The reactions of
RuCl2(PPh3)3 with a number of
diazoalkanes were surveyed, and alkylidene transfer to
give RuCl2(CHR)(PPh3)2
(R = Me (1), Et (2)) and
RuCl2(CH-p-C6H4X)(PPh3)2
(X = H (3), NMe2 (4),
OMe
(5), Me (6), F (7), Cl (8),
NO2 (9)) was observed for alkyl diazoalkanes
RCHN2 and various para-substituted
aryl
diazoalkanes
p-C6H4XCHN2.
Kinetic studies on the living ring-opening metathesis
polymerization (ROMP) of
norbornene using complexes 3−9 as catalysts
have shown that initiation is in all cases faster than propagation
(k
i/k
p
= 9 for 3) and that the electronic effect of X on the
metathesis activity of 3−9 is relatively small.
Phosphine
exchange in 3−9 with tricyclohexylphosphine
leads to
RuCl2(CH-p-C6H4X)(PCy3)2
10−16, which are efficient
catalysts for ROMP of cyclooctene (PDI = 1.51−1.63) and
1,5-cyclooctadiene (PDI = 1.56−1.67). The crystal
structure of
RuCl2(CH-p-C6H4Cl)(PCy3)2
(15) indicated a distorted square-pyramidal geometry, in
which the two
phosphines are trans to each other, and the alkylidene unit
lies in the Cl−Ru−Cl plane. The benzylidenes
RuCl2(CHPh)(PR3)2 (R = Cy (cyclohexyl)
(10), Cp (cyclopentyl) (17), i-Pr
(18)) are quantitatively available via
one-pot
synthesis with RuCl2(PPh3)3,
PhCHN2, and PR3 as reaction components.
10 is an efficient catalyst for metathesis
of
acyclic olefins: On reaction with excess ethylene, the methylidene
complex
RuCl2(CH2)(PCy3)2
(19) is formed
quantitatively, and various alkylidene compounds
RuCl2(CHR)(PCy3)3 (R
= Me (20), Et (21), n-Bu
(22)) are
isolated as the kinetic products from the reaction of 10
with an excess of the corresponding terminal or
disubstituted
olefins. Metathesis of conjugated and cumulated olefins with
10 results in the formation of vinylalkylidene
and
vinylidene complexes, as shown by the synthesis of
RuCl2(CHCHCH2)(PCy3)2
(23) and
RuCl2(CCH2)(PCy3)2
(24) from 1,3-butadiene or 1,2-propadiene, respectively.
Also, functional groups such as −OAc, −Cl, and
−OH
can be introduced into the alkylidene moiety via cross
metathesis with the appropriate alkene.