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Hinge motion is observed in macrocyclic, mortise-type molecular hinges using variable temperature NMR spectroscopy. The data is consistent with dynamic hinging from a folded-to-extended-to-folded enantiomeric state. Crystallographic and solution structures of the folded states are reported. Chemical shift predictions derived from crystallographic data corroborate fully revolute hinge motion. The rate of hinging is affected by steric congestion at the hinge axis. A macrocycle containing glycine, 1, hinges faster than one comprising aminoisobutyric acid, 2. The free energies of activation, ΔG ≠ , for 1 and 2 were determined to be 13.3±0.3 kcal/mol and 16.3±0.3 kcal/mol, respectively. This barrier is largely independent of solvent across those surveyed (CD 3 OD, CD 3 CN, DMSO-d 6 , pyridine-d 5 , D 2 O). Experiment and computation predict energy barriers that are consistent with disruption of an intramolecular network of hydrogen bonds. DFT calculations reveal a pathway for hinge motion., (© 2023 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

C-H amination and amidation by catalytic nitrene transfer are well-established and typically proceed via electrophilic attack of nitrenoid intermediates. In contrast, the insertion of (formal) terminal nitride ligands into C-H bonds is much less developed and catalytic nitrogen atom transfer remains unknown. We here report the synthesis of a formal terminal nitride complex of palladium. Photocrystallographic, magnetic, and computational characterization support the assignment as an authentic metallonitrene (Pd-N) with a diradical nitrogen ligand that is singly bonded to Pd II . Despite the subvalent nitrene character, selective C-H insertion with aldehydes follows nucleophilic selectivity. Transamidation of the benzamide product is enabled by reaction with N 3 SiMe 3 . Based on these results, a photocatalytic protocol for aldehyde C-H trimethylsilylamidation was developed that exhibits inverted, nucleophilic selectivity as compared to typical nitrene transfer catalysis. This first example of catalytic C-H nitrogen atom transfer offers facile access to primary amides after deprotection., (© 2021 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

The silylated hexatriynyl complex trans-(C 6 F 5 )(p-tol 3 P) 2 Pt(C≡C) 3 SiEt 3 (PtC 6 TES) is converted in situ to PtC 6 H (wet n-Bu 4 N + F - , THF) and cross coupled with the diyne H(C≡C) 2 SiEt 3 (HC 4 TES; CuCl/TMEDA, O 2 ) to give PtC 10 TES (71 %). This sequence is repeated twice to afford PtC 14 TES (65 %) and then PtC 18 TES (27 %). An analogous series of reactions starting with PtC 8 TES gives PtC 12 TES (60 %), then PtC 16 TES (43 %), and then PtC 20 TES (17 %). Similar cross couplings with H(C≡C) 2 Si(i-Pr) 3 (HC 4 TIPS) give PtC 12 TIPS (68 %), PtC 14 TIPS (68 %), and PtC 16 TIPS (34 %). The trialkylsilyl species (up to PtC 18 TES) are converted to 3+2 "click" cycloadducts or 1,4-disubstituted 1,2,3-triazoles trans-(C 6 F 5 )(p-tol 3 P) 2 Pt(C≡C) n-1 C=CHN(CH 2 C 6 H 5 )N=N (29-92 % after workups). The most general procedure involves generating the terminal polyynes PtC x H (wet n-Bu 4 N + F - , THF) in the presence of benzyl azide in DMF and aqueous CuSO 4 /ascorbic acid. All of the preceding complexes are crystallographically characterized and the structural and spectroscopic properties analyzed as a function of chain length. Two pseudopolymorphs of PtC 20 TES are obtained, both of which feature molecules with parallel sp carbon chains in a pairwise head/tail packing motif with extensive sp/sp van der Waals contacts., (© 2021 Wiley-VCH GmbH.)

We report the first f-block-ruthenocenophane complexes 1 (Dy) and 2 (Tb) and provide a comparative discussion of their magnetic structure with respect to earlier reported ferrocenophane analogues. While axial elongation of the rare trigonal-prismatic geometry stabilizes the magnetic ground state in the case of Dy 3+ and results in a larger barrier to magnetization reversal (U), a decrease in U is observed for the case of Tb 3+ ., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The platinum polyynyl complexes trans-(C 6 F 5 )(p-tol 3 P) 2 Pt(C≡C) n/2 H undergo oxidative homocoupling (O 2 , CuCl/TMEDA) to diplatinum polyynediyl complexes trans, trans-(C 6 F 5 )(p-tol 3 P) 2 Pt(C≡C) n Pt(Pp-tol 3 ) 2 (C 6 F 5 ) (n=4, 2; 6, 5; 8, 8; 92-97 %) as reported previously. When related reactions are conducted in the presence of CuI adducts of the 1,10-phenanthroline-based macrocycles 2,9-(1,10-phenanthrolinediyl)(p-C 6 H 4 O(CH 2 ) 6 O) 2 (1,3-C 6 H 4 ) (10, 33-membered) or 2,9-(1,10-phenanthrolinediyl)(p-C 6 H 4 O(CH 2 ) 6 O) 2 (2,7-naphthalenediyl) (11, 35-membered), excess K 2 CO 3 , and I 2 (oxidant), rotaxanes are isolated that feature a Pt(C≡C) n Pt axle that has been threaded through the macrocycle (2⋅10, 9 %; 5⋅10, 41 %; 5⋅11, 28 %; 8⋅10, 12 %; 8⋅11, 9 %). Their crystal structures are determined and analyzed in detail, particularly with respect to geometric perturbations and the degree of steric sp carbon chain insulation. NMR spectra show a number of shielding effects. UV/Vis spectra do not indicate significant electronic interactions between the Pt(C≡C) n Pt axles and macrocycles, although cyclic voltammetry data suggest rapid reactions following oxidation., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Reactions of (O=)PH(OCH 2 CH 3 ) 2 and BrMg(CH 2 ) m CH=CH 2 (4.9-3.2 equiv; m=4 (a), 5 (b), 6 (c)) give the dialkylphosphine oxides (O=)PH[(CH 2 ) m CH=CH 2 ] 2 (2 a-c; 77-81 % after workup), which are treated with NaH and then α,ω-dibromides Br(CH 2 ) n Br (0.49-0.32 equiv; n=8 (a'), 10 (b'), 12 (c'), 14 (d')) to yield the bis(trialkylphosphine oxides) [H 2 C=CH(CH 2 ) m ] 2 P(=O)(CH 2 ) n (O=)P[(CH 2 ) m CH=CH 2 ] 2 (3 ab', 3 bc', 3 cd', 3 ca'; 79-84 %). Reactions of 3 bc' and 3 ca' with Grubbs' first-generation catalyst and then H 2 /PtO 2 afford the dibridgehead diphosphine dioxides (4 bc', 4 ca'; 14-19 %, n'=2m+2); 31 P NMR spectra show two stereoisomeric species (ca. 70:30). Crystal structures of two isomers of the latter are obtained, out,out-4 ca' and a conformer of in,out-4 ca' that features crossed chains, such that the (O=)P vectors appear out,out. Whereas 4 bc' resists crystallization, a byproduct derived from an alternative metathesis mode, (CH 2 ) 12 P(=O)(CH 2 ) 12 (O=)P(CH 2 ) 12 , as well as 3 ab' and 3 bc', are structurally characterized. The efficiencies of other routes to dibridgehead diphosphorus compounds are compared., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A new dimeric macrolide xylopyranoside, cocosolide (1), was isolated from the marine cyanobacterium preliminarily identified as Symploca sp. from Guam. The structure was determined by a combination of NMR spectroscopy, HRMS, X-ray diffraction studies and Mosher's analysis of the base hydrolysis product. Its carbon skeleton closely resembles that of clavosolides A-D isolated from the sponge Myriastra clavosa, for which no bioactivity is known. We performed the first total synthesis of cocosolide (1) along with its [α,α]-anomer (26) and macrocyclic core (28), thus leading to the confirmation of the structure of natural 1. The convergent synthesis featured Wadsworth-Emmons cyclopropanation, Sakurai annulation, Yamaguchi macrocyclization/dimerization reaction, α-selective glycosidation and β-selective glycosidation. Compounds 1 and 26 potently inhibited IL-2 production in both T-cell receptor dependent and independent manners. Full activity requires the presence of the sugar moiety as well as the intact dimeric structure. Cocosolide also suppressed the proliferation of anti-CD3-stimulated T-cells in a dose-dependent manner., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A two-step reaction to convert terminal alkynes into triborylalkenes is reported. In the first step, the terminal alkyne and pinacolborane (HBpin) are converted into an alkynylboronate, which is catalyzed by an iridium complex supported by a SiNN pincer ligand. In the second step, treatment of the reaction mixture with CO generates a new catalyst which mediates dehydrogenative diboration of alkynylboronate with pinacolborane. The mechanism of the diboration remains unclear but it does not proceed via intermediacy of hydroboration products or via B2 pin2., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The Fe(I) organometallic complex [(µ-SCH(2)CH(2)CH(2)S)Fe(2)(CO)(6)] provides a structural model for the cyano-carbonyl diiron site of Fe-only hydrogenase as characterized by X-ray crystallography (the picture shows the structure (black) of the model overlaid with that of the Fe-Fe dimetallic site in the hydrogenase isolated from Desulfovibrio desulfuricans). Cyanide substitution of CO occurs readily and provides spectroscopic references for the active site.