Bis(benzene)tungsten W(η6-C6H6)2
Bis(benzene)tungsten W(h6-C6H6)2 is an organometallic tungsten compound investigated as potential precursor for the growth of metallic tungsten W films.
Properties of W(h6-C6H6)2: Green-yellow colored neutral, diamagnetic solid, mp. 160 °C, 18-valence electron system, volatile, soluble in most common organic (polar) solvents. Bonding synergism exists in W(h6-C6H6)2 from filled benzene HOMO (p-orbitals) to empty metal orbitals (p, dxz, dyx, dyz) and back-bonding from occupied, filled metal orbitals to empty benzene p*-orbitals.[[i]]
Synthesis of W(h6-C6H6)2:
1) WCl6 +2 Al / AlCl3 + C6H6(exc.) → W(h6-C6H6)2 + 2 AlCl3 ( (Fischer-Hafner synthesis; yield 2 %)
2) W + 2 C6H6 → W(h6-C6H6)2 (Metal Vapor Condensation; Yield: 30 – 40 %)
[i] Prof. Dr. Heinrich Lang « The Chemistry of Metal CVD, International Research Training Group, Materials and Concepts for Advanced Interconnects »
W(h6-C6H6)2 for W films by (MO)CVD
Table . Summary conditions/resutls W(C6H6)2 as precursor for W films by MOCVD
W(h6-C6H6)2 was applied as precursor for the growth of metallic W films on diverse substrates (graphite, glass, glass wool, ceramics, plastics, nylon, bakelite, Al, Cu, Ag, and stainless steel) in the hot-wall MOCVD reactor in low-pressure conditions, H2, N2, He or Ar carrier gases and deposition temperatures 300-600 °C. Higher temperatures resulted in the ligand decomposition / formation of free carbon and/or polymerizable hydrocarbons (the formed H2C=CH2, HC≡CH and other decomposition byproducts contaminated the obtained W coatings). The deposited metallic W films (0.01 – 50 μm thick after 3 – 6 hours growth time) were bright, shiny, well adherent, having only low concentration of impurities (no formation of carbides and oxides), exhibited good electrical conductance and corrosion protection. .[[i]]
[i] Prof. Dr. Heinrich Lang « The Chemistry of Metal CVD, International Research Training Group, Materials and Concepts for Advanced Interconnects »
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