Crystal structure of hexakis(trimethylsilylmethyl)dimolybdenum

Huq, Fazlul; Mowat, W.; Shortland, A.; Skapski, A. C.; Wilkinson, Geoffrey

doi:10.1039/c29710001079

Cited by 66 publications

(28 citation statements)

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“…Additionally, an empirical bond distance/force constant correlation for fifth period diatomics 13 predicts ν MotMo ) 363 cm -1 (in the diatomic approximation) with a force constant k ) 3.72 mdyn/Å for Mo 2 [CH 2 Si(CH 3 ) 3 ] 6 , from the crystallographically determined MotMo distance of 2.167 Å; 14 this predicted frequency agrees quite well with the observed value of 369 cm -1 . 6, 14,15 One further observation strengthens our ν MtM assignments. These force constants are larger than those reported for the quadruply bonded Mo 2 X 8 (ca.…”

supporting

confidence: 70%

Raman Spectra of M₂(OR)₆ and M₂R₆ (M = Mo, W) Compounds: Assignment of the M⋮M Stretching Frequency in M₂X₆ Dimers

et al. 1997

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Raman spectroscopy has been widely utilized to investigate the metal-metal stretching vibrations ν MtM in tetragonally substituted, metal-metal quadruply bonded M 2 X 8 transition metal dimers. 1-3 Assignments of ν MtM are generally straightforward for such compounds based on a combination of resonance Raman techniques, ligand substitution, and comparisons among homologous series of compounds.By contrast, the identification of ν MtM for the class of trigonally substituted, triply bonded compounds M 2 X 6 (M ) Mo, W), has been problematic. The only Raman study of X 3 MtMX 3 dimers in the literature involved the hexaamides M 2 [N(CH 3 ) 2 ] 6 (M ) Mo, W) and the corresponding perdeuterated analogues M 2 [N(CD 3 ) 2 ] 6 . 4,5 In that work, Chisholm, Cotton, and co-workers concluded that extensive coupling of low-frequency ligand vibrational modes with ν MtM made assignment of the latter impossible.In this communication, we report the results of Raman studies of a series of hexaalkyl compounds M 2 (CH 2 R) 6 [M ) Mo, W; R ) C(CH 3 ) 3 , Si(CH 3 ) 3 ] and hexaalkoxide compounds M 2 (OR) 6 [M ) Mo, W; R ) C(CH 3 ) 3 , C(CD 3 ) 3 , C(CH 3 ) 2 CF 3 , 1-adamantyl). The vibrational coupling of ν MtM with low-frequency ligand modes is weaker than in the hexaamide dimers, because these compounds display bands which can be confidently assigned to ν MtM .The M 2 X 6 complexes were prepared by standard methods, 6-10 and their Raman spectra were obtained using low-power red (632.8 nm) continuous-wave excitation. The spectra of the homologous pair of M 2 [CH 2 Si(CH 3 ) 3 ] 6 (M ) Mo, W) compounds appear in Figure 1; they are strikingly similar save for one band which shifts dramatically between the Mo and the W dimers. This situation contrasts with that observed in the M 2 -[N(CH 3 ) 2 ] 6 Raman experiments, where all of the low-frequency bands shifted when the metal was changed. The metal-sensitive band is located at 369 cm -1 for Mo 2 [CH 2 Si(CH 3 ) 3 ] 6 and at 299 cm -1 for the W analogue. The ratio of these frequencies (ν MotMo /ν WtW ) 1.23) compares well to the ratio of 1.38 expected for the hypothetical bare metal diatomics (Mo 2 and W 2 ) with equal force constants. We therefore assign these features as the metal-metal stretching frequencies ν MtM . Communications

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confidence: 70%

Raman Spectra of M₂(OR)₆ and M₂R₆ (M = Mo, W) Compounds: Assignment of the M⋮M Stretching Frequency in M₂X₆ Dimers

et al. 1997

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“…Furthermore, we applied the same protocol for the synthesis of heteroleptic and additionally functionalized alkoxide compounds, starting from the precursors 1-3. The conversion of 1 and 3 with neopentOH in a molar ratio of 1:4 afforded the desired complexes Mo 2 (OMBE) 2 -(Oneopent) 4 (5) and Mo 2 (OMMP) 2 (Oneopent) 4 (6) in 89% and 76 % yield, respectively. However, the partial alcoholysis of complex 2 in a molar ratio of 1:4 did not result in the replacement of the four TerpO ligands, but led to complex Mo 2 (OTerp) 4 (Oneopent) 2 (7) in 85 % yield (Scheme 2), as proven by 1 H NMR spectroscopy.…”

Section: Homoleptic Mo 2 (Or) 6 (1-3) (R = Mmp Terp and Mbe)mentioning

confidence: 98%

“…The conversion of 1 and 3 with neopentOH in a molar ratio of 1:4 afforded the desired complexes Mo 2 (OMBE) 2 -(Oneopent) 4 (5) and Mo 2 (OMMP) 2 (Oneopent) 4 (6) in 89% and 76 % yield, respectively. However, the partial alcoholysis of complex 2 in a molar ratio of 1:4 did not result in the replacement of the four TerpO ligands, but led to complex Mo 2 (OTerp) 4 (Oneopent) 2 (7) in 85 % yield (Scheme 2), as proven by 1 H NMR spectroscopy. Interestingly, when an excess of neopentOH was used in the reactions with 1-3, complete alkoxido exchange did not occur to give the homoleptic analogue Mo 2 (Oneopent) 6 .…”

Section: Homoleptic Mo 2 (Or) 6 (1-3) (R = Mmp Terp and Mbe)mentioning

confidence: 98%

“…[2] Among these systems, the dinuclear, triply bonded Mo III compounds of the type Mo 2 R 6 (R = organyl) represent a fascinating group. [3] The synthesis of the first example, Mo 2 (CH 2 SiMe 3 ) 6 , as described by Wilkinson et al, [4] was extended by the seminal studies of Chisholm et al on various systems with alkyl, dialkylamino [5] and alkoxido ligands at the molybdenum atoms. [6] The latter type of complexes, i.e.…”

Section: Introductionmentioning

confidence: 98%

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Facile Access to Homo‐ and Heteroleptic, Triply Bonded Dimolybdenum Hexaalkoxides with Unsaturated Alkoxide Ligands

Krackl

Aksu

et al. 2011

Eur J Inorg Chem

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A series of monodentate, triply bonded Mo 2 (OR) 6 complexes [R = MBE (1) (MBE = 2-methylbut-3-ene-2-yl), MMP (2) (MMP = 1-methoxy-2-methylpropane-2-yl), Terp (3) [Terp = 2-(4-methylcyclohex-3-enyl)propane-2-yl], which exhibit C-C double bonds or an ether function in the ligand sphere, were synthesized and characterized by multinuclear ( 1 H, 13 C and 95 Mo) NMR studies. The partial alcoholysis of the latter complexes with neopentyl alcohol (neopentOH) led to the heteroleptic alkoxides Mo 2 (OR) n (Oneopent) 6-n (4-7) {n = 2 [for R = tBu (4), MBE (5), MMP (6)], 4 [for R = Terp (7)]}. This concept was further applied to the synthesis of Mo 2 (O 2 DMH) 2 -(OtBu) 2 (8) (DMH = 2,5 dimethylhexyl) by starting from the Mo 2 (OtBu) 6 precursor. The 1 H NMR spectra for the heteroleptic complexes 4-8 show signals that are significantly shifted to a higher field for the RO ligand protons compared to those of their homoleptic analogues. This is the result of a change in the spatial position of the alkoxide ligands (RO) in the homoleptic compared to the heteroleptic complexes that

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“…On refluxing the Mo compound with acetic acid, molybdenum(n) acetate, Mo 2 (0COCH 3 ) 6 is formed, while with 12M HCl, and RbCl, the salt Rb 3 Mo 2 Cl 8 can be isolated, both reactions showing the persistence of the metal-metal bond. The x-ray structure of the molybdenum compound 37 shows a very short Mo-Mo distance, 2.167 A only slightly Ionger than that in Mo 2 (0COCH 3 ) 6 ; the alkyl groups are staggered. The Mo-CH 2 -Si angle of 121.1 o and possibly the Mo-Mo-CH 2 angle of 100.6° is probably a consequence of the mutual repulsion of the bulky trimethylsilyl groups, rather than of any electronic factors.…”

Section: Molybdenum and Tungstenmentioning

confidence: 99%

The transition metal to carbon sigma bond

Wilkinson¹

1972

Pure and Applied Chemistry

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On account of the apparent instabilities or difficulties in isolating simple alkyls oftransition metals it has commonly been assumed firstly that the bond strength is low and secondly that the presence of n-acid ligands such as CO, R 3 P, n-C 5 H 5 , etc. on the metal are necessary for the existence of stable metalcarbon cr-bonds. Although only a few bond strengths have been estimated, and these in compounds with other ligands present, there is no sound reason for assuming that the metal to carbon bond strengths are low. The reason for the instability of simple transition metal alkyls, Mn-Rn, generally is to be sought in the available possible pathways for decomposition reactions of the alkyls such as hydrogen transfer from rt or ß-carbon atoms of the alkyl chain alkene and/or alkane elimination reactions, etc.The synthesis of elimination-stabilized alkyls of transition metals in high oxidation states is discussed and illustrated primarily by consideration of trimethylsilylmethyl derivatives, from which alkene elimination is impossible due to the incapacity for forming silicon to carbon double bonds. The chemical properties and structures of compounds Mn(CH 2 SiMe 3 )n where M = VIV, Cr 1 v, Mom, wm etc., and of other related species are described together with appropriate infrared, nuclear magnetic resonance and electron spin resonance data.Despite the extraordinary rapid developments in the organametallic chemistry of the d-block transition elements during the last twenty years, such as the binding of delocalized aromatic or quasi-aromatic entities, alkenes, alkynes, carboranes, pyrazoboles, etc., to metals, as well as the classical cr-bonded alkyl and aryl groups and the synthesis of a multitude of different types of compounds with mixed ligands, there are some surprising gaps in our knowledge of the most simple dass of compounds, namely those where organic groups only are bound to metals by cr-bonds.The early efforts 1 to prepare alkyls or aryls of transition metals showed very clearly that simple 'binary' compounds, MRm R = alkyl or aryl, were generally unstable under ordinary conditions, although they might be present in solutions at low temperatures. Following the preparation of the first extensive series of cr-bonded alkyl compounds with other ligands present 2 , it appeared that only in the presence of such stabilizing ligands as 627Brought to you by | MIT Libraries Authenticated Download Date | 5/11/18 2:28 PM

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Crystal structure of hexakis(trimethylsilylmethyl)dimolybdenum

Cited by 66 publications

References 0 publications

Raman Spectra of M₂(OR)₆ and M₂R₆ (M = Mo, W) Compounds: Assignment of the M⋮M Stretching Frequency in M₂X₆ Dimers

Raman Spectra of M₂(OR)₆ and M₂R₆ (M = Mo, W) Compounds: Assignment of the M⋮M Stretching Frequency in M₂X₆ Dimers

Facile Access to Homo‐ and Heteroleptic, Triply Bonded Dimolybdenum Hexaalkoxides with Unsaturated Alkoxide Ligands

The transition metal to carbon sigma bond

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Crystal structure of hexakis(trimethylsilylmethyl)dimolybdenum

Cited by 66 publications

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Raman Spectra of M2(OR)6 and M2R6 (M = Mo, W) Compounds: Assignment of the M⋮M Stretching Frequency in M2X6 Dimers

Raman Spectra of M2(OR)6 and M2R6 (M = Mo, W) Compounds: Assignment of the M⋮M Stretching Frequency in M2X6 Dimers

Facile Access to Homo‐ and Heteroleptic, Triply Bonded Dimolybdenum Hexaalkoxides with Unsaturated Alkoxide Ligands

The transition metal to carbon sigma bond

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Raman Spectra of M₂(OR)₆ and M₂R₆ (M = Mo, W) Compounds: Assignment of the M⋮M Stretching Frequency in M₂X₆ Dimers

Raman Spectra of M₂(OR)₆ and M₂R₆ (M = Mo, W) Compounds: Assignment of the M⋮M Stretching Frequency in M₂X₆ Dimers