Synthesis Of Organometallic Cobalt Complexes Containing A Chelating Ortho-Carborane-1,2-dithiolate Ligand And Their Reactivities Toward Alkynes

During the past decades, research focusing on 1,2-dicarba-closo-dodecaborane derivatives has attracted tremendous attention due to their unique molecular structures, chemical properties, and a variety of potential applications in catalyst, energy, medicines, polymers, material science and supramolecular chemistry and so on. Of all the carborane derivatives, a class of 16e half-sandwich Co, Rh, Ir, Ru and Os complexes containing a chelating 1,2-dicarba-closo-dodecaborane-1,2-dichalcogenolate ligand, [E2C2B10H10]2-(E=S, Se), are becoming one of hot research fields because of their reactivities. Owing to their unsaturated metal center (16e), two reactive M-E (E=S, Se) bonds and potentially reactive carborane cage with activated B-H bonds, these sterically congested, mononuclear coordination compounds can be stored conveniently and be used for further transformations in a controlled way under various conditions. For example, these 16e products react with polycarbonyl ligands to give homometallic and heterometallic clusters. At the same time, with help of self-assemble technology, these 16e compounds react with polydentate bridging ligands to generate complexes of multi [E2C2B10H10]2- units. Moreover, reactions of these 16e compounds with alkynes lead to many structurally novel products. Previous studies have demonstrated that the structures and formation mechanisms of products are dependent on the metal center, the chalcogen element, the ancillary ligand on metal of the 16e complexes as well as the alkynes used.From previous literature we know that alkynes such as phenylacetylene, ethynylferrocenyl, methyl acetylene monocarboxylate and dimethyl acetylene dicarboxylate have often been used to react with 16e half-sandwich complexes. In contrast, the reactions of alkynes such as ferrocenyl alkynone,2-furyl alkynone and N-1-naphthylpropargylamide with the 16e half-sandwich complexes have not been reported. In this thesis, the study was mainly focused on the synthesis of half-sandwich 16e cobalt complexes containing [E2C2B10H10]2- units and their reactivities toward ferrocenyl alkynone,2-furyl alkynone and N-1-naphthylpropargylamide. This content contains three sections as follows:1. Reactivities of 16e half-sandwich complexes CpCo(S2C2B10H10) toward HC≡CC(O)R (R= Fc, fury1-2)The reactions of the 16e half-sandwich complex CpCo(S2C2B10H10) with HC≡CC(O)Fc at ambient temperature in a 1:1.5 molar ratio afforded complexes 1-11. Complex 1 is an addition product of the CpCo(S2C2B10H10) and HC=CC(O)Fc in a 1:1 molar ratio with the loss of the CpCo unit. Product 2 is 17e half-sandwich cobalt(Ⅱ) complex while product 3 is another kind of 17e half-sandwich cobalt(Ⅱ) complex. Unfortunately, we failed to get good-quality single crystals for the structural determination for 2 and 3. They were characterized by NMR spectra, mass spectra, IR spectra and so on. Complexes 4-6 are configurational isomers with the same molecular formula and the same molecular weight. Their differences lie only in the different configurations of the two C=C bonds. When the two C=C bonds are in Z/Z, Z/E, E/E configurations, the three isomers are 4,5 and 6, respectively. Compound 7 is a cyclotrimerization product of HC=CC(O)Fc catalyzed by CpCo(S2C2B10H10). Compounds 8-11 are a sort of structurally novel mon-functionalization products substituted at the B(3)/B(6) positions of carborane cage. They are also configurational isomers with the same molecular formula. They can be treated as the addition product of the CpCo(S2C2B10H10) and HC≡CC(O)Fc in a 1:2 molar ratio with the loss of the Co center. At the same time, the Cp in CpCo(S2C2B10H10) and the C=C unit undergo the Diels-Alder reaction. As a result, their structures are complicated. For example, due to the complicated structure, the resonances of NMR of compound 8 have been identified through the use of 2D1H-1H COSY and 2D 13C-1H HETCOR experiments. The reaction of the 16e half-sandwich complex CpCo(S2C2B10H10) with HC≡CC(O)Fc at ambient temperature in a 3:1 molar ratio afforded mon-functionalization compound 12 substituted at the B(3)/B(6) positions of carborane cage. Compound 12 can further react with excessive HC≡CC(O)Fc to generate bi-functionalization compound 13 substituted at the B(3)/B(6) positions of carborane cage. In the course of synthesizing CpCo(S2C2B10H10), a bi-nuclear Co compound 1S1 was isodated. 1S1 can react with HC≡CC(O)Fc to give compound 14. In complex 14, one BH unit in the carborane cage is intact. The reactions of the 16e half-sandwich complex CpCo(S2C2B10H10) with HC≡CC(O)furyl-2 at ambient temperature in a 1:1.5 molar ratio afforded complex 15. Compound 15 is also 17e half-sandwich cobalt(Ⅱ) complex and its structure is similar to that of compound 2. Compared with the reaction of CpCo(S2C2B10H10) with HC≡CC(O)Fc, the reaction of CpCo(S2C2B10H10) with HC≡CC(O)furyl-2 gives less product. Part of reason is that HC≡CC(O)furyl-2 is colorless, leading to loss of some colorless products.2. Reactivities of 16e half-sandwich complexes CpCo(Se2C2B10H10) toward HC≡CC(O)R(R= Fc, fury1-2)In the course of synthesizing CpCo(Se2C2B10H10), a bi-nuclear Co compound 16 was isodated.16 can be regarded as a dimer of two 16e products CpCo(Se2C2B10H10) and CpCoI(SeSeC2B10H11). The reaction of the 16e half-sandwich complex CpCo(Se2C2B10H10) with HC≡CC(O)Fc at ambient temperature in a 1:1.5 molar ratio afforded complex 7,17-19. The structure of 17 is similar to that of 4.18 is a B-H bond activation compound and can be transformed into compound 20 with the loss of CpCo unit catalyzed by silica gel. In compound 19, the carborane cage lost a BH apex at the B(3)/B(6) positions. Consequently, the closo-C2B10 cage became the nido-C2B9 cage. The reaction of the 16e half-sandwich complex CpCo(Se2C2B10H10) with HC≡CC(O)-furyl-2 at ambient temperature in a 1:1.5 molar ratio afforded complex 21. The structure of 21 is similar to that of 18.3. Reactivities of 16e half-sandwich complexes Cp*Co(Se2C2B10H10) (Cp*= η5-C5Me5)toward R1C≡CR2 (R1=H, R2=C(O)NH-naphthyl-1, C(O)Fc, C(O)furyl-2, Ph; R1=R2=CO2Me)The reaction of the 16e half-sandwich complex Cp*Co(S2C2B10H10) with excessive R1C≡CR2 (R1=H, R2=C(O)NH-naphthyl-2, C(O)Fc, C(O)furyl-1, Ph; R1 = R2= CO2Me) at ambient temperature afforded complexes 22 and 23,24 and 25,26 and 27,28,29, respectively.22 and 29 are the 18e half-sandwich cobalt(Ⅲ) complexes in which one alkyne molecule is inserted into one of the Co-S bonds of the 16e half-sandwich complex Cp*Co(S2C2B10H10), whereas 23-28 are the 18e half-sandwich cobalt(Ⅲ) complexes in which two alkyne molecules are inserted into one of the Co-S bonds of the 16e half-sandwich complex Cp*Co(S2C2B10H10). In complexes 23,24,26 and 28, the alkyne is twofold inserted into one Co-S bond in a head-head mode. In complexes 25 and 27, the alkyne is twofold inserted into one Co-S bond in a head-tail mode. The proposed mechanisms for complexes 22-28 were discussed.