Nickel poly-acetylide carbonyl clusters: structural features, bonding and electrochemical behaviour

Area of Science:

• Inorganic Chemistry
• Organometallic Chemistry
• Materials Science

Background:

• Nickel carbonyl clusters are versatile precursors in inorganic synthesis.
• Carbon halides are reactive species used in functionalization reactions.
• Acetylide clusters are of interest due to their unique electronic and structural properties.

Purpose of the Study:

• To investigate the reactions of tetrabutylammonium hexanickel dodecacarbonyl with carbon halides.
• To prepare and characterize novel nickel-acetylide clusters.
• To understand the structural and electronic properties of these clusters.

Main Methods:

• Reaction of [NEt(4)](2)[Ni(6)(CO)(12)] with carbon halides (CCl(4), C(4)Cl(6)) in dichloromethane.
• Isolation and full characterization of resulting nickel-acetylide clusters using spectroscopic and crystallographic techniques.
• Electrochemical studies and Extended Hückel Molecular Orbital (EHMO) calculations.

Main Results:

• Preparation of known clusters: [Ni(16)(C(2))(2)(CO)(23)](4-), [HNi(25)(C(2))(4)(CO)(32)](3-), and [Ni(22)(C(2))(4)(CO)(28)Cl](3-).
• Isolation and characterization of new clusters: [Ni(17)(C(2))(2)(CO)(24)](4-) and [Ni(25)(C(2))(4)(CO)(32)](4-).
• Structural analysis revealed clusters based on a Ni(16) square orthobicupola with interstitial C(2) moieties and short C-C bonds.
• Electrochemical studies showed diverse redox processes with limited stability.
• EHMO calculations indicated that tightly bonded C-C units are less effective in stabilizing the metal cluster cage compared to isolated carbon atoms.

Conclusions:

• The reaction conditions allow for the synthesis of various nickel-acetylide clusters.
• The structural motif of a Ni(16) square orthobicupola is a common feature.
• The stability of these clusters is influenced by the nature of the interstitial acetylide units, with isolated carbon atoms providing greater stabilization.