Explanation
In oxyhaemoglobin Fe2+ is diamagnetic in nature.
The bonding of CO to a metal as consisting of two components. The first component is a two electron donation of the lone pair on carbon into a vacant metal d-orbiatl. This electron donation makes the metal more electron rich and in order to compensate for this increased electron density, a filled metal d-orbital may interact with the empty pi* orbital on the carbonyl ligand to relieve itself of the added electron density. This second component is called pi-back bonding. Or pi-back donation. The two components of this bonding are synergistic.
The more sigma donation by the carbonyl, stronger is the pi-back bonding interaction. The occupation of pi* on CO does leads to a decreased bond order in CO molecule itself. Hence bond order between Ni-C bond is more than two.
Ti (C2H4)4 is an organometallic compound.
The metal-carbon bond in metal carbonyls have both σ and π character. The metal-carbon σ –bond is formed by the donation of lone pair of electrons from the carbonyl carbonyl carbon into a vacant orbital of the metal. The metal-carbon π-bond is formed by the donation of a pair of electrons from a filled d-orbital of metal into the vacant antibonding pi-molecular orbital (π*) of carbon monoxide. The metal to legand bonding creates a synergic effect which strengthes the bond between CO and the metal.
Therefore in [Ni(CO)4] , synergic effect will be present.
The Ziegler-Natta catalyst include many mixtures of halides of transitiron metals especially titanium, chromium, vanadium and zirconium with organic derivatives of nontransition metals , particularly alkyl aluminium compounds.Hence Ziegler-Natta catalyst is [ Al2(C2H5)6 + TiCl4 ]
Metallic carbonyls involve both sigma and Pi bonding. Sigma bond involves donation of lone pair on carbon of the CO ligand into a hybridized vacant metal orbital. Pi bond involves back donation of metal d electrons into vacant anti bonding π* 2p orbital on CO. The larger the electrons involved in back bonding, the lesser the order of CO ligand. Since Fe complex involves largest metal electrons for back bonding (i.e. 3d8) the CO in [Fe(CO)5] will have the lowest bond order.
Organometallic chemisty is the study of chemical compounds containing at least one bond between a carbon atom of an orgainc compounds and metal. Therefore KC4Hg , Tetraethyl tin, CH3MgI have carbon-metal-bond , hence these are organometallic compounds , where as C2H5ONa do not have Carbon-metal bond , hence it is not an organo-metallic compounds
Ziegler-Natta catalyst is a combination of TiCl4 and Al (C2H5)2Cl. Ziegler–Natta catalysts are used to polymerize terminal 1-alkenes (ethylene and alkenes with the vinyl double bond):
n CH2=CHR → −[CH2−CHR]n−
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