The Mo(η-allyl)(CO)₂ Moiety as a Robust Marker Group in Bioorganometallic Chemistry. Unusual Crystal Structure of the Phenylalanine Derivative Mo(C₅H₄-CO-Phe-OMe)(η-allyl)(CO)₂

Abstract

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).

Spectroscopic Properties, Electrochemistry, and Reactivity of Mo0, MoI, and MoII Complexes with the [Mo(bpa)(CO)3] Unit [bpa = bis(2-picolyl)amine] and Their Application for the Labelling of Peptides

“…[2,4,61,62] We have recently reported amino acid and peptide derivatives of [CpMo(allyl)(CO) 2 ]. [7] These compounds were readily isolated in the presence of water and showed promising spectroscopic properties. However, they could not be reversibly oxidized and did not show the required long-term stability in air.…”

Cyclopentadienyl molybdenum dicarbonyl η3-allyl complexes as catalyst precursors for olefin epoxidation. Crystal structures of Cp′Mo(CO)2(η3-C3H5) (Cp′ = η5-C5H4Me, η5-C5Me5)

“…1). Even though the structures of a considerable number of molybdenum dicarbonyleallyl complexes containing a Cp 0 aromatic ring have been reported [7,26], those which most resemble 2 and 3 were described in the 1980s: CpMo(CO) 2 (h 3 -C 3 H 5 ) by Faller et al [27], and (AcCp)Mo(CO) 2 (h 3 -C 3 H 5 ) (Ac ¼ acetyl) by Vanarsdale and Kochi [28]. Besides the striking similarities concerning the molybdenum coordination spheres, the allyl ligands in Table 1 Crystal and structure refinement data for (CpMe)Mo(CO) 2 (h 3 -C 3 H 5 ) (2) and Cp*Mo (CO) 2 (h 3 -C 3 H 5 ) (3).…”

“…The Mo II allyl complexes are also useful in organic synthesis because functional groups adjacent to the h 3 -allyl group can be transformed with excellent stereoselectivity and regioselectivity [6]. Another potential application concerns the use of the Cp 0 M(CO) 2 (h 3 -C 3 H 5 ) moiety as a labelling group in bioorganometallic chemistry [7].…”

Molybdenum complexes containing substituted cyclopenta[l]phenanthrenyl ligand

“…Lithiation of [CpMo(g 3 -C 3 H 5 )(CO) 2 ] followed by a treatment with CO 2 gives after water work up a compound with a carboxylic acid group in the cyclopentadienyl ring [(g 5 -C 5 H 4 COOH)Mo(g 3 -C 3 H 5 )(CO) 2 ]. This compound serves as the effective precursor for a variety of amino acid substituted cyclopentadienyl molybdenum compounds [13].…”