Two-, three-, and four-coordination at gold(I) supported by the bidentate selenium ligand [PH2P(Se)NP(Se)PH2]-

Article abstract of DOI:10.1021/ic010337h

Treatment of the gold(I) halide complexes LAuCl (L = PMe₃, PPh₃, CNC₆H₃Me₂-2,6) with K[Ph₂P(Se)NP(Se)Ph₂] provides the gold-selenium coordination compounds [{N(Ph₂PSe)₂-Se,Se′}AuL]. However, on standing for a number of days, the complex [{N(Ph₂PSe)₂-Se,Se′}AuPMe₃] gains a phosphine to provide the bis(phosphine) species [{N(Ph₂PSe)₂-Se,Se′}Au(PMe₃) ₂]. Treatment of the K[Ph₂P(Se)NP(Se)Ph₂] ligand with [(Ph₃PAu)₃O]BF₄ allows the isolation of [{N(Ph₂PSe)₂-Se,Se′}(AuPPh₃)2]BF ₄. Reaction of the complex [(dppm)(AuCl)₂] with AgSO₃CF₃ followed by addition of the ligand K[Ph₂P(Se)NP(Se)Ph₂] results in the formation of [{N(Ph₂PSe)₂Se,Se′}Au₂(dppm)]OSO ₂CF₃ and treatment of [(tht)AuCl] (tht= tetrahydrothiophene) with an equimolar quantity of K[Ph₂P(Se)NP(Se)Ph₂] affords the complex [{N(Ph₂PSe)₂-Se,Se′}₂Au₂]. The compounds [{N(Ph₂PSe)₂-Se,Se′} Au₂(dppm)]OSO₂CF₃, [{N(Ph₂PSe)₂-Se,Se′} AuPPh₃] and [{N(Ph₂PSe)₂-Se,Se′ Au(PMe₃)₂ have been investigated crystallographically. The results reveal that the metal centers are two-, three-, and four-coordinate, respectively. The cationic, eight-membered ring complex bearing the dppm ligand displays transannular aurophilic bonding and is further associated into dimers via intermolecular gold-selenium contacts. The six-membered rings in the other two structures have C₂-symmetrical twist conformations, however, the Au(I) coordination sphere in [N(PPh₂Se)₂]AuPPh₃ is not fully symmetrical. The Au-Se bond lengths increase dramatically as the coordination number of the metal atom becomes larger.