SYNTHESIS AND REACTIONS OF NOVEL DIPALLADIUM(II) COMPLEXES OF THE TYPE [(PD[PPH2CH=C(R)-N-N=C(R)CHPPH2])(2)] (R=BU-T OR PH) - CRYSTAL-STRUCTURE OF THE TERT-BUTYL COMPLEX CONTAINING 2 PD-C BONDS AND 5 FUSED CHELATE RINGS

Treatment of the neutral chloropalladium(II) complexes [PdCl{PPh2CH=C( R)-N-N=C(R)CH2PPh2}] (R = Bu-t 1a or Ph 1b) with two equivalents of Li [N(SiMe3)(2)] gave the novel dipalladium(II) complexes [{Pd[PPh2CH=C(R )-N-N=C(R)CHPPh2]}(2)] (R = Bu-t 2a or Ph 2b) containing two palladium -carbon bonds, five fused chelate rings and enamine type (C=C-N) moiet ies. Treatment of the chloroplatinum(lr) complex. [PtCl{PPh2CH=C(Bu-t) -N-N=C(Bu-t)CH2PPh2}] Ic with an excess of KOBut in dimethyl sulfoxide (dmso) gave what was probably the species [Pt{PPh2CH=C(Bu-t)-N-N=C(Bu -t)CHPPh2}(dmso)] 3 containing both a coordinated and an unco-ordinate d phosphine. The dipalladium(II) complex 2a or 2b underwent electrophi lic attack at the enamine carbon with acids (HX) to give salts of type [{Pd[PPh2CH2C(R)=N-N=C(R)CHPPh2]}(2)]X-2 4 (R = Bu-t or Ph, X = trifl uoroacetate, chloride or picrate); these, when treated with sodium met hoxide, deprotonated at the methylene carbon to give the neutral compl ex 2a or 2b. Treatment of 2a with less than 2 equivalents of trifluoro acetic acid gave the monoprotonated complex CHPPh2}{PPh2CH2C(Bu-t)=N-N =C(Bu-t)CHPPh2}][O2CCF3] 5a, mixed with 2a and 4a. Complex 2a with Br- 2 or Mel underwent attack at the enamine carbon C=C-N to give the corr esponding bromo or methyl derivatives [{Pd[PPh2CH(R)CBut=N-N=C(Bu-t)CH PPh2]}(2)]X-2 (R = Pr X = Pr 6a; R = Me, X = I 6b) respectively. When the methyl-substituted salt was treated with KOBut it gave the neutral dipalladium(lr) complex [{PdCl[PPh2C(Me)=C(Bu-t)-N-N=C(Bu-t)CHPPh2]}( 2)] 7. The crystal structure of 2a was determined.