The chemistry of manganese alkyls and aryls and of divalent titanium phenoxides

Morris, Robert Joseph

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Description

Title

The chemistry of manganese alkyls and aryls and of divalent titanium phenoxides

Author(s)

Morris, Robert Joseph

Issue Date

1990

Doctoral Committee Chair(s)

Girolami, Gregory S.

Department of Study

Chemistry, Inorganic

Discipline

Chemistry, Inorganic

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

Chemistry, Inorganic

Language

eng

Abstract

• The organometallic chemistry of divalent, trivalent, and tetravalent manganese has received little attention despite intensive interest in the organometallic chemistry of the transition metals over the last 25 years. Similarly, the development of divalent titanium and vanadium chemistry has been quite limited. The study of organomanganese complexes and low-valent early transition metal complexes can provide insight into processes such as organic oxidations by manganese-containing complexes and Ziegler-Natta olefin polymerizations, respectively.
• The reaction of MnCl$\sb2$ with 4 equiv of an organolithium reagent followed by the addition of N,N,N$\sp\prime$,N$\sp\prime$-tetramethylethylenediamine (tmed) gives a series of tetraalkyl manganate(II) complexes of stoichiometry (Li(tmed)) $\sb2$(MnR$\sb4$) (R = Me, Et, CH$\sb2$CH$\sb2$-t-Bu, n-Bu, CH$\sb2$SiMe$\sb3$, and Ph) in good yields. The molecular structures of the methyl, ethyl, and neohexyl complexes are the first transition metal peralkyls wich contain $\beta$-hydrogen atoms to be structurally characterized.
• The addition of 2 equiv. of methyllithium to MnMe$\sb4$(dmpe) followed by treatment with tmed gives the first tetravalent peralkyl manganate, (Li(tmed)) $\sb2$(MnMe$\sb6$), in good yield. This tetravalent species reacts with the divalent species (Li(tmed)) $\sb2$(MnMe$\sb4$) in diethyl ether to give the trivalent permethyl manganate (Li(tmed)) $\sb2$(MnMe$\sb5$) in a comproportionation reaction. If the comproportionation is performed in toluene, the product is the tetramethyl manganate(II) species (Li(tmed)$\sb2$) (MnMe$\sb4$).
• The interaction of manganous halides with 1/2 equiv. of the diarylmagnesium reagent MgMes$\sb2$(thf)$\sb2$ and 2 equiv. or trimethylphosphine in diethyl ether followed the addition of dry dioxygen leads to the isolation of a series of trivalent arylmanganese(III) species of stoichiometry Mn(Mes)X$\sb2$-(PMe$\sb3$)$\sb2$ (X = Cl, Br, and I). The molecular structure of Mn(Mes)-Br$\sb2$(PMe$\sb3$)$\sb2$ is a slightly distorted trigonalbipyramid with the phosphine ligands occupying the axial positions. Treatment of Mn(acac)$\sb3$ with 5 equiv. of LiMe leads to the isolation of the first oxoalkyl of manganese which has the stoichiometry $\{$Li$\sb2$(MnOMe$\sb3$) $\cdot$ 2Li$\sb2$(OCMe=CHCMe$\sb2$O) $\cdot$ tmed$\}\sb2$. The molecular geometry around the Mn$\sp{\rm III}$ center is also a slightly distorted square-plane.
• Treatment of Ti(BH$\sb4$)$\sb2$(dmpe)$\sb2$ with 2 equiv. of sodium phenoxide in tetrahydrofuran gives Ti(OPh)$\sb2$(dmpe)$\sb2$ which is the first divalent titanium aryloxide or alkoxide of any kind. Along with TiMe$\sb2$(dmpe)$\sb2$, these three compounds are the only octahedral d$\sp2$ metal centers of the first-row transition series to exhibit spin-pairing within the t$\sb{\rm 2g}$ manifold; the conplexes are diamagnetic. The spin-pairing of the two d-electrons in TiMe$\sb2$(dmpe)$\sb2$ is the result of $\pi$-bonding from the reduced titanium center to the triaklylphosphines; the spin-pairing in the phenoxide complexes is due to $\pi$-donation from the phenoxide groups.

Type of Resource

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Copyright 1990 Morris, Robert Joseph

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