Seven new unsymmetrical triazolylidene ligands 4-(4-R-phenyl)-1-R′-1,2,4-triazoly-1-lidene (where R = H, CH3, CF3, F; and R′ = CH3, iPr, Bzl, methylcyclohexane) were employed in a nickel-catalyzed dehydrogenation of ammonia borane to investigate the steric effects associated with the different N(1) substitutions in the triazole ring. The bulkier substituents benzyl and methylcyclohexane afforded the highest weight percent H2 gas produced. To quantify the steric effect, both percent buried volume (%Vbur) and solid angle G parameter (%) were employed. The G-parameter is a more useful tool when only the crystal structures of the precursor ligands are available.
Bibliographical noteFunding Information:
For financial support, we are indebted to the MHz Nuclear Magnetic Resonance (NMR) Spectrometer’; Dr. Daron E. Janzen, University of St. Thomas start-up funds, Partnership in Learning and Research Grant funds for M.A.G.; work-study study funds, Young Scholars and Collaborative Inquiry grants for M.T. and T.P.; the NSF–MRI grant No. 095322 ‘MRI–R2: Acquisition of a 400 St. Catherine University and the NSF–MRI grant No. 1125975 ‘MRI Consortium: Acquisition of a Single Crystal X-ray Diffractometer for a Regional PUI Molecular Structure Facility’; Dr. Victor Young, Jr., University of Minnesota-Twin Cities, NSF–MRI grant for the Bruker-AXS VENTURE PHOTON-100 under Award Number 1229400, and the Materials Research Facilities Network (MFRN) Program of NSF under Award Number DMR-0819885 ; Dr. Alvaro Romero, Cabrillo College, for the use vapor pressure of liquid water table.
- Triazolium salts
- Triazolylidene ligands