ربيطة

معقد كوبالت (HCo(CO)4) بخمس ربيطات
ست ربيطات من الأمونيوم تحيط بذرة الكوبالت في معقد كلوريد سداسي أمين الكوبالت الثلاثي

الربيطة بالإنجليزية: Ligand في الكيمياء عبارة عن ذرة أو أيون (شاردة) أو جزيء مرتبط بذرة الفلز المركزية في المعقدات التساندية.

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.

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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.

انظر أيضاً

الهامش