A mechanistic investigation of the ring expansion of vinylcyclopropenes to metallacyclohexadienes and cyclopentadienyl complexes through the use of isotopically labelled ligands
The reactions of 1,2,3-triphenyl-3-vinylcyclopropene 1,1,2-diphenyl-3-vinylcyclopropene 2, and 1,2,3-tri,tert-butyl-3-vinylcyclopropene 3 with Rh[sup I], Ir[sup I], and Fe[sup 0] complexes were investigated using trans-deutero-, 3-deutero-, and [[sup 13]C[sub 2]]vinylcyclopropenes. No scrambling was observed when 3-trans-d reacted with [Rh(Cl)(C[sub 2]H[sub 4])[sub 2]][sub 2], giving syn-deuterated [CHD-CH[double bond]C[sup t]Bu-C[sup t]Bu[double bond]C[sup t]Bu-RhCl][sub 2] 4, nor on ring closure of the idenyl derivative of 4 to endo-deuterated [(CHD-CH[double bond]C[sup t]Bu-C[sup t]Bu-C[sup t]Bu)-Rh(ind)] 5. 1-trans-d reacted with Fe[sub 2](CO)[sub 9] to give endo-deuterated cyclohexadienone complex [(CO-CHD-CH[double bond]CPh-CPh[double bond]CPh)Fe(CO)[sub 3]] 6. On heating or prolonged standing in solution, a hydride shift accompanied ring closure of 4, to give a rearranged cyclopentadiene complex [(CH[sup t]Bu-C[sup t]Bu[double bond]C[sup t]Bu-CH[double bond]CH) RhCl][sub 2]. On reaction of 1 with [Ir(PMe[sub 3])[sub 2] (acac)], rearrangement to 1,2,4-triphenyliridacyclohexadene cis-[CH[sub 2]-CPh[double bond]CH-CPh[double bond]CPh-Ir (PMe[sub 3])[sub 2](acac)] occurred as well as ring opening. A mechanism involves cleavage of a 1,2,3-triphenyl metallacyclohexadiene into carbene and cyclobutadene fragments, then recombination after cyclobutadiene slippage or rotation. On heating at 90[degrees], both iridium adducts converted to their trans isomers; on heating at 120[degrees], the 1,2-diphenyliridacyclohexadiene rearranged to the 1,4-diphenyl isomer trans-[CH[sub 2]-CPh[double bond]CH-CH[double bond]CPh-Ir(PMe[sub 3])[sub 2](acac)]. A consistent mechanism involves exchange of the [alpha]-hydrogens and [alpha][prime]-phenyl by migration across the metal, through iridabenzene intermediates. This rearrangement also occurs in the triphenyl complex. During attempts to prepare a rhodabenzene, 2 gave both a 2,3-diphenyl isomer and meridional rhodacyclohexadienes.
- Research Organization:
- Dartmouth Coll., Hanover, NH (United States)
- OSTI ID:
- 7235619
- Resource Relation:
- Other Information: Thesis (Ph.D.)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
CYCLOALKENES
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
LABELLING
IRIDIUM COMPLEXES
IRON COMPLEXES
RHODIUM COMPLEXES
DEUTERIUM COMPOUNDS
PROPYLENE
STEREOCHEMISTRY
ALKENES
COMPLEXES
HYDROCARBONS
HYDROGEN COMPOUNDS
KINETICS
ORGANIC COMPOUNDS
REACTION KINETICS
TRANSITION ELEMENT COMPLEXES
400201* - Chemical & Physicochemical Properties