Synthesis of [(HIPTNCH2CH2)3N]Cr Compounds (HIPT = 3,5-(2,4,6-i-Pr3C6H2)2C6H3) and an evaluation of chromium for the reduction of dinitrogen to ammonia.
Red-black [HIPTN3N]Cr (1) ([HIPTN3N]3- = [(HIPTNCH2CH2)3N]3- where HIPT = 3,5-(2,4,6-i-Pr3C6H2)2C6H3 = HexaIsoPropylTerphenyl) can be prepared from CrCl3, while green-black [HIPTN3N]Cr(THF) (2) can be prepared from CrCl3(THF)3. Reduction of {1|2} (which means either 1 or 2) with potassium graphite in ether at room temperature yields [HIPTN3N]CrK (3) as a yellow-orange powder. There is no evidence that dinitrogen is incorporated into 1, 2, or 3. Compounds that can be prepared readily from {1|2} include red [HIPTN3N]CrCO (4), blood-red [HIPTN3N]CrNO (6), and purple [HIPTN3N]CrCl (7, upon oxidation of {1|2} with AgCl). The dichroic (purple/green) Cr(VI) nitride, [HIPTN3N]CrN (8) was prepared from Bu4NN3 and 7. X-ray studies have been carried out on 4, 6, and 7, and on two co-crystallized compounds, 7 and [HIPTN3N]CrN3 (65:35) and [HIPTN3N]CrN3 and 8 (50:50). Exposure of a degassed solution of {1|2} to an atmosphere of ammonia does not yield "Cr(NH3)" as a stable and well-behaved species analogous to Mo(NH3). An attempt to reduce dinitrogen under conditions described for the catalytic reduction of dinitrogen by [HIPTN3N]Mo compounds with 8 yielded a substoichiometric amount (0.8 equiv) of ammonia, which suggests that some ammonia is formed from the nitride but none is formed from dinitrogen.
Smythe
Nathan C
NC
Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
Schrock
Richard R
RR
Müller
Peter
P
Weare
Walter W
WW
D000641:Ammonia / Q000138:chemical synthesis*; D002857:Chromium / Q000737:chemistry*; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D008968:Molecular Conformation; D009584:Nitrogen / Q000737:chemistry*; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D010084:Oxidation-Reduction; D013730:Terphenyl Compounds / Q000737:chemistry*
D009942:Organometallic Compounds; D013730:Terphenyl Compounds; D002857:Chromium; D000641:Ammonia; D009584:Nitrogen