Bei der Reduktion von Kobaltdichlorid mit Natriumamalgam oder Magnesium in b,thern wird in Gegenwart von Trimethylphosphin paramagnetisches L4Co (L = (CH3)3P) ge'ddet. Als Zwischenstufe der Reduktion wird ein komplexes Kobalt(1)-chlorid der Formel L~C O C I (L = (CH3)3P) isoliert. Dieses entsteht quantitatik aus L4Co und wasserfreiem Kobaltchlorid. Mit LiCH3 wird daraus die Titelverbindung L4CoCH3 dargestellt. Ihre Co -C-Bindung wird durch Protonensauren unter Methanentwicklung gelost, wobei z. B. das Kobalt(1)acetylid L4CoC "CC6H5 bzw. Polymere der Formel Co(OR)2 (R = CH3, CzH5, Si(CH3)3, C6H5) entstehen. Carbonylierung und Decarbonylierung unter Normalbedingungen liefert [L2(CO)rCo]z. L3(CO)CoCH3 und L2(C0)2CoCOCH3. Gegeniiber L4Co ist neben A cetylchlorid sogar noch Acetanhydrid zu einer oxidativen Additionsreaktion befahigt. L4CoCH3 ist stark reduzierend und reagiert sogar mit CO2. Die oxidative Addition von CH3X (X = Br, J) fiihrt in die Reihe der neuartigen Methylkobalt(II1)-Komplexe. -Die Protonenresonanz der CoCH3-Gruppe zeigt bei variabler Temperatur die enge Verwandtschaft im dynamischen Verhalten der isosteren Verbindungen L4CoCH3 und [L4NiCH31f.
Methylcobalt Compounds with Non-chelating Ligands, I Methyltetrakis(trimethylphosphine)cobalt and its DerivativesIn the presence of trimethylphosphine, cobalt dichloride is reduced with sodium am.ilgam or magnesium in ethers to give paramagnetic L4Co ( L = (CH,),P). As an intermediate of this reduction a complex cobalt([) halide of the formula L3CoCI (L = (CH3)3P) could be isolated which also arises quantitatively from LjCo and anhydrous cobalt dichloride. L3CoCI is converted into the title compound LdCoCH3 by LiCH,. The Co-C bond of this species is cleaved by protic acids with liberation of methane. Thus, e. g. a cobalt (1) acetylide L4CoC =CC6H5, or polymers of the formula Co(0R)z (R = CH3, C2H5, Si(CH3)3, C6H5) are formed. Carbonylation and decarbonylation under normal pressure lead to [ L~( C O )~C O ]~, L3(CO)CoCH3, and L~( C O )~C O C O C H~.L4cO undergoes oxidative addition with acetyl chloride and even with acetic anhydride. As a strong reducing agent L4CoCH3 attacks C02 to give a carbonyl complex. Addition of CH3X (X = Br, J) leads to novel methylcobalt(I11) complexes. -The temperature dependence of the IH n. m. r. of the Co-CH3 resonance reveals a strong relationship in the fluxional behaviour of the isosteric species L4CoCH3 and [L4NiCH3JC.
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