Ruthenium chloride (RuCl3), particularly in its hydrated form RuCl3·xH2O, is a versatile compound used extensively in chemical synthesis. It serves as a starting material for the preparation of many ruthenium complexes due to its ability to readily undergo ligand exchange reactions. Here are some notable applications in the realm of chemical synthesis:

1. **Olefin Metathesis Catalysts**: One of the most prominent uses of RuCl3 is in the preparation of catalysts for olefin metathesis, a reaction that rearranges the substituents on double bonds of alkenes. Catalysts derived from RuCl3, such as those containing the N-heterocyclic carbene ligands, have found immense utility in organic synthesis, polymer science, and the pharmaceutical industry for the formation of carbon-carbon bonds.

2. **Organometallic Chemistry**: RuCl3 is also an important precursor to synthesizing organoruthenium compounds. These compounds find applications in homogeneous catalysis where they facilitate a variety of transformations, including hydrogenation, oxidation, and C-C coupling reactions.

3. **Water Oxidation Catalysis**: RuCl3-derived catalysts have been investigated for their utility in catalyzing the oxidation of water to dioxygen, an important process in the development of sustainable energy systems, particularly in the field of artificial photosynthesis.

4. **Medicinal Chemistry**: RuCl3 is used in the synthesis of ruthenium complexes that mimic the behavior of iron in binding and transporting oxygen in biological systems. Such complexes are being studied for their potential as therapeutics, including as anticancer agents.

5. **Dye-Sensitized Solar Cells**: Ruthenium complexes synthesized from RuCl3 are used in the fabrication of dye-sensitized solar cells (DSSCs) as photosensitizers. The performance of DSSCs is significantly affected by the light absorption properties of the ruthenium complexes that are anchored to the titanium dioxide semiconductor.

6. **Surface Chemistry**: RuCl3 can be used to functionalize surfaces, such as in the deposition of ruthenium layers in the manufacture of advanced electronic components or catalytically active surfaces.

The versatility of RuCl3 in these applications lies in its ability to produce ruthenium centers in various oxidation states under different conditions, allowing chemists to tailor the properties of the complexes for specific applications.