VOLTAMMETRY OF CARBOCATIONS STABILIZED BY COORDINATION WITH TETRAHEDRAL MOLYBDENUM AND TUNGSTEN CARBON CLUSTERS - CO)(4)-MU-ETA(2)ETA(3)-(HCCCR(1)R(2))](BF4-)-B(-I) COMPLEXES() (M=MO, W, R(1), R(2)=H, ME, AND PR)
Iv. Barinov et al., VOLTAMMETRY OF CARBOCATIONS STABILIZED BY COORDINATION WITH TETRAHEDRAL MOLYBDENUM AND TUNGSTEN CARBON CLUSTERS - CO)(4)-MU-ETA(2)ETA(3)-(HCCCR(1)R(2))](BF4-)-B(-I) COMPLEXES() (M=MO, W, R(1), R(2)=H, ME, AND PR), Russian chemical bulletin, 43(3), 1994, pp. 375-380
The electrochemical reduction of the carbocationic complexes [CP(2)M(2
)(CO)(4)-mu-eta(2) 2:eta(3) (HCCCR(1) R(2))](BF4-)-B-+ where M/R(1), R
(2) = Mo/H, H (1(+)), Mo/H, Me (2(+)), Mo/Me, Me (3(+)), Mo/H, Pr-i (4
(+)), has been studied by polarography and cyclic voltammetry on a Hg-
electrode in THF solution. It has been suggested that carbocationic ce
nter-directed reversible two-electron reduction of 1(+)-4(+) takes pla
ce according to an ECE-mechanism and results in the carbanionic comple
xes [Cp(2)M(2)(CO)(4)-mu-eta(2):eta(3)-(HCCCR(1)R(2))] (1(-)-4(-)) as
final products via carbon-centered radicals as intermediates. Anions 1
(-)-4(-) are capable of irreversible two-electron reduction at more ne
gative potentials or protonation resulting in their transformation int
o the corresponding acetylene complexes [Cp(2)M(2)(CO)(4)(HCCCHR(1)R(2
))], which are also capable of irreversible two-electron reduction. An
ions 1(-)-4(-) and their protonated forms are reduced with cleavage of
the Mo-Mo bond. The reduction pathways of complexes 1(+), 2(+), and 4
(+) with C-H bonds at the carbon atom of the carbocationic center are
different on a Pt-electrode. It is suggested that this difference is d
ue to the abstraction of a H-atom from the intermediate radical specie
s by platinum.