Crystal structure of cis-(1,4,8,11-tetraazacyclotetradecane-κ4 N)bis(thiocyanato-κN)chromium(III) bromide from synchrotron X-ray diffraction data

The crystal structure of the title complex, cis-[Cr(NCS)2(cyclam)]Br (cyclam = 1,4,8,11-tetraazacyclotetradecane, C10H24N4), has been determined from synchrotron X-ray data. The asymmetric unit contains one [Cr(NCS)2(cyclam)]+ cation and one bromide anion. The CrIII ion of the complex cation is coordinated by the four N atoms of the cyclam ligand and by two N-coordinating NCS groups in a cis arrangement, displaying a distorted octahedral coordination sphere. The Cr—N(cyclam) bond lengths are in the range 2.075 (3) to 2.081 (3) Å while the average Cr—N(NCS) bond length is 1.996 (16) Å. The macrocyclic cyclam moiety adopts the most stable cis-V conformation. The crystal structure is stabilized by intermolecular hydrogen bonds involving the cyclam N—H groups as donor groups, and the bromide anion and the S atom of one of the NCS ligands as acceptor groups.

Crystal structure of 2-[(naphthalen-2-yl)methyl]isothiouronium bromide

Herein we report the crystal structure of 2-[(naphthalen-2-yl)methyl]isothiouronium bromide, C12H13N2S+·Br−, which crystallizes in the monoclinic P21/c centrosymmetric space group. The asymmetric unit contains one 2-[(naphthalen-2-yl)methyl]isothiouronium cation and one bromide anion. The methylene carbon lies in plane of the naphthalene core. In comparison with reference structures, elongation of C—S bonds as well as tilting of the isothiouronium group is observed. Given the ionic nature of the compound, the structure is held by charge-assisted N—H...Br hydrogen bonds, with a noteworthy contribution of dipole–dipole interactions, which form bilayers in the structure. The bilayers are held by the weak London forces.

Minisci C-H Alkylation of Heteroarenes Enabled by Dual Photoredox/bromide Catalysis in Micellar Solutions

Microstructured aqueous solutions were employed to engage non-activated alkyl bromides in the visible-light-promoted C‑H functionalization of heteroarenes. The reactive carbon-centered alkyl radicals were generated by merging the photoredox approach, bromide anion co-catalysis and spatial pre-aggregation of reacting species in the mixture. The presented methodology allowed obtaining alkylated heteroarenes without stoichiometric radical-promoters, in acid-free conditions and using blue LEDs as the light source.

Minisci C-H Alkylation of Heteroarenes Enabled by Dual Photoredox/bromide Catalysis in Micellar Solutions

Microstructured aqueous solutions were employed to engage non-activated alkyl bromides in the visible-light-promoted C‑H functionalization of heteroarenes. The reactive carbon-centered alkyl radicals were generated by merging the photoredox approach, bromide anion co-catalysis and spatial pre-aggregation of reacting species in the mixture. The presented methodology allowed obtaining alkylated heteroarenes without stoichiometric radical-promoters, in acid-free conditions and using blue LEDs as the light source.

Isonitrile Ruthenium and Iron PNP Complexes: Synthesis, Characterization and Catalytic Assessment for Base-Free Dehydrogenative Coupling of Alcohols

Neutral and ionic ruthenium and iron aliphatic PNPH-type pincer complexes (PNPH= NH(CH2CH2PiPr2)2) bearing benzyl, n-butyl or tert-butyl isocyanide ancillary ligands have been prepared and characterized. Reaction of [RuCl2(PNPH)]2 with one equivalent CN-R per ruthe-nium center affords complexes [Ru(PNPH)Cl2(CNR)] (R= benzyl, 1a, R= n-butyl, 1b, R= t-butyl, 1c), with cationic [Ru(PNPH)(Cl)(CNR)2]Cl 2a-c as side-products. Complexes 2a-c are selectively prepared upon reaction of [RuCl2(PNPH)]2 with 2 equiva-lents of isonitrile per ruthenium center. Dichloride species 1a-c react with excess NaBH4 to afford [Ru(PNPH)(H)(BH4)(CN-R)] 3a-c, analogues to benchmark Takasago catalyst [Ru(PNP)(H)(BH4)(CO)]. Reaction of 1a-c with a single equivalent of NaBH4 under protic conditions results in formation of hydrido chloride derivatives [Ru(PNPH)(H)(Cl)(CN-R)] (4a-c), from which 3a-c can be prepared upon reaction with excess NaBH4. Use of one equivalent of NaHBEt3 with 4a and 4c affords bishydrides [Ru(PNPH)(H)2(CN-R)] 5a and 5c. In the case of bulkier t-butylisonitrile, two isomers were observed by NMR, with the PNP framework in either meridional or facial confor-mation. Deprotonation of 4c by KOtBu generates amido derivative [Ru(PNP’)(H)(CN-t-Bu)] (6, PNP’= -N(CH2CH2PiPr2)2), unstable in solution. Addition of excess benzylisonitrile to 4a provides cationic hydride [Ru(PNPH)(H)(CN-CH2Ph)2]Cl (7). Concerning iron chemis-try, [Fe(PNPH)Br2] reacts one equivalent benzylisonitrile to afford [Fe(PNPH)(Br)(CNCH2Ph)2]Br (8). The outer-sphere bromide anion can be exchanged by salt metathesis with NaBPh4 to generate [Fe(PNPH)(Br)(CNCH2Ph)2](BPh4) (9). Cationic hydride species [Fe(PNPH)(H)(CN-t-Bu)2](BH4) (10) is prepared from consecutive addition of excess CN-t-Bu and NaBH4 on [Fe(PNPH)Br2]. Ruthenium complexes 3a-c are active in acceptorless alcohol dehydrogenative coupling into ester under base-free conditions. From kinetic follow-up, the trend in initial activity is 3a ≈ 3b > [Ru(PNPH)(H)(BH4)(CO)] >> 3c; for robustness, [Ru(H)(BH4)(CO)(PNPH)] > 3a > 3b >> 3c. Hy-potheses are given to account for the observed deactivation. Complexes 3b, 3c, 4a, 4c, 5c, 7, cis-8 and 9 were characterized by X-ray crystallography.

Isonitrile Ruthenium and Iron PNP Complexes: Synthesis, Characterization and Catalytic Assessment for Base-Free Dehydrogenative Coupling of Alcohols

Neutral and ionic ruthenium and iron aliphatic PNPH-type pincer complexes (PNPH= NH(CH2CH2PiPr2)2) bearing benzyl, n-butyl or tert-butyl isocyanide ancillary ligands have been prepared and characterized. Reaction of [RuCl2(PNPH)]2 with one equivalent CN-R per ruthe-nium center affords complexes [Ru(PNPH)Cl2(CNR)] (R= benzyl, 1a, R= n-butyl, 1b, R= t-butyl, 1c), with cationic [Ru(PNPH)(Cl)(CNR)2]Cl 2a-c as side-products. Complexes 2a-c are selectively prepared upon reaction of [RuCl2(PNPH)]2 with 2 equiva-lents of isonitrile per ruthenium center. Dichloride species 1a-c react with excess NaBH4 to afford [Ru(PNPH)(H)(BH4)(CN-R)] 3a-c, analogues to benchmark Takasago catalyst [Ru(PNP)(H)(BH4)(CO)]. Reaction of 1a-c with a single equivalent of NaBH4 under protic conditions results in formation of hydrido chloride derivatives [Ru(PNPH)(H)(Cl)(CN-R)] (4a-c), from which 3a-c can be prepared upon reaction with excess NaBH4. Use of one equivalent of NaHBEt3 with 4a and 4c affords bishydrides [Ru(PNPH)(H)2(CN-R)] 5a and 5c. In the case of bulkier t-butylisonitrile, two isomers were observed by NMR, with the PNP framework in either meridional or facial confor-mation. Deprotonation of 4c by KOtBu generates amido derivative [Ru(PNP’)(H)(CN-t-Bu)] (6, PNP’= -N(CH2CH2PiPr2)2), unstable in solution. Addition of excess benzylisonitrile to 4a provides cationic hydride [Ru(PNPH)(H)(CN-CH2Ph)2]Cl (7). Concerning iron chemis-try, [Fe(PNPH)Br2] reacts one equivalent benzylisonitrile to afford [Fe(PNPH)(Br)(CNCH2Ph)2]Br (8). The outer-sphere bromide anion can be exchanged by salt metathesis with NaBPh4 to generate [Fe(PNPH)(Br)(CNCH2Ph)2](BPh4) (9). Cationic hydride species [Fe(PNPH)(H)(CN-t-Bu)2](BH4) (10) is prepared from consecutive addition of excess CN-t-Bu and NaBH4 on [Fe(PNPH)Br2]. Ruthenium complexes 3a-c are active in acceptorless alcohol dehydrogenative coupling into ester under base-free conditions. From kinetic follow-up, the trend in initial activity is 3a ≈ 3b > [Ru(PNPH)(H)(BH4)(CO)] >> 3c; for robustness, [Ru(H)(BH4)(CO)(PNPH)] > 3a > 3b >> 3c. Hy-potheses are given to account for the observed deactivation. Complexes 3b, 3c, 4a, 4c, 5c, 7, cis-8 and 9 were characterized by X-ray crystallography.

Isonitrile Ruthenium and Iron PNP Complexes: Synthesis, Characterization and Catalytic Assessment for Base-Free Dehydrogenative Coupling of Alcohols

Neutral and ionic ruthenium and iron aliphatic PNPH-type pincer complexes (PNPH= NH(CH2CH2PiPr2)2) bearing benzyl, n-butyl or tert-butyl isocyanide ancillary ligands have been prepared and characterized. Reaction of [RuCl2(PNPH)]2 with one equivalent CN-R per ruthe-nium center affords complexes [Ru(PNPH)Cl2(CNR)] (R= benzyl, 1a, R= n-butyl, 1b, R= t-butyl, 1c), with cationic [Ru(PNPH)(Cl)(CNR)2]Cl 2a-c as side-products. Complexes 2a-c are selectively prepared upon reaction of [RuCl2(PNPH)]2 with 2 equiva-lents of isonitrile per ruthenium center. Dichloride species 1a-c react with excess NaBH4 to afford [Ru(PNPH)(H)(BH4)(CN-R)] 3a-c, analogues to benchmark Takasago catalyst [Ru(PNP)(H)(BH4)(CO)]. Reaction of 1a-c with a single equivalent of NaBH4 under protic conditions results in formation of hydrido chloride derivatives [Ru(PNPH)(H)(Cl)(CN-R)] (4a-c), from which 3a-c can be prepared upon reaction with excess NaBH4. Use of one equivalent of NaHBEt3 with 4a and 4c affords bishydrides [Ru(PNPH)(H)2(CN-R)] 5a and 5c. In the case of bulkier t-butylisonitrile, two isomers were observed by NMR, with the PNP framework in either meridional or facial confor-mation. Deprotonation of 4c by KOtBu generates amido derivative [Ru(PNP’)(H)(CN-t-Bu)] (6, PNP’= -N(CH2CH2PiPr2)2), unstable in solution. Addition of excess benzylisonitrile to 4a provides cationic hydride [Ru(PNPH)(H)(CN-CH2Ph)2]Cl (7). Concerning iron chemis-try, [Fe(PNPH)Br2] reacts one equivalent benzylisonitrile to afford [Fe(PNPH)(Br)(CNCH2Ph)2]Br (8). The outer-sphere bromide anion can be exchanged by salt metathesis with NaBPh4 to generate [Fe(PNPH)(Br)(CNCH2Ph)2](BPh4) (9). Cationic hydride species [Fe(PNPH)(H)(CN-t-Bu)2](BH4) (10) is prepared from consecutive addition of excess CN-t-Bu and NaBH4 on [Fe(PNPH)Br2]. Ruthenium complexes 3a-c are active in acceptorless alcohol dehydrogenative coupling into ester under base-free conditions. From kinetic follow-up, the trend in initial activity is 3a ≈ 3b > [Ru(PNPH)(H)(BH4)(CO)] >> 3c; for robustness, [Ru(H)(BH4)(CO)(PNPH)] > 3a > 3b >> 3c. Hy-potheses are given to account for the observed deactivation. Complexes 3b, 3c, 4a, 4c, 5c, 7, cis-8 and 9 were characterized by X-ray crystallography.

Redox Neutral and Acid-Free Minisci C-H Alkylation of Heteroarenes Enabled by Dual Photoredox/bromide Catalysis in Micellar Solutions

Microstructured aqueous solutions were employed to engage non-activated alkyl bromides in the visible-light-promoted C‑H functionalization of heteroarenes. The reactive carbon-centered alkyl radicals were generated by merging the photoredox approach, bromide anion co-catalysis and spatial pre-aggregation of reacting species in the mixture. The presented methodology allowed obtaining alkylated heteroarenes without stoichiometric radical-promoters, in acid-free conditions and using blue LEDs as the light source.

Crystal structure of (2-{[(8-aminonaphthalen-1-yl)imino]methyl}-4,6-di-tert-butylphenolato-κ3 N,N′,O)bromidonickel(II)

The title compound, [NiBr(C25H29N2O)], contains an NiII atom with a slightly distorted square-planar coordination environment defined by one O and two N atoms from the 2-{[(8-aminonaphthalen-1-yl)imino]methyl}-4,6-di-tert-butylphenolate ligand and a bromide anion. The Ni—O and Ni—N bond lengths are slightly longer than those observed in the phenyl backbone counterpart, which can be attributed to the larger steric hindrance of the naphthyl group in the structure of the title compound. The molecule as a whole is substantially distorted, with both the planar naphthalene-1,8-diamine and imino–methyl–phenolate substitutents rotated against the NiN2OBr plane by 38.92 (7) and 37.22 (8)°, respectively, giving the molecule a twisted appearance. N—H...Br hydrogen bonds and N—H...C(π) contacts connect the molecules into dimers, and additional C—H...Br contacts, C—H...π interactions, and an offset stacking interaction between naphthyl units interconnect these dimers into a three-dimensional network.