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John C. Huffman

Bio: John C. Huffman is an academic researcher from Indiana University. The author has contributed to research in topics: Triple bond & Crystal structure. The author has an hindex of 62, co-authored 750 publications receiving 17918 citations. Previous affiliations of John C. Huffman include Marion Merrell Dow & University of Chicago.


Papers
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TL;DR: In this paper, achiral and chiral C3-symmetric complexes LMOR have been synthesized and employed in the ring-opening polymerization of l-, rac-, and meso-lactide in CH2Cl2 at 25 °C and below.
Abstract: Single-site achiral and chiral C3-symmetric complexes LMOR, where M = Mg and Zn, L = an η3-trispyrazolyl- or η3-trisindazolyl-borate ligand and R = Et, tBu, Ph, or SiMe3, have been synthesized and employed in the ring-opening polymerization of l-, rac-, and meso-lactide in CH2Cl2 at 25 °C and below. The polymerization occurs by acyl cleavage and gives rise to polylactide, PLA, with PDI of 1.1−1.25 up to 90% conversion. Studies of the kinetics of polymerization reveal first order behavior in both lactide and metal catalyst. For L = tris(3-tert-butylpyrazolyl)borate, (tBupz)3BH, polymerization of ∼500 equiv of l-lactide proceeds to 90% conversion within 1 h and 6 d for the magnesium and zinc catalysts, respectively. The zinc complexes are, however, more tolerant to air and moisture and solid samples where R = SiMe3 are persistent in air for several days. The rate of polymerization is also significantly influenced by the nature of the η3-L spectator ligand. Chiral C3-symmetric catalysts, where L = tris(indaz...

417 citations

Journal ArticleDOI
25 Jun 1993-Science
TL;DR: The crystal structure of a stable silyl cation, triethylsilylium, in the form of its tetrakis (pentafluorophenyl)borate salt [Et3Si+ (C6F5)4B-] (Et, ethyl) shows no coordination between cation and anion.
Abstract: The crystal structure of a stable silyl cation, triethylsilylium, in the form of its tetrakis (pentafluorophenyl)borate salt [Et(3)Si(+) (C(6)F(5))(4)B(-)] (Et, ethyl) shows no coordination between cation and anion. The closest silicon-fluorine distance is greater than 4 angstroms. A toluene solvent molecule is close enough to cause some deviations from planarity at the silicon, but the silicon-toluene distance is well beyond the sum of the silicon and carbon covalent radii. The toluene molecule is essentially planar and undistorted, as expected if little or no positive charge has been transferred from silicon to toluene.

285 citations

Journal ArticleDOI
TL;DR: In this paper, it has been shown that the Mo=Mo bond in M02(OR)6 compounds is labile toward a number of oxidative-addition reactions, including those involving molecular oxygen.
Abstract: : It has previously been shown that the Mo=Mo bond in M02(OR)6 compounds is labile toward a number of oxidative-addition reactions. Treatment with halogens leads to the formation of Mo2(OR)6X4 (M-M) compounds (R = i-Pr, X = C1, Br and I), and addition of ROOR to formation of Mo2(OR)8 (R = i-Pr). Reaction with benzoyl peroxide gave a compound Mo2(OR)6(02CPh)2 (R = i-Pr), believed to contain a Mo-Mo bond. These earlier findings prompted us to continue to investigate oxidative-additions with simple X2 molecules. Reported here are studies involving molecular oxygen.

227 citations


Cited by
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TL;DR: The geometries of 131 SBUs, their connectivity and composition of transition-metal carboxylate clusters which may serve as secondary building units (SBUs) towards construction and synthesis of metal-organic frameworks (MOFs).
Abstract: This critical review presents a comprehensive study of transition-metal carboxylate clusters which may serve as secondary building units (SBUs) towards construction and synthesis of metal–organic frameworks (MOFs). We describe the geometries of 131 SBUs, their connectivity and composition. This contribution presents a comprehensive list of the wide variety of transition-metal carboxylate clusters which may serve as secondary building units (SBUs) in the construction and synthesis of metal–organic frameworks. The SBUs discussed here were obtained from a search of molecules and extended structures archived in the Cambridge Structure Database (CSD, version 5.28, January 2007) which included only crystals containing metal carboxylate linkages (241 references).

2,145 citations

Journal ArticleDOI
TL;DR: Concentrating on recent advances, this article covers industrial aspects, inorganic materials, organic synthesis, cocrystallisation, pharmaceutical aspects, metal complexes, supramolecular aspects and characterization methods.
Abstract: The aim of this critical review is to provide a broad but digestible overview of mechanochemical synthesis, i.e. reactions conducted by grinding solid reactants together with no or minimal solvent. Although mechanochemistry has historically been a sideline approach to synthesis it may soon move into the mainstream because it is increasingly apparent that it can be practical, and even advantageous, and because of the opportunities it provides for developing more sustainable methods. Concentrating on recent advances, this article covers industrial aspects, inorganic materials, organic synthesis, cocrystallisation, pharmaceutical aspects, metal complexes (including metal–organic frameworks), supramolecular aspects and characterization methods. The historical development, mechanistic aspects, limitations and opportunities are also discussed (314 references).

2,102 citations

Journal ArticleDOI
Chao-Jun Li1
TL;DR: Reaction of R,â-Unsaturated Carbonyl Compounds 3127: Reaction of R-UnSaturated Carbonies 3127 7.1.6.
Abstract: 4.2.8. Reductive Coupling 3109 5. Reaction of Aromatic Compounds 3110 5.1. Electrophilic Substitutions 3110 5.2. Radical Substitution 3111 5.3. Oxidative Coupling 3111 5.4. Photochemical Reactions 3111 6. Reaction of Carbonyl Compounds 3111 6.1. Nucleophilic Additions 3111 6.1.1. Allylation 3111 6.1.2. Propargylation 3120 6.1.3. Benzylation 3121 6.1.4. Arylation/Vinylation 3121 6.1.5. Alkynylation 3121 6.1.6. Alkylation 3121 6.1.7. Reformatsky-Type Reaction 3122 6.1.8. Direct Aldol Reaction 3122 6.1.9. Mukaiyama Aldol Reaction 3124 6.1.10. Hydrogen Cyanide Addition 3125 6.2. Pinacol Coupling 3126 6.3. Wittig Reactions 3126 7. Reaction of R,â-Unsaturated Carbonyl Compounds 3127

2,031 citations

Journal ArticleDOI
TL;DR: This work focuses on the characterization of the phytochemical components of Lactide ROP and their role in the regulation of cell reprograming.
Abstract: 23 Stereocontrol of Lactide ROP 6164 231 Isotactic Polylactides 6164 232 Syndiotactic Polylactides 6166 233 Heterotactic Polylactides 6166 3 Anionic Polymerization 6166 4 Nucleophilic Polymerization 6168 41 Mechanistic Considerations 6168 42 Catalysts 6169 421 Enzymes 6169 422 Organocatalysts 6169 43 Stereocontrol of Lactide ROP 6170 44 Depolymerization 6170 5 Cationic Polymerization 6170 6 Conclusion and Perspectives 6171 7 Acknowledgments 6173 8 References and Notes 6173

2,014 citations