The reactivity of
Cp2(THF)ZrN-t-Bu (1a) toward a
series of organic and metal carbonyl complexes has
been examined. The ZrN linkage of 1a undergoes
imido/oxo exchange reactions with the carbonyl compounds
and generates three different types of oxozirconocene products:
(Cp2ZrO)
n
(3),
(Cp2Zr)2(μ-O)(μ-N-t-Bu)
(9), and
(Cp2Zr)2O3CCPh2
(12) were obtained from the reactions of 1a with
RR‘CO (R = R‘ = Me (2b); R = Ph, R‘ =
H
(2c); R = i-Pr, R‘ = H (2d)),
CpCo(CO)2 (7), and Ph2CCO
(10), respectively. The coproducts in these
reactions
were imines RR‘CN-t-Bu (4b−d),
isonitrile complexes CpCo(CO)(CN-t-Bu)
(8a), and ketenimines Ph2CCN-t-Bu (11a), respectively. With more highly
hindered carbonyls containing α-hydrogen atoms, the reaction
followed
a different pathway leading to the formation of the enolate complexes
Cp2Zr(NH-t-Bu)(OCR3CR2R1)
(R1 = H, R2
and R3 =
(CH2)3CH(CCH3)3
(5e); R1 = R2 = H,
R3 = C(CH3)3 (5f);
R1 = R2 = CH3, R3
= CH(CH3)2
(5g)).
Possible mechanisms for these transformations, as well as the
factors that might control the dependence of the fate
of “Cp2ZrO” on its method of generation, are
discussed.
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