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Title: Exciplex Formation and Aggregation Induced Emission in Di-( N -benzyl)cyclen and Its Complexes - Selective Fluorescence with Lead(II), and as the Cadmium(II) Complex, with the Chloride Ion: Exciplex Formation and Aggregation Induced Emission in Di-(N-benzyl)cyclen and Its Complexes - Selective Fluorescence with Lead(II), and as the Cadmiu
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Publication Date:
Journal Name:
European Journal of Inorganic Chemistry
Page Range or eLocation-ID:
3736 to 3747
Wiley Blackwell (John Wiley & Sons)
Sponsoring Org:
National Science Foundation
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  1. The formation of amide bonds represents one of the most fundamental processes in organic synthesis. Transition-metal-catalyzed activation of acyclic twisted amides has emerged as an increasingly powerful platform in synthesis. Herein, we report the transamidation of N-activated twisted amides by selective N–C(O) cleavage mediated by air- and moisture-stable half-sandwich Ni(II)–NHC (NHC = N-heterocyclic carbenes) complexes. We demonstrate that the readily available cyclopentadienyl complex, [CpNi(IPr)Cl] (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene), promotes highly selective transamidation of the N–C(O) bond in twisted N-Boc amides with non-nucleophilic anilines. The reaction provides access to secondary anilides via the non-conventional amide bond-forming pathway. Furthermore, the amidation of activated phenolic and unactivated methyl esters mediated by [CpNi(IPr)Cl] is reported. This study sets the stage for the broad utilization of well-defined, air- and moisture-stable Ni(II)–NHC complexes in catalytic amide bond-forming protocols by unconventional C(acyl)–N and C(acyl)–O bond cleavage reactions.
  2. The gyroscope like dichloride complexes trans -Pt(Cl) 2 (P((CH 2 ) n ) 3 P) ( trans -2; n = c, 14; e, 18; g, 22) and MeLi (2 equiv.) react to yield the parachute like dimethyl complexes cis -Pt(Me) 2 (P((CH 2 ) n ) 3 P) ( cis -4c,e,g, 70–91%). HCl (1 equiv.) and cis -4c react to give cis -Pt(Cl)(Me)(P((CH 2 ) 14 ) 3 P) ( cis -5c, 83%), which upon stirring with silica gel or crystallization affords trans -5c (89%). Similar reactions of HCl and cis -4e,g give cis / trans -5e,g mixtures that upon stirring with silica gel yield trans -5e,g. A parallel sequence with trans -2c/EtLi gives cis -Pt(Et) 2 (P((CH 2 ) 14 ) 3 P) ( cis -6c, 85%) but subsequent reaction with HCl affords trans -Pt(Cl)(Et)(P((CH 2 ) 14 ) 3 P) ( trans -7c, 45%) directly. When previously reported cis -Pt(Ph) 2 (P((CH 2 ) 14 ) 3 P) is treated with HCl (1 equiv.), cis - and trans -Pt(Cl)(Ph)(P((CH 2 ) 14 ) 3 P) are isolated (44%, 29%), with the former converting to the latter at 100 °C. Reactions of trans -5c and LiBr or NaI affordmore »the halide complexes trans -Pt(X)(Me)(P((CH 2 ) 14 ) 3 P) ( trans -9c, 88%; trans -10c, 87%). Thermolyses and DFT calculations that include acyclic model compounds establish trans > cis stabilities for all except the dialkyl complexes, for which energies can be closely spaced. The σ donor strengths of the non-phosphine ligands are assigned key roles in the trends. The crystal structures of cis -4c, trans -5c, trans -7c, and trans -10c are determined and analyzed together with the computed structures.« less