ربيطة
الربيطة بالإنجليزية: Ligand في الكيمياء عبارة عن ذرة أو أيون (شاردة) أو جزيء مرتبط بذرة الفلز المركزية في المعقدات التساندية.
![](/w/images/thumb/f/fd/CoA6Cl3.png/300px-CoA6Cl3.png)
تتشكل الرابطة بين الفلز والربيطة عادة بأن تقوم الربيطة بمنح زوج أو أكثر من الإلكترونات إلى ذرة الفلز، أي تنشأ رابطة تساندية بين الربيطة والفلز.
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أمثلة لربيطات شائعة (حسب قوة المجال)
In the following table the ligands are sorted by field strength (weak field ligands first):
الربيطة | الصيغة (الذرة الرابطة بخط عريض) | الشحنة | Most common denticity | تعليق |
---|---|---|---|---|
يوديد (iodo) | I− | monoanionic | monodentate | |
بروميد (bromo) | Br− | monoanionic | monodentate | |
Sulfide (thio or less commonly "bridging thiolate") | S2− | dianionic | monodentate (M=S), or bidentate bridging (M-S-M') | |
Thiocyanate (S-thiocyanato) | S-CN− | monoanionic | monodentate | ambidentate (see also isothiocyanate, below) |
كلوريد (كلورو) | Cl− | monoanionic | monodentate | also found bridging |
نيترات (نيتراتو) | O-NO2− | monoanionic | monodentate | |
أزيد (azido) | N-N2− | monoanionic | monodentate | |
فلوريد (فلوريدو) | F− | monoanionic | monodentate | |
هيدروكسيد (hydroxo) | O-H− | monoanionic | monodentate | often found as a bridging ligand |
اوكسالات (oxalato) | [O-C(=O)-C(=O)-O]2− | dianionic | bidentate | |
ماء (aqua) | H-O-H | neutral | monodentate | monodentate |
نيتريت (nitrito) | O-N-O− | monoanionic | monodentate | ambidentate (see also nitro) |
Isothiocyanate (isothiocyanato) | N=C=S− | monoanionic | monodentate | ambidentate (see also thiocyanate, above) |
Acetonitrile (acetonitrilo) | CH3CN | neutral | monodentate | |
Pyridine (pyridino) | C5H5N | neutral | monodentate | |
أمونيا (ammine or less commonly "ammino") | NH3 | neutral | monodentate | |
Ethylenediamine | en | neutral | bidentate | |
2,2'-Bipyridine | bipy | neutral | bidentate | easily reduced to its (radical) anion or even to its dianion |
1,10-Phenanthroline | phen | neutral | bidentate | |
Nitrite (nitro) | N-O2− | monoanionic | monodentate | ambidentate (see also nitrito) |
Triphenylphosphine | PPh3 | neutral | monodentate | |
سيانيد (cyano) | CN− | monoanionic | monodentate | can bridge between metals (both metals bound to C, or one to C and one to N) |
أول أكسيد الكربون (carbonyl) | CO | neutral | monodentate | can bridge between metals (both metals bound to C) |
ربيطات أخرى عامة (أبجدياً)
In this table other common ligands are listed in alphabetical order.
الربيطة | الصيغة (الذرة الرابطة بخط عريض) | الشحنة | Most common denticity | تعليق |
---|---|---|---|---|
Acetonitrile | MeCN | neutral | monodentate | |
Acetylacetonate (Acac) | CH3-C(O)-CH-C(O)-CH3 | monoanionic | bidentate | In general bidentate, bound through both oxygens, but sometimes bound through the central carbon only, see also analogous ketimine analogues |
ألكينs | R2C=CR2 | neutral | compounds with a C-C double bond | |
بنزين | C6H6 | neutral | and other arenes | |
1,2-Bis(diphenylphosphino)ethane (dppe) | Ph2PC2H4PPh2 | neutral | bidentate | |
1,1-Bis(diphenylphosphino)methane (dppm) | C25H22P2 | neutral | Can bond to 2 metal atoms at once, forming dimers | |
Corroles | tetradentate | |||
Crown ethers | neutral | primarily for alkali and alkaline earth metal cations | ||
2,2,2-crypt | hexadentate | primarily for alkali and alkaline earth metal cations | ||
Cryptates | neutral | |||
Cyclopentadienyl (Cp) | [C5H5]− | monoanionic | ||
Diethylenetriamine (dien) | C4H13N3 | neutral | tridentate | related to TACN, but not constrained to facial complexation |
Dimethylglyoximate (dmgH−) | monoanionic | |||
Ethylenediaminetetraacetate (EDTA) | tetra-anionic | hexadentate | actual ligand is the tetra-anion | |
Ethylenediaminetriacetate | trianionic | pentadentate | actual ligand is the trianion | |
glycinate (Glycinato) | monoanionic | bidentate | other α-amino acid anions are comparable (but chiral) | |
Heme | dianionic | tetradentate | macrocyclic ligand | |
Nitrosyl | NO+ | cationic | bent (1e) and linear (3e) bonding mode | |
Pyrazine | N2C4H4 | neutral | ditopic | sometimes bridging |
Scorpionate ligand | tridentate | |||
Sulfite | monoanionic | monodentate | ambidentate | |
2,2',5',2-Terpyridine (terpy) | neutral | tridentate | meridional bonding only | |
Triazacyclononane (tacn) | (C2H4)3(NR)3 | neutral | tridentate | macrocyclic ligand see also the N,N',N"-trimethylated analogue |
Tricyclohexylphosphine | (C6H11)3P or (PCy3) | neutral | monodentate | |
Triethylenetetramine (trien) | neutral | tetradentate | ||
Trimethylphosphine | PMe3 | neutral | monodentate | |
Tri(o-tolyl)phosphine | P(o-tolyl)3 | neutral | monodentate | |
Tris(2-aminoethyl)amine (tren) | (NH2CH2CH2)3N | neutral | tetradentate | |
Tris(2-diphenylphosphineethyl)amine (np3) | neutral | tetradentate | ||
Terpyridine | C15H11N3 | neutral | tridentate | |
Tropylium | C7H7+ | cationic |
تبادل الربيطات
Ligand exchange (also ligand substitution) is a type of chemical reaction in which one ligand in a chemical compound is replaced by another ligand. In organometallic chemistry this can take place by associative substitution or by dissociative substitution.