Steric Protection of Rhodium-Nitridyl Radical Species

10.26434/chemrxiv.8187608 ◽

2019 ◽

Author(s):

Christophe Rebreyend ◽

Valentinos Mouarrawis ◽

Jarl Ivar van der Vlugt ◽

Bas de Bruin

Keyword(s):

Carbon Monoxide ◽

Rhodium Complex ◽

Synthetic Route ◽

Stille Coupling ◽

Radical Species ◽

Tert Butyl ◽

Butyl Group ◽

Tert Butyl Group ◽

Combined Data

In an attempt to synthesize a mononuclear rhodium nitridyl complex with a reduced tendency to undergo nitridyl radical N-N coupling we synthesized a bulky analog of Milstein’s bipyridine-based PNNH ligand, bearing a tert-butyl group at the 6’ position of the bipyridine moiety. A three-step synthetic route toward this new bulky tBu3PNNH ligand was developed, involving a selective nucleophilic substitution step, followed by a Stille coupling and a final hydrophosphination step to afford the desired 6-(tert-butyl)-6'-((di-tert-butylphosphino)methyl)-2,2'-bipyridine (tBu3PNNH) ligand. This newly developed tBu3PNNH ligand was incorporated in the synthesis of the sterically protected azide complex [Rh(N3)(tBu3PNNH)]. We explored N2 elimination form this species using photolysis and thermolysis, hoping to synthesize a mononuclear rhodium complex with a terminal nitrido moiety. Characterization of the reaction product(s) using NMR, coldspray HR-ESI-MS and EPR spectroscopy shows that the material is both EPR and NMR silent, and data obtained by MS spectrometry revealed masses corresponding with both monomeric and dimeric nitrido/nitridyl complexes. The combined data point to formation of a paramagnetic [(tBu3PNN)Rh(µ-N)Rh(tBu3PNN)] species. It thus seems that despite its three tBu groups the new ligand is not bulky enough to prevent formation of Rh-N-Rh bridged species. However, the increased steric environment does prevent further reaction with carbon monoxide, which is unable to coordinate to rhodium.

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Medium-sized cyclophanes, part 59:1 Nitration of [3.3]- and [3.3.3]metacyclophanes Through-space electronic interactions between two or three benzene rings

Canadian Journal of Chemistry ◽

10.1139/v02-009 ◽

2002 ◽

Vol 80 (2) ◽

pp. 207-215 ◽

Cited By ~ 2

Author(s):

Takehiko Yamato ◽

Koji Tsuchihashi ◽

Noriko Nakamura ◽

Mai Hirahara ◽

Hirohisa Tsuzuki

Keyword(s):

Acetic Anhydride ◽

Electronic Interaction ◽

Reaction Conditions ◽

Tert Butyl ◽

Mixed Acid ◽

Butyl Group ◽

Tert Butyl Group ◽

Starting Compound ◽

Nitration Product ◽

Fuming Nitric Acid

The two tert-butyl groups of anti-6,15-di-tert-butyl-9,18-dimethoxy[3.3]metacyclophane (anti-4) are both ipso-nitrated even under mild reaction conditions such as copper(II) nitrate in an acetic anhydride solution because of the decreased deactivation of the second aromatic ring by the introduced nitro group. On the other hand, anti-5,13-di-tert-butyl-8,16-dimethoxy[2.2]metacyclophane (anti-1) undergoes replacement of only one tert-butyl group under the same reaction conditions. The higher yields of the twofold ipso-nitration product anti-7 were obtained in nitration of anti-4 with fuming nitric acid or mixed acid (HNO3H2SO4). Thus, the number of ipso-nitrations at the tert-butyl groups of anti-4 was strongly affected by the reactivity of the nitration reagent. Nitration of the corresponding syn-conformer syn-4 with copper(II) nitrate in an acetic anhydride solution, however, led only to the recovery of the starting compound. The presently developed procedure was further applied to the direct removal of the tert-butyl group by electrophilic substitution of the larger-sized ring macrocyclic metacyclophanes, cone- and partial-cone-tri-tert-butyl[3.3.3]metacyclophanes 11.Key words: [3n]metacyclophanes, conformation, ipso-nitration, through-space electronic interaction, crystal structure.

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Reactions of benzyl methyl substituted-benzyl phosphites with tert-butyl hypochlorite: "balanced TS" validating reactivity/selectivity principle

Canadian Journal of Chemistry ◽

10.1139/v98-081 ◽

1998 ◽

Vol 76 (6) ◽

pp. 836-842

Author(s):

Sung Soo Kim ◽

Yu Zhu ◽

In Seok Oh ◽

Chang Gyeong Lim

Keyword(s):

Benzyl Chloride ◽

Activation Parameters ◽

Differential Activation ◽

Tert Butyl ◽

Benzyl Chlorides ◽

Butyl Group ◽

Tert Butyl Group ◽

Polar Transition ◽

Isokinetic Relations ◽

Selectivity Principle

Reactions of a series of several benzyl methyl substituted-benzyl phosphites with tert-butyl hypochlorite were investigated. The reactions produced phosphates, isobutene, alkyl chlorides, and benzyl chlorides via phosphonium chlorides as intermediates. Furthermore, the phosphates bearing a tert-butyl group underwent fragmentation to yield isobutene and another phosphates. Relative rates of formations of substituted benzyl and benzyl chloride (kY/kH) were measured at the temperatures (-20, 0, 20, 40°C). Logarithms of the rates (log kY/kH) were plotted against sigma + and 1/T, respectively. The former gave Hammett correlations to suggest a polar transition state (TS). The latter yielded differential activation parameters (ΔΔ Hdouble daggerY-H and ΔΔ Sdouble daggerY-H ), which indicate isokinetic relations and enthalpy control of rates. The selectivities (kY/kH) decrease with higher temperatures and thereby follow the reactivity/selectivity principle.Key words: phosphites, tert-butyl hypochlorite, Hammett correlations, differential activation terms, reactivity/selectivity principle.

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Evaluation of the tert-butyl group as a probe for NMR studies of macromolecular complexes

Journal of Biomolecular NMR ◽

10.1007/s10858-021-00380-y ◽

2021 ◽

Author(s):

Rashmi Voleti ◽

Sofia Bali ◽

Jaime Guerrero ◽

Jared Smothers ◽

Charis Springhower ◽

...

Keyword(s):

Nmr Studies ◽

Macromolecular Complexes ◽

Tert Butyl ◽

Butyl Group ◽

Tert Butyl Group

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Michael addition of amines to sterically crowded ortho-benzoquinone completed with unprecedented 1,2-shift of a tert-butyl group

Tetrahedron ◽

10.1016/j.tet.2020.131841 ◽

2021 ◽

Vol 79 ◽

pp. 131841

Author(s):

Eugeny Ivakhnenko ◽

Vasily Malay ◽

Galina Romanenko ◽

Oleg Demidov ◽

Pavel Knyazev ◽

...

Keyword(s):

Michael Addition ◽

Tert Butyl ◽

Butyl Group ◽

Tert Butyl Group

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Tri(Terf-Butyl)plumbyl-phosphanes, Synthesis and Multinuclear Magnetic Resonance

Zeitschrift für Naturforschung B ◽

10.1515/znb-2000-1008 ◽

2000 ◽

Vol 55 (10) ◽

pp. 939-945 ◽

Cited By ~ 8

Author(s):

Max Herberhold ◽

Christian Köhler ◽

Volker Tröbs ◽

Bernd Wrackmeyer

Keyword(s):

Magnetic Resonance ◽

Phosphorus Atom ◽

Coupling Constants ◽

Tert Butyl ◽

Nmr Data ◽

Butyl Group ◽

Tert Butyl Group ◽

Multinuclear Magnetic Resonance

AbstractThe reaction of tri(tert-butyl)plumbyl-lithium (1) with various phosphorus chlorides was studied. With diphenyl- and amino(phenyl)phosphorus chlorides the formation of hexa(tertbutyl) diplumbane (2) and tetraphenyldiphosphane (3) or the respective 1,2-bis(am ino)-1,2-diphenyl- diphosphanes [e. g. 5: amino = PhCH2(tBu)N] was dominant. The presence of at least one tert-butyl group at the phosphorus atom gave access to tri(tert-butyl)plumbyl-di(tert-butyl) phosphane (4) and to tri(tert-butyl)plumbyl-amino(tert-butyl)phosphanes [amino = tBu(H)N (6), Me(Ph)N (7), PhCH2(Me)N (8), PhCH2(tBu)N (9)] via the reaction of 1 with the corresponding phosphorus chlorides. Side products were again 2 and the corresponding diphosphanes, unidentified compounds, and in two cases, bis(phosphanyl)-di(tert-butyl)plumbanes [phosphanyl = tBu(H)N(tBu)P (10), Me(Ph)N(tBu)P (11)]. Trimethylplumbyl-benzyl(methyl)- amino(tert-butyl)phosphane (12) was prepared for comparison. All compounds were characterized by their 1H , 13C, 15N (9 ),31P and 207Pb NMR data. The coupling constants 1J(207Pb,31P) are large and negative, whereas the coupling constants 1J(207Pb, 13C) are small and can be of either sign. The coupling constants 2J(31P-N-13C) of 6 - 12 indicate a preferred conformation of the substituents at phosphorus and nitrogen

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