Weatherford-Pratt, J.; Dickie, D. A.; Harman, W. D. CCDC 1970047: Experimental Crystal Structure Determination. CSD Communication 2019.
Publications
2019
Weatherford-Pratt, J.; Dickie, D. A.; Harman, W. D. CCDC 1938216: Experimental Crystal Structure Determination. CSD Communication 2019.
Dickie, D. A.; Turner, J. M.; Nie, Z.; Geraghty, C.; Ling, T.; Cai, C. CCDC 1911622: Experimental Crystal Structure Determination. ICSD Communication 2019.
Dickie, D. A.; Cai, C.; Turner, J. M.; Nie, Z.; Geraghty, C.; Ling, T. CCDC 1911619: Experimental Crystal Structure Determination. ICSD Communication 2019.
Gilliard Jr., R. J.; Miller, P. D.; Dickie, D. A. CCDC 1900382: Experimental Crystal Structure Determination. CSD Communication 2019.
Krantz, K. E.; Weisflog, S. L.; Yang, W.; Dickie, D. A.; Frey, N. C.; Webster, C. E.; Gilliard Jr., R. J. Extremely twisted and bent pyrene-fused N-heterocyclic germylenes. Chemical Communications 2019, 55, 14954-14957.
The first examples of pyrene-fused Janus-type N-heterocyclic germylenes (NHGe) are reported. Remarkably, the pyrene linker and the germanium containing rings are extremely twisted, with “twist angles” up to 64°. Coordination of a Lewis base modifies the twisting of pyrene to an overall bent core (141° bend angle).
Walley, J. E.; Wong, Y. O.; Freeman, L. A.; Dickie, D. A.; Gilliard Jr., R. J. N-Heterocyclic Carbene-Supported Aryl- and Alk- oxides of Beryllium and Magnesium. Catalysts 2019, 9, 934.
Recently, we have witnessed significant progress with regard to the synthesis of molecular alkaline earth metal reagents and catalysts. To provide new precursors for light alkaline earth metal chemistry, molecular aryloxide and alkoxide complexes of beryllium and magnesium are reported. The reaction of beryllium chloride dietherate with two equivalents of 1,3-diisopropyl-4,5-dimethylimidizol-2-ylidine (sIPr) results in the formation of a bis(N-heterocyclic carbene) (NHC) beryllium dichloride complex, (sIPr)2BeCl2 (1). Compound 1 reacts with lithium diisopropylphenoxide (LiODipp) or sodium ethoxide (NaOEt) to form the terminal aryloxide (sIPr)Be(ODipp)2 (2) and alkoxide dimer [(sIPr)Be(OEt)Cl]2 (3), respectively. Compounds 2 and 3 represent the first beryllium alkoxide and aryloxide species supported by NHCs. Structurally related dimers of magnesium, [(sIPr)Mg(OEt)Brl]2 (4) and [(sIPr)Mg(OEt)Me]2 (5), were also prepared. Compounds 1-5 were characterized by single crystal X-ray diffraction studies, 1H, 13C, and 9Be NMR spectroscopy where applicable.
Freeman, L. A.; Walley, J. E.; Dickie, D. A.; Gilliard Jr., R. J. Low-nuclearity magnesium hydride complexes stabilized by N-heterocyclic carbenes. Dalton Transactions 2019, 48, 17174-17178.
Herein we report the synthesis and characterization of dinuclear magnesium–hydride complexes, [(IiPrMe2)Mg(μ-H)(HMDS)]2 [4, IiPrMe2 = N,N′-diisopropyl-2,3-dimethylimidazol-2-ylidine, HMDS = bis(trimethylsilyl)amide] and [(IiPrMe2)Mg(μ-H)(ASCP)]2 (5, ASCP = 2,2,5,5-tetramethyl-2,5-disila-1-azacyclopent-1-yl). Compounds 4 and 5 exhibit the lowest nuclearity of any carbene–magnesium hydride complex to date.
Wilde, J. H.; Smith, J. A.; Dickie, D. A.; Harman, W. D. Molybdenum-Promoted Synthesis of Isoquinuclidines with Bridgehead CF3 Groups. Journal of the American Chemical Society 2019, 141, 18890–18899.
The preparation of the complex MoTp(NO)(DMAP)(4,5-η2-(2-trifluoromethyl)pyridine) (DMAP = 4-(dimethylamino)pyridine; Tp = tris(pyrazolyl)borate) is described. The CF3 substituent is found to preclude κ-N coordination, allowing for direct coordination without protection of the nitrogen. The dihapto-coordinate complex can be isolated as a single diastereomer, methylated, and reacted with a range of nucleophiles. Oxidative decomplexation affords the free dihydropyridines in good yield (75–90%). As a demonstration of synthetic utility, a series of novel bridgehead CF3-substituted isoquinuclidines was prepared from these decomplexed dihydropyridines.
Dakermanji, S. J.; Smith, J. A.; Westendorff, K. S.; Pert, E. K.; Chung, A. D.; Myers, J. T.; Welch, K. D.; Dickie, D. A.; Harman, W. D. Electron-Transfer Chain Catalysis of η2-Arene, η2-Alkene, and η2-Ketone Exchange on Molybdenum. ACS Catalysis 2019, 9, 11274–11287.
An oxidant-initiated, substitution process for dihapto-coordinated ligands is described for the {MoTp(NO)(DMAP)} system. Complexes of the form MoTp(NO)(DMAP)(η2-alkene), MoTp(NO)(DMAP)(η2-ketone), and MoTp(NO)(DMAP)(η2-arene) (where Tp = hydridotris(pyrazolyl)borate and DMAP = 4-(dimethylamino)pyridine) undergo an alkene-to-ketone exchange that is catalyzed by the addition of <0.1 equiv of a metallocene oxidant (ferrocenium, permethylferrocenium, or cobaltocenium). A similar acceleration was observed in the presence of the H-bond donor hexafluoroisopropanol (HFIP). From experimental observations, a radical chain propagation mechanism is proposed that is dependent on the equilibrium between dihapto-coordinated (C, O-η2) and monocoordinated (κ-O) isomers and the differing redox characteristics of these two isomeric forms. This concept was then applied to the search of sodium-free reduction conditions for the conversion of MoTp(NO)(DMAP)(I) to various molybdenum(0) complexes of unsaturated ligands, including MoTp(NO)(DMAP)(η2-naphthalene) and MoTp(NO)(DMAP)(α-pinene).