Ring-Functionalized Molybdenocene Complexes

Abstract

The synthesis and characterization of new ring-functionalized molybdenocene derivatives [CpCp′Mo(CO) 2 ] 2+ and [CpCp′Mo(CO)Br] + (η 5 -C 5 H 4 R; R ) CH 2 CH 2 OMe, CH 2 CH 2 COOEt, CH 2 CH 2 OOCMe, COOMe) are reported. Three alternative routes were used to assemble the CpCp′Mo moiety. Following route I, the unsubstituted precursor [CpMo(CO) 2 (NCMe) 2 ] + reacts with substituted cyclopentadienes (Cp′H) to give after oxidation dicationic compounds [CpCp′Mo(CO) 2 ] 2+ . Alternatively, route II introduces the substituent in the first reaction step upon the synthesis of [Cp′Mo(CO) 2 (NCMe) 2 ] + . In this case, the bis-cyclopentadienyl compounds [CpCp′Mo(CO) 2 ] 2+ were obtained after reaction with cyclopentadiene (C 5 H 6 ) and subsequent oxidation. The NMR spectroscopic measurements prove that the reaction pathways of routes I and II go through different intermediates. The bromo complexes [CpCp′Mo(CO)Br] + were synthesized using route III. Reaction of [Cp′Mo(CO) 2 (NCMe) 2 ] + with C 5 H 5 SiMe 3 gives hydride complexes [CpCp′Mo(CO)H] + . Appropriate bromo complexes were obtained upon reaction with bromine. The ring-functionalized bis-cyclopentadienyl molybdenum(IV) compounds and their monocyclopentadienyl precursors were characterized by spectroscopic methods. Structures of, [(η 5 -C 5 H 4 SiMe 3 )Mo(CO) 2 (NCMe) 2 ][BF 4 ], and [CpMo(η 5 -C 5 H 4 COOMe)(CO)H][BF 4 ] were determined with X-ray diffraction analysis.

Effect of the Substitution on the Protonation of Allyl Cyclopentadienyl Molybdenum(II) Compounds

“…We have previously observed that the attachment of only one COOMe group at the Cp ligand does not influence the reaction path. 16 The herereported unexpected switch of the reactivity can be explained by much higher affinity of the functional groups in the cyclopentadienyl toward protonation. The second electronwithdrawing group crosses the borderline between attack of the allyl and cyclopentadienyl ligands.…”

“…C 5 H 4 COOMe). 16 In the case of compounds 6 and 7, we observe a very different product. Reaction with HBF 4 in the solution containing acetonitrile gives cationic allyl compound [(η 3 -C 3 H 5 )Mo(CO) 2 (NCMe) 3 ][BF 4 ] (11) as the sole product; see Scheme 4.…”

“…12−14 This procedure was found to be suitable for a variety of mixed cyclopentadienyl− indenyl compounds 12,14,15 as well as for bis-cyclopentadienyl compounds containing a functionalized cyclopentadienyl ring. 16 ansa-Molybdenocenes [(η 5 -Ind′)Mo(η 5 -C 5 H 4 CH 2 -η 1 -CH 2 )-(CO)][BF 4 ] (Ind′ = substituted indenyl) were synthesized by a modified route starting from [(η 5 -Ind′)Mo(CO) 2 (NCMe) 2 ]-[BF 4 ] and spiro[2.4]hepta-4,6-diene. 17 This work is focused 1,2-disubstituted cyclopentadienyl ligands bearing strong electron-withdrawing functional groups.…”

“…Compound 8 has two crystallographically independent but essentially the same complexes in the unit cell. The angles 16 The cationic parts of complexes 11 and 14 have a distorted octahedral structure with the centroid of the allyl ligand and nitrogen atom of the acetonitrile in the axial positions. The carbon atoms of two carbonyl ligands and the nitrogen atoms of two acetonitrile ligands are placed in equatorial positions; see Figures 4 and 5.…”

Stabilization of η3-indenyl compounds by sterically demanding N,N-chelating ligands in the molybdenum coordination sphere

“…The structural parameters, describing the coordination sphere of molybdenum, are in line with data of structurally related cyclopentadienyl and indenyl compounds described previously. 13,14,[44][45][46] The reaction of 2 with lower than stoichiometric amount of bpy or phen gives a material insoluble in common organic solvents that strongly contrasts with properties of the starting compounds as well as the products 4a and 5a. Elemental analysis of the products together with their insolubility suggests an appearance of the ionic pair consisting of a large complex cation and a large complex anion [(h 5 -4,7-Me 2 C 9 H 5 )Mo(CO) 2 ( N,N L)] [(h 5 -4,7-Me 2 C 9 H 5 )Mo(CO) 2 Cl 2 ] (4b-9: N,N L ¼ bpy, 5b-9: N,N L ¼ phen), see Scheme 5.…”