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TL; DR: coordination number of carbon atom in methyllithium tetramer is indeed 7, arising from 6 intramolecular interactions, as you suggested, and an extra bond with the lithium atom of the next tetramer. The key point is that you need to look beyond the tetramer. I'm sorry to inform you that the image from Wikipedia of the standalone cubane $\ce{Li4(CH3)4}... 5 Some parts of this answer probably border a bit on personal opinion, but I will at least try to justify having such an opinion. The first thing to do is to actually examine the heterocycle. What kind of ligand is it? This is a carbene. It donates two electrons via the lone pair on the carbon in plane with the ring. Notice that there is a smear of positive ... 4 Quoting from Page 1063 of Advanced Organic Chemistry FIFTH EDITION, Part B - Reactions and Synthesis, FRANCIS A. CAREY, and RICHARD J. SUNDBERG: Benzyne can also be generated from o-dihaloaromatics. Reaction with lithium amalgam or magnesium results in the formation of transient organometallic compounds that decompose with elimination of lithium halide. ... 4 Due to the aromatic character of the cyclopentadienyl ligands, ferrocene can undergo electrophilic aromatic substitution reactions typical of aromatic compounds such as benzene. Ferrocene shows very high reactivity towards electrophiles, making it more closely comparable to phenol than to benzene, references and examples here and here. 4 THF has a number of differences with diethyl ether: Oxygen non-bonding doublets are more available for bonding with magnesium because the 2 ethyl groups are not freely rotating around (you may think of THF as diethyl ether with its arms tied in its back). THF boils at 66°C (ether 34.6°C). Because the reaction is usually carried out so to maintain a gentle ... 3 In their 2005 The Journal of American Society publication, Genêt, et al. have reported a gold-promoted cyclization reaction of bis-homopropagylic diols (see Graphical Abstract below), which afforded bicyclic ketals at room temperature in very good to excellent yields (ref. 1). This cycloisomerization reaction was catalyzed by either Au(I) or Au(II) chloride ... 2 Yes there are more carbonylate ions than metal carbonyl cations, but the latter do exist. A salt$\ce{[Mn(CO)6^+][BF4^-]•SO2}$has been synthesized in a superacid medium. Metal carbonyl cations are often disfavored because they have to contend with counterions that are anions, which may compete with the carbon monoxide ligands. Such a competition is ... 2 Chlorophyll (chl) is involved in two ways in photosynthetic organisms firstly as a light gathering pigment and second in electron transfer once the light is captured. It is unique in this role. In the first case, that of gathering light there are pigment protein complexes containing many chl (100's) and work in such a way that energy absorbed in one ... 2 Yes we can have hydroxyferrocene. See here for a brief summary description of possible synthesis and a nucleophile substitution reaction forming alkoxyferrocenes. 1 Chemical shift data dug up for a number of iron compounds in the website of Hans Reich reveals that the shift is not unique to aromatic compounds, but rather appears due to Fe(2+): The base shift for a vinyl proton (C=C-H) is 5.25 ppm. The following is a series of spectra from magritek, illustrating the effect of Fe(2+) complexation on the shift of the ... 1 When aluminum metal is exposed to the oxygen of the air at room temperture, it forms a protective air-tight layer of aluminum oxide. So as long as nothing is present that will disrupt the oxide layer on aluminium it is OK for aluminium at 20 oC to be in contact with air. If an aluminium alkoxide is exposed to water then the aluminium alkoxide will react ... 1 Silane can not be considered as one of these. This is mainly because the electronegativities of silicon and hydrogen are 1.8 and 2.1 respectively.$\ce{Si^{-4}}$compounds include compounds of the form$\ce{SiM2}$where$\ce{M}$is a group 2 metal as$-4 + 2\cdot 2 = 0$. Examples of these include magnesium silicide$(\ce{Mg2Si})$, dicalcium silicide$(\ce{...