What is Ligands: Definition and 21 Discussions

In coordination chemistry, a ligand is an ion or molecule (functional group) that binds to a central 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. The nature of metal–ligand bonding can range from covalent to ionic. Furthermore, the metal–ligand bond order can range from one to three. Ligands are viewed as Lewis bases, although rare cases are known to involve Lewis acidic "ligands".Metals and metalloids are bound to ligands in almost all circumstances, although gaseous "naked" metal ions can be generated in a high vacuum. Ligands in a complex dictate the reactivity of the central atom, including ligand substitution rates, the reactivity of the ligands themselves, and redox. Ligand selection is a critical consideration in many practical areas, including bioinorganic and medicinal chemistry, homogeneous catalysis, and environmental chemistry.
Ligands are classified in many ways, including: charge, size (bulk), the identity of the coordinating atom(s), and the number of electrons donated to the metal (denticity or hapticity). The size of a ligand is indicated by its cone angle.

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  1. W

    Poor convergence using Fe HMOs for FMO in Gamess

    Hello! I'm trying to model an interaction between ligands and a heme group using FMO in Gamess. I've tried to make HMOs for the FMOBND section of the input file (using an Fe-F complex), the HMOs are shown below: STO-3G 19 5 0 1 0.992624, 0.019366, 0.000000, 0.000000,-0.000001,-0.014838...
  2. U

    Chemistry How Does Mg2+ Complex Formation Influence Ca2+ Concentration?

    No template, thread moved from the main chemistry forum. Summary:: Requesting help! Mg2+ (aq) is also likely to form a complex with the ligand or ligands in your chosen complex. Show how the formation of the Mg2+ complex will affect the concentration of Ca2+ (aq). More details in post below...
  3. H

    Ligands vs transition metals

    Transition metals, being metals, are electropositive.Ligands like ammonia,oxygen,chlorine etc ,on the other hand,are mostly electronegative(electron loving).How come the Ligands donate electrons to the electro positive(electron hating)transition metals when both have contradictory...
  4. jappy190

    Calculating charge density of particular ligands

    Hi everyone, this is my first thread! I am currently undergoing a personal investigation that is based on one of the factors which effect the splitting of d orbitals in central metal ion by the charge density of ligands (in a complex ion). However, recently I got stumped by trying to...
  5. H Psi equal E Psi

    In which temperature range does WF_6 melt?

    Hi Everyone I'm studying material Engineering and I'm currently preparing chemistry for the summer exams. Now, there is an old exam question which I don't know how to solve: "In which temperature range does ##[W^{+VI}F_{6}^{-I}]## melt?" My solution: Well, the 18-Electron rule is not...
  6. F

    Synthetic pathways to produce the provided complex

    Question Describe the color changes that occur when ##NH_{3(aq)}## is gradually added, with stirring to ##[CuCl_4]^{2-}_{(aq)}## until the ##NH_{3(aq)}## is in excess. Identify the three compounds or ions responsible for the new colors. Now the marking scheme shows that somehow...
  7. KarolinaPL

    The infulence of ligands in complexes

    Hello! I analise metal chemical shifts, its formula is MR4, where M is transition metal, like Palladium, and there is some trend: I > CN > Br > NH3 > NO2 > Cl > H2O, the same trend is observed for similar complex of formula: Pd(R)3Cl, Pd(NH3)2X2, Pd(R)Cl3 So, the metal signal shielding...
  8. KarolinaPL

    What Factors Affect the Polarizability of Ligands?

    Hi, why polarizability of ligand -OH2 is bigger than of -H? what is the polarizability of NO2 comparing to them and e.g. I? i know that for halogens, it increase with increase of size of halogen down the group (electrons have more space on bigger atom), but how it is with other ligands? Thank you.
  9. A

    How do you know the order of ligands?

    Homework Statement So i have triammineaquadihydroxochromium(III) chloride and i have to write the formula. Homework EquationsThe Attempt at a Solution So there's (NH3)3, H2O, (OH)2, Cr and a Cl anion I know the transition metal goes first, and the charge of the complex is 1+ so it'll be = {Cr...
  10. ReidMerrill

    Coordination Chemistry: Ligands

    Homework Statement Describe, using sketches, how the following ligands can act as both σ-donors and π-acceptors: CN- P(CH3)3 SCN- Homework EquationsThe Attempt at a Solution I suspect it has something to do with these ligands having lone pair electrons AND open π* orbitals. How correct is this...
  11. AryaUnderfoot

    Understanding Ligand Strength: [Cu(H2O)6]2+ to [CuCl4]2-

    Homework Statement From what I've read, [Cu(H2O)6]2+ when reacts with concentrated hydrochloric acid, the chloro ligand will displace the aqua ligand and form [CuCl4]2- Homework Equations [Cu(H2O)6]2+ + 4Cl- <--> [CuCl4]2- + 6H2O ( <---> means reversible reaction, I don't know how to type it...
  12. C

    What are axial and peripheral ligands in coordination chemistry?

    In this article: http://jredman.kombyonyx.com/thesis/Ch16.htm they mention "axial ligands" and "peripheral ligands". What exactly does that mean? Heres the molecule they use as an example: http://jredman.kombyonyx.com/thesis/Ch16_files/image002.gif I can see that the porphyrin rings both...
  13. J

    Ligands and strong electrical fields

    What determines if a ligand will have a strong electrical field?
  14. P

    Why is [NiF6]2- Diamagnetic Despite F- Being a Weak Field Ligand?

    Homework Statement So I'm looking at the spectrochemical series of ligands which has that I- < Br- < Cl- < F- < OH- < ox2- < H20 < NH3 < en <bpy< phen <CN- Where the left side are weak field ligands and the right side are strong field ligands. A lot of my homework problems involve...
  15. C

    Ligands and lowering reduction potential

    Hi I have a question I was wondering if y'all could clear up. Let's say I have two metal cations, Iron (III) and Manganese (II). Will binding them to an anionic ligand lower their reduction potentials (making each a better redundant) and if so why? Is it because the anionic charge of the...
  16. H

    Understanding SELEX to Systematic Evolution of Ligands

    Could someone explain SELEX (systematic evolution of ligands by exponential enrichment) or at least direct me to a good resource online because so far I have'nt found a decent explanation or website regarding SELEX online.
  17. M

    Rank ability of ligands to increase or decrease Δ in a square planar compound

    Homework Statement Homework Equations I am working on a formal lab report for an inorganic chem course and forget how to construct a spectrochemical series. I have 4 complexes, each has a single absorption band in the UV-Vis spectrum. [NiBr(Mes)(PPh3)2] 450nm [Ni(Mes)Br(bipy)]...
  18. C

    Anionic ligands in coordination complexes

    I read that all ligands are Lewis bases but I then read that the number of anionic ligands attached to a metal will determine its oxidation state. Which is it? Let's use chlorine as an example. Before this ligand binds to the metal is it a Cl- ion or a neutral Cl atom? If its the former I can...
  19. Y

    A level chemistry - ligands, d-block elements and complexes

    Homework Statement Draw out the electron configuration of [Fe(H2O)6]3+ The Attempt at a Solution I did the work, but i am not sure if its correct: Is the following electron configuration correct for this complex? [Fe(H2O)6]3+: [Ar] 4s [ i L ] 3d [ i L l i L l i L l...
  20. E

    Phosphine ligands: trans vs. cis

    phosphine ligands on transition metals generally tend to orient trans to one another in order to minimize steric interactions (ESPECIALLY so for bulky PR3 groups)... under what conditions, if any, would BULKY PR3 ligands orient themselves in a cis formation? in other words... what other...