Formation of large chelate rings from NNN′N′-tetramethyl-pentane-1,5-diamine, -heptane-1,7-diamine, and -decane-1,10-diamine and bis(benzonitrile)dichloropalladium(II): crystal structures of di-µ-(NNN′N′-tetramethylpentane-1,5-diamine-NN′)- and di-µ-(NNN′N′-tetramethyl-heptane-1,7-diamine-NN′)-bis[dichloropalladium(II)]–benzene (1/1) containing sixteen- and twenty-atom rings respectively

Abstract

Treatment of [PdCl₂(NCPh)₂] with Me₂N[CH₂]_nNMe₂(n= 5, 7, or 10) gives binuclear complexes trans-[Pd₂Cl₄{Me₂N(CH₂)_nNMe₂}₂] in good yield. The crystal structures of the 16-atom ring (n= 5) and 20-atom ring (n= 7) complexes were determined from 2577 and 1154 diffractometer data, respectively, and were refined to R of 0.034 and 0.057, respectively. They are compared with the structures of trans-[Pd₂Cl₄{Bu^t₂P(CH₂)_nPBu^t₂}₂](n= 5 or 7). The rings in the amine complexes adopt an elongated-chair (‘sofa’) conformation whilst those of the phosphine complexes have an elongated-boat (‘barge’) conformation. Factors affecting the conformations and stabilities of these large chelate rings are discussed. Crystal data are: [Pd₂Cl₄{Me₂N(CH₂)₅NMe₂}₂]·C₆H₆, space group P, Z= 1, a= 8.425(2), b= 12.624(2), c= 8.217(2)Åα= 105.16(2), β= 98.12(2), γ= 71.83(2)°; [Pd₂Cl₄{Me₂N(CH₂)₇NMe₂}₂]·C₆H₆, space group Cmca, Z= 4, a= 29.387(4), b= 8.030(2), c= 15.177(3)Å.