160:, because the metal’s positive charge is reduced by delocalization of electron density from the ligand into the ligand-metal bond. But we have the distinction that with a class-a metal there is little concomitant polarization of the electron density away from the
59:
will have a destabilizing effect on each other. The effect is also found with borderline metals in the presence of high trans effect ligands. For example the selenocyanate ion trans to the soft carbon dioxide in
72:“With two π-acid ligands in mutual trans positions at a class-b metal, there would be a destabilizing competition for the dπ electrons on the metal. A π-acid bonded to a soft metal thus makes a metal a harder
141:
bases (electronegative donor atoms) retain their valence (outer shell) electrons when attached to a given central metal ion, thus enabling the metal ion to retain more of its positive charge, making it a
76:. Similarly a soft σ-donor will tend to polarize the electron density on a soft metal, causing it to favour an electrovalently bonded ligand in the trans position.”
68:(CO)(NCSe) bonds via the nitrogen, the harder of its two donors. The phenomenon may be explained in terms of a trans influence:
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214:; Some reactions of a ditertiary arsine ligand; Ph.D. thesis; University College London, 1973.
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was first used in chemistry by C. K. Jørgensen in 1964, to refer to the process by which a
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Sulphur donor. A more definitive example are the halopentamminocobalt(III) ions, Co(NH
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105:(SCN) is an example of chemical symbiosis. The cyclopentadienyl directs the
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directional, and is just as effective in, say, tetrahedral complexes.”
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than with iodide, and the halopentcyanocobalt(III) ions, Co(CN)
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X, which are most stable when the halogen is iodine.
35:
one. Two superficially antithetical phenomena occur:
27:
on a metal predisposes the metal to receive another
314:""Symbiotic" Ligands, Hard and Soft Central Atoms"
85:This effect occurs with class-a metals such as
8:
262:J. L. Burmeister & N. J. DeStefano;
186:
153:bases the central metal atom is made a
312:Jorgensen, C. Klixbull (August 1964).
7:
226:"Antisymbiosis and the trans effect"
55:metals. Two soft ligands in mutual
294:M. A. Jennings & A. Wojcicki;
121:X, which are more stable when the
14:
224:Pearson, Ralph G. (March 1973).
172:, is probably not specifically
51:This is found principally with
1:
164:of the metal. In addition,
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210:R. G. Pearson, quoted in
373:Coordination chemistry
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78:
47:Chemical antisymbiosis
296:J. Organometal. Chem.
135:
70:
31:ligand rather than a
351:Anthony Nicholl Rail
280:Anthony Nicholl Rail
212:Anthony Nicholl Rail
109:to bond through its
16:The biological term
330:10.1021/ic50018a036
318:Inorganic Chemistry
242:10.1021/ic50121a052
230:Inorganic Chemistry
81:Chemical symbiosis
193:C. K. Jørgensen;
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324:(8): 1201–1202.
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91:Cyclopentadienyl
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236:(3): 712–713.
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162:trans position
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57:trans position
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60:trans-Rh(PPh
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264:Chem. Comm.
107:thiocyanate
89:(II). The
181:References
158:Lewis acid
147:Lewis acid
93:complex (C
74:Lewis acid
338:0020-1669
250:0020-1669
168:, unlike
166:symbiosis
37:symbiosis
18:symbiosis
367:Category
355:op. cit.
298:; 1968,
284:op. cit.
197:; 1971,
149:. With
127:fluoride
125:, X, is
270:, 1698.
201:, 1097.
123:halogen
101:)Fe(CO)
336:
302:, 231.
248:
155:softer
111:softer
25:ligand
174:trans
334:ISSN
268:1970
246:ISSN
151:soft
144:hard
139:Hard
87:iron
53:soft
39:and
33:soft
29:hard
22:hard
326:doi
238:doi
369::
353:;
332:.
320:.
316:.
300:14
282:;
266:;
244:.
234:12
232:.
228:.
199:10
43:.
340:.
328::
322:3
252:.
240::
137:“
131:5
119:5
117:)
115:3
103:2
99:5
97:H
95:5
66:2
64:)
62:3
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