Hexaamine complex

Forms a number of coordination compounds (ammonia complex) with several metals adds to AgCl forming soluble complex [Ag(NH3)2]Cl forms tetraamine complex [Cu(NH3)4]S04 with CUSO4 and forms many hexaamine complexes with cobalt, chromium, palladium, platinum and other metals. 

The room temperature values of x(2E) for most hexaamine chromium(III) complexes fall into a fairly narrow range in fluid solutions (ca 10 6 1 s- ). This small range, and the variety of solvent media used by different investigators tends to make any correlations difficult. If we take Cr(en) + and Cr(sen)2+ to be representative of an "average" and a shortlived hexaamine complex, then in a single medium the variations in x(2E) (ca 2 and 0.05 ps, respectively, at 298 K) again parallel the variations in Ttr (ca 240 and 190K, respectively). ... 

Table 11.2 Observed and calculated electron self-exchange rates of cobalt(III/II) hexaamine complexes t23l).

The hexaamine complex can only be prepared in sealed tube reactions (equation 34), unless the incorporation of the sixth ammine ligand is catalyzed by ethanol. In contrast, the pentaammine complexes are very accessible, and their anation and aquation reactions (Scheme 11) have been exhaustively... 

Bernhardt and Comba have combined molecular mechanics and the angular overlap model (AOM) to predict the d-d electronic spectra of several hexaamine compounds.The force field used, which had been described earlier, is appropriate for the modeling of Cu(II), Ni(II) (S = 1), Co(III), Fe(III), Cr(III), Zn(II), and Rh(III) complexes of amines, carboxylates, pyridines, and thia ethers. The AOM requires several parameters including metal-ligand cr-and TT-bonding terms [e and e ), interelectronic repulsion terms P- and F" ), and spin-orbit coupling terms Q. The current application uses the empirical relationship e r) = C/r to determine the value of e, where r is the bond distance and C is a constant whose value increases with alkyl substitution. This choice is consistent with the view that N-alkylation increases donor strength. The d-d electronic spectra of a variety of Cr(III), Co(III), and Ni(Il) hexaamine complexes are predicted to within 1000 cm. ... 

Strictly anaerobic conditions combined with a considerable excess of ligand are required for the synthesis of Co(II)-hexaamine complexes. A large excess of ligand must be used as a consequence of the characteristically high substitution rate at the center and competition for coordination sites by the solvent. In contrast to their counterparts in oxidation state III, the Co(II) amines are quite delicate compounds, the study of which often requires elaborate techniques and exclusion of air. 

Co-N bond length is similar to that of the hexaamine complex at 1.958 A, despite the greater steric hindrance due to the hydroxo group as compared to a proton. 

Fig. 12. Plot of number of amine protons versus log of the self-exchange rate constant (M s ) for cobalt hexaamine complexes at 25°C. No correction has been made for ionic strength differences. The data include some nonhomoleptic complexes. (1) [CoCNHslg], (2) [Co(en)3]3+ 2+, (3) [Co(chxn) ] + 2+ (4) [Co(tmen) ]3+ 2+, (5) [Co(dien)"]"+ 2+, (6) [Co(pet) P+ 2+, (7) [Co(linpen)P" 2 + (g) lCo(medien)(9) [Co(tacn)(dien)]3+ 2+, (10) [Co(tacn) (pet) (11) [Co(tacn) (etdien) (12) [Co(tacn) (budien) p+ 2+ 3 [Co(tacn)(medien)P, (14) [Co(diAmsar)] , (15) [Co(taptacn)P, (16) [Co(metacn) ] 2+, (17) [Co(diAmsar)P 2+, (18) [Co(sar)(19) [Co(sep)P 2, (20) [Co(dtne)] , (21) [Co(Amsartacn)], (22) [Co(Amsartacn)] , (23) [Co-(diAmchxnsar)] , (24) [Co(diAmchxnsar)] . The data for homoleptic complexes are taken from Table IV the other data are from reference U02). The line was calculated without the data for the sep and sar derivative cages and the [Coftmenls] couple.

The vNiN vibrations were assigned in 2,6-diacetylpyridine dioxime at 416, 341 and 276 cm and at 370 and 265 cm in hexaamine complexes, at 410 and 334 cm in triethylendiamine derivatives, around 240 cm" in pyridine derivatives and in imidazol complexes between 325 and 210cm"Gobemado-Mitre et al attributed the vCuN mode in copper complex of naphthalocya-nine to those bands observed at 341 and 221 cm" In Cu(II) tri-azamacrocycles it has been proposed the bands at 383 and 314 cm" as due to vCuN. This mode was observed in copper complexes of cyclam at 437 cm" and in Cu(II) hexaazacyclophane at 390 and 280 cm" In phenantroline Cu(II) complexes the vCuN vibration was identified with the bands at 300 and 430 cm" In the case of the Zn complexes, some tetraamine derivatives display the vZnN band at 432cm" and in triethylendiamine complexes were observed at 405 and 291 cm" in imidazole complexes the vZnN mode was assigned to the bands between 325 and 210 cm" The vZnN mode of bis(phenylhydrazine)-l, 10-phenantroline Zn(II) was attributed to the bands at 376 and 267cm" ... 

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