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Manganese catalysis has attracted significant attention in the last few years. In comparison with the extensively studied Mn complexes bearing phosphine‐based pincer ligands, catalysis with Mn containing N‐heterocyclic carbenes (NHC) is poorly developed. In this work, new manganese(I) complexes bearing an NHC ligand with picolyl wingtip substituents (an N,C,N ligand) have been synthesized and fully characterized. The structure of fac‐[Mn(CO)3(κ2N,C,N)Br] and fac‐[Mn(CO)3(κ3N,C,N)](OTf) complexes with a bidentate and tridentate coordination of the N,C,N ligand, respectively, has been elucidated by single crystal X‐ray diffraction studies. These Mn complexes were applied as catalysts for the visible light‐induced hydrosilylation of ketones. The mild protocol operated efficiently at room temperature under visible light irradiation (blue LED), enabling the conversion of a wide variety of aromatic ketones to their respective alcohols in high yields. Evidence for radical intermediates and the participation of Mn‐H species has been demonstrated by a series of trapping experiments. [ABSTRACT FROM AUTHOR]

A group of new mononuclear boron chelate compounds [BPh2{κ2N,N′-5-R-NC4H2-2-C(H)＝N–Ar}] (R = Ar = C6H57; R = C6H5, Ar = 2,6-iPr2C6H38; R = Anthracen-9-yl (Anthr), Ar = C6H59; R = Anthr, Ar = 2,6-iPr2C6H310) were synthesized via the reaction of B(C6H5)3 with the corresponding 5-substituted 2-(N-arylformimino)pyrrole ligand precursors 3–6. These complexes were prepared in order to evaluate the luminescence potential derived from the substitution of the position 5 of the pyrrolyl ring with an aromatic group. Compounds 7–10 were photophysically characterized in solution and in the solid state. The 5-phenyl-2-iminopyrrolyl-BPh2 complexes 7 and 8 are blue emitters and have enhanced photoluminescence quantum yields in the solid state (ΦPL) up to 0.95, whereas the 5-anthracenyl derivatives 9 and 10 have green-bluish fluorescence and a ΦPL of 0.49 and 0.24, respectively. DFT and TDDFT studies were performed, considering the effect of solvent and dispersion, in order to show how the geometries of compounds 7–10 changed from the ground to the excited state, to assign electronic transitions, and to rationalize the observed luminescence. These materials were applied in organic light-emitting diodes (OLEDs), with various device structures, the best showing an external quantum efficiency of 2.75% together with a high luminance of 23 530 cd m−2. [ABSTRACT FROM AUTHOR]

A series of new cationic Rn-substituted-indenyl nickel(II) complexes containing arsine or stibine ligands were synthesized in moderate to very high yields by the protonation of the corresponding bis(indenyl) nickel derivatives [Ni(η-Rn- Ind)2] with HBF4, in the presence of 2 equiv. of AsPh3 or SbPh3 donor ligands. These complexes, with the general formula [Ni(η- Rn-Ind)(EPh3)2]BF4 (E = As, Sb), were structurally characterized by NMR spectroscopy and X-ray diffraction, and subsequently tested as single-component catalysts for the oligomerization of styrene, leading to the formation of very low molecular weight head-to-tail oligomers (typically consisting of dimers, trimers and tetramers). The new 1- or 2-monosubstituted-indenyl NiII catalyst precursors exhibit extremely high catalytic activities, considerably higher than those observed for the symmetrical unsubstituted- and the 1,3-disubstituted-indenyl nickel analogues (i.e. monosubstituted >> non-substituted > 1,3-disubstituted), their reactivity pattern showing similarities with that of the corresponding allyl derivatives. A simpler and more straightforward experimental procedure for the high yield preparation of [NiBr2(DME)], an important nickel starting material, which was used in the preparation of the bis(indenyl) nickel precursors of this work, is also described. [ABSTRACT FROM AUTHOR]

New bis- and tris(iminopyrrole)-functionalized linear (1,2-(HNC4H3-C(H)N)2-C6H4 ( 2), 1,3-(HNC4H3-C(H)N)2-C6H4 ( 3), 1,4-(HNC4H3-C(H)N)2-C6H4 ( 4), 4,4′-(HNC4H3-C(H)N)2-(C6H4-C6H4) ( 5), 1,5-(HNC4H3C-(H)N)2-C10H6 ( 6), 2,6-(HNC4H3C-(H)N)2-C10H6 ( 7), 2,6-(HNC4H3C-(H)N)2-C14H8 ( 8)) and star-shaped (1,3,5-(HNC4H3-C(H)N-1,4-C6H4)3-C6H3 ( 9)) π-conjugated molecules were synthesized by the condensation reactions of 2-formylpyrrole ( 1) with several aromatic di- and triamines. The corresponding linear diboron chelate complexes (Ph2B[1,3-bis(iminopyrrolyl)-phenyl]BPh2 ( 10), Ph2B[1,4-bis(iminopyrrolyl)-phenyl]BPh2 ( 11), Ph2B[4,4′-bis(iminopyrrolyl)-biphenyl]BPh2 ( 12), Ph2B[1,5-bis(iminopyrrolyl)-naphthyl]BPh2 ( 13), Ph2B[2,6-bis(iminopyrrolyl)-naphthyl]BPh2 ( 14), Ph2B[2,6-bis(iminopyrrolyl)-anthracenyl]BPh2 ( 15)) and the star-shaped triboron complex ([4′,4′′,4′′′-tris(iminopyrrolyl)-1,3,5-triphenylbenzene](BPh2)3 ( 16)) were obtained in moderate to good yields, by the treatment of 3- 9 with B(C6H5)3. The ligand precursors are non-emissive, whereas most of their boron complexes are highly fluorescent; their emission color depends on the π-conjugation length. The photophysical properties of the luminescent polyboron compounds were measured, showing good solution fluorescence quantum yields ranging from 0.15 to 0.69. DFT and time-dependent DFT calculations confirmed that molecules 10 and 16 are blue emitters, because only one of the iminopyrrolyl groups becomes planar in the singlet excited state, whereas the second (and third) keeps the same geometry. Compound 13, in which planarity is not achieved in any of the groups, is poorly emissive. In the other examples ( 11, 12, 14, and 15), the LUMO is stabilized, narrowing the gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital (HOMO-LUMO), and the two iminopyrrolyl groups become planar, extending the size of the π-system, to afford green to yellow emissions. Organic light-emitting diodes (OLEDs) were fabricated by using the new polyboron complexes and their luminance was found to be in the order of 2400 cd m−2, for single layer devices, increasing to 4400 cd m−2 when a hole-transporting layer is used. [ABSTRACT FROM AUTHOR]

Two new Ar-BIAN Cu(II) complexes (where Ar-BIAN = bis(aryl-imino)acenaphthene) of formulations [CuCl2(Mes-BIAN)] (1) (Mes = 2,4,6-Me3C6H2) and [CuCl2(Dipp-BIAN)] (2) (Dipp = 2,6-iPr2C6H3) were synthesised by direct reaction of CuCl2 suspended in dichloromethane with the respective ligands Mes-BIAN (L1) and Dipp-BIAN (L2), dissolved in dichloromethane, under an argon atmosphere. Attempts to obtain these compounds by solubilising CuCl2 in methanol and adding a dichloromethane solution of the corresponding ligand, under aerobic conditions, gave also compound 1, but, in the case of L2, the Cu(I) dimer [CuCl(Dipp-BIAN)]2 (3) was obtained instead of compound 2. The compounds were fully characterised by elemental analyses, MALDI-TOF mass spectrometry, FT-IR, 1H NMR and EPR spectroscopic techniques. The solid-state molecular structures of compounds 1-3 were determined by single crystal X-ray diffraction, showing the expected chelation of the Ar-BIAN ligands and two chloride ligands completing the coordination sphere of the Cu(II) centre. In the case of the complex 1, an intermediate coordination geometry around the Cu(II) centre, between square planar and tetrahedral, was revealed, while the complex 2 showed an almost square planar geometry. The structural differences and evaluation of energetic changes were rationalised by DFT calculations. Analysis of the electrochemical behaviour of complexes 1-3 was performed by cyclic voltammetry and the experimental redox potentials for Cu(II)/ Cu(I) pairs have been compared with theoretical values calculated by DFT in the gas phase and in dichloromethane and methanol solutions. The complex 1 exhibited good activity in the reverse atom transfer radical polymerisation (ATRP) of styrene. [ABSTRACT FROM AUTHOR]

A series of new cationic and neutral (Ar-BIAN)copper(I) complexes [in which Ar-BIAN = bis(aryl)acenaphthenequinonediimine] was synthesised and characterised by elemental analysis, 1D and 2D NMR spectroscopy and single-crystal X-ray diffraction. The cationic complexes of the general formula [Cu(Ar-BIAN) L2]BF4 [ L2 = (PPh3)2 ( 1), dppe ( 2), dppf ( 3), (AsPh3)2 ( 4); Ar = 4- iPrC6H4 ( a), 4-MeOC6H4 ( b), 4-NO2C6H4 ( c), 2- iPrC6H4 ( d), Ph2PCH2CH2PPh2 (dppe), (Ph2PC5H4)2Fe (dppf)] were synthesised by reaction of [Cu(EPh3)4]BF4 (E = P or As) and equimolar amounts of Ar-BIAN ligands, or by reaction of equimolar amounts of [Cu(NCMe)4]BF4, 4- iPrC6H4-BIAN ( a) and diphosphanes dppe or dppf, in dichloromethane, whereas the neutral complexes of the types [CuX(Ar-BIAN)(EPh3)] [X = Cl, E = P ( 5); X = I, E = P ( 6); X = Cl, E = As ( 9)] and [{CuX(Ar-BIAN)}2] [X = Cl ( 7), I ( 8); Ar = a, b, c, d, 2,4,6-Me3C6H2 ( e), 2,6- iPr2C6H3 ( f)] were prepared by reaction of CuCl or CuI with equimolar amounts of Ar-BIAN and EPh3 (E = P, As or Sb) in acetonitrile under reflux conditions. The type of ancillary ligand EPh3 and the aryl substituents on Ar-BIAN play crucial roles in determining the formation of cationic or neutral copper(I) complexes. No copper(I) complexes containing coordinated SbPh3 were isolated; all the corresponding attempts led to dimeric complexes 7 or 8. Most of the complexes crystallised easily. Their study by X-ray diffraction revealed distorted-tetrahedral geometries around the copper(I) centres, which are quite influenced by the various aryl substituents on Ar-BIAN and the ancillary ligands EPh3. All complexes 1- 9 except cationic dppf derivative 3a are active catalysts for cycloaddition reactions of alkynes and azides, and also show good tolerance towards functionalised substituents of alkynes and azides. Among them, the PPh3-coordinated complexes 1, 5 and 6 afforded the highest catalytic activities [turnover frequency = 26.9-45.7 h-1]. [ABSTRACT FROM AUTHOR]

New 2-iminophenanthro[9,10-c]pyrrole tigand precursors containing phenyl or 2,6-disopropyiphenyl groups at the imine nitrogen substitsent, 2-arylformiminophenanthro[9,10-cjpyrroles (aryl=phenyl lie, 2,6-d(sopropylphenyl IIb) were synthesized and deprotonaled in situ with NaH, originating solutions of the corresponding sodium salts (IVa, lVb). The reaction ot these salts with zinc chloride gave the homoleptic bis-ligand Zn(ll) complexes [Zn(κ2N,W-2-aryltormiminophenanthro[9,10-cjpyrrotyt)2] (alyl=phenyl 2a, 2,6-diisopropylphenyt 2b). The new ligand precursors and complexes were characterized by NMR, elemental analysis, UV/vis spectroscopy, and X-ray crystallography, when possible. The photophysical characterization was carried out using steady-stale and picosecond lime-resolved luminescence techniques in solution. The influence of the π-extended conjugation of the condensed phenanthro group on the deprotonated iminopyrrolyl ligands coordinated to Zn2+ greatly enhances fluorescence quantum yields of the complexes (2a, 2b) in relation to those of their ligand precursors (IIa, IIb). Complex 2a shows emission in the green spectral region (λmax=494 nm), presenting the highest fluorescence quantum yield (ø1=8.8%). In the case of the complex 2b (4=3.9%), the bulkiness of the 2,6-disopropyl substituents ot the arylimino group highly restricts the aryl ring rotation toward coplanarity with the ligand framework, inducing a shift in the emission to the blue region (λmax= 459 nm). The values of the radiative (kf) and radiationless rate constants (knr) show that the fluorescence quantum yield enhancement in the complexes results trom a 50-told increase in kf values, indicating much more allowed π-π* transitions in complexes 2a and 2b than those occurring in the ligand precursors IIa and IIb, with an essentially n-π* character. These assignments were confirmed by density-functional theory (DFT) and time-dependent DFT (TD-DFT) molecular orbital calculations. Simple 2-aryliminopyrrole ligand precursors (Ia, Ib) and their Zn(ll) complexes (1a, 1b) were also prepared to compare their pholophysicat properties with those of the corresponding 2-aryliminophenanthro- [9,10-c]pyrrolyl compounds. [ABSTRACT FROM AUTHOR]

A series of new catalysts is synthesized and tested in the title reaction. [ABSTRACT FROM AUTHOR]