SYNTHESIS, CHEMICAL AND ELECTROCHEMICAL DEPROTONATION REACTIONS OF AMINOCARBENE COMPLEXES OF PALLADIUM(II) AND PLATINUM(II) - X-RAY STRUCTURE OF ((PPH3)CLPT[MU-COCH2CH2N-C,N])2

The diaminocarbene complexes cis-Cl2(PPh3)Pt[activated CN(Bu(t))CH2CH2NH] (1) and cis-Cl2Pt[activated CN(C6H4-p-OMe)CH2CH2NH]2 (2) have been prepared by reaction of the corresponding isocyanide derivatives with aziridine/ClCH2CH2NH3+Cl- and aziridine alone, respectively. The aminooxycarbene complex cis-Cl2Pt[activated CN(C6H4-p-OMe)CH2CH2O]2 (3) has been prepared by reaction of the bis-isocyanide derivative with 2-chloroethanol/n-BuLi. The dimeric complexes {(PPh3)BrPd[mu- activated CN(Me)CH2CH2N-C,N]}2 (4), {(PPh3)ClPd[mu- activated CN(C6H4-p-OMe)CH2CH2N-C,N]}2 (5), {(PPh3)ClPt[mu- activated CN(C6H4-p-OMe)CH2CH2N-C,N]}2 (6) have been prepared by deprotonation reaction of the NH group of the corresponding mononuclear derivatives with n-BuLi. The X-ray structure of {(PPh3)ClPt[mu- activated COCH2CH2N-C,N]}2 (7) is reported. The structural model was refined to R = 0.055 (R(w) = 0.061) for 7442 independent reflections. Crystal data: triclinic, space group P1BAR, a = 19.564(3), b = 16.497(3), c = 13.243(2) angstrom, alpha = 88.93(3), beta = 97.88(3), gamma = 91.97(3)-degrees, Z = 4. The crystal contains two crystallographically independent dimer units and a disordered dichloroethane molecule. Each dimer is formed by two bridging carbene ligands which are coordinated to one platinum on one side via a Pt-N bond and to the second platinum via a Pt-C bond. The coordination geometry around each platinum atom is an irregular square with deviations in the tetrahedral direction of the bonded atoms. The anodic behaviour of these and related monocarbene, dicarbene or dinuclear dicarbene complexes has been studied by cyclic voltammetry and controlled potential electrolysis in aprotic media and shown to present irreversible oxidation waves commonly with a multi-electron character (up to four electrons) and involving liberation of protons (in a number similar to that of the transfered electrons) conceivably resulting from anodically induced N-H or C-H bond cleavage, the former at an amino group and the latter occurring at methylene groups activated by adjacent amino- or oxy-carbene moieties.