Tricationic Metal Complexes ([ML][NO₃]₃, M = Ga, In) of N,N‘,N‘‘-Tris(2-pyridylmethyl)- cis-1,3,5-triaminocyclohexane:  Preparation and Structure

Abstract

The novel hexadentate chelator tachpy, composed of the cis-1,3,5-triaminocyclohexane framework with N-pendant 2-pyridylmethyl arms, forms Ga3+ and In3+ complexes. The solid-state structures of the M(tachpy)3+ units show distortion of the coordination sphere toward trigonal prismatic from octahedral as the metal radius increases. There is also a slight expansion of the triaminocyclohexane nitrogens as the metal radius increases, with concomitant flattening of the cyclohexyl ring. Proton NMR over greater than 4 weeks indicates that Ga(tachpy)3+ is inert to aqueous hydrolysis over the pH range 2−8, while In(tachpy)3+ hydrolyzes immediately under these conditions.

Pyridine‐Ring Alkylation of Cytotoxic r‐1,c‐3,c‐5‐Tris[(2‐pyridylmethyl)amino]cyclohexane Chelators: Structural and Electronic Properties of the MnII, FeII, NiII, CuII and ZnII Complexes

“…Characteristic patterns of proton–proton coupling between cyclohexyl H atoms indicate “closed”, complexed tach as opposed to “open” tach 1. The two methylene protons of the coordinated pendant arms are diastereotopic, indicating that the arms of these complexes are twisted about the metal ion in the Δ or Λ configuration, and Δ–Λ interconversion does not occur on the NMR time‐scale at room temperature, also as previously found for [M(tachpyr)] 2+ (M = Fe II , Zn II , Ga III , In III ) 1,2,18…”

Tris(1‐methyl‐imidazol‐2‐yl)phosphane Complexes of Pnictogen, Tetrel, and Triel Cations

“…The triflate anions do not interact with the metal center in either compound as all six coordination sites at the octahedral gallium or indium centers are occupied by nitrogen atoms of a methyl‐imidazole unit (Figure ). The average interatomic bond distances for the metal nitrogen interactions (M=Ga 2.052, M=In 2.191 Å) are slightly shorter than those in [Ga(Bipy) 3 ] 3+ (Ga−N 2.064 Å) or [In(tachpy) 3 ] 3+ (In‐N 2.242 Å) . The phosphorus–metal distance is slightly shorter for gallium (P−Ga 3.494 Å) than for indium (P−In 3.596 Å), likely due to the larger ionic radius of indium, and are similar to their tricationic pnictogen analogues [P(Im) 3 Pn][OTf] 3 (P−As 3.486 Å and P−Sb 3.685 Å).…”

“…Compounds containing Group 13 metals in the oxidation state +1 (M=Al, Ga, In) are susceptible to disproportionation to form M III and M 0 , as was observed for “GaI” in the presence of bipyridine to yield [Ga(bipy) 3 ][I] 3 and gallium metal . Tricationic complexes of indium have only been stabilized with oxygen donors, such as crown ethers and dimethyl sulfoxide, or with 1,3,5‐triaminocyclohexane, and the only tricationic complexes of gallium show elaborate EPR spectra…”

“…[1] For example, complexes of Ga + with cryptand, [2] phosphine, [3] pyrazine, [4] or arene [5] ligands, complexes of Ge 2 + with crown ethers, [6] carbenes, [7] ammonia, water, [8] pyridines, [9] phosphines, [10] or isocyanides [11] andc omplexes of As 3 + with pyridine derivatives [12] demonstrate the diversity of this emerging coordination chemistry.C ompounds containing Group13 metals in the oxidation state + 1( M= Al, Ga, In) are susceptible to disproportionation to form M III and M 0 , [13] as was observed for "GaI" [14] in the presence of bipyridine to yield [Ga(bipy) 3 ][I] 3 and gallium metal. [15] Tricationic complexes of indiumh ave only been stabilized with oxygen donors, [16] such as crown ethers [17] and dimethyl sulfoxide, [18] or with 1,3,5-triaminocyclohexane, [19] and the only tricationic complexes of gallium [20] show elaborate EPR spectra. [21] Tridentate Ld onors have promise as genericl igandsf or a wide array of metals and main-group elements.…”

Crystal structure of 1,3,5-trideoxy-1,3,5- tris((2-pyridylmethyl)amino)-cis-inositolcobalt(III) bromide tetrahydrate, [Co(pmaci)]Br3 · 4H2O

“…The reaction of aromatic aldehydes with primary amines forming Schiff bases is an efficient route to multidentate chelate ligands [2]. Derivatisation of the versatile ligand taci with O-pendant groups via Schiff bases as intermediates has recently been published [3].…”