Alkyne coupling reactions mediated by organolanthanides. Probing the mechanism by metal and alkyne variation

This contribution addresses, using the non-redox-active ion La[sup 3+], the constraints under which lanthanide M-C[triple bond]CR functionalities undergo facile coupling to yield binuclear M[sub 2]([mu]-RC[sub 4]R) complexes. The reaction of Cp[prime][sub 2]LaCHTMS[sub 2] (Cp[prime] = [eta][sup 5]-M...

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Bibliographic Details
Published in:Organometallics 1993-09, Vol.12 (9), p.3618-3623
Main Authors: Forsyth, Craig M, Nolan, Steven P, Stern, Charlotte L, Marks, Tobin J, Rheingold, Arnold L
Format: Article
Language:English
Subjects:
02 PETROLEUM
020400 - Petroleum- Processing
400201 - Chemical & Physicochemical Properties
ALKYNES
CATALYSTS
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
Chemistry
COMPLEXES
COUPLING
DIMERS
Exact sciences and technology
HYDROCARBONS
INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY
KINETICS
Kinetics and mechanisms
Organic chemistry
ORGANIC COMPOUNDS
ORGANOMETALLIC COMPOUNDS
RARE EARTH COMPLEXES
REACTION KINETICS
Reactivity and mechanisms
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Summary:This contribution addresses, using the non-redox-active ion La[sup 3+], the constraints under which lanthanide M-C[triple bond]CR functionalities undergo facile coupling to yield binuclear M[sub 2]([mu]-RC[sub 4]R) complexes. The reaction of Cp[prime][sub 2]LaCHTMS[sub 2] (Cp[prime] = [eta][sup 5]-Me[sub 5]C[sub 5]) with PhCCH at room temperature yields the coupled product (Cp[prime][sub 2]La)[sub 2]([mu]-PhC[sub 4]Ph) (monoclinic space group C2/m, [alpha] = 15,600(2) A, b = 14.318 (2) A, c = 15.368(2) A, [beta] = 114.17(1)[degrees], Z = 2, R = 0.050, R[sub w] = 0.063) plus CH[sub 2]TMS[sub 2]. Reaction of Cp[prime][sub 2]LaCHTMS[sub 2] with t-BuCCH at 0[degrees]C, yields the uncoupled dimer (Cp[prime][sub 2]LaC[sub 2]-t-Bu)[sub 2] (plus CH[sub 2]TMS[sub 2]), which, in toluene solution at 50 and 60[degrees]C, undergoes clean unimolecular conversion to the coupled dimer (Cp[prime][sub 2]La)[sub 2]([mu]-t-BuC[sub 4]-t-Bu) (monoclinic space group P2[sub 1]/n, a = 11.232(2) A, b = 14.199(3) A, c = 15.309(4) A, [beta] = 103.35(2)[degrees], Z = 2, R = 0.027, R[sub w] = 0.034). These results argue that excursions in formal metal oxidation state (+3 = +2) are not important along the reaction coordinate, that acetylene aryl substituents are not necessary for the coupling process to occur, and that the immediate kinetic precursor to the coupled product is an uncoupled dimer. 18 refs., 3 figs., 4 tabs.
ISSN:0276-7333
1520-6041
DOI:10.1021/om00033a038