Reactions of unisolable homoleptic aryls of niobium and tantalum with PMe<sub>2</sub>Ph and Bu<sup>t</sup>NC. Crystal structures of M(2,5-Me<sub>2</sub>C<sub>6</sub>H<sub>3</sub>)<sub>2</sub>(η<sup>2</sup>-2,5-Me<sub>2</sub>C<sub>6</sub>H<sub>2</sub>)(PMe<sub>2</sub>Ph)<sub>2</sub>, M = Nb or Ta, and Ta(η<sup>2</sup>-PhCNBu<sup>t</sup>)(η<sup>2</sup>-Ph<sub>2</sub>CNBu<sup>t</sup>)<sub>2</sub>(CNBu<sup>t</sup>)
                                
                                    
                                        作者:Stefan U. Koschmieder、Bilquis Hussain-Bates、Michael B. Hursthouse、Geoffrey Wilkinson                                    
                                    
                                        DOI:10.1039/dt9910002785
                                    
                                    
                                        日期:——
                                    
                                    The tetraaryls, MR4, M = Nb or Ta, R = 2-MeC6H4 or 2,5-Me2C6H3, made in situ by interaction of MCl4 and LiR or MgRBr react with PMe2Ph to give the eta-2-aryne compounds MR2(eta-2-aryne) (PMe2Ph)2.  From the reaction of TaCl5 and LiPh in Et2O in the presence of PMe3 the similar tantalum(IV) benzyne, TaPh2(eta-2-C6H4) (PMe3)2, is obtained.  Interaction of a green solution probably of TaPh5 with Bu(t)NC produces the tantalum(V) compound, Ta(PhCNBu(t)) (Ph2CNBu(t))2(CNBu(t)), via multiple insertion reactions of Bu(t)NC into the Ta-C bonds.  The X-ray structures of M(2,5-Me2C6H3)2(eta-2-2,5-Me2C6H2) (PMe2Ph)2 (M = Nb or Ta) and Ta(eta-2-PhCNBu(t)) (eta-2-Ph2CNBu(t)) (CNBu(t)) have been determined.  The isostructural arynes can be regarded as having a square-pyramidal structure with the C-C aryne bond occupying the axial site.  The tantalum(V) compound contains one eta-2-iminoacyl and two eta-2-imine ligands.