through the reaction of Grignard reagent C6F5MgBr with BF3·Et2O,(C6F5)2BF have been prepared and trimerized to transparent crystal[(C6F5)2BF]3(14),which have been successful characterized.Compound 14 is the first case of B3F3 six membered boron complexes containing B-F-B fluorine bridge bond.The B-F-B bond show the homogenization of chemical bond,in which a pair of electrons of fluorine form the coordination bond with boron,and one electron of fluorine form the covalent bond with boron.And there is no conjugated unsaturated bond.The B3F3 six-membered ring is twisted in the molecule due to the sp3 hybridization of boron atoms.This work efficiently synthesized a new ?-diketiminato gemanium(?)radical 7.EPR measurements and theoretical calculations have verified that 7 is essentially a two-coordinated germylene with an N-heterocyclic radical ligand and the unpaired electrons mainly distribute on the NC3N backbone.The gram-scale synthesis of radical 7 and ?/?-donor character of active Ge centre could provide a novel coordination feature to transition metals.