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High-valent Diphenylacetylene Complexes of Tungsten

DOI: 10.1039/DT9950001153

Source and publish data:

Journal of the Chemical Society, Dalton Transactions p. 1153 - 1162 (1995)

Update date:2022-07-30

Topics:

Authors:

Nielson, Alastair J.Nielson, Alastair J.

Boyd, Peter D. W.Boyd, Peter D. W.

Clark, George R.Clark, George R.

Hunt, Patricia A.Hunt, Patricia A.

Hursthouse, Michael B.Hursthouse, Michael B.

et al.et al.

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Article abstract of DOI:10.1039/DT9950001153

The W(4f7/2) binding energy of <2> 1 obtained by X-ray photoelectron spectroscopy is similar to that of <2> and is consistent with a d0 tungsten(VI) formulation.The reaction of complex 1 and 2 with NaOH-EtOH gave cis-stilbene, indicating considerable electron transfer from the metal to the co-ordinated alkyne.Reduction of complex 1 with 2 equivalents of sodium-mercury amalgam in the presence of phosphines gave the complexes (L = PMe3, PMe2Ph or PMePh2) with magnetic moments and W(4f7/2) binding energies similar to those of the d1 tungsten(V) organoimido complex .Decomposition of the alkyne complexes with NaOH-EtOH again gave cis-stilbene.The crystal structure of 3 has been determined.The W-Cl bond trans to the alkyne ligand is long <2.479(3) Angstroem>, and the W-C bond lengths <2.011(13) and 2.038(12) Angstroem> indicate a four-electron-donor alkyne ligand.The geometry is similar to that of .Reduction of <2> using 4 equivalents of sodium-mercury amalgam in the presence of phosphines gave the complexes (L = PMe3 or PMe2Ph) which again produced cis-stilbene on decomposition with NaOH-EtOH.The acetylenic carbon resonance at δ 223.15 in the 13C-<1H> NMR spectrum of 6 is also indicative of a four-electron-donor alkyne ligand.Its W(4f7/2) binding energy is similar to and is consistent with tungsten(IV).A crystal structure of complex 6 shows a similar ligand geometry to , and the W-C bond lengths <2.019(11) and 2.006(11) Angstroem> indicate a four-electron-donor alkyne ligand.Hartree-Fock and scattered wave Xα calculations have been performed on the model complexes (1-) 8, 9 and 10.Molecular orbital and population analyses indicated that the acetylene-tungsten bond in each involves W(5d?)-->HC2H(?*) back donation as well as HC2H(?)-->W(5d?) and HC2H(?<*>)-->W(5d?) forward donation, consistent with a four-electron-donor alkyne formalism.Electron withdrawal from the tungsten to the more electronegative Cl ligand in complexes 8 and 9 is minimised by rotation of the alkyne away from the meridional vectors.In complex 10 the HC2H(?<*>)-->W(5d?) donation and phosphine contributions compensate and no rotation is observed.The total d atomic orbital population of complex 8 is close to that of WCl6, and populations of complexes 9 and 10 step up linearly from this.The computational results support the experimental evidence that <2> 1, 3 and 6 are complexes of tungsten-(VI), -(V) and -(IV) respectively.

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Product name:{WCl5((CC6H5)2)}(1-)*{N(CH2CH3)4}(1+)={WCl5((CC6H5)2)}{N(CH2CH3)4}

Cas No:143281-00-9

143281-00-9

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