Activation of a coordinated alkyne by electron transfer: crystal structures of [Pd{PPh2CH = C(Bu-t)NN = C(Bu-t)CH2PPh2}-{C(CO2Me)= CH(CO2Me)}] and [Pd{(Z,Z)PPh2CH2C(Bu-t)= NN = C(Bu-t)CH2PPh2}-{C(CO2Me) C(CO2Me)}]

摘要

A new zerovalent complex [Pd{PPH2CH2C(Bu ')double bond NN double bond C(Bu ')CH2PPh2}{C(CO2Me)drop C(CO2Me)}] (1) was prepared and its crystal structure was determined by X-ray diffraction analysis, which shows it crystallises in the C2/C monoclinic space group with a = 10.930(1) Angstrom, b = 22.086(1) Angstrom, c = 19.042(2) Angstrom and beta = 92.692(9)degrees. The azine diphosphine ligand chelates the metal in a (Z,Z) configuration with a P-Pd-P bite angle of 114.63(4)degrees. The alkyne carbon atoms lie essentially in the P-Pd-P plane. The electrochemical reduction of 1 promoted the conversion of the alkyne ligand to a vinyl species, and of the azine diphosphine to ene-hydrazone diphosphine, with formation of [Pd{PPh2CH double bond C(Bu ')NN double bond C(Bu ')CH2PPh2}{C(CO2Me)double bond CH(CO2Me)}] (2). X-ray diffraction analysis of complex 2 shows it crystallises in the triclinic space group with a =11.302(1) Angstrom, b=12.528(1) Angstrom, c = 16.028(2) Angstrom, alpha = 107.64(2)degrees, beta = 92.27(1)degrees and gamma = 111.79(2)degrees. It displays a square-planar geometry with the two phosphorus atoms in trans position. Extended Huckel MO calculations were performed in order to elucidate the redox process. (C) 2000 Elsevier Science S.A. All rights reserved. [References: 16]