This thesis discusses reduction and oxidation reactions catalysed by the perrhenate anion and oxidation reactions catalysed by other oxo-anions i.e. sulfate and nitrate. Chapter one introduces catalytic hydrosilylation, hydroboration, deoxydehydration and alkene epoxidation and some of their applications, with a focus on high oxidation state complexes. Chapter two describes the synthesis of a salt of perrhenate [N(hexyl)4][ReO4] which is highly soluble in organic solvents. The use of this salt as a catalyst for both the hydrosilylation and hydroboration of carbonyl compounds and carbon dioxide is discussed. Catalytic methylation of amines and anilines with carbon dioxide and hydrosilanes is also reported. Labelled carbon dioxide reactions and DFT calculations are conducted in order to understand the mechanism of carbon dioxide reduction using hydrosilanes. Chapter three outlines the synthesis of a number of alkylammonium and pyridinium perrhenate salts and their application in the deoxydehydration reaction, converting vicinal diols to alkenes. The role of the counterion is discussed with pyridinium perrhenates shown to be more effective catalysts. DFT calculations are conducted to identify the most likely pathway of the catalytic cycle. Alternative reducing agents to the triphenylphosphine initially used are also studied. Chapter four reports results of organic salts of perrhenate, sulfate and nitrate as oxidation catalysts, specifically their ability to catalyse epoxidations of alkenes. By the formation of supramolecular ion pairs (SIPs), these anions are made organic soluble which is found to significantly enhance their catalytic ability, however, the organic counterions used to form these SIPs were found to be of importance. Ionic liquids are also used for the epoxidation of alkenes. Solution studies are presented to further understanding of how these compounds interact with one another in solution. Chapter five contains experimental conditions and characterisation for compounds discussed in this work.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1947. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (2 leaves at end).

Thesis (Ph. D.)--University of Hong Kong, 1999. / Includes bibliographical references (leaves 278-296).

Thesis (Ph. D.)--University of Hong Kong, 1997. / Includes bibliographical references (leaf 331-359).

Berlin, Freie Universiẗat, Diss., 1999. / Dateiformat: zip, Dateien im PDF-Format.

Berlin, Freie Universiẗat, Diss., 1998. / Dateiformat: zip, Dateien im PDF-Format.

A series of rhenium(I) complexes with monodentate benzazole ligands containing the fac-[Re(CO)3]+ was synthesized. The rhenium(I) compound [ReCl(Hmbt)2(CO)3] was prepared from the reaction of [Re(CO)5Cl] and 2-aminobenzothiazole (Hmbt) in toluene. The ligand coordinates in a monodentate manner via the thiazole nitrogen atom. A similar reaction between [Re(CO)5Cl] and N-(1,3-benzothiazol-2-yl)-2- chloroacetamide (Hbct) resulted in the formation of [ReCl(Hbct)(CO)3(NCMe)], where only one ligand binds per rhenium in a monodentate fashion. The reaction of ligands 2-mercaptobenzimidazole (Hmbi) (dibenzothiazol-2-yl)tetraazathiapentalene (Hdbt) with rhenium(I) gave [ReCl(Hmbi)2(CO)3] and [ReCl(Hdbt)2(CO)3] respectively. The study on the coordination behaviour between ethyl-(1H-benzimidazol-2-yl-sulfanyl) acetate (Hbsa) and [Re(CO)5Cl] surprisingly gave the dimeric species (μ-Cl)2[Re(Hbsa)(CO)3]2, where the two rhenium atoms are bridged by two chloro ligands. The coordination of Hbsa occurs through the imidazole nitrogen, leaving the ethoxy tail free on each Hbsa ligand. The coordination behaviour of benzimidazole and benzothiazole derivatives gave rhenium complexes in oxidation states I, III and V, where all the ligands coordinate as bidentate N,N-chelating ligands. The study on 2-(2-aminophenyl)-1-benzothiazole (Hapt) and 2-(2-aminophenyl)-1-benzimidazole (H2apz) with [ReVOCl3(PPh3)2] resulted in the formation of [ReVOCl2(apt)(OPPh3)] and [ReVCl2(apz)(PPh3)2](ReO4), respectively. 1,2-Bis(2-benzimidazole)-1,2-ethanediol (Hbed) and 2,6-bis(2- benzimidazol-2-yl)pyridine (H2bip) were studied towards rhenium(I) and rheniumV) respectively. The former gave a dimeric species (μ-bbi)[Re(CO)4]2 (H2bbi – bisbenzimidazole) by reaction with [Re(CO)5Cl], whereas H2bip produced the rhenium(III) cationic salt [ReCl3(H3bip)(PPh3)]Cl, where the ligand coordinates as a cationic H3bip+ with protonation of an uncoordinated imidazole nitrogen atom. The pyridine derivatives 2-hydrazino-pyridinyl-2-benzothiazole (Hhpt) and (E)-1-benzo[d]thiazol-2-yl)-2- (pyridin-2-ylmethylene)hydrazine (btp) were reacted with [Re(CO)5Cl]. The neutral complex [ReCl(Hhpt)(CO)3] was isolated upon reaction with Hhpt, where Hhpt coordinates as a neutral bidentate ligand. The reaction of [Re(CO)5Cl] with btp gave two different complexes when using different solvents. In methanol, [ReCl(btp)(CO)3] was isolated, whereas in toluene, the conjugate of btp (btp1) was formed which resulted in the formation of [ReCl(btp1)(CO)3]. The study on potentially bidentate thiourea derivatives containing a benzothiazole moiety towards [ReI(CO)3]+ and [ReVO]3+ cores gave rise to a wide variety of complexes. The reaction of [Re(CO)5Cl] with N-phenyl-N-(2-benzothiazole)thiourea (Hpbt) produced the rhenium(I) complex [Re(Hpbt)(pbt)(CO)3]. Hpbt coordinates both as a monodentate neutral ligand and as a bidentate monoanionic chelate. The study of the reaction between trans-[ReOCl3(PPh3)2] and Hpbt gave the rhenium(V) product [ReOCl2(pbt)(PPh3)], with pbt acting as a bidentate ligand. The reaction of 1-(1,3- benzothiazol-2-yl)-3-benzoylthiourea (Hbbt) with [Re(CO)5Cl] led to the isolation of [ReCl(Hbbt)(CO)3]. Similar reaction of Hbbt with trans-[ReOCl3(PPh3)2] gave the unique compound [ReOCl2(Hbnt)(PPh3)], where the ligand coordinates via the ketonic oxygen and a methine carbon. The complex [Re(Hmby)(mby)(CO)3] was isolated upon reacting [Re(CO)5Cl] with methylbenzothiazol-2-ylidenecarbamodithioate (Hmby), with Hmby coordinating as a monodentate neutral ligand and mby as a bidentate monoanionic chelate. The coordination behaviour of N-(benzothiazol-2-yl)-S,S’- dimethyldithiocarboimine (Hbdc) towards rhenium(I) led to the formation of [ReCl(Hbdc)(CO)3]. The reactivity of 1-(benzothiozol-2-yl)-3,3-dimethylthiourea (Hbdm), a derivative of Hmby, was studied with trans-[ReOCl3(PPh3)2] and trans- [ReO(OEt)I2(PPh3)2] producing the square pyramidal compound [ReOCl(bdm)2] and the salt [Re(bdm)2(MeCN)2]I3, respectively. Pyrazole derivatives containing a benzothiazole ring were studied towards rhenium in oxidation states +I and +V. The reaction between 2-(3,5-dimethylpyrazol-1-yl)benzothiazole (Hdmp) and [Re(CO)5Cl] gave the neutral rhenium complex [ReCl(Hdmp)(CO)3], whereas its reaction with [ReOCl3(PPh3)2] surprisingly results in the formation of a dimeric complex (μ-O)[ReOCl2(Hdmp)]2. The study on the reactivity of 1-(benzo[d]thiazol-2-yl)-4-methyl-1H-pyrrol-2-ol (Hbtm) with [Re(CO)5Cl] gave the unexpected trimer [Re(btm)(CO)3]3 containing the fac-[Re(CO)3]+ core. The ligand btm forms a bridge between each rhenium metal, serving as a bidentate ligand to one rhenium, and a monodentate ligand to another rhenium atom. The study on the coordination chemistry between trans-[ReOCl3(PPh3)2] and Hbtm gave two different complexes when using different solvents. In ethanol, [ReOCl(btm)(btm1)] formed, whereas [ReOCl(btm1)(btz)] (Hbtz = 1-(benzo[d]thiazol-2-yl)-4-(1-iminoethyl)-3- methyl-1H-pyrazol-5-ol) was isolated in acetonitrile. The reaction of cis-[ReO2I(PPh3)2] also gave two different products when using different solvents, where the respective solvents coordinate to the metal. The rhenium(V) compound [ReO(OMe)(btm)(btm1)] was formed in methanol, whereas [ReO(OEt)(btm)(btm1)] was formed in ethanol. The coordination chemistry of 2-(2-Benzothiazoleyl)-4,5,6,7-tetrahydro-2H-indazol-3-ol (Hbth) was studied towards [Re(CO)5Cl] and trans-[ReOCl3(PPh3)2]. The resulting complexes which formed are [ReCl(Hbth)(CO)3] and [ReOCl(bth)(bth1)] respectively. The reactivity of potentially tridentate Schiff base ligands towards rhenium(I) and (V) was studied. The rhenium(I) precursor [Re(CO)5Cl] was reacted with (E)-1- (benzo[d]thiazol-2-yl)-2-(phenol-2-ylmethylene)hydrazine (H3bph) to give [ReCl(CO)3(H3bph)], which contains the kinetically inert fac-[Re(CO)3]+ core coordinated to a neutral bidentate ligand. The reaction of [ReO2(py)4Cl] with H3bph gave the dimeric species (μ-O)[ReO(Hbph)(py)]2, where the ligand coordinates as a tridentate dianionic chelate. A similar complex was isolated with (E)-1- (benzo[d]thiazol-2-yl)-2-(2,4-dihydroxy-2-ylmethylene)hydrazine (H3bdh) to give (μ-O)[ReO(Hbdh)(py)]2. The reaction of trans-[ReOCl3(PPh3)2] with H3bph afforded [Re(abt)(imp)Cl2(PPh3)] (abt = 2-aminobenzothiazole, imp = 2-(iminomethyl)phenol), where the ligand broke up into two fragments, both of which coordinated without any modification. The dioxo rhenium precursor cis-[ReO2I(PPh3)2] gave [ReO(Hbdh)(imp)] upon reaction with H3bdh. Ligand imp coordinates as a bidentate monoanionic ligand via the imine nitrogen and deprotonated phenolic oxygen and ligand Hbdh coordinatesas a tridentate dianionic chelate.

The reaction of the potentially tridentate Schiff-base chelate Hhaep [Haep = N’-(1- (2-hydroxyphenyl)ethylidene)benzohydrazide] with [ReCl3(benzil)(PPh3)] and trans-[ReOCl3(PPh3)2] produced the neutral oxorhenium(V) complexes cis- [ReOCl2(mep)] [Hmep = 2-(1-iminoethyl)phenol] and cis-[ReOCI2(meb)(PPh3)] [Hmeb = N’-(propan-2-ylidene)benzohydrazide] in ethanol and acetone respectively. In both reactions the Hhaep molecule cleaves to give different coordinated bidentate NO-donor chelates coordinated to the rhenium(V) centers. The X-ray studies reveal that mep is present as a bidentate, monoanionic Schiffbase coordinating through the neutral imino nitrogen and the deprotonated phenolate oxygen in cis-[ReOCl2(mep)]. The bond distances and angles in cis- [ReOCI2(meb)(PPh3)] confirm that meb coordinates to the metal in the enolate form. The distorted octahedral complex fac-[ReCl3(dpa)(PPh3)] was prepared by the reaction of trans-[ReCl3(MeCN)(PPh3)2] with a twofold molar excess of dpa in acetonitrile under a nitrogen atmosphere. The compound dpa.HCl.2H2O was obtained as a by-product in the reaction of dpa with trans-[ReCI3(MeCN)(PPh3)2] in acetonitrile. The reaction of trans-[ReCl3(MeCN)(PPh3)2] with a twofold molar excess of 6- amino-3-methyl-1-phenyl-4-azahept-2-ene-1-one (Hamp) in acetonitrile led to the isolation of cis-[ReCl2(bat)(PPh3)2]. On complexation to the metal center Hamp decomposed to give the coordinated benzoylacetone (bat). Bat is present as a monoanionic bidentate chelate. The complexes [ReVOCI(had)] and [ReIVCl(had)(PPh3)](ReO4) were prepared from the reaction of trans-[ReCl3(MeCN)(PPh3)2] with N,N-bis((2-hydroxybenzyl)-2- aminoethyl)dimethylamine (H2had) in ethanol under various reaction conditions. The treatment of [ReCl3(benzil)(PPh3)] with 2-[((2- pyridinylmethyl)amino)methyl]phenol (Hham) in a 2:1 molar ratio in acetonitrile led to the isolation of the hydrogen-bonded dimer [ReOCl2(ham)]2. The distorted octahedral complex [ReOCl(hap)] [H2hap = N,N-bis(2- hydroxybenzyl)aminomethylpyridine] was prepared from the reaction of trans- [ReCl3(MeCN)(PPh3)2] with a twofold molar excess of H2hap in acetonitrile. The X-ray crystal structure analysis shows that the chloride is coordinated trans to the tripodal tertiary amino nitrogen, with a phenolate oxygen trans to the oxo oxygen.

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.

The complex trans-[Re(dab)Cl3(PPh3)2] (H2dab = 1,2-diaminobenzene) was prepared from the reaction of trans-[ReOCl3(PPh3)2] with H2dab in ethanol. The ligand dab is coordinated to the rhenium(V) centre through a dianionic imido nitrogen only in a distorted octahedral coordination geometry around the metal ion. The complex trans- [Re(ada)Cl3(PPh3)2] (H2ada = 2-aminodiphenylamine) was prepared from the reaction of trans-[ReOCl3(PPh3)2] with H2ada in acetonitrile. The ligand ada is coordinated to the rhenium(V) centre through a dianionic imido nitrogen only, in a distorted octahedral coordination geometry around the metal ion. The ‘2 + 1’ complex fac- [Re(CO)3(Hamp)(amp)] (Hamp = 2-aminophenol) was isolated from the reaction of a two molar ratio of Hamp with [Re(CO)5Br] in toluene. The reaction of a 1:1 molar ratio of [Re(CO)5Br] and H2ada led to the isolation of the Re(I) complex, fac- [Re(CO)3Br(H2ada)]. The reaction of equimolar quantities of cis-[ReO2I(PPh3)2] with 5,6-diamino-1,3- dimethyluracil (H2ddd) in acetonitrile led to the formation of [Re(ddd)(Hddd)I(PPh3)2](ReO4). The X-ray crystal structure shows that the ligand ddd is coordinated monodentately through the doubly deprotonated amino nitrogen and is therefore present as an imide. The chelate Hddd is coordinated bidentately via the neutral amino nitrogen, which is coordinated trans to the imido nitrogen, and the singly deprotonated amido nitrogen, trans to the iodide. The reaction of trans-[ReOCl3(PPh3)2] with N-(2-aminobenzylidene)-5-amino-1,3-dimethyl uracil (H3dua) in ethanol gave a mixed crystal which contains both the neutral oxorhenium(V) complex [ReOCl(Hdua)] and the imido rhenium(V) [Re(dua)Cl2(PPh3)] in an equimolar ratio in the asymmetric unit. The reaction of equimolar quantities of [NH4(ReO4)] with H2ddd in methanol under reflux led to the isolation of [C12H12N6O4] as only product. The [ReO4]- anion is therefore instrumental in the formation of [C12H12N6O4], and since the product contains no rhenium in any oxidation state, the conclusion is that [ReO4]- catalyses the oxidative deamination Abstract I.N. Booysen Nelson Mandela Metropolitan University vii of H2ddd. The X-ray crystal structure consists of two centrosymmetric, tricyclic rings, comprising a central pyrazine ring and two terminal pyrimidine rings. The reaction of 2-(2-aminophenyl)benzothiazole (Habt) with [Re(CO)5Br] led to the isolation of the rhenium(I) complex fac-[Re(Habt)(CO)3Br]. With trans-[ReOCl3(PPh3)2], the ligand Habt decomposed to form the oxofree rhenium(V) complex [Re(itp)2Cl(PPh3)] (itp = 2-amidophenylthiolate). From the reaction of trans-[ReOBr3(PPh3)2] with 2-(2- hydroxyphenyl)benzothiazole (Hhpd) the complex [ReVOBr2(hpd)(PPh3)] was obtained. The reaction of a twofold molar excess of H2apb (2-(2-aminophenyl)-1-benzimidazole) with trans-[ReO2(py)4]Cl in ethanol gave the green product of formulation [ReO(Hapb)(apb)] in good yield. The rhenium atom lies in a distorted trigonalbipyramidal environment. The two imidazole N(2) atoms lie in the apical positions trans to each other, with the oxo-oxygen and two amido N(1) atoms in the trigonal plane. A new nitrosylrhenium(II) complex salt, [Re(NO)BrL2(PPh3)2](ReO4) (H2L2 = 2-amino-5- (triphenylphosphino)phenol), is the first example of a complex containing the triphenylphosphonium-amidophenolate ligand L2, formed by the nucleophilic attack of a PPh3 on a coordinated amidophenolate ring. The complex salt trans-[Re(mps)Cl(PPh3)2](ReO4) (H3mps = N-(2-amino-3- methylphenyl)salicylideneimine) was prepared by the reaction of trans-[ReOCl3(PPh3)2] with a twofold molar excess of H3mps. The X-ray crystal structure shows that the trianionic ligand mps acts as a tridentate chelate via the doubly deprotonated amino nitrogen (an imide), the neutral imino nitrogen and the deprotonated phenolic oxygen. The six-coordinated complex cis-[Re(mps)Cl2(PPh3)2] was prepared by the reaction of trans-[ReOCl3(PPh3)2] with a twofold molar excess of H3mps in benzene. The X-ray crystal structure show that the mps ligand coordinates as a tridentate chelate via the doubly deprotonated 2-amino nitrogen, the neutral imino nitrogen and the phenolate oxygen. The imide and phenolate oxygen coordinate trans to each other in a distorted octahedral geometry, around the rhenium(V) centre, with the two chlorides in cis positions. A new oxofree rhenium(V) complex salt, [Re(bbd)2](ReO4) ( H2bbd = N-(2- Abstract I.N. Booysen Nelson Mandela Metropolitan University viii aminobenzylidene)benzene-1,2-diamine), has been synthesized and the chelates bbd are coordinated as dianionic tridentate N,N,N-donor diamidoimines. The rhenium(V) ion is centered in a distorted trigonal prism. The rhenium(I) compound fac-[Re(CO)3(daa)].Hpab.H2O (Hpab = N1,N2-(1,2- phenylene)bis(2-aminobenzamide); Hdaa = 2-amino-N-(2-aminophenyl)benzamide) was synthesized from the reaction of [Re(CO)5Br] with a two equivalents of Hpab in toluene. The monoanionic tridentate ligand daa was formed by the rhenium-mediated cleavage of an amido N-C bond of the potentially tetradentate ligand Hpab. Daa is coordinated as a diaminoamide via three nitrogen-donor atoms. The reaction of a twofold molar excess of H2amben (H2amben = N1,N2-bis(2-aminobenzylidene)ethane-1,2-diamine) with trans- [ReOBr3(PPh3)2] gave the oxorhenium(V) cationic complex [ReO(amben)]X (X = Br-, PF6 -). The Re(V) oxo-bridged compound, {μ-O}[ReO(omben)]2.H2O (H2omben = N1,N2- bis(2-hydroxybenzylidene)ethane-1,2-diamine) was isolated from the reaction of a 2:1 molar ratio of H2omben and trans-[ReO2(py)4]Cl in methanol. The seven-coordinate rhenium(III) complex cation [ReIII(dhp)(PPh3)2]+ was isolated as the [ReO4]- salt from the reaction of cis-[ReVO2I(PPh3)2] with 2,6-bis(2- hydroxyphenyliminomethyl)pyridine (H2dhp) in ethanol. In the complex fac- [Re(CO)3(H2dhp)Br], prepared from [Re(CO)5Br] and H2dhp in toluene, the H2dhp ligand acts as a neutral bidentate N,N-donor chelate. An equimolar ratio reaction of 2-aminobenzaldehyde and 2-(2-aminophenyl)-1- benzimidazole in methanol led to 2-(5,6-dihydrobenzimidazolo[1,2-c]-quinazolin-6- yl)aniline. In an attempt to explore the template formation of this class of ligand with rhenium, the reaction of salicylaldehyde and 2-(2-aminophenyl)-1-benzimidazole in ethanol which was followed by the addition of trans-[ReOBr3(PPh3)2] led to the formation of the salt, 6-(2-hydroxyphenyl)-5,6-dihydrobenzimidazolo[1,2-c]quinazolin- 12-ium bromide. The compound 6-(2-methylthiophenyl)-5,6-dihydrobenzimidazolo[1,2- c]quinazolin-12-ium was synthesized via the reaction of 2-aminobenzaldehyde and 2- methylthiobenzaldehyde in methanol.