Half-sandwich molybdenum compounds with phosphine–alkylthiolate and phosphine–thioether ligands. Crystal structure of [CpMo(SCH2CH2PPh2)2][BPh4]

Abstract

The reaction of CpMoCl2 with Ph2PCH2CH2SR (R = H, CH3) yields the corresponding addition products CpMoCl2(Ph2PCH2CH2SR), but only the derivative with R = CH3 (compound 5) is sufficiently stable to be isolated as a crystalline solid. The derivative with R = H evolves rapidly to afford a mixture of compounds [CpMo(SCH2CH2PPh2)2] + Cl -, 1, and [CpMoCl(SCH2CH2-PPh2)]2, 2, the former being favored by a larger ligand/Mo ratio. Compound 1 undergoes metathesis with NaBPh4 to afford [CpMo(SCH2CH2PPh2)2] + BPh4 -, 3, which has been characterized by X-ray crystallography. The reaction of CpMoCl2 with 2 equiv of Ph2PCH2CH2S -Li + affords the paramagnetic complex CpMo(SCH2CH2PPh2)2, 4, which is readily oxidized by Cp2Fe 1 or by H + to the corresponding cation. The salts 1 and 3, in turn, may be reduced by Na amalgam, MeLi, or Bu t OK to compound 4. The reversible redox process interconverting 4 and its cation occurs at E1/2 = -1.23 V relative to the ferrocene standard, while compound 5 shows a reversible oxidation process at E1/2 = 0.12 V by cyclic voltammetry. The comparison between these potentials and that previously reported for CpMoCl2(dppe) indicates relative donor abilities in the order Ph2P > MeS and RS -> Cl -. Compound 5 can also be synthesized by Na amalgam or Zn reduction of CpMoCl4(Ph2PCH2CH2SCH3) 6, which is obtained by addition of the ligand to CpMoCl4.

P−H-Functionalized 2-(Phosphanyl)ethanethiols, Their Titanocene Derivatives [Cp2Ti(SCH2CH2PHR)2] (R = Ph, 2,4,6-Me3C6H2, 2,4,6-iPr3C6H2) and Reaction of [Cp2Ti(SCH2CH2PHPh)2] with [Cu(CH3CN)4]BF4

“…Other related mononuclear transition metal complexes with S,P chelating phosphanylalkanethiolato ligands which have been structurally characterized include [MoX( S , P ‐SCH 2 CH 2 PPh 2 ) 2 ] n + ( n = 0, X = O;18 n = 1, X = Cp36), [Re(SCH 2 Ph)( S , P ‐SCH 2 CH 2 PPh 2 ) 2 ],22 [Tc( S , P ‐SC 6 H 4 PPh 2 ) 3 ],14 [Tc( S , P ‐SCH 2 CH 2 PPh 2 ) 2 ( S ‐SCH 2 CH 2 POPh 2 )],15 [FeCl(CO)(PPh 3 )( S , P ‐SC{( t Bu)(SCOMe)}CH 2 PPh 2 )],21[Fe{η 2 ‐C(OMe)S}P(OMe) 3 ( S , P ‐SC( t Bu)=CHPPh 2 )],24 [Ir(H)( S , P ‐SCH 2 CH 2 PPh 2 )( S , P ‐HSCH 2 CH 2 PPh 2 )(CO)] + ,17 [Ni( S , P ‐SCH 2 CH 2 PR 2 ) 2 ] (R = Me,23 Ph25). Complexes with tri‐, tetra‐ or hexadentate phosphanylalkanethiolato ligands which also have been studied are [Mo{ S , P , S ‐(SCH 2 CH 2 ) 2 PPh} 2 ],6 [Ni{ S , S , P , P ‐SCH 2 CH 2 P(Ph)CH 2 CH 2 CH 2 P(Ph)CH 2 CH 2 S}],20 and [Os{ P , P , S , S , S , S ‐P(CH 2 CH 2 S)(CH 2 CH 2 SSCH 2 CH 2 ) 2 P(CH 2 CH 2 S)}] 9…”

PPh(2-C6H4S)2 as a Pincer Ligand in Nickel(II) and Palladium(II) Complexes — X-ray Structure of [Ni{PPh(C6H4S)2}(PPh2Me)], [Pd2(μ-dppe){PPh(C6H4S)2}2] and [Ni{PPh(C6H4S)2}]2

“…For this reason the chemistry of polydentate ligands with sulfur and phosphorus donor atoms in their frameworks has attracted increasing interest, augmented by the observation of unusual structures and reactivities in the resulting transition metal complexes 9. In this regard, the systems most studied have been the proligands PR 2 (CH 2 SH), PR 2 (CH 2 CH 2 SH) and PR 2 (C 6 H 4 SH) 10−16…”

Different Approaches to Mid-Valent, Paramagnetic Half-Sandwich Complexes of the Heavier Group 6 Metals

“…are also being prepared and characterized. 48,49 Equation 5 A few more words on the versatile CpMoCl 2 reagent are in order. Its structure is inferred as dinuclear with four bridging chloride ligands by analogy with the crystallographically characterized [(C 5 H 4 Pr i )MoCl 2 ] and [(C 5 Me 4 Et)MoCl 2 ] 2 compounds.…”

“…are also being prepared and characterized. 48,49 4,50 The bromo and iodo complexes [Cp*MoX 2 ] 2 (X = Br, I) and [(h 5 -C 9 H 7 )MoI 2 ] 2 also display an analogous structure. 14,[51][52][53][54] However, this compound is essentially insoluble in all common solvents, preventing its spectroscopic characterization in solution and its purification.…”

“…The bifunctional ligand Ph 2 PCH 2 CH 2 SMe satisfies all necessary requirements, the one-pot reduction of CpMoCl 4 in the presence of this ligand providing a good yield synthesis of CpMoCl 2 (Ph 2 SCH 2 CH 2 SMe). 49 The intermediate CpMoCl 4 (MeSCH 2 CH 2 PPh 2 ) derivative may even be isolated as a pure product. Diene ligands do not allow a direct one-pot synthesis of CpMoCl 2 (h 4 -diene) using sodium, because of the parasite anionic diene polymerization under these conditions.…”