Synthesis and Structure of Chromium(VI) Nitrido Cyclopentadienyl Complexes

Abstract

A series of rare nitrido cyclopentadienyl complexes have been prepared of chromium(VI). An improved synthesis of NCr(I)(NPr i 2 ) 2 is provided, which reacts with NaCp to give NCr(η 1 -Cp)(NPr i 2 ) 2 (1) in 82% isolated yield. The η 1 -indenyl complex 2 can be prepared using a similar procedure. Replacement of one diisopropylamido ligand was accomplished to prepare NCr(NPr i 2 )Cp(O 2 CPh) (3), NCr-(NPr i 2 )Cp(Cl) (4), and [NCr(NPr i 2 )Cp(NCMe)] + [SbF 6 ] − (5). In the series, the Cr−C interactions increase in bond order, 3 < 4 < 5, as the cyclopentadienyl compensates for the decreasing donor ability of the other ligands on chromium. The Ligand Donor Parameters (LDPs) for the η 1 -cyclopentadienyl and η 1 -indenyl ligands were measured as 13.73 and 13.76 kcal/ mol, respectively. Compounds 1−5 were characterized by single-crystal X-ray diffraction.

Catalytic Imido-Transfer Reactions of Well-Defined Silica-Supported Titanium Imido Complexes Prepared via Surface Organometallic Chemistry

“…While chloride is a very poorly donating ligand and η 5 -Cp is a strong σ-/π-donor, η 1 -Me 2 Pyr is known to be a good σ-donor but a weak π-donor, and thus the overall electron-donating ability of these ligands can be ranked as follows: Cl < Me 2 Pyr < Cp. , In this context the superior activity of the pyrrolyl catalyst 1s is surprising, especially considering the fact that the preference for the electron-rich metal center in this reaction could be rationalized as a result of the imido nitrogen lone pair being in that case less involved in bonding with Ti and more localized on the nitrogen atom (this is also reflected in longer d TiN , see above), which in turn makes the imido group more prone toward the nucleophilic attack on the ketone…”

Weakly Coordinating yet Ion Paired: Anion Effects on an Internal Rearrangement

“…NCr(N-i-Pr 2 ) 2 I was prepared as previously described. 38 The phosphines PMe 3 and PPhMe 2 were purchased from Strem Chemical and used as received. AgSbF 6 ,TlPF 6 , and AgBPh 4 were purchased from Sigma-Aldrich and used as received.…”

“…All procedures were carried out under an N 2 atmosphere in an MBraun glovebox or using Schlenk techniques. NCr­(N- i -Pr 2 ) 2 I was prepared as previously described . The phosphines PMe 3 and PPhMe 2 were purchased from Strem Chemical and used as received.…”

Chromium Nitride Umpolung Tuned by the Locus of Oxidation

“…Similarly to Mn salens, Cr salen complexes have found use as catalysts in a number of applications such as epoxidation, copolymerization, and phenol cross-coupling . Cr nitrides have also been explored as heterogeneous catalysts, and a number of stable Cr V , and Cr VI − nitrides have been reported, with the Cr V nitrides generally acting as nucleophiles . In many cases, Mn nitrides are utilized as nitrogen atom transfer agents in the preparation of Cr nitrides, ,, demonstrating the increased stability of the latter.…”