Extending the chemistry of formamidinate complexes : from the C-N bond cleavage of ligands to the formation of polynuclear chain complexes /
N,N'-Disubstituted formamidinate anions [RNC(H)NR]- have been successful in stabilizing dinuclear metal-metal bonded complexes of middle and later transition metals. In this work, the chemistry of formamidinate complexes has been further explored in two aspects: the reaction of formamidinate...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
1998.
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| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=737703811&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | N,N'-Disubstituted formamidinate anions [RNC(H)NR]- have been successful in stabilizing dinuclear metal-metal bonded complexes of middle and later transition metals. In this work, the chemistry of formamidinate complexes has been further explored in two aspects: the reaction of formamidinate ligands with the early transition metal tantalum, and the synthesis of polynuclear compounds with linear chain structures. It is found that the formamidinate ligand loses its identity in the presence of tantalum under various reaction conditions, either by adding another molecule or by cleavage of a C-N bond to give different ligands. At low temperature, the reaction of TaCI5 with KC8 and LiDPhF, where DPHF- = anion of N,N'-diphenylformamidine, yields eight coordinated compounds Ta(DPhF)4 and PhN(CH)N(Ph)C(H)(NPh)2Ta(DPhF)3. The latter consists of a ligand that resulted from the coupling of two DPHF- ions.Reduction of tantalum(V) chloride with lithium borohydride at low temperature produces diborane dianion bridged tantalum(III) compounds (DPhF)2Ta(m4, n2-B2H6)Ta(DPhF)2 and (DTolF)2Ta(m4,n2-B2H6)Ta(DTolF)2, where DTOlF- = anion of N,Ndi(p- tolyl)formamidine. When the reaction is carried out at ambient temperature, breakage of a C-N bond in the ligands gives imido complexes, such as the dinuclear species Ta2(mNPh)2(-DPhFA)2(n2-DPhF)2. Two fragments resulting from the C-N bond cleavage of formamidinate, namely the arylimido (ArN 2-) and formimidoyl (ArNCH) anions, were observed in products from the reactions of Ta2CI6(SMe2)3 with arylformamidinates. The formimidoyl fragment is deprotonated when reducing agents are used. In the absence of reducing agents, the reaction gives a ditantaluni compound in high yield in which the formimidoyl (ArNCH-) fragment bridges both tantalum atoms. These reactions are a consequence of the oxidative addition of the arylformamidinate ligands on the Ta-Ta double bond of the starting material. With the use of the anion of NN-di(2-pyridyl)formamidine, (DpyF-), as supporting ligand, the dinuclear compound Cr2(DpyF)4, the linear trinuclear and tetranuclear complexes [Cr3(DpyF)4][PF6]2 and [Cr4(DpyF)4CI21CI2, and the heteropolynuclear compounds [MO2Co(DpyF)41 [COC14] and [MO2(DpyF)4CU4CI2][CUC12]2 have been synthesized and structurally characterized. |
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| Item Description: | Vita. "Major Subject: Chemistry". |
| Physical Description: | xiv, 188 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilms Inc. |
| Bibliography: | Includes bibliographical references: pages 180-184. |