## 4 Supported Catalysts in Ring-opening Metothesis Polymerization (ROMP)  
The first example of supported catalyst used in ROMP is also the first well-defined polymer-supported olefin metathesis catalyst [16]. In this study by [PERSON] and [PERSON], a series of polystyrene-divinylbenzene (DVB-PS)-supported Cl\({}_{2}\)(PR\({}_{3}\))\({}_{2}\)Ru=CH-CH=CP\({}_{2}\) olefin metathesis catalysts **6**, **47**, and **48** were synthesized as shown in Scheme 2. These solid-supported catalysts showed activities that were similar to that seen for their homogeneous analogs where the catalyst reactivity varied depending on the nature of PS-supported phosphine ligands. For example, while catalyst **48** can only catalyze ROMP reaction of highly strained cyclic olefins such as norbornene, **6** and **47** can catalyze ROMP of the less strained cyclic olefins such as cyclootene. Although **6**, **47**, and **48** were competent catalysts for ROMP of norbornene, the PDIs of the resulting polymer products were significantly higher than those prepared by the homogeneous analogs. For example, polynorbornene prepared from **6** had PDI values of 5.5, while **1** could be used to prepare similar polymers with PDI values ranging from 1.1 to 1.3. The broader molecular weight range for the polynorbornene prepared by the immobilized catalyst was postulated to be a result of the slow initiation rate of immobilized catalyst that could reflect its inhomogeneity or perhaps the fact that the actual catalyst is a complex that dissociates from the support. The amount of Ru contamination in the ROMP products was not reported. Alternative insoluble organic supports that have been used as catalyst supports for Ru ROMP catalysts include monolithic materials. While such materials have been known since the 1970s [53] but have received more attention [54; 55] after studies by [PERSON] and [PERSON] highlighted their utility as high-performance separation media, scavengers, and reagent supports [56; 57]. Such media have been used too as metathesis catalyst supports as noted above. That work includes studies by [PERSON] whose group described a synthetic route to a monolith-supported ruthenium olefin metathesis catalyst **50** (Scheme 3) [58]. The monolith was generated through ring-opening metathesis copolymerization of norbornene (NBE) and 1,4,4a,5,8,8a-hexahro-1,4,5,8-_exo-endo_-dimethanolenqhthalene (DMN'H6) in the presence of dichloromethane and 2-propanol within a borosilicate column. The functionalization of the catalyst onto the monolith was achieved by grafting a mixture of compound **49** and norbornene onto this solid support. After the grafting process was complete, it was terminated by addition of ethyl vinyl ether. The resulting grafts contained imidazolium salts that were then deprotonated with dimethylaminopyridine (DMAP) to generate an NHC ligand. The immobilization of a ruthenium  
Figure 10: Polyolefin-supported Hoveyda-Grubbs catalysts **44–46**. catalyst onto the monolith support using these NHC ligands was then achieved by treating this monolith-immobilized NHC ligand with **1**. As noted above, the monolith-supported ruthenium complex **50** showed high activity toward RCM. This RCM catalyst was also used in ROMP reactions, where the _cis_ and _trans_ ratio of ROMP products of norbornene and _cis_-cyclodextrinene were the same as those obtained using the analogous homogeneous catalyst. In the ROMP chemistry, the PDI of polymer products ranged from 1.2 to 2.6. However, while the extent of Ru leaching in RCM products was reported as 70 ppm, Ru leaching in the ROMP products was not reported. Schrock's molybdenum catalysts that are used in ROMP have been also immobilized on heterogeneous supports. However, perhaps because of their sensitivity toward air and moisture, there are relatively few reports discussed about immobilizing these Mo-based ROMP catalysts onto solid supports. One example was reported by [PERSON] group in 1996 [PERSON] (1996).