Chapter 1 reviews the literature concerning the principal synthetic routes to hydroxyphosphine transition-metal complexes and their reactions, which have led to the formation of some unusual diphosphoxane derivatives. The preparation and characterization of aminophosphine complexes of chromium, molybdenum, and tungsten are presented in Chapter 2. The phosphorus-nitrogen bond is readily cleaved by HC1 gas and other aqueous acids, to afford phosphorus-chlorine and phosphorus-oxygen bonded derivatives. The chromium and tungsten aminophosphine complexes have been found to be particularly useful for the preparation of chlorodiphenylphosphine derivatives. In addition their reactions with alcohols have also been investigated. The study of aminophosphine complexes has been extended to Pt(II) derivatives in Chapter 3. Cleavage of the phosphorus-nitrogen bond in these complexes is again observed to proceed smoothly with gaseous HC1 and aqueous HC1, but not with other aqueous acids. Treatment of the chlorodiphenylphosphine complex, cis-[PtC12(PPh2C1)2], with sodium sulphide afforded a four-membered metallacycle. A similar four-membered metallacycle was also obtained by refluxing the hydroxyphosphine complex, cis-[PtC12(PPh2OH)2], in toluene for 12h. Other reactions of the hydroxyphosphine complex with chlorodiphenylphosphine and dichlorophenyl- phosphine led to the formation of six-membered ring systems. The molecular structure of the complex [NHEt3] [Pt(C?CPh)(Ph2PO)2 (Ph2POH)] has been established by X-ray crystallography and reveals an unsymmetrical hydrogen-bridged system. Some of the complexes have been characterised via their 1,2-dithiolene derivatives. Treatment of cis-[PtC12(PNEt2Ph2)2] with diphenacyl sulphone in the presence of silver(I) oxide afforded the metallathietane-3, 3-dioxide complex, L2Pt-CHR-S (O)2-CHR (L=Ph2PNEt2; R = C(O)Ph). The final chapter describes the preparation of some Rh(I) and Ir(I) aminophosphine complexes. Their oxidative addition reactions with methyl iodide, tetracyanoethylene, dioxygen, and HC1 gas have been investigated. In addition, some interesting metal-mercury bonded complexes were prepared by the treatment of trans-[IrC1 (CO) (PNEt2Ph2)2] with mercuric halides, HgX2 (X=C1, Br or I). Satellite peaks due to mercury-199 coupling (I=1/2, 16.9%) were readily observed in the 31P-{1H} n.m.r. spectra.

Cette thèse porte sur la synthèse et la caractérisation de complexes octaédrique de fer(II) et fer(III) coordinés par un ligand tridente de type scorpionate (symétrie fac) et par trois ligands cyanures. Leur utilisation en tant que metalloligand face à des ions métalliques partiellement bloqués est étudiée. Les ligands cyanures, de par leur caractère ambidente, permettent un accès facile aux espèces hétérobimétalliques. De plus, ces ligands sont connus pour transmettre efficacement l'interaction d'échange magnétique et donc pour favoriser la communication électronique intramoléculaire entre les ions métalliques qu'ils relient. La fonctionalisation des ligands scorpionates permet de contrôler les propriétés électroniques intrinsèques des complexes précurseurs de fer, et donc de moduler les propriétés des espèces polynucléaires obtenues à partir de ces dernières par auto-assemblage. Dans cette thèse, un intérêt particulier est porté aux systèmes {FeCo} en raison de leur capacité à présenter une bistabilité électronique (propriétés photomagnétiques ou de molécules/chaines aimants). Les systèmes cyanuré {FeCo} sont particulièrement adaptés pour l'observation de réarrangements électroniques thermo- et/ou photo-induit, comme en témoignent le nombre important de composés cyanurés photomagnétiques dans la littérature. / The work presented in this PhD dissertation focuses on the synthesis and the characterisation of octahedral iron(II) and iron(III) complexes coordinated by a tridentate ligand of the scorpionate family (fac- geometry) and three cyanide ligands. Their use as metalloligands in respect to partially blocked metal ions is studied. Because of their ambidentate character, cyanide ligands open the door to facile synthesis of heterobimetallic species. Moreover, these ligands are known to be efficient magnetic exchange interaction transmitter, thus favouring intramolecular electronic communication between the metal ions they are bridging. The functionalisation of scorpionate ligands allows control over the intrinsic electronic properties of the iron precursor complexes, thus allows to tune the properties of the obtained polynuclear species from the latter by self-assembly. In this PhD dissertation, a particular interest was taken in {FeCo} systems because of their potential ability to exhibit electronic bistability (photomagnetic properties or SMM/SCM behaviour). Cyanide-bridged {FeCo} systems are particularly suitable for the observation of thermally or light-induced electron rearrangements, as testified by the wide range of photomagnetic cyanide-bridged compounds in the literature.

M.Sc. / Please refer to full text to view abstract

Magister Scientiae - MSc / G1 and G2 dendrimeric salicylaldimine ligands containing both substituted and unsubstituted aryl rings were synthesized via a Schiff base condensation of the appropriate salicylaldehyde and the peripheral amino groups of the corresponding G1 and G2 polypropyleneimine dendrimers. The new ligands were characterized using FTIR, 1H NMR and 13C NMR spectroscopy, elemental analysis and ESI mass spectrometry. The dendrimeric ligands were converted to multinuclear nickel complexes by reaction with nickelacetate. The metal complexes were characterized by FTIR spectroscopy, elemental analysis and ESI mass spectrometry.Some of the dendritic complexes were evaluated as catalyst precursors in the oligomerization of α-olefins such as ethylene and 1-pentene, using aluminium alkyls such as EtAlCl2 and modified methylaluminoxane (MMAO) as activators. All the dendrimeric catalysts evaluated are active in the oligomerization reactions. From the oligomerization results it was observed that there is a clear dendritic effect, in that both catalyst activity as well as selectivity are impacted by the dendrimer generation. In most cases it was observed that the second generation complexes show higher activity than the corresponding first generation complexes.The dendrimeric complexes were also evaluated as catalyst precursors in the vinyl polymerization of norbornene. In this case methylaluminoxane (MAO) were employed as an activator. Once again it was noted that a dendritic effect is operative, with second generation metallodendrimers having a higher activity than the first generation complexes. / South Africa

The anionic tridentate chelating ligands [MeGa(pz)₃]⁻, [MeGa(dmpz)₃]⁻, and [MeGa(mpz)₃]⁻ have been synthesized and their coordinative properties studied. The [MeGa(pz)₃]⁻ ligand acts as a six-electron chelating ligand to divalent transition metal ions giving complexes of the type [MeGa(pz)₃]₂M (M=Mn,Co,Ni,Cu,Zn), believed to possess an octahedral MN₆ core. The ligand also forms numerous carbonyl complexes with Mn, Mo and W. The tridentate chelating nature of this new ligand has been demonstrated through a crystal structure determination of the complex [MeGa(pz)₃]Mo(CO)₂(n³-C₃H₅). The [MeGa(dmpz)₃]⁻ ligand also forms carbonyl complexes of Mn, Mo and W. The ready conversion of this ligand to the less sterically demanding tris-chelating "hydroxy" ligand [MeGa(dmpz)₂(OH)]⁻ occurs in the attempted synthesis of "n³-allyl" complexes [MeGa(dmpz)₃]M(CO)₂ " n³-allyl" (where M=Mo or W, "n³-allyl"=n³-C₅H₅, n³-C₄H₇). The tridentate chelating nature of this "hydroxy" ligand is conclusively demonstrated in the crystal structure determination of the complex [MeGa(dmpz)₂(OH) ]Mo(C0)₂(n³-C₄H₇) . The [MeGa(mpz)₃]⁻ ligand forms transition metal complexes of the type [MeGa(mpz)₃]₂M (M=Co,Ni) and also carbonyl complexes of Mo and W. Less definitive results were obtained with this ligand, as characterization of the resulting complexes was complicated by the inability to separate the isomers possible for each complex The synthesis of the [H₂B(OCH₂CH₂NR₂)(pz)]⁻ (R=H, Me) ligands and their reaction with divalent transition metal ions is also described. In this case, the only products isolated were the previously characterized [H₂B(pz)₂]₂M and [HB(pz)₃]₂M (M=Co,Ni, Cu,Zn) complexes. Finally, details of the synthesis and characterization of the [R₂Ga(CH₃C0₂)] and [R₂Ga(C₄H₈NC0₂)] (R=Me,Et) compounds are given. The crystal structure of the [Me₂Ga(C₄H₈NC0₂)] derivative consisted of monomeric units linked to two others by weak Ga-0 bonds to form a chain-like polymeric structure. The gallium atom in this compound is five-coordinate and has distorted trigonal bipyramidal geometry. / Science, Faculty of / Chemistry, Department of / Graduate

We investigated the role of Fas ligand in the development of anti-tumor immunity. The LSA tumor specific cytotoxic T lymphocyte (CTL) clone, PE-9, expressed both Fas and Fas ligand. This CTL clone upregulated Fas and Fas ligand expression upon activation through the T-cell receptor and induced apoptosis in Fas+, LSA tumor cells using the FasL-based pathway. However, LSA and EL-4 tumor cells constitutively expressed Fas ligand and killed Fas+ PE-9 CTLs and Fas+, but not Fas-negative (Fas-) activated T cells and thymocytes. These data suggested that T cells and cancer cells can kill each other and that cancer cells may use Fas ligand to evade the action of the immune T cells. In addition to the expression of membrane-bound form, FasL+ LSA and EL-4 tumor cells produced a soluble form of Fas ligand when they grew in vivo and in vitro. Serum from EL-4 or LSA-bearing wild type mice contained significant levels of Fas ligand. The soluble FasL induced apoptosis in liver and thymus of C57BL/6 wild type (Fas+) mice, but not C57BL/6 lpr/lpr (Fas-) mice. The detection of apoptosis in the liver of C57BL/6 gld/gld (FasL-defective) mice suggested that the source of Fas ligand found in the sera of EL-4 or LSA-bearing mice was from the tumor cells rather than the host cells. CTL or NK cells used FasL-based apoptosis to kill the target cells when activated. To this end, we tested whether constitutive expression of Fas on tumor cells generate enhanced anti-tumor immunity. IL-2 or poly-I-C induced/ activated NK/LAK cells displayed higher cytotoxicity against L1210 Fas+, but not L1210 Fas- tumor cells. Furthermore, growth of L1210 Fas+, but not Fas- tumor, in vivo, generated Fas-specific cytotoxic T lymphocytes. Therefore, mice bearing L1210 Fas+ tumor cells survived for a longer time than mice bearing L1210 Fas- tumor cells. To determine the role of the Fas, FasL, and perforin in the initiation of tumor, C57BL/6 +/+ (FasL+, Fas+), C57BL/6 lpr/lpr (Fas-), C57BL/6 gld/gld (FasL-), and perforin knock-out (PKO) (FasL+, Fas+, but perforin-deficient) mice were injected with methylcholanthrane (MCA). Tumor development in lpr or gld mice was faster and uncontrollable, compared to C57BL/6 (wild-type) and PKO mice. However, wild-type and PKO mice showed delayed tumor appearence and were able to suppress tumor growth. In addition to the deficiency of Fas or FasL, high levels of TGF-b and IL-10 expression detected in lpr and gld mice were also responsible for the early tumor development. Together these data suggested that interactions between Fas and Fas ligand, expressed on immune cells and tumor cells, play an important role in the generation of anti-tumor immunity. Tumor cells use FasL to evade the action of the immune system, and upregulation of FasL makes T cells more cytolytic. Tumor growth may depend on the number of cancer cells vs. the number of cancer specific T cells. / Ph. D.

Metal-Ligand Cooperation (MLC) has been under study over the past two decades as a powerful tool for small molecule activation and functionalization. However, more mechanistic details are needed in order to understand the detailed steps that are enabled by the bifunctional cooperation between ligand and metal. In this regard, the hydroboration reaction offers a useful platform through which to assess the details of bifunctional reaction pathways and catalyst speciation. This dissertation focuses on the synthesis, characterization, and catalytic activity of base-metal complexes with cooperative N-, S-, and O-donor ligands to explore reaction pathways that are a consequence of diverging from traditional phosphine-based ligands. In Chapter 1 concepts and examples of MLC, especially as applied to hydroboration catalysis, are presented. In Chapter 2, three new Zn(II)-(κ²-SNS)₂ complexes were synthesized to directly compare the bifunctional catalytic activity rendered by amido and thiolate SNS ligands. Although all three complexes catalyzed carbonyl hydroboration, a detailed catalyst speciation study showed that the Zn amido complex reacts with pinacolborane (HBpin) to generate Zn-H and an unbound borylamido ligand. Subsequent substrate-derived zinc alkoxide formation followed by a second equiv of HBpin generates the product, regenerating the Zn hydride catalyst. In contrast, the Zn thiolate complex adds HBpin to the ligand imine unit, followed by aldehyde deoxygenation to give a benzothiazoline heterocycle and [Zn](OBpin). Reaction of the latter with HBpin then gives pinBOBpin and Zn-H, leading to the same active catalyst as that derived from the Zn amido precatalyst! For these systems, then, the bifunctional N- and S-donors serve to activate the catalyst rather than participating in a bifunctional catalytic cycle. Dissociation of the borylamido SNS ligand in Chapter 2 led us to reinvestigate a previously reported Cu(I) amido complex Cu[(κ²-SNS)(IPr) that was proposed to hydroborate carbonyls via an outer sphere process [IPr = bis(2,6-diisopropylphenyl)imidazol-2-ylidene]. Indeed, we showed that this complex also undergoes ligand borylation-dissociation to form the active catalyst [CuH(IPr)]₂ which had been reported previously as a carbonyl hydrosilylation catalyst. To compare these complexes with their heavier Group 10 analogue, we prepared and structurally characterized the silver amido SNS complex. Interestingly, this complex was not able to serve as a carbonyl hydroboration catalyst. Then we sought to use the MLC catalyst activation strategy to prepare an especially active Zn hydride hydroboration catalyst. Using a bidentate amine-pyrollide ligand with an aryl ether side-group, the 5-coordinate Zn complex, Zn(κ²-ONN)₂(DDI) (2.11Zn) was prepared and structurally characterized (DDI = 4,5-dichloro-1,3-dimethylimidazol-2-ylidene). On treatment with excess HBpin, formation of ONN(Bpin)₂ [(Bpin)₂-L3] gave rise to the reactive NHC-stabilized ZnH₂ catalyst that effected the rapid hydroboration of nitriles and quinoline derivatives under ambient conditions with only 0.01 and 0.05 mol% catalyst loading, respectively. In Chapter 3, in an attempt to prepare a cobalt complex containing both amido and thiolate SNS ligands, we obtained instead the Co(II) dithiolate complex, Co(κ³-SNS)(DDI) (3.2Co). This complex showed a unique selectivity for aldehyde hydroboration, over other functional groups such as ketones, cyanides, nitriles and olefins. A DFT study, in collaboration with Prof. Erin Johnson from Dalhousie University, showed that 3.2Co bifunctionally assembles the HBpin and aldehyde substrates, with Co binding the aldehyde oxygen and sulfur binding the boron of HBpin. With aromatic aldehyde substrates, interesting aromatic-aromatic dispersion effects led to catalyst inhibition which could be reversed by simply rinsing off the product with hexane. These effects were not observed for catalytic hydroboration of aliphatic aldehydes. In Chapter 4 we focused on expanding our MLC investigation to include additional donors beyond N and S. First, a dimeric Zn(II)-(κ⁴-NSNO) complex (4.1Zn) was synthesized and evaluated as a catalyst for nitrile dihydroboration to compare aryloxide and amido donors for B-H bond activation. In fact, 4.1Zn successfully catalyzed dihydroboration of a range of different aromatic and aliphatic nitriles under neat condition. Mechanistic studies determined that the aryloxide donor activates the B-H bond in the first step and the mechanism then likely proceeds through an inner-sphere insertion. As detected by our kinetic study, at high turnovers the catalyst decomposes when Bpin also binds to the amido donor. To compare the potential of other donors for B-H bond activation, a series of divalent NiᴵᴵX(κ³-NNN) complexes were synthesized, with X = bromide (4.3Ni), phenoxide (4.4Ni), thiophenoxide (4.5Ni), 2,5-dimethylpyrrolide (4.6Ni), diphenylphosphide (4.7Ni), and phenyl (4.8Ni), and employed as precatalysts for nitrile dihydroboration. Superior activity of the phenoxy derivative (vs. thiophenoxy or phenyl) suggests that B-H bond activation occurs at the Ni-X (vs. ligand Ni-N_pyrrolide) bond. Furthermore, stoichiometric treatment of 4.3Ni-4.8Ni with a nitrile showed no reaction, whereas stoichiometric reactions of 4.3Ni-4.8Ni with pinacolborane (HBpin) afforded the same Ni-H complex for 4.3Ni, 4.4Ni and 4.6Ni. Considering that only 4.3Ni, 4.4Ni and 4.6Ni successfully catalyzed nitrile dihydroboration reaction, we suggest that the catalytic cycle involves a conventional inner sphere pathway initiated by substrate insertion into Ni-H. In summary, our investigations confirm the importance of mechanistic studies and catalyst speciation for studies involving potential bifunctional catalysis. In Chapter 5 we summarize the findings of this thesis, placing them in the context of the current state of the art and speculating on future investigations they may enable.

As an extension of the previous work on the post-modification strategy of pyridine-based PN3P group 10 metal complexes, the triazine-based PN3P pincer ligands incorporating nickel complexes, Me-Et-PN3PNiCl, and Me-Et-PN3PNiI, were synthesized and characterized. The solid state structures suggest that the N-donor atom of triazine-based PN3P ligands have more electron donating than the pyridine-based PNP pincer ligands. A new non-symmetric PONNP pincer ligand system was developed to: (1) give more parameters for electronic and steric properties (2) to block the influence of acidic proton. However, the unstable metal-hydride complexes indicate the degradable O–P bond or N–P bond of the PONNP ligand. Treating the three ligands, including tert-butyl, phenyl, and cyclopentyl substituents with NiCl2(DME) individually all resulted in the production of [(PtBuONNPtBu)NiCl]+Cl-. It suggests that both O‒P and N‒P can cleave and rearrange during the complexation. The solvent effect and time tracing experiments demonstrated that the O‒P and N‒P bond rearrangement occurs after forming the nickel complex. The finding of [(ONNPtBu)NiCl]22+(Cl-)2 indicates the weakness of the O‒P bond, suggesting the degradation of an oxygen-phosphorus bond may be the initial step of substituents rearrangement. To ensure the ligand-centered reactivity of (PtBuONNPtBu)*NiCl, a nickel-silver bimetallic complex, [(PtBuONNPtBu)*NiCl]2[AgOTf]2, was produced. In contrast to pyridine-based PN3P*NiH, there are two active sites of [(PtBuONNPtBu)*NiCl]2[AgOTf]2, the N atoms on the imine arm and pyrimidine ring. The solid-structure of the acid-base adduct compound, {[(PtBuONNPtBu)*NiCl][B(C6F5)3], demonstrates that the nitrogen atom on the pyrimidine ring is a better active site than the imine arm because of the steric effect. The molecular structures of [(PtBuONNPtBu)*NiCl]2[AgOTf]2 and {[(PtBuONNPtBu)*NiCl][B(C6F5)3] exhibit that the pyrimidine ring of [(PtBuONNPtBu)*NiCl]2[AgOTf]2 tends to be an aromatic zwitterionic form. The ligand backbone of {[(PtBuONNPtBu)*NiCl][B(C6F5)3] favors the dearomatized form.

The kinetics for the bridge-to-chelate isomerization of the dppe ligand in H4Ru4(CO)10(dppe) have been investigated by UV-vis and NMR spectroscopies over the temperature range of 308-328 K. The isomerization of the ligand-bridged cluster 1,2-H4Ru4(CO)10(dppe) was found to be reversible by 31P NMR spectroscopy, affording a Keq = 15.7 at 323 K in favor of the chelating dppe isomer. The forward (k1) and reverse (k-1) first-order rate constants for the reaction have been measured in different solvents and in the presence of ligand trapping agents (CO and PPh3). On the basis of the activation parameters and reaction rates that are unaffected by added CO and PPh3, a sequence involving the nondissociative migration of a phosphine moiety and two CO groups between basal ruthenium centers is proposed and discussed. The substitution of the MeCN ligands in the activated cluster 1,2-Os3(CO)10(MeCN)2 by the diphosphine ligands dppbz proceeds rapidly at room temperature to furnish a mixture of bridging and chelating Os3(CO)10(dppbz) isomers and the ortho-metalated product HOs3(CO)9[μ-(PPh2)C=C{PPh(C6H4)}C4H4]. Thermolysis of the bridging isomer 1,2-Os3(CO)10(dppbz) under mild conditions gives the chelating isomer 1,1-Os3(CO)10(dppbz), molecular structure of both the isomers have been determined by X-ray crystallography. The kinetics for the ligand isomerization has been investigated by UV-vis and 1H NMR spectroscopy in toluene solution over the temperature range of 318-343 K. On the basis of kinetic data conducted in the presence of added CO and the Eyring activation parameters, a non-dissociative phosphine migration across one of the Os-Os bonds is proposed. Ortho metalation of one of the phenyl groups associated with the dppbz ligand is triggered by near-UV photolysis of the chelating cluster 1,1-Os3(CO)10(dppbz). The triosmium cluster 1,2-Os3(CO)10(MeCN)2 reacts with the diphosphine ligand 3,4­bis(diphenylphosphino)-5-methoxy-2(5)H-furanone (bmf) at 25 ºC to give the bmf-bridged cluster 1,2-Os3(CO)10(bmf). Heating 1,2-Os3(CO)10(bmf) leads to an equilibrium with the chelating isomer 1,1-Os3(CO)10(bmf). The molecular structure of each isomer has been crystallographically determined, and the kinetics for the isomerization has been investigated by UV-vis and 1H NMR spectroscopy. The reversible nature of the diphosphine isomerization has been confirmed by NMR measurements, and the forward (k1) and reverse (k-1) first-order rate constants for the bridge-to-chelate isomerization have been determined. Thermolysis of the SEQ CHAPTER h r 11,1-Os3(CO)10(bmf) cluster (>110 ºC) leads to regiospecific activation of C-H and P-C bonds, producing the hydrido clusters HOs3(CO)9[µ-PPh2C=C{PPh(C6H4)} CH(OMe)OC(O)] and the benzyne clusters HOs3(CO)8(μ3-C6H4)[µ-PPhC=C(PPh2)CH(OMe)OC(O)]. The hydride and benzyne clusters, which exist as a pair of diastereomers, have been fully characterized in solution by IR and NMR spectroscopy, and the molecular structure of one benzyne cluster (major diastereomer) has been determined by X-ray crystallography.

Ce travail de thèse présente la synthèse, la caractérisation et la réactivité de métallylènes stabilisés par différents ligands pinces fonctionnalisés par des substituants soufrés à différents états d'oxydation. Les métallylènes, analogues lourds des carbènes, présentent dans leur état fondamental singulet une paire d'électrons et une orbitale p vacante. Ces caractéristiques donnent à ces espèces un comportement et une réactivité particulière. La littérature décrit de nombreux exemples de métallylène stabilisés par différents types de ligands, parmi lesquels les ligands de type pince gagnent actuellement en importance. Dans la chimie des complexes de métaux de transition, il a déjà été démontré que les ligands de type pince constituent un type de plateforme efficace grâce aux possibilités de modulation des propriétés des complexes liées à la modulation du squelette du ligand. Au cours des dernières décennies, ces ligands se sont révélés efficaces pour la stabilisation de métallylènes stables. Cependant, un seul exemple de métallylène stabilisé par un ligand de type pince contenant du soufre a été reporté dans la littérature. Au cours de cette étude, des ligands pinces O,C,O chélatants contenant des groupement sulfonyles et sulfinyles ont été conçus, synthétisés et complètement caractérise par les méthodes physico-chimiques et computationnelle et leurs effets sur la stabilisation des métallylènes ont été étudiés. Dans un premier temps, un ligand pince de type bis-sulfone a été obtenu et étudié pour la synthèse de nouveaux métallylènes. A partir de ce ligand, un germylène et un stannylène ont été caractérisés, le germylène étant le premier exemple dans la littérature d'une espèce de germanium divalente stabilisée par un ligand pince de donneur d'oxygène. La réactivité des métallylènes a été testée pour obtenir des produits de cycloaddition avec l'ortho-benzoquinone et des complexes des métaux de transition (fer et tungstène). Il a été démontré que la bis-sulfone se comporte comme un ligand ajustable de type pince O,C,O-chélatant, la coordination pouvant être possible par l'un ou l'autre des atomes d'oxygène des groupements sulfonyles. [...] / This work presents the synthesis, characterization and reactivity of metallylenes stabilized by different functionalized pincer ligands with substituents containing sulfur atoms in different oxidation states. Metallylenes, the heavier analogues of carbenes, have in their singlet ground state a lone pair of electron and a vacant p orbital. These features give the particular behavior and reactivity of these species. The literature describes many examples of metallylenes stabilized by different types of ligands, among which lately the pincer type ligands are gaining importance. In the chemistry of transitional metal complexes it was shown for a long time that the pincer-type ligands are a versatile ligand platform thanks to the possibilities of modulating the properties of the complexes through small changes of the ligand backbone. In the last few decades these ligands proved to be effective for obtaining stable metallylenes. However, in the literature there is one sole example of metallylene stabilized through sulfur containing pincer-type ligands. For this study, para substituted sulfonyl and sulfinyl containing O,C,O-chelating pincer ligands were designed, synthesized and completely characterized by the physico-chemical and computational methods and their effects on the stabilization of metallylenes was investigated. First, a bis-sulfone pincer ligand was obtained and studied for the synthesis of novel metallylenes. With this ligand a germylene and stannylene were obtained and characterized, the germylene being the first example in the literature of a divalent germanium species stabilized by an oxygen donor pincer ligand. The reactivity of the metallylenes was tested for obtaining cycloadducts with ortho-benzoquinone and transition metal complexes (iron and tungsten). It was shown that the bis-sulfone behaves as an adjustable O,C,O-chelating pincer type ligand, the coordination could be possible with either one of the oxygen atoms of the sulfonyl groups. [...]