The exceptional stereoselectivity of coordination (RS
isomer favored) of the prochiral olefinic alcohol 2-methyl-3-buten-2-ol in
cis(N,olefin)-chloro(2-methyl-3-buten-2-ol)(sarcosinato)platinum(II),
1, prompted this investigation
of the effect of olefin structure on the equilibrium constant for
platinum binding (K
d) and on the
stereoselectivity
of coordination, as measured by K
i =
[RR]/[RS], for 32 other monosubstituted
ethylenes with the same chiral
template. The only other olefins which show significant preference
for the RS diastereomer (K
i < 0.5)
contain
hydrogen-bond acceptor atoms in close proximity to the N−H proton of
the coordinated olefin which is cis to
that nitrogen. Increasing the distance between the N−H proton
and the proton acceptor atom by one C−C link
has a dramatic effect on K
i. Almost no
correlation was found between K
d and
K
i, but a significant correlation
between the formation constant, K
f, for
formation of PtCl3(olefin)- species of 14 of
the olefins and the 195Pt
chemical shift suggested a way to separate electronic effects from
steric and hydrogen-bonding effects on the
relative stabilities of the mixed olefin−amino acid complexes.
Deviations from a simple correlation between log
K
d and log K
f are
discussed in terms of this model, but a clean separation of electronic
effects from other effects
cannot be claimed.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.