Synthesis, characterisation and reactivity of the first heptamethylindenyl-molybdenum complexes: crystal structures of [Mo(CO)(η2-MeCCMe)2(η5-C9Me7)]BF4 and MO(CO)2(η3-C3H5)(η5-C9Me7)]
“…The average bonding distance of molybdenum to the five-membered indenyl ring is 2.36 Å, the average bond lengths of molybdenum to the CO units are 2.00 Å, while the bond length Mo−I is 2.85 Å. These bond lengths are in close accordance to those in tricarbonyliodo(η 5 -indenyl)molybdenum(II), (η 3 -allyl)dicarbonyl(η 5 -indenyl)molybdenum(II), and dicarbonyldi(ethanonitrile)(η 5 -indenyl)molybdenum(II)tetrafluoroborate (av Mo−C(ind) distances, 2.35, 2.36, and 2.34 Å; av Mo−CO distances, 1.93, 1.94, and 1.99 Å). The CO ligands are almost linearly bonded (av Mo−CO angle = 177.3°) and the average L−Mo−L angle between CO and I is 76.1°.…”
Optically active complexes of Rh, Ir, Co, and Mo containing the chiral, menthyl-substituted
indenyl ligands (−)-2-menthylindene and (−)-2-menthyl-4,7-dimethylindene are described.
Metathetic reaction of the chiral lithium salts of these indenyl systems (1, 2) with the
appropriate starting materials of Rh and Ir yielded the complexes (−)-(2-menthylindenyl)Rh(COD) (3), (−)-(2-menthyl-4,7-dimethylindenyl)Rh(COD) (4), (−)-(2-menthylindenyl)Rh(C2H4)2 (5), (−)-(2-menthyl-4,7-dimethylindenyl)Rh(C2H4)2 (6), (−)-(2-menthylindenyl)Ir(COD)
(7), (−)-(2-menthylindenyl)Ir(C2H4)2 (8), (−)-(2-menthyl-4,7-dimethylindenyl)Ir(C2H4)2 (9),
and (−)-(2-menthyl-4,7-dimethylindenyl)Ir(COE)2 (10). Co2(CO)8 and CoCl2(dppe) react
with (−)-2-menthylindenyllithium (1) yielding (−)-(2-menthylindenyl)Co(CO)2 (11) and
(+)-(2-menthylindenyl)Co(dppe) (12). (−)-Li[(2-menthylindenyl)Mo(CO)3](THF)2 (13), formed
by transmetalation of Mo(CO)6, is oxidized by I2, yielding (−)-(2-menthylindenyl)Mo(CO)3I
(14), or by allylic chloride, yielding (allyl)(2-menthylindenyl)Mo(CO)2 (15). All compounds
were formed stereomerically pure and were obtained after chromatography by dried alumina
under nitrogen. The structures of 3, 4, 6, 7, and 14 were determined by single-crystal X-ray
diffractometry. Variable temperature 1H NMR spectra of 5, 6, 8, and 9 were recorded to
determine the energy barriers for rotation of ethylene along the metal−indenyl and metal−ethylene axes.
“…The average bonding distance of molybdenum to the five-membered indenyl ring is 2.36 Å, the average bond lengths of molybdenum to the CO units are 2.00 Å, while the bond length Mo−I is 2.85 Å. These bond lengths are in close accordance to those in tricarbonyliodo(η 5 -indenyl)molybdenum(II), (η 3 -allyl)dicarbonyl(η 5 -indenyl)molybdenum(II), and dicarbonyldi(ethanonitrile)(η 5 -indenyl)molybdenum(II)tetrafluoroborate (av Mo−C(ind) distances, 2.35, 2.36, and 2.34 Å; av Mo−CO distances, 1.93, 1.94, and 1.99 Å). The CO ligands are almost linearly bonded (av Mo−CO angle = 177.3°) and the average L−Mo−L angle between CO and I is 76.1°.…”
Optically active complexes of Rh, Ir, Co, and Mo containing the chiral, menthyl-substituted
indenyl ligands (−)-2-menthylindene and (−)-2-menthyl-4,7-dimethylindene are described.
Metathetic reaction of the chiral lithium salts of these indenyl systems (1, 2) with the
appropriate starting materials of Rh and Ir yielded the complexes (−)-(2-menthylindenyl)Rh(COD) (3), (−)-(2-menthyl-4,7-dimethylindenyl)Rh(COD) (4), (−)-(2-menthylindenyl)Rh(C2H4)2 (5), (−)-(2-menthyl-4,7-dimethylindenyl)Rh(C2H4)2 (6), (−)-(2-menthylindenyl)Ir(COD)
(7), (−)-(2-menthylindenyl)Ir(C2H4)2 (8), (−)-(2-menthyl-4,7-dimethylindenyl)Ir(C2H4)2 (9),
and (−)-(2-menthyl-4,7-dimethylindenyl)Ir(COE)2 (10). Co2(CO)8 and CoCl2(dppe) react
with (−)-2-menthylindenyllithium (1) yielding (−)-(2-menthylindenyl)Co(CO)2 (11) and
(+)-(2-menthylindenyl)Co(dppe) (12). (−)-Li[(2-menthylindenyl)Mo(CO)3](THF)2 (13), formed
by transmetalation of Mo(CO)6, is oxidized by I2, yielding (−)-(2-menthylindenyl)Mo(CO)3I
(14), or by allylic chloride, yielding (allyl)(2-menthylindenyl)Mo(CO)2 (15). All compounds
were formed stereomerically pure and were obtained after chromatography by dried alumina
under nitrogen. The structures of 3, 4, 6, 7, and 14 were determined by single-crystal X-ray
diffractometry. Variable temperature 1H NMR spectra of 5, 6, 8, and 9 were recorded to
determine the energy barriers for rotation of ethylene along the metal−indenyl and metal−ethylene axes.
“…Another remarkable feature of 3a in this crystal structure is the endo conformation of the allyl ligand. All solid-state structures reported so far for Mo(η-C 3 H 5 )(CO) 2 complexes with different Cp derivatives show an allyl- exo conformation, − although an equilibrium between both geometrical isomers in solution has been demonstrated. ,,− An endo conformation was found crystallographically for the methyl-allyl derivative Mo(η 5 -Cp)(η 3 -2-CH 3 −C 3 H 4 )(CO) 2 , for which the exo conformation was considered unfavorable due to steric interaction of the methyl group with the Cp ring. An allyl- endo conformation was also observed in the Mo nitrosyl iodo complex Mo(η 5 -Cp)(NO)(I)(η 3 -allyl).…”
Section: Resultsmentioning
confidence: 99%
“…On the basis of NMR spectroscopic data the two isomers were shown to be due to exo and endo conformations of the allyl ligand (Scheme ) . Of the two, the exo isomer was shown to be the major isomer in solution and was also the only isomer to be found in X-ray crystal structures of 1 and various derivatives thereof. − 1 Two Conformations of 1 and Labeling Scheme for Protons of 1 …”
The MoCp(η-C 3 H 5 )(CO) 2 (Cp ) η-cyclopentadienyl) moiety is introduced as a new labeling group in bioorganometallic chemistry. The acid Mo(C 5 H 4 -CO 2 H)(η-C 3 H 5 )(CO) 2 (2) was obtained from the reaction of MoCp(η-C 3 H 5 )(CO) 2 (1) with BuLi and solid CO 2 followed by aqueous workup. Coupling of 2 to amino acids with various complexity and C-terminal functionality by standard peptide chemistry methods yielded the amino acid derivatives). In addition, the dipeptide derivative Mo(C 5 H 4 -CO-Leu-Phe-OCH 3 )-(η-C 3 H 5 )(CO) 2 (4) was synthesized by reacting 2 with H-Leu-Phe-OCH 3 . All new compounds are characterized by elemental analysis, IR, MS, and NMR spectroscopy. X-ray analysis on 3a shows the unit cell to contain two independent molecules, A and B, which differ mainly by the orientation of the allyl and carbonyl groups with respect to the amino acid substituent on the Cp ring. Furthermore, an allyl-endo conformation for both A and B is observed. This is the first example of such a conformation in the crystal structure of a MoCp(C 3 H 5 )(CO) 2 derivative. In solution, both the exo and endo isomer are present, as concluded from 1 H NMR spectroscopy approximately in a 4:1 ratio. The activation barriers of interconversion were determined to be 62.7 ( 0.5 kJ mol -1 (3a) and 60.5 ( 0.5 kJ mol -1 (3c).
“…In contrast to the parent indenyl ligand, there are presently relatively few applications of its permethylated counterpart in organometallic chemistry. Permethylindenyl complexes are, nevertheless, known for titanium, chromium, iron, , cobalt, − zirconium, molybdenum, rhenium, rhodium, 7b,− lanthanum, neodymium, erbium, thorium, and uranium, although the majority of these studies have focused on mono(permethylindenyl) derivatives. For the actinides, in particular, the chemistry of bis(permethylindenyl) derivatives remains unexplored, even though bis(permethylcyclopentadienyl) complexes have been extensively studied .…”
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