Chemistry of Highly Electrophilic Binuclear Cations. 3. Reactivity of [W₂(η⁵-C₅H₅)₂(μ-CO)(CO)₂(μ-Ph₂PCH₂PPh₂)][B{3,5-C₆H₃(CF₃)₂}₄]₂toward Small Donor Molecules

Abstract

Reaction of the unsaturated tricarbonyl complex [W 2 Cp 2 (µ-CO)(CO) 2 (µ-dppm)](BAr′ 4 ) 2 with HSPh leads to the thiolate-bridged complex [W 2 Cp 2 (µ-SPh)(µ-CO)(CO) 2 (µ-dppm)](BAr′ 4 ), which is obtained as a mixture of two isomers. This reaction proceeds faster in the presence of a base (1,8-diazabicyclo[5.4.0]undec-7-ene, DBU), as expected. The title compound also reacts at room temperature with stoichiometric amounts of phosphines HPRwhich display a trans relative geometry of their phosphide and diphosphine ligands. Deprotonation of these hydride complexes with DBU gives the cis phosphide compounds [W 2 Cp 2 (µ-PR 1 R 2 )(CO) 2 (µ-dppm)](BAr′ 4 ), through an unexpected reduction and dehydrogenation/isomerization pathway. This overall deprotonation process is not reversible, and treatment of the latter compound with HBF 4 ‚OEt 2 gives the hydride isomer cis-[W 2 Cp 2 (µ-H)(µ-PR 1 R 2 )(CO) 2 (µ-dppm)](BAr′ 4 )(BF 4 ), which displays a strong hydrogen bond interaction between the bridging hydride ligand and the external BF 4anion. Treatment of the title compound with N 2 CHSiMe 3 or HCtC(p-tol) leads to dicarbonyls [W 2 -Cp 2 {µ-κ 1 -N 2 CH(SiMe 3 )}(CO) 2 (µ-dppm)](BAr′ 4 ) 2 or [W 2 Cp 2 {µ-η 2 :η 2 -HCC(p-tol)}(CO) 2 (µ-dppm)]-(BAr′ 4 ) 2 (two isomers), displaying four-electron-donor diazoalkane or alkyne bridging ligands.

Chemistry of highly electrophilic binuclear cations. 6. Synthesis of the alkyne-bridged complexes [Mo2(η5-C5H5)2{μ-η2:η2-HC2(p-tol)}(CO)2(μ-L2)][B{3,5-C6H3(CF3)2}4]2 and their isocyanide derivatives (L2=Ph2PCH2PPh2, Me2PCH2PMe2)

“…In contrast, the very minor isomer trans-3 has presumably the same geometry as compound 2, since its characteristic methyne resonance displays also very low P-H couplings (2 Hz). Interestingly, the ditungsten analogue of compound 2 was found to exist in solution as a roughly equimolar mixture of two isomers, these having spectroscopic properties resembling respectively those of 2 and 3 [6]. In particular, the P-H couplings of the methyne proton were found to be 1.5 and 1.5 Hz for one isomer, and 12 and 10 Hz for the other one.…”

“…We then turned our attention to the oxidation reactions of compounds 1, since these could lead to dipositive and unsaturated cations able to activate the alkyne ligand with respect to either deprotonation or other rearrangements. We have previously shown that the presence of multiple metal-metal bonds combined with high positive charges at binuclear transition-metal complexes enhances the Lewis acidity of the dinuclear centre and promotes novel transformations of interest [4][5][6]. In this paper we report our results on the oxidation reactions of radicals 1a,b with [FeCp 2 ]X [X = BF 4 and BAr 0 4 ] and some reactivity studies of the resulting dipositive cations.…”

Protonation reactions of the oxo complex cis-[Mo2(η5-C5H5)2(O)(μ-PPh2)2(CO)]. Hydroxo and tetrafluoroborate derivatives

“…We have shown previously that bridging hydride ligands in related dipositive ions can exhibit quite deshielded 1 H NMR resonances (d H ca. 4 ppm in the [W 2 Cp 2 (m-H)(m-PRR 0 )(CO) 2 (m-Ph 2 PCH 2 PPh 2 )] 2þ cations [8]), thus facilitating its masking with other resonances in the spectrum. Besides this, the strong deshielding of the hydroxyl resonance of 4 is neither unexpected for a dipositive cation (cf.…”

Hydrogen Atom Transfer Reactions of the Unsaturated Hydroxycarbyne Complex [W2Cp2(μ-COH)(μ-PPh2)2]BF4

“…For instance, we have shown previously that the resonance of the bridging hydride in the 32-electron cations [W 2 Cp 2 (μ-H)­(μ-PR 2 )­(μ-Ph 2 PCH 2 PPh 2 )­(CO) 2 ] 2+ (PR 2 = PPh 2 , PHCy) is displaced from ca. −5 to + 3 ppm by just exchanging the relative positions of the PR 2 and H ligands …”