Photochemically reactive polymers. Photochemical reactions of polyurethanes containing bis(cyclopentadienylmolybdenum) hexacarbonyl [Cp2Mo2(CO)6] or bis(cyclopentadienyliron) tetracarbonyl [Cp2Fe2(CO)4] molecules along the polymer backbone

Abstract

The hotochemiatry of the [ -o C H 2 C ( O ) C~4 ( C O )~M o -M o ( C O ) 3 C~C ( O ) C H~~~O~~~C H~~C~O~-] n and [-OCH2CH2C6H4(CO)2Fe-Fe(C0)2C6H4CH2CH2OC(O)NH(CH2)6NHC(O)-]n (4) oligomers was investigated. Because of the metal-metal bonds along the oligomer backbone, these polyurethanes are photochemically reactive, undergoing reactions similar to the C~, M O~( C O )~ and Cp2Fe2(CO)4 dimers. Irradiation leads to homolysis of the metal-metal bonds, as evidenced by formation of C1-(CO) MoC5H4-R-C5H4Mo(C0),C1 or Cl(C0)2FeC6H4-R-CsH4Fe(CO)2Cl (R = CH2CH20C(0)NH(CH2)6N-HC(6)OCH2CH2 or C(0)CH20C(O)NH(CH2)6NHC(O)OCH2C(O)) when the oligomers are irradiated in the presence of CCL. In the presence of triethyl phosphite, disproportionation of the Mo-Mo and Fe-Fe bonded units occurred to give a fragmentation product containing (C5H4R)Mo(C0)c and (C6H4R)Mo-(CO)2(P(OEt)3)2+ or (C6H4R)Fe(C0)f and (C5H4R)Fe(CO)(P(OEt)&+ groups, respectively.Photochemical decomposition of the polyurethanes also occurred over several weeks to months in the solid state. Both light and oxygen are necessary for this decomposition in the solid state. It is proposed that cleavage of the metal-metal bonds leads to oligomer fragmentation and the formation of metal oxide species in these solid state reactions. Oligomer 2, containing the singly bonded C~(CO),M~-MO(CO)~C~ unit, was converted (photochemically or thermally) to a polymer containing triply bonded Cp(CO)2M~Mo(CO)2Cp groups.

Synthesis of Main‐Chain Metal Carbonyl Organometallic Macromolecules (MCMCOMs)

“…FT‐IR analysis of the polymer revealed that the product was actually a mixture containing both Mo‐Mo and Mo≡Mo units. The fraction with Mo≡Mo units resulted from the loss of two CO groups . Extending the reaction time to 6 h lead to degradation of the polymer product.…”

“…The fraction with Mo≡Mo units resulted from the loss of two CO groups. [ 37 ] Extending the reaction time to 6 h lead to degradation of the polymer product. [ 33 ] Copyright 2009, Springer .…”

“…Figure shows an example for the synthesis of polyurethanes with Mo‐Mo bonds via the reaction between metal‐metal bonded diol complex 1 and hexamethylene diisocyanate (HMDI). Based on the same strategy, other types of polyurethane, polyureas and polyamides with Mo‐Mo bonds in the polymer's backbone have been prepared . The molecular weight of the synthesized polymers usually falls into the range of 5000–20 000 g mol −1 (DP = 7–25).…”

Organometallic Polymers of the Transition Metals

“…Tyler and coworkers have synthesized polyurethanes, amides and ureas containing photodegradable metal-metal bonds in their backbones. [338][339][340][341][342] Vinyl monomers were also polymerized in the presence of AIBN to produce polymers with Fe-Fe bonds in their backbones as shown in Scheme 77. A number of polymerization reactions with organic monomers were also described using monomer 245.…”

Recent Advances in Stimuli‐Responsive Commodity Polymers

“…In solution state, homolysis, or disproportionation of metal–metal bonds may occur depending on irradiation conditions, and in solid state, both light and oxygen are required for cleavage and results in chemical fragmentation and formation of metal oxide. [ 138,139 ]…”