Studies On The Reactivity Of Half-sandwich Transition-metal Complexes Containing A Chelating1,2-dicarba-closo-Dodecaborane-1,2-dithiolate Ligand With Organic Azides

1,2-dicarba-closo-dodecaborane is of particular interest with the properties of thermal and chemical stabilization, highly electron-deficiency and special three-dimensional cage structure, thus1,2-dicarba-closo-dodecaborane derivatives has attracted tremendous attention due to their potential applications in material synthesis, catalysis, energy and medicines. In organometallic chemistry,16e half-sandwich complexes Cp’M(E2C2B10H10)(Cp’=η5-C5H5,η5-C5Me5,η5-1,3-’Bu2C5H3; E=S, Se; M=Co, Rh, Ir) and Cp"M(E2C2B10H10)(Cp"=η6-C6Me6, p-cymene; E=S, Se; M=Ru, Os) containing [E2C2B10H10]2-(E=S, Se) ligand present rich chemistry due to their pseudoaromatic MS2C2metallacycles, active M-E bond,16e unsaturated metal centre and potential B(3)/B(6) active site, and the reactivities mainly concern as follows:reacting with a series of Lewis bases to generate their18e congeners; reacting with low valent transition-metal complexes to construct metal-metal bond to synthesize homo-, hetero-, di-, and multi-nuclear clusters; reacting with small organic molecules to afford various ligand-inserted products or B-H activation adducts.On the other hand, organic azides have been widely applied in the field of organic synthesis and organometallic chemistry because of their particular molecular structure and properties. Basing on the rich chemical reactivities of16e half-sandwich complexes with organic substrates such as alkynes and diazo compound, and in order to explore the scope of organic substrates, in this thesis the study was focused on the reactivity of half-sandwich transition-metal complexes containing a chelating 1,2-dicarba-closo-dodecaborane-1,2-dichalcogenolate ligand with organic azides and systematical studies are performed on the reactivity of CPC0S2C2B10H10and Cp*MS2C2B10H10(M=Co, Rh, Ir) with various organic azides. This dissertation is mainly concerned with following four parts:1. Reactivity of unsaturated16e half-sandwich complex CpCo(S2C2B10H10) with organic azides and alkynes insertion into the imido-bridged adducts16e complex CPCoS2C2B10H10(1) reacting with various organic azides have been investigated and the results showed that only acyl azides and sulfonyl azides can react with1to afford three kinds of products3-5in different conditions. Among them, both Co-S and Co-N bonds in imido-bridged adducts CpCo(S2C2B10H10)(NSO2R)(3a:R=4-MePh;3b:R=Me) are active and can be further inserted by alkynes, which form three types insertion products6-8by the C=C triple bond inserting into either Co-S or Co-N bond according to the nature of alkyne. The mechanism of these insertion products is proposed and supported by DFT calculations. The processes of such insertion reactions are two competitive pathways of the intramolecular nucleophilic addition between sulfur and nitrogen atoms and are dominated by both kinetic and thermodynamic factors. The formation of final products is controlled by thermodynamic factors.2. Study on the reactivity of unsaturated16i half-sandwich complexes Cp*M(S2C2B10H140)(M=Co, Rh, Ir) with organic azidesConsidering the influence of the change of Cp*ligand and metal centre, studies on the reactivity of unsaturated16e half-sandwich complexes Cp*M(S2C2B10H10)(2a: M=Co;2b:M=Rh;2c:M=Ir) with organic azides have been performed. The change of metal centre exhibited marked difference:For/p-toluenesulfonyl azide,2a gave rise to the addition product9of both azide ligand and water;2b generated two insertion products10and11on Rh-S bond with two and one azide ligand, respectively;2c afforded12containing Ir-B bond. For acyl azides,2a-2c gave the same type products13a-13c and14a-14c with M-S-N-C-0five-membered metallacycle, in particular,2c yielded an additional product15with C-H activation of one methyl of Cp*ligand to construct a C-N bond, accompanied by C=O coordinating to metal certre; Only2c reacted with phenyl azide to give product16which C-H activation on aryl ring happened to construct a new C-S bond; For benzyl azide,2a-2c did not react in many conditions at all.Some of these products were chose to do biological activity test and found that compounds9and11exhibited significant growth inhibitory effect and induction of cellular apoptosis to the lung cancer cells, which may act as a potential metal-based chemotherapy for lung cancer.3. Study on the reactivity of unsaturated16e half-sandwich complex Cp*Ir(S2C2B10H10) with2,6-disubstituted phenyl azidesBoth thermal and photochemical reactions of Cp*IrS2C2B10H10(2c) with2,6-disubstituted phenyl azides led to C-C coupling via C-H activation in17and C-S bond formation via ortho-substituted electron-withdrawing group migration in18-23. The formations of these compounds involve radical intermediate, which was supported by radical capture experiments by ESR spectrum. Thus, a possible mechanism involving radical intermediate and electron-withdrawing group migration was proposed for the formation of compounds17—23.4. Study on the reactivity of unsaturated16e half-sandwich complex Cp*Ir(S2C2B10H10) with ortho-and meta-substituted phenyl azidesTo test the influence of the position and electronic effect of the substituted group to the reaction system, detailed studies on the reactivity of unsaturated16e half-sandwich complex2c with ortho-and meta-substituted phenyl azides were performed. Reaction of2c with ortho-and meta-substituted phenyl azides led to the formation of products24-26in which C-H activation at ortho-position of aryl ring happened to construct a new C-S bond. Different from other substituted phenyl azides,1-azido-3-nitrobenzene exhibited rich reactivity to afford not only C-S bond formation products25a and26a but also27-29with C-H activation of Cp*ligand or/and ortho-position of aryl ring. Additionally, the-NH group in28and29could act as nucleophile and reacted with excess1-azido-3-nitrobenzene to yield compounds30and31via ring-expanded addition reaction.ESR signals of radical have been observed in the radical capture experiments with DMPO under photolytic condition. Furthermore, ESI-MS test have captured the signal of combination of radical intermediate and DMPO which fitted the molecular weight well. Basing on these facts, a possible mechanism involving radical intermediate via C-H activation to construct C-S and C-C bonds was proposed for the formation of compounds24-29.