Meta and para metallation of EPh4+ (E = P, As) and N(PPh3)2+ by the dinuclear acylanion [Re2(μ-H)(μ-PCy2)(CO)7ax-(C(Ph)O)]-.: Formation of zwitterionic cluster complexes Re2(μ-H)(μ-PCy2)(CO)7(x-C6H4EPh3) (E = P, As; x = m, p) and Re2(μ-H)(μ-PCy2)(CO)7(x-C6H4PPh2NPPh3)

On treating the dirhenium salt Li[Re-2(mu-H)(mu-PCy2)(CO)(7)ax-(C(Ph)O)] (Li(1)) with EPh4Cl (E = P, As) or N(PPh3)(2)Cl, respectively, in THF at room temperature, metathesis of the cations occurs to give the intermediates EPh4[Re-2(mu-H)(mu-PCy2)(CO)(7)ax-(C(Ph)O)] (EPh4(1)) or N(PPh3)(2)[Re-2(mu-H)(mu-PCy2)(CO)(7)ax-(C(Ph)O)] (N(PPh2)(2)(1)). PPh4(1) was isolated and its X-ray structure was determined. Upon stirring these intermediates in THF solution at 20 degrees C for 2 days, benzaldehyde (PhCHO) is eliminated and the para and meta metallated products Re-2(mu-H)(mu-PCy2)(CO)(7)(x-C6H4EPh3) (E = P, x = m: 2a, x = p: 2b; As, x = m: 3a,x = p: 3b) and Re-2(mu-H)(mu-PCy2)(CO)(7)(x-C6H4PPh2NPPh3) (x = m: 4a, x = p: 4b) are formed by C-H oxidative addition. Heating to 45 degrees C shortens the reaction time to 4 h. The products are zwitterionic, consisting of a negatively charged dirhenium unit and a positively charged phosphonium, arsonium or bistriphenylphosphine iminium ligand, respectively, bound to one of the rhenium atoms. In each case, the m- and p-isomers could be separated by PLC. Moreover, 2b was crystallized from a benzene solution and its molecular structure was confirmed by X-ray analysis. The above sequence of reactions was repeated with d(20)-PPh4Br. It reacts completely analogous to give the deuterated products Re-2(mu-D)(mu-PCy2)(CO)(7)(x-C6D4(d(15)-EPh3)) (E = P, x = m: d(20)-2a, x = p: d(20)-2b). Hence, the mu-H and mu-D ligands, respectively, of the new compounds originate from the corresponding aromatic cation. The reaction of Li(1) with SbPh4Br proceeds completely different. PhCHO is eliminated again, but no metallated products were found. Only the decomposition product Re-2(mu-Br)(mu-PCy2)(CO)(7)(eq-SbPh3) (5) was isolated in 19% yield. (C) 1999 Elsevier Science S.A. All rights reserved.