M. Albrecht et al., Transmetalation reactions with nitrogen-containing "pincer"-class ligands on platinum(II) centers, CAN J CHEM, 79(5), 2001, pp. 709-718
Citations number
62
Categorie Soggetti
Chemistry
Journal title
CANADIAN JOURNAL OF CHEMISTRY-REVUE CANADIENNE DE CHIMIE
The transmetalation reaction of the aryllithium compound [Li(NCN)](2) (NCN
is the monoanionic "pincer" ligand [C6H3(CH2NMe2)(2)-2,6](-)) with the cycl
ometalated arylplatinum complex [PtCl(NCN)] afforded the bisaryl platinum(I
I) complex [Pt(NCN)(2)] (3) containing one eta (3)-N,C,N-terdentate and the
other eta (1)-C-monodentate-bonded pincer ligand. Spectroscopic analyses o
n 3 suggest that eta (3) to eta (1) interconversion of the ligand binding m
ode (or vice versa) is inhibited. Two independent X-ray structure determina
tions on crystals of 3 revealed the existence of a rare polymorph containin
g one and three crystallographically independent molecules, respectively, i
n the unit cell. A similar transmetalation reaction with lithium and platin
um complexes containing heteroleptic NCNRR' ligands (NCNRR' is [C6H3(CH2NRR
')-2,6](-) with R = R' = Me or R = Me, R' = Et) pointed to the formation of
a heterodinuclear cationic bisaryl platinum lithium species as an intermed
iate of a preequilibrium to the final transmetalation products, involving,
rapid transcyclometalation (TCM) reactions. These TCM reactions comprise th
e exchange of the monoanionic NCNRR' ligands between the platinum(II) and l
ithium centers. A consequence of the latter properties is that the strong P
t-N bonds in [PtX(NCN)] complexes are considerably weakened by the presence
of Li+ cations.