Details

Autor(en) / Beteiligte

• Zeng, Yi
• Yu, Ying
• Feng, Hao
• King, R. Bruce
• Schaefer, Henry F

Titel

Nickelacyclopentadienylchromium Tricarbonyl Unit as a Bulky Pseudohalogen in Cyclopentadienylchromium Complexes Leading to Low-Energy High-Spin Structures

Ist Teil von

• Inorganic chemistry, 2015-06, Vol.54 (11), p.5309-5315

Ort / Verlag

United States: American Chemical Society

Erscheinungsjahr

2015

Link zum Volltext

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• Recent studies, particularly from the laboratory of Buchalski and co-workers, have resulted in the syntheses of nickelacyclopentadienyl and nickelafluorenyl metallacycles that can function as pentahapto ligands in transition-metal complexes, similar to the ubiquitous cyclopentadienyl ligand. The structures and energetics of the neutral binuclear chromium carbonyls (CpNiC4H4)2­Cr2(CO) n (n = 6, 5, 4, 3; Cp = η5-C5H5) containing the unsubstituted nickelacyclopentadienyl ligand have been investigated by density functional theory. The lowest energy (CpNiC4H4)2­Cr2(CO) n (n = 6, 4) structures are similar to the corresponding experimentally characterized Cp2­Cr2(CO) n structures with predicted Cr–Cr distances of ∼3.22 and ∼2.27 Å corresponding to the formal single and triple bonds, respectively. This gives the chromium atoms, as well as the nickel atoms, the favored 18-electron configuration. These species appear to be promising synthetic targets. However, the lowest energy (CpNiC4H4)2­Cr2(CO) n (n = 5, 3) structures, as well as two (CpNiC4H4)2­Cr2(CO)4 structures ∼10 to 12 kcal/mol in energy above the global minimum, can be dissected into a discrete pseudohalogen (CpNiC4H4)­Cr­(CO)3 unit and a (CpNiC4H4)­Cr­(CO) n−3 unit linked by a Cr–Cr bond flanked by one to three generally weakly semibridging CO groups. In most cases, the chromium atoms in the (CpNiC4H4)­Cr­(CO) n−3 units of these structures have 14–16-electron configurations rather than the favored 18-electron configuration. This leads to triplet and even quintet spin states in the lowest energy structures.