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Efficient catalysts for Guerbet-type ethanol/methanol upgrading to iso-butanol have been developed via Michael addition of a variety of amines to ruthenium-coordinated dppen (1,1-bis(diphenylphosphino)ethylene). All catalysts produce over 50% iso-butanol yield with >90% selectivity in 2 h with catalyst 1 showing the best activity (74% yield after this time). The selectivity and turnover number approach 100% and 1000 respectively using catalyst 6. The presence of uncoordinated functionalised donor groups in these complexes results in a more stable catalyst compared to unfunctionalised analogues. [ABSTRACT FROM AUTHOR]

The reactions of R2P–PR2 with R′E–ER′, (where E = Se, S, O, Te) to give R2P–ER′ have been explored experimentally and computationally. The reaction of Ph2P–PPh2 with PhSe–SePh gives Ph2P–SePh (1) rapidly and quantitatively. The P–P/Se–Se reaction is inhibited by the addition of the radical scavenger TEMPO which is consistent with a radical mechanism for the heterometathesis reaction. Compound 1 has been fully characterised, including by X-ray crystallography. A range of other Ar2P–SeR (R = Ph, nBu or CH2CH2CO2H) have also been prepared and characterised. The reaction of 1 with [Mo(CO)4(nbd)] (nbd = norbornadiene) gives two products which, from their characteristic 31P NMR data, have been identified as cis-[Mo(CO)4(Ph2PSePh–P)2] (8) and the mixed-donor complex cis-[Mo(CO)4(Ph2P–SePh–P)(Ph2P–SePh–Se)] (9). It is deduced that the P and Se atoms in ligand 1 have comparable capacity to coordinate to Mo(0). The reaction of Ph2P–PPh2 with PhS–SPh gives Ph2P–SPh (2) quantitatively but no reaction was observed between Ph2P–PPh2 and PhTe–TePh. Heterometathesis between Ph2P–PPh2 and tBuO–OtBu does not occur thermally but has been observed under UV irradiation to give Ph2P–OtBu along with P(V) oxidation by-products. DFT calculations have been carried out to illuminate why heterometatheses with dichalcogenides R′E–ER′ occur readily when E = S and Se but not when E = O and Te. The calculations show that heterometathesis is predicted to be thermodynamically favourable for E = O, S and Se and unfavourable for E = Te. The fact that a metathesis reaction between Ph2P–PPh2 with tBuO–OtBu is not observed in the absence of UV radiation, is therefore due to kinetics. [ABSTRACT FROM AUTHOR]

Reactionof the alkenyl-substituted carbene complex [Ru(κ2-O2CMe)(OC{Me}O(CCHCH2)(PPh3)2]+with PPh3resultsin the formation of the vinylidene-containing species [Ru(κ1-O2CMe)(κ2-O2CMe)(CCHCH2PPh3)(PPh3)2]+, among other products. This complex could also be obtained by reactionof [Ru(κ2-O2CR)(PPh3)2] (R = Me, Ph) with [HCCCH2PPh3]+although in this instance competitive formation of allene-containing[Ru(κ1-O2CR)(κ2-O2CR)(η2-H2CCCHPPh3)(PPh3)2] occurred. Reaction of [Ru(κ2-O2CMe)2(PPh3)2] with [H2CCCHPPh3]+gives this allene complex in a selective fashion. Similar resultswere obtained when [RhCl(PiPr3)2]2was used as the metal precursor. The reaction with [H2CCCHPPh3]+gave [RhCl(η2-H2CCCHPPh3)(PiPr3)2]+, whereas treatment with[HCCCH2PPh3]+afforded amixture of the same complex and [RhCl(η2-HCCCH2PPh3)(PiPr3)2]+, which subsequently isomerized to vinylidene-containing [RhCl(CCHCH2PPh3)(PiPr3)2]+via the alkynyl hydride complex [RhCl(H)(CCCH2PPh3)(PiPr3)2]+. Consistent with previous findings [HCCCH2PPh3]+isomerizes to [H2CCCHPPh3]+in the absence of a metal and the balance betweenthe vinylidene and allene complexes formed in these reactions appearsto relate to the efficiency of the reaction with each substrate. [ABSTRACT FROM AUTHOR]

Efficient catalysts for Guerbet-type ethanol/methanol upgrading to iso-butanol have been developed via Michael addition of a variety of amines to ruthenium-coordinated dppen (1,1-bis(diphenylphosphino)ethylene). All catalysts produce over 50% iso-butanol yield with >90% selectivity in 2 h with catalyst 1 showing the best activity (74% yield after this time). The selectivity and turnover number approach 100% and 1000 respectively using catalyst 6. The presence of uncoordinated functionalised donor groups in these complexes results in a more stable catalyst compared to unfunctionalised analogues.

The reactions of R 2 P-PR 2 with R'E-ER', (where E = Se, S, O, Te) to give R 2 P-ER' have been explored experimentally and computationally. The reaction of Ph 2 P-PPh 2 with PhSe-SePh gives Ph 2 P-SePh (1) rapidly and quantitatively. The P-P/Se-Se reaction is inhibited by the addition of the radical scavenger TEMPO which is consistent with a radical mechanism for the heterometathesis reaction. Compound 1 has been fully characterised, including by X-ray crystallography. A range of other Ar 2 P-SeR (R = Ph, n Bu or CH 2 CH 2 CO 2 H) have also been prepared and characterised. The reaction of 1 with [Mo(CO) 4 (nbd)] (nbd = norbornadiene) gives two products which, from their characteristic 31 P NMR data, have been identified as cis -[Mo(CO) 4 (Ph 2 PSePh- P ) 2 ] (8) and the mixed-donor complex cis -[Mo(CO) 4 (Ph 2 P-SePh- P )(Ph 2 P-SePh- Se )] (9). It is deduced that the P and Se atoms in ligand 1 have comparable capacity to coordinate to Mo(0). The reaction of Ph 2 P-PPh 2 with PhS-SPh gives Ph 2 P-SPh (2) quantitatively but no reaction was observed between Ph 2 P-PPh 2 and PhTe-TePh. Heterometathesis between Ph 2 P-PPh 2 and t BuO-O t Bu does not occur thermally but has been observed under UV irradiation to give Ph 2 P-O t Bu along with P(V) oxidation by-products. DFT calculations have been carried out to illuminate why heterometatheses with dichalcogenides R'E-ER' occur readily when E = S and Se but not when E = O and Te. The calculations show that heterometathesis is predicted to be thermodynamically favourable for E = O, S and Se and unfavourable for E = Te. The fact that a metathesis reaction between Ph 2 P-PPh 2 with t BuO-O t Bu is not observed in the absence of UV radiation, is therefore due to kinetics.

The structure of three functionalized chalcones (1,3-di-aryl-prop-2-en-1-ones), containing combinations of nitro and di-methyl-amino functional groups, are presented, namely, 1-[4-(di-methyl-amino)-phen-yl]-3-(3-nitro-phen-yl)prop-2-en-1-one, C 17 H 16 N 2 O 3 , Gp8m, 3-[3-(di-methyl-amino)-phen-yl]-1-(3-nitro-phen-yl)prop-2-en-1-one, C 17 H 16 N 2 O 3 , Hm7m and 1-(3-nitro-phen-yl)-3-phenyl-prop-2-en-1-one, C 15 H 11 NO 3 , Hm1-. Each of the mol-ecules contains bonding motifs seen in previously solved crystal structures of functionalized chalcones, adding to the large dataset available for these small organic mol-ecules. The structures of all three of the title compounds contain similar bonding motifs, resulting in two-dimensional planes of mol-ecules formed via C-H⋯O hydrogen-bonding inter-actions involving the nitro- and ketone groups. The structure of Hm1- is very similar to the crystal structure of a previously solved isomer [Jing (2009 ▸). Acta Cryst. E 65 , o2510]., (© Hall et al. 2020.)

The title compound, C 15 H 10 I 2 O, is a halogenated chalcone formed from two iodine substituted rings, one para -substituted and the other meta -substituted, linked through a prop-2-en-1-one spacer. In the mol-ecule, the mean planes of the 3-iodo-phenyl and the 4-iodo-phenyl groups are twisted by 46.51 (15)°. The calculated electrostatic potential surfaces show the presence of σ-holes on both substituted iodines. In the crystal, the mol-ecules are linked through type II halogen bonds, forming a sheet structure parallel to the bc plane. Between the sheets, weak inter-molecular C-H⋯π inter-actions are observed. Hirshfeld surface analysis showed that the most significant contacts in the structure are C⋯H/H⋯C (31.9%), followed by H⋯H (21.4%), I⋯H/H⋯I (18.4%). I⋯I (14.5%) and O⋯H/H⋯O (8.1%)., (© Spruce et al. 2020.)

Manganese-catalyzed C-H bond activation chemistry is emerging as a powerful and complementary method for molecular functionalization. A highly reactive seven-membered Mn(I) intermediate is detected and characterized that is effective for H-transfer or reductive elimination to deliver alkenylated or pyridinium products, respectively. The two pathways are determined at Mn(I) by judicious choice of an electron-deficient 2-pyrone substrate containing a 2-pyridyl directing group, which undergoes regioselective C-H bond activation, serving as a valuable system for probing the mechanistic features of Mn C-H bond activation chemistry., (© 2016 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)

The coordination modes of the [Au(PPh3)](+) cation to metal alkynyl complexes have been investigated. On addition to ruthenium, a vinylidene complex, [Ru(η(5)-C5H5)(PPh3)2([double bond, length as m-dash]C[double bond, length as m-dash]CPh{AuPPh3})](+), is obtained while addition to a gold(iii) compound gives di- and trinuclear gold complexes depending on the conditions employed. In the trinuclear species, a gold(i) cation is sandwiched between two gold(iii) alkynyl complexes, suggesting that coordination of multiple C-C triple bonds to gold is facile.

Co-crystallisation of, in particular, 4-iodotetrafluorophenol with a series of secondary and tertiary cyclic amines results in deprotonation of the phenol and formation of the corresponding ammonium phenate. Careful examination of the X-ray single-crystal structures shows that the phenate anion develops a C=O double bond and that the C-C bond lengths in the ring suggest a Meissenheimer-like delocalisation. This delocalisation is supported by the geometry of the phenate anion optimised at the MP2(Full) level of theory within the aug-cc-pVDZ basis (aug-cc-pVDZ-PP on I) and by natural bond orbital (NBO) analyses. With sp(2) hybridisation at the phenate oxygen atom, there is strong preference for the formation of two non-covalent interactions with the oxygen sp(2) lone pairs and, in the case of secondary amines, this occurs through hydrogen bonding to the ammonium hydrogen atoms. However, where tertiary amines are concerned, there are insufficient hydrogen atoms available and so an electrophilic iodine atom from a neighbouring 4-iodotetrafluorophenate group forms an I⋅⋅⋅O halogen bond to give the second interaction. However, in some co-crystals with secondary amines, it is also found that in addition to the two hydrogen bonds forming with the phenate oxygen sp(2) lone pairs, there is an additional intermolecular I⋅⋅⋅O halogen bond in which the electrophilic iodine atom interacts with the C=O π-system. All attempts to reproduce this behaviour with 4-bromotetrafluorophenol were unsuccessful. These structural motifs are significant as they reproduce extremely well, in low-molar-mass synthetic systems, motifs found by Ho and co-workers when examining halogen-bonding interactions in biological systems. The analogy is cemented through the structures of co-crystals of 1,4-diiodotetrafluorobenzene with acetamide and with N-methylbenzamide, which, as designed models, demonstrate the orthogonality of hydrogen and halogen bonding proposed in Ho's biological study., (© 2014 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.)