Preparation and reactivity of an organometallic Lewis acid bearing two accessible coordination sites

Abstract

Treatment of the ij3-allyl complex Cp(CO)2Mo(CH2CHCH2) with 1 equiv of HBF4 generates the tj2-propene compound Cp-(CO)2Mo(CH2=CHCHj)(FBF3) (7), a covalent molecule containing ligated propene and FBF3~, as a rapidly equilibrating mixture (on the NMR time scale) of cis and trans isomers. Carbonylation (1 atm) of 7 thus gives the propene salt Cp(CO)3Mo(CH2= CHCH3)*BF4". Of more importance, 7 functions as a labile precursor to the formally 14-electron (or doubly unsaturated) Lewis acid Cp(CO)2Mo+. For example, both latent coordination sites on 7 are available for selectively forming the disubstituted derivatives Cp(CO)2Mo(PPh3)2+ and (Cp(CO)2MoI)2 upon treatment with PPh3 and , respectively, under mild conditions. The corresponding Lewis acid Cp(CO)3MoFBF3 (la) with only one latent coordination site (ligated FBFf), in contrast, gives only the monosubstituted derivatives Cp(CO)3Mo(PPh3)+ and Cp(CO)3MoI under comparable reaction conditions. A study was also instituted to see if the Lewis acids 7 and la convert Cp(CO)3MoCH3 and Cp(CO)3MoH to their bimetallic and symmetric M-(j;2-C,0)-acyl complexes [Cp(CO)2Mo]2(COR)+, where R = CH3 and H, respectively. [Note that using 7 instead of la now entails a net conservation of CO ligands in the formal Lewis acid promoted alkyl (or hydride) migration.] Reaction between 7 and Cp(CO)3MoCH3 indeed gives the known M-(7jz-C,0)-acetyl compound (42% yield vs. 36% from la), whereas 7 and Cp(CO)3MoH afford no discernible reaction products.

Interactions of Cationic and Neutral Molybdenum Complexes with β-Cyclodextrin Host Molecules

“…19g This involves the protonation of Cp′Mo(η 3 -C 3 H 5 )(CO) 2 with HBF 4 ‚Et 2 O in CH 2 Cl 2 to give a red solution of [Cp′Mo(η 2 -C 3 H 6 )(CO) 2 (FBF 3 )]. 20 Addition of 1,3-cyclohexadiene to this solution leads to the rapid formation of 1. We have now extended this to the preparation of the indenyl analogue [IndMo(η 4 -C 6 H 8 )(CO) 2 ][BF 4 ] (2) (Scheme 1).…”

Highly Water‐Soluble Cyclopentadienyl and Indenyl Molybdenum(II) Complexes – Second Generation of Molybdenum‐Based Cytotoxic Agents

“…[8,16] Treatment of the starting complexes 11-14 with HBF4, in presence of a coordinating solvent, leads to protonation of allyl ligand. Following ligand-exchange gives unstable acetonitrile intermediates.…”

“…[19] All the compounds under the study (15)(16)(17)(18)(19)(20)(21)(22)(23) are highly active against both cell lines. Their IC50 values are much lower than reported for DDP, see Table 3.…”

“…The reaction was carried out as was described for compound 11, but with C9H7CH2CH2NMe2 ( (16). [(η 3 -C3H5)(η 5 -C5H4CH2CH2NMe2)Mo(CO)2] (11; 0.23 g, 0.70 mmol) was dissolved in CH2Cl2 (5 ml), cooled at 0°C, treated with acetonitrile (1 ml) and then with HBF4•Et2O (192 μl,1.40 mmol).…”

π-Complexes of Chromium, Molybdenum and Tungsten, Excluding those of Cyclopentadienyls and Arenes

“…The tetrafluoroborate complex [Mo(CO) 3 4 ] via facile displacement of BF 4 " from the metal coordination sphere 45 and treatment o f [Mo(CO) 2 (t| 3 -C 3 H 5 )Cp] with HBF 4 affords [Mo(CO) 2 (FBF 3 )(Ti 2 -CH 2 =CHMe)Cp] which is a source o f the 14-electron fragment Mo(CO) 2 Cp + via displacement o f both BF 4 " and propene ligands. 46 Chelate phosphine derivatives [Mo(CO)(P-P)(ri 2 -RHC=CH 2 )Cp] + [P-P = dmpe, dppe or (MeO) 2 PCH 2 CH 2 P(OMe) 2 ; R = H, Ph, CO 2 Me, etc.] have been obtained by photolysis o f [Mo(CO) 2 (P-P)Cp] + in acetone followed by treatment with alkene; the (MeO) 2 PCH 2 CH 2 P(OMe) 2 derivatives are relatively resistant to alkene dissociation and exhibit stereoselective binding of RJK^CH^4 7 ' 48 The chelating TI 5:1 -C 5 …”