The reaction of LiTeMe with C(CH2Br)4 in thf gives (CH2TeMe)2 irrespective of the ratio of reactants, in contrast to the reaction with LiSeMe, which gives either C(CH2SeMe)4 or (CH2SeMe)2 depending upon the reaction conditions. The synthesis and properties of [(CH2TeMe2)2]I2, (CH2TeMeI2)2, [Mn(CO)3Cl{(CH2EMe)2}] (E = Se or Te) and [MCl(η6-p-cymene){(CH2EMe)2}]PF6 (M = Ru or Os) are described. X-ray crystal structures are reported for [(CH2TeMe2)2]I2, [Mn(CO)3Cl{(CH2TeMe)2}], [MCl(η6-p-cymene){(CH2TeMe)2}]PF6 (M = Ru, E = Se or Te and M = Os, E = Se). The effect of the cyclopropyl ring in the ligand backbone is to open up the C–C–C angle within the chelate ring, compared with trimethylene linked analogues. Selenium–carbon bond fission occurs on attempted quaternisation of o-C6H4(CH2SeMe)2 or (CH2SeMe)2 with MeI yielding [Me3Se]I.
Graphical abstract
The synthesis of (CH2TeMe)2, some organotellurium(IV) derivatives and complexes [Mn(CO)3Cl{(CH2EMe)2}] (E = Se or Te) and [MCl(η6-p-cymene){(CH2EMe)2}]PF6 (M = Ru or Os) are described.
Detailed studies have shown that neutral selenium and tellurium donor ligands (chalcogenoethers R2E, E = Se or Te) are better donors than the more familiar sulphur analogues. They also exhibit ready oxidation at the heteroatom, and cleavage of the weaker and more reactive E–C bonds, properties less commonly found with thioethers [1], [2], [3]. We recently reported the synthesis and some metal carbonyl complexes of the tetradentates 1,2,4,5-C6H2(CH2EMe)4 (E = S or Se) and C(CH2EMe)4 [4], and found that when E = Se, the reaction of MeSeLi with C(CH2Br)4 produces either C(CH2SeMe)4 or (CH2SeMe)2 depending upon the reaction conditions. The corresponding (CH2TeMe)2 was mentioned some years ago in a paper dealing with the synthesis of ditelluroethers [5], but the reaction was not investigated in detail. In the present paper we have explored the synthesis of the cyclopropyl-based telluroethers, and report some organotellurium derivatives, and a series of metal complexes of the 1,1-bis(methyl selenomethyl/telluromethyl)cyclopropanes. The use of selenium compounds, mostly based upon selenoalkenes, as reagents for the formation of cyclopropyl rings in organic synthesis, is well established [6].
Section snippets
Experimental
Infrared spectra were recorded as Nujol mulls between CsI plates over the range 4000–200 cm−1 or as chlorocarbon solutions in NaCl solution cells over the range 2200–1700 cm−1, using Perkin–Elmer 983G or PE Spectrum100 instruments. 1H and 13C{1H} NMR spectra were recorded at ambient temperatures unless stated otherwise, using a Bruker AV300 spectrometer and referenced internally to the solvent resonance, and 77Se{1H}, 125Te{1H} and 55Mn NMR spectra on a Bruker DPX400 spectrometer and are
Synthesis of the telluroether and organotellurium(IV) derivatives
We recently reported [4] that the reaction of MeSeLi with C(CH2Br)4 produces C(CH2SeMe)4 when the molar ratio of the reactants is 4.5:1, whilst increasing the amount of MeSeLi, progressively forms (CH2SeMe)2, the yield being ∼90% with an 8:1 molar ratio. We have now re-examined the corresponding reactions of MeTeLi with C(CH2Br)4, which was reported [5] to give only (CH2TeMe)2, to establish whether the tetratelluroether, C(CH2TeMe)4, could be obtained. However, using varying molar ratios of
Conclusions
The formation of (CH2TeMe)2 and Me2Te2 as the only significant products of the reaction of C(CH2Br)4 with LiTeMe has been confirmed, and the reaction chemistry of this novel ligand and its selenium analogue has been explored with selected metal reagents. Some new organotellurium species have also been thoroughly characterised. The cyclopropyl unit seems unreactive in metal complexation chemistry, although the (CH2SeMe)2 (but not the telluroether) is cleaved upon quaternisation with MeI.
Acknowledgements
We thank Dr. M. Jura and Dr. W. Zhang for assisting with the X-ray data collections.
References (29)
W. Levason et al.
Coord. Chem. Rev.
(2002)
E.G. Hope et al.
Coord. Chem. Rev.
(1993)
W. Levason et al.
J. Organomet. Chem.
(2009)
H.D. Flack
Acta Crystallogr., Sect. A
(1983)
C. Gurnani et al.
Dalton Trans.
(2008)
S.D. Reid et al.
Dalton Trans.
(2007)
W. Levason et al.
J. Chem. Soc., Dalton Trans.
(1997)
W. Levason, G. Reid, in: F.A. DeVillanova (Ed.), Handbook of Chalcogen Chemistry, RSC, 2007 (Chapter...
E.G. Hope et al.
Organometallics
(1988)
C. Paulmier
Selenium Reagents and Intermediates in Organic Synthesis
This article details the chemistry of manganese carbonyl (Mn-CO) and isocyanide (Mn-CNR) complexes, from 2005 through 2020, with a focus on synthesis and reactivity. This article does not cover the chemistry of Mn–CO/CNR cyclic and non-cyclic pi complexes because these are covered in a different chapter. Similarly, applications are covered in a different chapter and therefore applications are only briefly discussed herein.
A number of new resonances appear in the 1H NMR spectrum, the major one having δ = 2.55 is tentatively assigned to [Me3Se]+, since there appear to be no associated CH2 resonance(s), whilst the 77Se NMR shows a new resonance at δ ∼ +264 which increases in intensity relative to that of the initial complex over time. The chemical shift of [Me3Se]+ is solvent and anion sensitive, but lies in the range δ ∼ 245–265 [13,30,31]. Dimethylene linkages in diselenoethers have been found to eliminate CH2=CH2 and form RSeSeR in the presence of some d-block Lewis acids, including TiCl4 or ZrCl4 [32,33], but the reaction here with BF3 is more complex, and also involves alkylation of the selenium.
The complexes [BX3(μ-L−L)BX3] (X = Cl, Br, I; L−L = EtS(CH2)2SEt, MeSe(CH2)2SeMe), [BX′3{o-C6H4(SMe)2}] (X’ = Cl, I), [(BBr3)2{o-C6H4(SMe)2}], [(BBr3)2{o-C6H4(SeMe)2}] and [BI3{o-C6H4(SeMe)2}] have been prepared as moisture-sensitive pale solids by reaction of the appropriate BX3 with the dichalcogenoether in anhydrous n-hexane solution, and characterised by microanalysis, IR and multinuclear (1H, 11B, 77Se{1H}) NMR spectroscopy. In contrast, the [BF3(μ-L−L)BF3], [(BF3)2{o-C6H4(SMe)2}] and [(BF3)2{o-C6H4(SeMe)2}], made from BF3 and the neat ligands, are viscous oils which have a significant vapour pressure of BF3 at ambient temperatures. X-ray crystal structures are reported for [BX3{μ-EtS(CH2)2SEt}BX3] (X = Cl, Br, I), [BBr3{μ-MeSe(CH2)2SeMe}BBr3], [BCl3{o-C6H4(SMe)2}] and [(BBr3)2{μ-o-C6H4(SeMe)2}]. The complexes [(BX3)2{MeTe(CH2)3TeMe}] (X = F, Cl, Br) have been identified in solution by multinuclear NMR spectroscopy, but decompose rapidly, whilst o-C6H4(TeMe)2 decomposes immediately on contact with BBr3 or BCl3. Dealkylation of some of the chalcogenoether ligands at room temperature by BI3, to yield complexes including [BI2{o-C6H4S(SMe)] and [BI2{o-C6H4Se(SeMe)], has been identified and the X-ray structure of [BI2{o-C6H4Se(SeMe)] determined. The trends in behaviour along the series of boron halides and with the various chalcogenoethers are described and compared with the behaviour of BX3 with neutral phosphorus and arsenic donor ligands (Burt et al., Inorg. Chem., 2016, 55, 8852) and with [BX3(EMe2)] (E = S, Se, Te) (Okio et al., J. Organometal. Chem., 2017, 848, 232).
The [BF3(SeMe2)] fumes in air and is very sensitive to moisture which generates [BF4]− and a species with δ (1H) = 2.59 and δ (77Se) = 247, which is tentatively identified as [Me3Se]+ (lit. δ (77Se) = 253 (H2O) [34], 259 (acetone) [35]). The only report [28] found of the reaction of BF3 with TeMe2 described “immediately upon addition of BF3 the solution assumed a brilliant red hue and a volatile orange coloured sublimate quickly formed”.
The [BX3(EMe2)] (X = Cl, Br, I; E = Se or Te) have been prepared by reaction of BX3 with the EMe2 in hexane under anhydrous conditions. The X-ray crystal structures of [BX3(TeMe2)] (X = Cl, Br, I) and [BX3(SeMe2)] (X = Cl, Br) have been determined; all are pseudo-tetrahedral monomers and show d(B−E) decreases with halogen, Cl > Br > I. Multinuclear NMR data (1H, 11B, 77Se and 125Te) are reported and compared with data on the corresponding [BX3(SMe2)], and the trends discussed. The unstable [BF3(SeMe2)], prepared from BF3 and SeMe2 in the absence of a solvent, has been similarly characterised by multinuclear NMR spectroscopy, and evidence for the existence of unstable [BF3(TeMe2)] obtained for the first time, although it could not be obtained pure. The results are discussed in the light of recent theoretical modelling of boron halide adducts.
Chelating bidentate [99,136–143], tridentate [144,145], macrocyclic [146–150] and heterocyclic [151] telluroether ligands have been employed for the synthesis of platinum group metals complexes. 1,1-Di-R-telluromethane [137,138,142], 1,3-di-R-telluropropane (R = Me or Ph) [136,141,152], 1,1-bis(methyl telluro)methylcyclopropane [143], 1,1-bis(butyltelluromethyl)dimethylsilane [139] and o-phenylene bis(methyl telluride) [101] have been used to prepare both neutral and cationic complexes. Ligands in these complexes act in a chelating fashion.
This article focuses on recent developments in the chemistry of platinum group metals (Ru, Os, Rh, Ir, Pd and Pt) with tellurium ligands. Attempts have been made to present a comprehensive account of the subject matter. Platinum group metal complexes with different kinds of tellurium ligands, such as diorganoditellurides, tellurolates, telluroethers, tellurides, polytellurides and tellurium(IV), are described. Various aspects of these complexes like synthesis, reactivity, structures and applications are covered in this review.
All preparations were carried out under a N2 atmosphere. The tetrathioether and tetraselenoether ligands were made as described [5] and [{Ru(η6-p-cymene)Cl2}2] and [{Os(η6-p-cymene)Cl2}2] [7] were prepared by literature methods. [Ru(η6-p-cymene)Cl2]2 (0.100 g, 0.16 mmol) was dissolved in dry ethanol (20 mL).
The reaction of [Ru(η6-p-cymene)Cl2]2 with 2.0 mol equivalents of C(CH2SMe)4, C(CH2SeMe)4, 1,2,4,5-C6H2(CH2SMe)4 or 1,2,4,5-C6H2(CH2SeMe)4 (L4) and [NH4][PF6] in ethanol solution forms the [RuCl(η6-p-cymene){κ2-L4}][PF6] complexes. Similar Os(II) complexes are obtained starting with [Os(η6-p-cymene)Cl2]2. Treatment of [RuCl(η6-p-cymene){κ2-L4}][PF6] with a further 0.5 mol equivalents of [Ru(η6-p-cymene)Cl2]2 or reaction of [Ru(η6-p-cymene)Cl2]2 directly with 1.0 mol equivalent of L4 forms the homobimetalllic [{RuCl(η6-p-cymene)}2{κ2κ′2-L4}][PF6]2. Reaction of [OsCl(η6-p-cymene)-{κ2-C(CH2SeMe)4}][PF6] with [Ru(η6-p-cymene)Cl2]2 or [PtCl2(MeCN)2] affords the heterobimetallic [{OsCl(η6-p-cymene)}{RuCl(η6-p-cymene)}{κ2κ′2-C(CH2SeMe)4}][PF6]2 and [{OsCl(η6-p-cymene)}{PtCl2}{κ2κ′2-C(CH2SeMe)4}][PF6] respectively. The complexes have been characterised by multinuclear NMR and IR spectroscopy and X-ray crystallography.
