The coordination chemistry of Rhenium(V) with multidentate no-donor ligands

摘要

The neutral distorted octahedral complexes [ReOCl(L)] {H2L = N,N-bis(2- hydroxybenzyl)-2-(2-aminoethyl)dimethylamine (H2had), N,N-bis(2-hydroxybenzyl) aminomethylpyridine (H2hap); N,N-bis(2-hydroxybenzyl)-2-(2-aminoethyl)pyridine (H2hae)} were prepared by the reaction of trans-[ReOCl3(PPh3)2] with a twofold molar excess of H2L in ethanol. The X-ray structure determinations of [ReOCl(had)] and [ReOCl(hap)] were performed, and in both complexes the chloride is coordinated trans to the tripodal tertiary amino nitrogen, with a phenolate oxygen trans to the oxo oxygen. Treatment of trans-[ReO2(py)4]I with two equivalents and one equivalent each of H2had in acetone afforded the iodide salts of the oxypyridinium-ammonium zwitterions N1-(2-hydroxybenzyl)-N2,N2- dimethyl-N1-((2-oxypyridinium)-1-methyl)ethane-1,2-diamine [Hhpd]+ and N2,N2- dimethyl-N1-bis((2-oxypyridinium)-1-methyl)ethane-1,2-diamine [dod]+ respectively. In [Hhpd]I, one of the 2-hydroxyphenyl groups of H2had is substituted by an oxypyridinium group, and in [dod]I, both 2-hydroxyphenyl groups are converted. The X-ray crystal structure determination of the starting material H2had, [Hhpd]I and [dod]I reveals trigonal pyramidal geometries around the central amino nitrogen. The complex salt [ReO(bsa)]PF6 (H2bsa=bis(N-methylsalicylicylideneiminopropyl) amine) was prepared from the reaction of cis-[ReO2I(PPh3)2] with H2bsa in toluene. The dianionic pentadentate ligand bsa is coordinated to the ReO3+ moiety via one secondary amino and two imino nitrogens, and two anionic phenolate oxygens. The complex was characterized by spectroscopy and analytical data, and the structure has been determined by single-crystal X-ray diffraction analysis. The complex exhibits a distorted octahedral geometry around the central rhenium(V) ion, with the basal plane being defined by a phenolate oxygen, two imino nitrogens and the secondary amino. ix A. Abrahams Nelson Mandela Metropolitan University The reaction of a two-fold molar excess of the potentially NN-donor ligand 2,2’- dipyridylamine (dpa) with trans-[ReO(OEt)Cl2(PPh3)2] in ethanol led to the isolation of [ReOCl2(OEt)(dpa)]. The X-ray crystal structure shows that the NN-chelated dpa is coordinated in the equatorial plane cis to the oxo and ethoxo groups, which are in trans positions relative to each other. The treatment of trans- [ReOCl3(PPh3)2] with a tenfold molar excess of dpa in ethanol at the refluxing temperature yielded the trans-dioxo complex [ReO2(dpa)2]Cl, but with a twofold molar excess only (μ-O)[{ReOCl2(dpa)}2] was isolated. Repeating the latter reaction with (n-Bu4N)[ReOCl4] as starting material in ethanol at room temperature a dark green product, also with the formulation (μ-O)[{ReOCl2(dpa)}2], was isolated. The reaction of equimolar quantities of bis(pyridin-2-yl)methyl)amine (HBPA) with (n-Bu4N)[ReOCl4] in acetone at room temperature led to the isolation of the sixcoordinate rhenium(V) complex [ReOCl(H2O)(BPA)]Cl. IR, NMR and X-ray crystallographic results indicate that BPA is coordinated as a tridentate uninegative chelate, with deprotonation of the amine nitrogen. The water molecule is coordinated trans to the oxo group, with the Re=O and Re-OH2 bond distances equal to 1.663(9) and 2.21(1) Å respectively. Complexes of the general formula [ReOX2{(C5H4N)CH(O)CH2(C5H4N)}] (X = Cl, I) were prepared by the reactions of trans-[ReOCl3(PPh3)2] and trans- [ReOI2(OEt)(PPh3)2] with cis-1,2-di-(2-pyridyl)ethylene (DPE) in ethanol and benzene in air. Experimental evidence shows that the coordinated DPE ligand has undergone addition of water at the ethylenic carbons, and that the (C5H4N)CH(O)CH2(C5H4N) moiety acts as a uninegative tridentate NON-donor ligand. The X-ray crystal structures of both complexes show a distorted octahedral geometry around the rhenium(V) centre. The treatment of trans-[ReOCl3(PPh3)2] with H2dbd in a 2:1 molar ratio in acetonitrile led to the isolation of the ligand-bridged dimer (μ-dbd)[ReOCl2(PPh3)]2. The X-ray crystal structure of the complex reveals a dinuclear structure in which two rhenium(V) ions are bridged by the dbd ligand. Each rhenium ion is in a x A. Abrahams Nelson Mandela Metropolitan University distorted octahedral geometry. The basal plane is defined by a phosphorus atom of the PPh3 group, two chlorides cis to each other, and a pyridyl nitrogen atom of dbd. The oxo group and alcoholate oxygen of dbd lie in trans axial positions. The complexes cis-[ReOX2(msa)(PPh3)] (X = Cl, Br, I) were prepared from trans- [ReOCl3(PPh3)2], trans-[ReOBr3(PPh3)2] or trans-[ReOI2(OEt)(PPh3)2] with 2-(1- iminoethyl)phenol (Hmsa) in acetonitrile. An X-ray crystallographic study shows that the bonding distances and angles in the comlexes are nearly identical, and that the two halides in each complex are coordinated cis to each other in the equatorial plane cis to the oxo group. The oxo-bridged dinuclear rhenium(V) complex [(μ-O){ReOCl(amp)}2] was prepared by the reaction of trans-[ReOCl3(PPh3)2] and 6-amino-3-methyl-1-phenyl- 4-azahept-2-ene-1-one (Hamp) in acetone. The characterization of the complex by elemental analysis, infrared and 1H NMR spectroscopy and X-ray crystallography shows that amp is coordinated as a monoanionic NNO-donor chelate as an amino-amido ketone. However, the reaction of the similar ligand 7- amino-4,7-dimethyl-5-aza-3-octen-2-one (Hada) with [Re(CO)5Br] produced the product fac-[Re(CO)3Br(Hada)], with Hada coordinated as a neutral NN-donor amino-imino-ketone.