Synthesis of Silver(I) and Gold(I) Complexes Containing Enantiopure Pybox Ligands. First Assays on the Silver(I)-Catalyzed Asymmetric Addition of Alkynes to Imines

Abstract

Dinuclear complexes [Ag2(CF3SO3){(S,S)-(i)Pr-pybox}2][CF3SO3] (1), [Ag2(R-pybox)2][X]2 [R-pybox = 2,6-bis[4-(S)-isopropyloxazolin-2-yl]pyridine (S,S)-(i)Pr-pybox and X = PF6 (2) and BF4 (3); R-pybox = 2,6-bis[(3aS,8aR)-8,8a-dihydro-3aH-indeno[1,2-d]oxazol-2-yl]pyridine (3aS,3a'S,8aR,8a'R)-indane-pybox and X = CF3SO3 (4)], [Ag2{(S,S)-(i)Pr-pybox}{(3aS,3a'S,8aR,8a'R)-indane-pybox}][CF3SO3]2 (5), and [Ag2(R-pybox)3][X]2 [R-pybox = (3aS,3a'S,8aR,8a'R)-indane-pybox and X = CF3SO3 (10), SF6 (11), and PF6 (12)] as well as mononuclear complexes [Ag(R-pybox)2][X] [R-pybox = (S,S)-(i)Pr-pybox and X = SbF6 (6), PF6 (7), and BF4 (8); R-pybox = (3aS,3a'S,8aR,8a'R)-indane-pybox) and X = BF4 (9)] have been prepared by the reaction of the corresponding silver salts and pybox ligands using the appropriate molar ratio conditions. The first gold(I)/pybox complex [Au6Cl4{(S,S)-(i)Pr-pybox}4][AuCl2]2 (13) has been synthesized by the reaction of [AuCl{S(CH3)2}] and (S,S)-(i)Pr-pybox (1:1 molar ratio) in acetonitrile. The structures of the dinuclear (1, 4, 5, 10, and 11) and mononuclear (6 and 9) silver complexes and the hexanuclear gold complex 13 have been determined by single-crystal X-ray diffraction analysis. These studies have been complemented with a solution-state study by NMR spectroscopy, which included structure elucidation, variable-temperature measurements, and diffusion studies using diffusion-ordered spectroscopy (DOSY; for complexes 1, 4, 10, and 12). Complexes 1, 2, 4, and 10 have been assayed as catalysts in the asymmetric addition of phenylacetylene to N-benzylideneaniline.

Synthesis of AgN5 and its extended 3D energetic framework

“…Ag2 is coordinated by four cyclo -N 5 ˉ rings, where four N atoms (N1, N4, N6, N9) adopt a distorted tetrahedral configuration around Ag2, with intermediate Ag2–N distances ranging from 2.332 to 2.370 Å, whereas Ag1 is surrounded by three pairs of cyclo -N 5 ˉ rings (N3, N7, and N10) adopting an octahedral geometry with two cyclo -N 5 ˉ rings at the apical positions and four cyclo -N 5 ˉ rings at the equatorial sites. The average Ag1–N distance of 2.519 Å is much longer than the reported values for triazole complexes of Ag(I) (average 2.11 Å) 16 , and the longest bond in the structure, Ag1-N10 (2.669 Å), indicates that the interaction between Ag and cyclo -N 5 ˉ is weak.

Fig. 3Crystal structure of [Ag(NH 3 ) 2 ] + [Ag 3 (N 5 ) 4 ]ˉ. a ORTEP plot of [Ag(NH 3 ) 2 ] + [Ag 3 (N 5 ) 4 ]ˉ at the 50% probability level.

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Silver(i) complexes of bis- and tris-(pyrazolyl)azine derivatives – dimers, coordination polymers and a pentametallic assembly

“…The tpp ligands in this case are only coordinated through the tridentate metalbinding domain, with the pendant 4-pyrazolyl groups projecting from the periphery of the molecules. The dimeric helicate motif is well-known in coinage metal complexes of tris-heterocycle ligands, [4][5][6][15][16][17][18][20][21][22][23][24] including derivatives of bpp (Scheme 1). 21 Rare examples of such dimeric helicates associating into higher order molecular assemblies through unsupported dispersion interactions are known.…”

“…2,3 Alternatively, [Ag n (terpy) m ] n+ helicate structures are also wellknown, usually in dimeric complexes ( n = m = 2) [4][5][6][15][16][17][18] although larger molecular 1,6 or polymeric 6 helicate assemblies of this type are also known. Other "terpyridine analogue" trisheterocycles also mostly yield square planar dimers 19 or helicate assemblies [20][21][22][23][24][25][26] when complexed to silver(I). However examples of circular helicates, 22 molecular squares 27 and rare homoleptic octahedral silver(I) complexes 23 have also been reported with such ligands.…”

“…Other "terpyridine analogue" trisheterocycles also mostly yield square planar dimers 19 or helicate assemblies [20][21][22][23][24][25][26] when complexed to silver(I). However examples of circular helicates, 22 molecular squares 27 and rare homoleptic octahedral silver(I) complexes 23 have also been reported with such ligands.…”

Mechanistic Investigation of the Pd-Catalyzed Intermolecular Carboetherification and Carboamination of 2,3-Dihydrofuran: Similarities, Differences, and Evidence for Unusual Reaction Intermediates

“…To gain additional information on the extent of aggregation in 6c , d , a series of DOSY experiments were carried out . To obtain an estimate of the molecular weight of these supramolecular architectures, two complementary models were applied: (i) the perfect sphere approximation based on the Stokes–Einstein equation (SE) and (ii) the correlation function recently developed by Morris and co-workers . The former has been used routinely for organometallic species despite the fact that it relies on the assumption that molecules are hard spherical objects.…”