Synthesis, X-ray Structure, and Ring-Opening Polymerization of Pentacoordinate Silicon-Bridged [1]Ferrocenophane

Abstract

The cationic ring-opening polymerization of cyclic pentacoodinate sila[1]ferrocenophanes was carried out in dichloromethane to give poly(ferrocenylsilanes) having pentacoordinate silicon moieties in the polymer backbone. The silyl cation gave the best results as an initiator for the polymerization, affording pentacoordinate poly(ferrocenylsilane) (M w is 9.0 × 103) in high yields.

Strained Metallocenophanes and Related Organometallic Rings Containing π‐Hydrocarbon Ligands and Transition‐Metal Centers

“…[70,74,75] The significant structural changes upon hypercoordination of the silicon center include a longer FeÀSi separation, a change to a trigonal bipyramidal geometry at the silicon atom accompanied by narrower q angles and elongated C ipso ÀSi bonds. [74,75] In 17, the weaker C ipso ÀSi bond is easily cleaved in the presence of a cationic catalyst to initiate ROP, unlike the analogous tetracoordinate sila [1]ferrocenophane, which is inert under similar conditions. [74] Higher-coordinate [1]ferrocenophanes are useful models for the nucleophilic ringopening polymerization [77] of tin-bridged [1]ferrocenophanes.…”

“…[74,75] In 17, the weaker C ipso ÀSi bond is easily cleaved in the presence of a cationic catalyst to initiate ROP, unlike the analogous tetracoordinate sila [1]ferrocenophane, which is inert under similar conditions. [74] Higher-coordinate [1]ferrocenophanes are useful models for the nucleophilic ringopening polymerization [77] of tin-bridged [1]ferrocenophanes. Interestingly, ROP of sila [1]ferrocenophanes leads to water-soluble organometallic polymers after introduction and quaternization of pendent amino substituents.…”

Synthesis and Solution Self‐Assembly of Polyisoprene‐block‐poly(ferrocenylmethylsilane): A Diblock Copolymer with an Atactic but Semicrystalline Core‐Forming Metalloblock

“…15 Hypercoordinate silicon-bridged [1]ferrocenophanes can also be synthesised from chlorosila[1]ferrocenophanes Fe(η 5 -C5H4)2SiRR' (R = R' = Cl or R = Me, R' = Cl) and Li or Fe(η 5 -C5H4)2SiCl(CH2Cl) and N-methyl-N-(trimethylsilyl)acetamide. 16,17 These pentacoordinate species show a pronounced Si-N or Si-O interaction with a pseudo trigonal bipyramidal geometry at the bridging silicon atom in the solid state. 17,18 In addition, spirocyclic sila[1]ferrocenophanes can be prepared in a similar manner to that already described: for example the reaction of Fe(η 5 -C5H4Li)2·TMEDA with Cl2Si(CH2)3 gives silacyclobutyl[1]ferrocenophane (Scheme 2 [B]).…”

“…16,17 These pentacoordinate species show a pronounced Si-N or Si-O interaction with a pseudo trigonal bipyramidal geometry at the bridging silicon atom in the solid state. 17,18 In addition, spirocyclic sila[1]ferrocenophanes can be prepared in a similar manner to that already described: for example the reaction of Fe(η 5 -C5H4Li)2·TMEDA with Cl2Si(CH2)3 gives silacyclobutyl[1]ferrocenophane (Scheme 2 [B]). 19 These species are of importance in the preparation of PFS materials as they function as crosslinkers during polymerisation reactions.…”

“…17 The resulting PFS appears to retain the pentacoordinate Si centres but the molar mass was low (Mw = ca. 9000 Da).…”