Redox-Induced Indenyl Slippage in [IndCpMoL₂]^2+/+/0 Complexes

Abstract

The dicationic complexes [IndCpMoL2]2+ (Ind = indenyl; Cp = cyclopentadienyl; 1, L2 = dppe; 2, L = PMe3; 4, L2 = Bipy; 5, L2 = tBu2bipy; 6, L2 = H2biim; 7, L = CO and CNMe; 8, L = CNMe; 9, L = CNtBu; 10, L = NCMe and NMF; 11, L = NMF) were synthesized from [IndCpMoL‘2]2+ (L‘ = CO, NCMe), [IndCpMo(NCMe)Cl]BF4, or IndCpMoCl2 by ligand substitution. The neutral complexes (η3-Ind)CpMoL2 (13, L2 = dppe; 14, L = PMe3; 15, L2 = Bipy; 16, L = CO and CNMe; 17, L = CNtBu) were obtained upon reduction of the respective dications with Cp2Co. (η 3-Ind)CpMo(dppe) (13) was also prepared by deprotonation of the cyclopentadiene cation [IndMo(η4-C5H6)(dppe)]BF4 (12) with NEt3. The cyclic voltammograms of the dications present one reversible 2e reduction step from Mo(IV) to Mo(II) except for 1, 2, and 6, in which cases two reversible 1e waves are observed. The ring-slipped complexes (η 3-Ind)CpMoL2 and the parent dications present similar CV's. The X-ray crystal structures of [IndCpModppe][BF4]2 and (η 3-Ind)CpMo(dppe) confirm the indenyl ring planar η5 coordination and slip-folded η3, respectively.

Synthesis and structural characterization of new mixed-ring indenyl derivatives of molybdenum containing phosphorus ligands

“…Similar trends are observed for the unsubstituted complex [IndMo(g 4 -C 5 H 6 )(dppe)]BF 4 (2) in (CD 3 ) 2 CO, also assigned as the endo conformer (bridgehead CH 2 cis to the indenyl ring as in Scheme 1) [14]. However, concerning the chemical shifts of the methylene protons of the C 5 H 6 ring, H endo was assigned as the higher field resonance at d 2.80 ppm and H exo as the lower field resonance at d 3.29 ppm.…”

“…It was shown previously that H À adds to the Cp ring of the dication in [IndCpMo(dppe)](BF 4 ) 2 (1) to afford the diene complex [IndMo(g 4 -C 5 H 6 )(dppe)]BF 4 (2) [14]. In fact, the preparation of pure 2 only occurs if acetone and diethyl ether are used.…”

“…[IndCpMo(dppe)](BF 4 ) 2 (1) [14] and [IndCpMo-{P(OMe) 3 } 2 ](BF 4 ) 2 (4) [17] were obtained as described previously.…”

Modified molybdenum and tungsten metallocenes and ring-slippage reactions: new compounds and revisited concepts

“…The bulkiness of the CN(tBu) ligand may explain this result and the lower relative stability of the tetracoordinated bisisonitrile complex. 25 No analogous parent Group 6 metallocenes with the metal in the formal oxidation state 3 are known. 24 The related two-electron (2e) redox processes of Eqn [2] also involve hapticity changes and are, therefore, redox-induced ring-slippage reactions.…”

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

“…The solid state structure of the compound 6a was determined by X-ray diffraction analysis, see 22,42,43 According to the initial aim, the compound 6a is isostructural with allyl complex [(h 3 -C 3 H 5 )Mo(CO) 2 (pyma)Cl] (6-allyl) that was also conrmed by X-ray diffraction analysis (cf. Fig.…”