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Vinylidene Complexes of the Molybdenum Auxiliary Mo(Ph2PCH2CH2PPh2)(C7H7). Structural and Spectroscopic Investigations on Vinylidene Ligand Orientation

DOI: 10.1039/DT9950002873

Source and publish data:

Journal of the Chemical Society, Dalton Transactions p. 2873 - 2884 (1995)

Update date:2022-08-05

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Authors:

Beddoes, Roy L.Beddoes, Roy L.

Bitcon, CarolineBitcon, Caroline

Grime, Richard W.Grime, Richard W.

Ricalton, AllenRicalton, Allen

Whiteley, Mark W.Whiteley, Mark W.

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Article abstract of DOI:10.1039/DT9950002873

The new vinylidene complexes (L-L)(η-C7H7)>(1+) have been synthesised by reaction of an excess of alk-1-yne, RCCH, either with (1+) (L-L = dppe or dppm) 6-C6H5Me)(η-C7H7)>(1+) and dppe or dmpe in acetone> or with (L-L = dppe or dppm) in methanol in the presence of .The formation of (dmpe)(η-C7H7)>(1+) is accompanied by conversion of the excess of alkyne into polymeric t-BuCCH with respective Mn and Mw values of 2.9E4 and 6.3E4 as determined by gel permeation chromatography.Deprotonation of (dppe)(η-C7H7)>(1+) with KOBu-t yields the alkynyl .The disubstituted vinylidenes (dppe)(η-C7H7)>(1+) (R = Bu-t or Bu-n) were obtained by Cβ methylation of with MeI.One-electron oxidation of the alkynyls (R = Bu-n or Ph) with (1+) yields the 17-electron radicals (1+) (R = Bu-n or Ph) which undergo coupling at Cβ to yield dimeric, divinylidene-bridged (2+) (R = Bu-n or Ph).The crystal structures of (dppe)(η-C7H7)> and 2, have been determined.In the former the vinylidene substituents lie approximately in the pseudo-mirror plane of the Mo(dppe)(η-C7H7) moiety (a vertical orientation) with the phenyl substituent directed 'up' towards the cycloheptatrienyl ring.In the latter centrosymmetric dimer the vinylidene ligand is rotated by 19.1 deg away from an exact vertical orientation and the phenyl substituents are located 'down' into a pocket enclosed by two phenyl groups of the dppe ligand.Variable-temperature 1H NMR investigations on (1+) are consistent with a preffered vertical orientation of the vinylidene ligand in solution at low temperature and the barrier to vinylidene rotation has been estimated as 51.9 +/- 1 kJ mol-1.The 1H and 31P NMR solution spectra of (dppe)(η-C7H7)>(1+) (R' = H or Me) are also consistent with a vertically orientated vinylidene ligand and reveal the existence of two isomeric forms of each complex which differ in the location of the n-butyl substituent in the 'up' or 'down' position.

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Product name:[MoCl(Ph2PCH2PPh2)(η-C7H7)]

Cas No:171415-68-2

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