DEPROTONATION AND PROTONATION REACTIONS OF SOME DIAMINOCARBENE COMPLEXES OF PD(II) AND PT(II) AND THEIR REDOX PROPERTIES

Treatment of the diaminocarbene complexes cis-[MCl2{CN(H)CH2CH2NR} (PP h3)] (1, M = Pd or Pt, R = C6H4OMe-4) with NaN3 or PPh3 (in the presen ce of AgBF4), forms the azide compounds [M(N3)nCl2-n{CN(H)CH2CH2N } (P PH3)] (2, M = Pd or Pt, n = 1 or 2) or trans-[MCl{CN(H)CH2CH2NR)(PPh3) 2] [BF4] (3), respectively. Deprotonation of the aminocarbene ligand i n (1) occurs by reaction with K/Na (in the presence of PPh3) to give t he imino-complexes trans-[MCl(C=NCH2CH2NR)(PPh3)2] (4) which, upon fur ther reduction, form zero-valent metal phosphine products (also obtain ed by reaction of (1) with LiBu(n) in the presence of PPh3), whereas, by treatment with HBF4, generate (3). Complexes (1) and (2) are also p rotonated by HBF4 to give the corresponding acid adducts in which the site of proton addition has not been clearly established; they are dep rotonated by base to form the known dinuclear species [{MCl(CNCH2CH2NR ) (PPh3)}2]. By cyclic voltammetry at a Pt electrode, in 0.2 M [NBu4n] [BF4]/NCMe, complexes (3) undergo a partially reversible oxidation at E1/2ox ca 1.5 V vs SCE, whereas the species derived from protonation o f (1) exhibits an irreversible anodic wave at E(p)ox ca 1.6 V. The imi ne complexes (4) are oxidized irreversibly at a much lower potential ( ca 0.8 V). Other anodic waves are usually observed at higher potential s and compounds (3) also present irreversible cathodic waves at potent ials below -1.3 V.