Metallocene Polymers. XVIII. Poly(ferrocenylphosphine oxides)

Abstract

The Lewis acid-catalyzed polycondensation of ferrocene with phenyldichlorophosphine is described. Under a variety of conditions, using melt and solution condensation conditions, followed by a mild postoxidation treatment, polymers composed of ferrocenylene units interconnected by phenylphosphoryl groups are obtained. The soluble, but largely infusible, products possess number-average molecular weights up to 3500 (6000 upon subfractionation). Elemental compositions vary with reaction conditions; optimal consistency with the ideal ferrocenylene(pheny1)phosphoryl recurring unit results from use of a moderate ferrocene excess and smallest possible solvent concentrations at temperatures not exceeding 105". Much as in previously described polyacylations of ferrocene, a minor side reaction is observed which involves rupture of the metal-to-ring bond in ferrocene with subsequent incorporation of cyclopentylene groups into the polymer. This departure, however insignificant, from the purely aromatic polyphosphine oxide composition results in thermal and oxidative stabilities not markedly superior to those of earlier ferrocenylene-methylene polymers. The promising synthetic results reported on various polymeric systems containing arsine or arsine oxide, phosphine or phosphoryl units in the backbone [for representative publications see (2-9)] has led us to investigate, as part of our efforts in the field of metallocene polymers, the feasibility of synthesizing ferrocene-containing phosphine oxide polymers of type (I). The high aromaticity of * For Part XVII, see Ref. (1).the ferrocene system should permit the preparation of such polymers by direct electrophilic substitution of ferrocene under Friedel-Crafts conditions much as in the analogous syntheses of polyferrocenylketones and ferrocenoylbenzoyl polymers described previously ( I J O ) . The present paper discusses the results of this investigation, which show that under appropriate experimental conditions, using ferrocene and phenyldichlorophosphine as reactants, phosphoryl-bridged polymeric compounds can indeed be prepared. RESULTS AND DISCUSSION Polyeondensation Reactions and Polymer StructureThe synthetic approach selected for the preparation of (1) involved the condensation of ferrocene with phenyldichlorophosphine," followed by hydrolysis and postoxidation of the primary polyphosphine. The over-all reaction sequence can be depicted by Eqs. (1) and (2): n + n CI-P-CI & b * * Earlier attempts to prepare (1) by condensation of ferrocene with phenyldichlorophosphine oxide, thus eliminating the subsequent postoxidation step, gave unsatisfactory results. Despite long reaction periods and/or high catalyst concentrations, polymer yields were low, and the products obtained showed poor solubility characteristics. Downloaded by [Otto-von-Guericke-Universitaet Magdeburg] at 01:41 21 October 2014 METALLOCENE POLYMERS. Will 373 H \ The aluminum chloride-catalyzed reaction of ferrocene with phenyldichlorophosphine had previously been described by Sollott et al. (11). These authors...

Organometallic Polymers with Transition Metals in the Main Chain

“…A similar route was reported by Neuse and Pittman for the synthesis of phosphorus-bridged poly(ferrocenes) ( 7 , 8 ). Reaction of ferrocene with PPhCl 2 , P(O)PhCl 2 , or P(S)PhCl 2 in the presence of a Lewis acid catalyst in the melt or in solution at 80−170 °C yielded low molecular weight materials ( M n < 6000, by VPO), the composition of which depended on the reaction conditions.…”

Metal−Metal Interactions in Linked Metallocenes

“…167 A number of oligomeric and polymeric phosphorus-(III) and phosphorus(V) species have been prepared. Low molecular mass H[Fe(C 5 H 4 ) 2 P(X)Ph] n OH (X ) O, S) were first prepared in 1967 by an aluminum chloride-catalyzed condensation of ferrocene and Ph-PCl 2 , followed by oxidation with hydrogen peroxide, 293 and by the ZnCl 2 -catalyzed condensation of ferrocene and PhP(X)Cl 2 (X ) O, S). 294 Phosphorus-bridged [1]ferrocenophanes have also been found to undergo anionic 295 or thermal 296 ring-opening oligomerization and polymerization reaction like their silicon-bridged analogues.…”

Novel Synthesis and Characterization of Side-Chain Ferrocene-Containing Polymers

“…The metallocene unit can be incorporated into polymers either as a side group or as a chain backbone unit. − It is a challenge to synthesize polymeric systems which include organometallic moiety as a main-chain element using traditional synthetic methods such as addition polymerization because the preparation of metal compounds with suitably reactive multiple bonds is difficult . In the 1960s and 1970s, much attention was directed to polycondensation of bifunctional monomers . Since the purification of these monomers is difficult, the reaction stoichiometry could not be precisely maintained, and often only low molar mass oligomers were produced …”