Oxidative-addition of organic monochloro derivatives to dinuclear iridium complexes: The detection of tautomeric equilibria and their implications onthe reactivity
C. Tejel et al., Oxidative-addition of organic monochloro derivatives to dinuclear iridium complexes: The detection of tautomeric equilibria and their implications onthe reactivity, ORGANOMETAL, 19(24), 2000, pp. 4977-4984
Reactions of MeCOCH2Cl, MeCO2CH2Cl, and (-)-methyl(S)-2-chloropropionate wi
th [(Ir-mu -Pz)(CNBut)(2)}(2)] (Pz = pyrazolate, 1) gave the metal-metal bo
nded diiridium(II) complexes [(CNBut)(2)(Cl)Ir(mu -Pz)(2)Ir(eta (1)-CH2R)(C
NBut)(2)] (R = COMe (2), CO2Me (3)) and the two enantiomers of [(CNBut)(2)(
Cl)Ir(mu -Pz)(2)Ir(eta (1)-CH(Me)CO2Me)(CNBut)(2)] (4). Similar reactions o
f 1 with equimolar amounts of benzyl chloride and allyl chloride rendered [
(CNBut)(2)(Cl)Ir(mu -Pz)(2)Ir(eta (1)-CH2R)(CNBut)(2)] ((R = Ph (5), CH=CH2
(7)), which were found to be the metal-metal bonded complexes in the solid
state, but in equilibrium with the mixed-valence Ir(I)Ir(III) complexes [(
CNBut)(2)Ir(mu -Pz)(2)Ir(Cl)(eta (1)-CH2R)(CNBut)(2)] in solution. Replacem
ent of chloride by iodide in 5 affords only the diiridium(II) complex [(CNB
ut)(2)(I)Ir(mu -Pz)(2)Ir(eta (1)-CH2Ph)(CNBut)(2)] (6). Complexes 5 and 7 r
eacted further with a second molar equivalent of chloro derivative to rende
r dialkyldiiridium(III) complexes [{Ir(mu -Pz)(eta (1)-CH2R)(CNBut)(2)}(2)(
mu -Cl)] Cl, ((R = Ph (8), CH=CH2 (10a)), while those showing a single stat
ic species in solution (2-4 and 6) were inactive. The reaction of 7 with al
lyl chloride gave also the isomer [(CNBut)(2)(Cl)Ir(eta (1),eta (2)-CH2CH=C
H2)(mu -Pz)(2)Ir(eta (1)-allyl)(CNBut)(2)]Cl (10b), in which one allyl grou
p bridges the two iridium atoms in an unsymmetrical fashion. This complex i
somerizes into the thermodynamic product [{Ir(mu -Pz)(eta (1)-allyl)(CNBut)
(2)}(2)(mu -Cl)]Cl, an stereoisomer of 10a. The structures of 10b and 5 wer
e solved by single-crystal X-ray diffraction methods.