Abstract
In this thesis, N-heterocyclic carbene, b-diketiminate and diamide ligands have been employed as supporting moieties for manganese compounds. The experimental results demonstrate that steric bulk and additional intramolecular coordination of these ligands can stabilize some unusual and unique compounds, which otherwise are inaccessible. In addition, these compounds may be useful as starting materials for further reactions. The stable N-heterocyclic carbene adducts {[C(Me)N(iPr)]2C}2MnX2 (X = Cl (2), I (3), MeCOO (4)) were obtained from the reaction of the N-heterocyclic carbene [C(Me)N(iPr)]2C (1) and the corresponding manganese(II) reagents in THF, respectively. The X-ray solid-state structural analyses show that all complexes 2 - 4 are monomeric and the N-heterocyclic carbene ligands in these complexes are differently arranged around the central metal atoms. The metalate compound LMn(m-Cl)2Li(OEt2)2 (7) (L = HC(CMeNAr)2, Ar = 2,6-iPrC6H3) and dimeric compound [LMn(m-Cl)]2 (8) were synthesized from the reaction of MnCl2 with LLi(OEt2) (5) and LK (6) in diethyl ether, respectively. However, the reaction of MnCl2(THF)1.5 and LK (6) afforded the trinuclear complex LMn(m-Cl)2Mn(THF)2(m-Cl)2MnL (9) in THF. This obviously indicates the reaction is solvent dependent. Attempts to prepare the di-b-diketiminate complex by using 2 equiv. of 5 or 6 were unsuccessful. The molecular structures of compounds 7 - 9 have been determined by X-ray solid-state structural analyses. When the N-heterocyclic carbene 1 was employed as the acceptor for the proton of LH, the novel ionic compound [LMnCl2][{C(Me)N(iPr)}2CH] (10) was easily obtained in high yield from the reaction of LH, MnCl2(THF)1.5 and 1 in THF. The organomanganese(II) complexes LMnCp(THF) (11), [LMn(µ-Me)]2 (12) and LMnPh (13) were synthesized from 8 and appropriate reaction partners. Treatment of 9 with C3H5MgCl and PhCCLi in toluene, respectively, readily provided the monomeric compound LMnC3H5(THF)(14) and the dimer [LMn(m-CCPh)]2 (15). [LMn(µ-MeCOO)]2 (16), the first example of a doubly carboxylate-briged complex with four-coordinate manganese(II), was prepared from the reaction of 6 and Mn(MeCOO)2 in THF. The monomeric compound LMnI(THF) (17) was isolated from the reaction of LK (6) and MnI2 in THF. Refluxing 17 in toluene and removal of the volatiles in vacuum afforded the dimer [LMn(m-I)]2 (18). Compound 17 can also be obtained by dissolving 18 in THF. Displacement of the THF in 17 by the strong Lewis base [C(Me)N(iPr)]2C (1) readily afforded the carbene adduct LMnI{C[N(iPr)C(Me)]2} (19), which can also be obtained by adding 1 to the solution of 18 in toluene. Complexes 17 and 18 have been characterized by X-ray solid-state structural analyses. Reduction of 19 by Na/K alloy resulted in the formation of the monomer LMnNHAr{C[(N(iPr)C(Me)]2} (20), which can also be prepared by the reaction of 19 with LiNHAr. Treatment of [LMn(m-I)]2 (18) with Na/K alloy in toluene afforded [LMn]2 (21) the first example of three-coordinate manganese(I) containing a Mn-Mn bond. A mixture of 21 and excess KMnO4 in toluene afforded the dimeric oxide [LMn(m-O)]2 (22), which is the first example of a doubly oxo-bridged complex with four-coordinate Mn(III) centers. The reaction of ArNH(CH2)3NHAr with 2 equiv. of MeLi in diethyl ether resulted in the formation of the monomeric dilithium salt [ArN(CH2)3NAr][Li(OEt2)]2 (23) in high yield. Further reaction of 23 with MnCl2 affords the complex Mn2[ArN(CH2)3NAr]2 (24) with three-coordinate metal centers. The two complexes contain nonplanar M2N2 central cores.
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