Synthesis and Characterization of Novel Fluorophosphazene-Derived Cobaltacyclopentadienyl Metallacycles:  Reagents for Assembly of Aryl-Bridged Fluorophosphazenes

Abstract

Reaction of (beta-phenylethynyl)pentafluorocyclotriphosphazene, F5P3N3C identical with CPh, with in situ generated eta5-(MeOC(O)C5H4)Co(PPh3)2 resulted in the formation of two isomers of cobaltacyclopentadienylmetallacycles, (eta(5)-carbomethoxycyclopentadienyl)(triphenylphosphine)-2,5-bis(pentafluorocyclotriphosphazenyl)-3,4-diphenyl cobaltacyclopentadiene (1) and (eta5-carbomethoxycyclopentadienyl)(triphenylphosphine)-2,4-bis(pentafluorocyclotriphosphazenyl)-3,5-diphenyl cobaltacyclopentadiene (2), along with the sandwich compound [eta5-carbomethoxycyclopentadienyl]-[eta4-1,3-bis(pentafluorocyclotriphosphazenyl)-2,4-diphenylcyclobutadiene]cobalt (3). Formation of cobaltacyclopentadienylmetallacycles or cyclobutadienylmetallocene having two fluorophosphazene units on vicinal carbon atoms of the rings was not observed in this reaction. Reaction of 1 with diphenylacetylene resulted in the formation of a novel aryl-bridged fluorophosphazene, 1,4-bis(pentafluorocyclotriphosphazenyl)-2,3,5,6-tetraphenyl benzene (4), and the conversion of cobaltametallacycle to the sandwich compound, [eta5-(MeOC(O)C5H4]Co(eta4-C4Ph4) (5). Reaction of 1 with phenylacetylene resulted in the formation of aryl-bridged fluorophosphazene, 1,4-bis(pentafluorophosphazenyl)-2,3,5,-triphenyl benzene (6). New compounds 1-4 were structurally characterized. In compound 1, the two fluorophosphazene units were oriented in gauche form with respect to each other. However, in compounds 2 and 3, they were eclipsed to each other, and in compound 4, they were oriented anti to each other.

Synthesis of the cobalt–alkyne complex (η5-C5H5)(PPh3)Co{η2-(Me3Si)CC(CO2Et)} and structural characterization of trimethylsilyl substituted cobaltacyclopentadiene complexes derived therefrom

“…These differences are presumably a consequence of steric congestion between the TMS substituent and the cyclopentadienyl/phosphine ligands. The observation that the CoeC(4)eC (11) angle in 7 is 3.6 smaller than the CoeC1eH angle of 8 points to greater steric congestion between the C(4) ester and the C(3) trimethylsilyl substituents than between the C(4) ester and the cyclopentadienyl/phosphine ligands. In 7, the trimethylsilyl group on C(3) is displaced 0.201 A above the CoeC(1)eC(2)eC(3)eC(4) mean plane whereas the trimethylsilyl group on C(1) is displaced by only 0.030 A.…”

DFT Studies on the Reaction of CpCo(PPh3)2 with Diphenylphosphinoalkynes: Formation of Cobaltacycles and Cyclobutadiene-Substituted CpCoCb Diphosphines

“…Therefore, it is predicted from the computational study that both conformers can be obtained in comparable quantities. Although crystal data for the conformer 3P 1 _n_Ph are not available, the fact that several closely related compounds have been isolated and structures determined by X-ray diffraction methods provides a strong support for this assertion . In contrast, the energy barrier for the conversion of 3 1 _n_H to 4 1 _n_H is higher than that to 3P 1 _n_H .…”

“…Although crystal data for the conformer 3P 1 _n_Ph are not available, the fact that several closely related compounds have been isolated and structures determined by X-ray diffraction methods provides a strong support for this assertion. 34 In contrast, the energy barrier for the conversion of 3 1 _n_H to 4 1 _n_H is higher than that to 3P 1 _n_H. In addition, the latter is more stable than 4 1 _n_H.…”

Cobalt, rhodium and iridium

“…The half-sandwich complex 6 was shown to react with a fluorophosphazene modified acetylene to give three new organometallic compounds 7-9. 6 Compounds 7 and 8 are isomers whilst 9 contained a Z 4 -cyclobutadiene unit with trans fluorophosphazene groups (N 3 P 3 F 5 ). The yields of 7-9 were shown to be dependent on reaction time.…”