Synthesis and Selectivity in the Formation of Cyclophosphazene-Derived 1,3-Cyclohexadienes from Reactions of RCpCo(COD) [R = MeOC(O)] with Alkynes and Alkenes

Abstract

The first examples of mono and bisfluorophosphazene derived [eta (5)-cyclopentadienyl] [eta (4)-1,3-cyclohexadiene] cobalt complexes have been prepared along with the sandwich compound [eta (5)-carbomethoxycyclopentadienyl] [eta (4)-1,3-bis(pentafluorocyclotriphosphazenyl)-2,4-diphenylcyclobutadiene] cobalt and acetylene trimerized products from the reactions of [eta (5)-MeOC(O)C 5H 4]Co[COD], PhCCP 3N 3F 5 and phenylacetylene in the presence or absence of an additional cycloalkene or indene. Formation of these mono and bis fluorophosphazene derived cobalt cyclohexadiene complexes provide experimental evidence for a metallacyclopentadiene pathway for cyclohexadiene formation in CpCo catalyzed reactions. Selectivity is also observed in the formation of bisfluorophosphazene derived cyclohexadienes which stems from the fact that two P 3N 3F 5 units cannot be accommodated on vicinal carbon atoms of a carbacycle or metallacycle. Interestingly, reactions of (beta-phenylethynyl)pentafluorobenzene with [eta (5)-MeOC(O)C 5H 4]Co[COD] in the presence and absence of external cycloalkene under identical reaction conditions yielded only the cis and trans isomers of the metallocene [eta (5)-MeOC(O)C 5H 4]Co[eta (4)-C 4Ph 2(C 6F 5) 2] along with alkyne trimerized product indicating that the selectivity in cyclohexadiene formation is governed more by steric than electronic factors. All the new compounds were characterized by (1)H, (13)C, (31)P, and (19)F NMR as well as mass spectrometry and elemental analysis. Mono and bispentafluorocyclotriphosphazene derived [eta (5)-cyclopentadienyl] [eta (4)-1,3-cyclohexadiene] cobalt complexes and [eta (5)-carbomethoxycyclopentadienyl] [eta (4)-bis(1,3-pentafluorophenyl)-2,4-diphenylcyclobutadiene] cobalt have also been structurally characterized by single crystal X-ray analysis.

The first substitution reactions of N,N-spiro bridged octachlorobiscyclotriphosphazene

“…Hexachlorocyclotriphosphazene (N 3 P 3 Cl 6 ) is the most popular compound in the cyclophosphazene series, so it is commonly used as a precursor to prepare of other cyclophosphazene derivatives [8][9][10][11][12][13][14][15][16][17].…”

Ansa versus spiro selectivity in substitution reactions of a mono ansa fluorodioxycyclotriphosphazene derivative with diols

“…The determination of substitution patterns is very important for cyclophosphazene chemistry due to the fact that the multiple available pathways in these nucleophilic substitution reactions lead to a large number of cyclophosphazene derivatives [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. Systematic studies of the substitution patterns will lead to a fundamental understanding of the factors which control these processes.…”

Organophosphazenes. 26. Factors Controlling the Pathways Observed in the Reactions of Ethynyl Lithium Reagents with Hexafluorocyclotriphosphazene

“…With the exception of the region and stereospecific t -butyl lithium case, the observed pathways are all regioselective with nongeminal products accompanying geminal products. , The resulting organofunctional phosphazenes have proved to be useful synthetic intermediates. The alkenylphosphazenes undergo addition polymerization at the exocyclic olefin site. − The ethynyl center in phenylethynyl phosphazenes can react with metal carbonyls to give the appropriate organometallic derivatives ,,− or undergo cyclooligomerization reactions. − Recent detailed work by Elias and co-workers has shown how these processes may be used to create phosphazenes with structurally complex organic substituents. − In order to understand better the role of the carbanionic species in the observed reaction pathways of N 3 P 3 F 6 and to provide additional ethynylphosphazenes for reactions with organometallic reagents, we have examined the reactions of alkylethynyl lithium reagents and mixed substituent ethynyl lithium reagents and aryl lithium reagents.…”