Abp. Lever et Si. Gorelsky, Comparison of o-benzoquinonediimine with bipyridine and bipyrazine in electronic coupling to ruthenium(II), as a function of spectator ligand, COORD CH RE, 208, 2000, pp. 153-167
When comparing [Ru(LL)(3)](2+) with [Ru(NH3)(4)(LL)](2+), the question is r
aised whether the replacement of the relatively poor LL (LL = 2,2'-bipyridi
ne, 2,2'-bipyrazine or o-benzoquinonediimine) pi-acceptor and sigma-electro
n ligands by the o-electron rich ammonia ligands permits a significant impr
ovement in coupling/pi-back donation to the remaining LL. Using a ZINDO ana
lysis of the electronic structures of these species, it is shown that 2,2'-
bipyridine is unable to accept the extra electron density from the rutheniu
m center, while o-benzoquinonediimine can readily do so. The ligand 2,2'-bi
pyrazine is slightly more able to accept the electron density than 2,2'-bip
yridine, (C) 2000 Elsevier Science S.A. All rights reserved.