## 1 Introduction  
The use of metal complexes in catalysis has become a standard practice in organic synthesis. Olein metathesis is among these various catalytic reactions. The carbon-carbon double bond rearrangements effected by olefin metathesis have developed into one of the most powerful tools in organic synthesis due to the facility with which this chemistry constructs carbon-carbon double bonds and the compatibility of this reaction with other functionalities [1; 2]. The search for novel applications of olefin metathesis reactions and study of improvements of the catalysts' reactivity, stability, and selectivity have been extremely active fields since the breakthrough introduction of the current two most recognized alkylidene-types of catalyst families of ruthenium and molybdenum based complexes introduced in the 1980s by the [PERSON] and [PERSON] groups, respectively (Figure 1) [3; 4]. Examples of these catalysts are bis(tricyclohexylphosphine)benzylidine ruthenium(II) dichloride (a [PERSON] 1 st generation catalyst) **1** and 2,6-disopropylylimidonephylidene molybdenum(IV) bis(hexafluoro-\(t\)-butoxide) (a [PERSON] catalyst) **4**. A critical aspect of the development of these families of catalysts is the fact that the properties of these olefin metathesis catalysts can be modified by alteration of the organic ligands in these ruthenium and molybdenum complexes. The success and impact of such modifications have been the subject of many studies that have led to a variety of organic ligands for both of the catalyst families (Figure 1). For example, in the case of Ru metathesis catalysts, these studies led to a variety of \(N\)-heterocyclic carbene complexes including(1,3-bis-(2,4,6-trimethylphenyl)-2-imidazolylidene)-dichloro(o-isopropylphenylmethylene) ruthenium (an example of a Hoveyda-Grubbs 2 nd generation catalyst) **2** and [1,3-bis(2,4,6-trimethylphenyl)-2-imidazolylidene]dichloro-(phenylmethylene)bis(3-bromopyridine) ruthenium(II) (a Grubbs 3 rd generation catalyst) **3**. Similar studies that use ligands to influence catalyst utility have been carried out with Mo catalysts leading, for example, to more useful chiral catalysts like 2,6-disopropylmethylindo-neophylidene-[(S)-(-)-BIPHEN]-molybdenum(IV) catalysts (an (\(S\))-Schrock-Hoveyda catalyst) **5**. Although these studies have led to newer versions of olefin metathesis catalysts that have improved reactivity, air and moisture stability, functional groups tolerance, and stereoselectivity, challenges still remain in using these transition metal complexes. Challenges that remain include: (i) the high cost of the transition metal complexes used as catalysts or precatalysts; (ii) the cost and/or tediousness of the ligand syntheses; and (iii) the potential environmental toxicological or practical concerns that ensue when there is significant metal or ligand contamination in the product. This last issue is a green chemistry issue in that additional process steps have to be used to sequester or remove metals or ligands from products. Such steps increase overall process cost and can be an environmental issue because of the waste that is typically generated in such catalyst/ligand/product separation steps. The last issue is especially critical in pharmaceutical industry and in materials synthesis. In the case of pharmaceuticals, the acceptable level of ruthenium content in products should be less than 10 ppm in the final compound [5; 6; 7]. An efficient separation of ruthenium impurities is also important in the case of polymeric materials used in electronic or device applications. In addition, other issues can arise. For example, in some syntheses, an efficient separation of ruthenium impurities is important as ruthenium residues can lead to undesirable side-reactions like hydrogenation or alkene isomerization in reaction products [8; 9]. There are several ways to approach the three issues noted above. Perhaps the simplest approach is to simply reduce the amount of catalyst that is used in the reaction.