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In coordination chemistry, a ligand [a] is an ion or molecule with a functional group that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves formal donation of one or more of the ligand's electron pairs , often through Lewis bases . [ 1 ]
Compounds that obey the 18-electron rule are typically "exchange inert". Examples include [Co(NH 3) 6]Cl 3, Mo(CO) 6, and [Fe(CN) 6] 4−. In such cases, in general ligand exchange occurs via dissociative substitution mechanisms, wherein the rate of reaction is determined by the rate of dissociation of a ligand. On the other hand, 18-electron ...
In the covalent bond classification method, κ 1-carbonate is anX ligand and κ 2-carbonate is an X 2 ligand. With two metals, the number of bonding modes increases because carbonate often serves as a bridging ligand. It can span metal-metal bonds as in [Ru 2 (CO 3) 4 Cl 2] 5-, where again it functions as an (X) 2 ligand.
In this example, the cyanide ligands are "innocent", i.e., they have a charge of −1 each, −5 total. To balance the fragment's overall charge, the charge on {CrNO} is thus +2 (−3 = −5 + 2). Using the neutral electron counting scheme, Cr has 6 d electrons and NO· has one electron for a total of 7. Two electrons are subtracted to take ...
For example, the IR spectrum of Fe 2 (CO) 9 displays CO bands at 2082, 2019 and 1829 cm −1. The number of IR-observable vibrational modes for some metal carbonyls are shown in the table. The number of IR-observable vibrational modes for some metal carbonyls are shown in the table.
Typical examples of this type of complex are group 14 metal complexes such as CpSiMe 3. An example of both is (Cp 2 Fe(CO) 2). It is probable that η 1-Cp complexes are intermediates in the formation of η 5-Cp complexes. Still rarer, the Cp unit can bond to the metal via three carbons. In these η 3-Cp complexes, the bonding resembles that in ...
When given a metal complex and the trends for the ligand types, the complex can be written in a more simplified manner with the form [ML l X x Z z] Q±. The subscripts represent the numbers of each ligand type present in that complex, M is the metal center, and Q is the overall charge on the complex. Some examples of this overall notation are ...
For the purpose of electron-counting, C-bonded acyl ligands count as 1-electron ligands, akin to pseudohalides. η 2-Acyl ligands count as 3-electron "L-X" ligands. bridging acyl ligands are also well known, where the carbon bonds to one metal and the oxygen bonds to a second metal. One example is the bis(μ-acetyl) complex [(CO) 3 Fe(C(O)CH 3 ...