Styrene Polymerization under Ambient Conditions by using a Transient 1,3,2‐Diazaphospholane‐2‐oxyl Complex

Abstract

A combined theoretical and experimental study on the formation and reactivity of a P-OTEMP (P-bound TEMPO (TEMPO=2,2,6,6-tetramethyl-piperidin-1-oxyl)) substituted 1,3,2-diazaphospholane W(CO) complex is presented, including DFT-based mechanistic details. The complex possesses a thermally labile O-N bond that cleaves homolytically yielding the transient 1,3,2-diazaphospholane-2-oxyl complex [(CO) W(R PO )], which acts as a radical initiator for styrene polymerization under ambient conditions.

1,3,2-Diheterophospholane complexes: access to new tuneable precursors of phosphanoxyl complexes and P-functional polymers

“…The 2.5335(5) Å P-W bond and 1.6595(15) Å P-O1 bond are slightly elongated in comparison with the N-methyl derivative (4-NMe) of 4. 37 A decrease in the bond length is observed for the O1-N3 distance of 1.4770 (18) Å in contrast to the distance observed in 4-NMe of 1.495 Å. The larger i Pr substituent seems to prohibit a shorter P-O1 bond which comes together with a shorter O1-N3 distance.…”

“…6), i.e., one of them was found to have the diazaphospholidine P-oxide end group (A) as reported before. 37 The most intense peak in the MALDI-MS corresponds to an n max of 48 monomeric units. According to the MALDI-MS, the other polymer (B) has one diazaphospholidine P-oxide and one terminal hydrogen atom as end groups.…”

“…To probe the influence of the substituent at nitrogen (α-position to phosphorus) in 1,3,2-diazaphospholidine complexes, the 1,3-diisopropyl-2-OTEMP-1,3,2-diazaphospholidine tungsten complex 4 (OTEMP; 2,2,6,6-tetramethylpiperidin-Noxyl) was synthesised using a methodology reported earlier. 37 Complexation of the 2-chlorophosphane 1 to the pentacarbonyl tungsten moiety with subsequent reduction via lithium aluminum hydride Li[AlH 4 ] (LAH) yielded the secondary phosphane complex 3 as a light yellow solid (Scheme 1).…”

“…For the conversion of 3 into 4, the TEMPO substituted precursor complex, the most efficient way would be the addition of 2 eq. of TEMPO to complex 3, according to Heurich et al 37 The reaction had to be carried out at 0 °C as preliminary studies revealed an instability at ambient temperature. The reaction yielded almost quantitatively complex 4 with a chemical shift of 142 ppm in the 31 P NMR spectrum and, after purification at −20 °C, as a bright yellow, temperature sensitive solid.…”

Formation and Reactivity of Transient Phosphanoxyl Manganese Complexes

“…We found that a 1,3,2-diazaphospholane complex (Z = W(CO) 5 , R 2 = −N(Me)(CH 2 ) 2 (Me)N−) was prone to homolytic O−N bond cleavage, already at ambient temperature, but still stable enough that allowed for its isolation. 8 It was also shown that styrene polymerization occurred already at room temperature if this precursor complex was employed. 8 As the influence of the metal center (apart from group 6 metals) on the tendency of O−N bond homolysis in phosphane ligands of the type R 2 PO-TEMP was not yet investigated, new studies were launched to gain further knowledge.…”