Chromium Azide Complexes

Chromium Azide Complexes In attempting to prepare Cr azide from a soln of CrfNOsX and NaNj in pyridine, Oliveri-Mandala (Ref 5)... 

Chromic Azide Complexes. See Chromium Azide Complexes in Vol 1, pA530-R and also Azidopentammine-chromium (III) Perchlorate, Chloropentamminechromium (III) Azide and Hexamminechromium Azide on pA277 under Ammines... 

Strecker Schwinn (Ref 8) prepd the following chromium azide complex salts ... 

Chloronitroanilinopropanols A436-R Chromium Azide A530-L Chromium Azide Complexes A530-R Chromium Carbide. See under Acetylides and Carbides A72-R... 

Aq sol ns of sodium chromium azide did not react with Cr or N3 but with AgNOt gave an expl complex salt. The sodium chromium azide is considered to be the Na salt of chromihy-drazoic acid, HsCr(N3)6, but this acid was not isolated because it decomposed too readily. Attempts to obtain it by the methods of Wohler Martin (Ref 4) failed... 

The kinetics of aquation of a number of azidochromium(III) complexes have been investigated.303,655 Compared with other acidochromium(III) complexes, the chromium-azide bonds in these species seem remarkably stable to thermal substitution. Hence in the base hydrolysis of [CrN3(NH3)s]2+ a pathway involving initial loss of NH3 concurs with the usual base hydrolysis pathway involving loss of Nj. The aquation of azidochromium(III) complexes is H+-assisted with protonation of the azido ligand accounting for the enhanced reactivity. 

A similar approach to the hydrolytic methodology uses a chromium-salen complex to open an epoxide with trimethylsilyl azide, as illustrated by the synthesis of the antihypertensive agent, (S)-propranolol (10) (Scheme 9.15).118,119... 

There has been a report of bridged dinitrogen complexes of iron(III) and chromium(lll) complexes, formed by reaction of the metallo(IlI)porphyrinate triftate with [Re(N2)(PMe2Ph)4Cl] to make the Fe-N-N-Re or Cr-N-N-Re bridged complexes. The Fe complex has a magnetic moment of about 4.4 /u-b at room temperature, consistent with a S = 312,512 admixed spin state for the iron(lll), and a pyrrole-H shift of -3.23 ppm, consistent with the expected weak-fteld nature of the N2 ligand. The stracture shows a linear Fe-N-N-Re unit (Fe-Nl-N2 = 170°, Nl-N2-Re = 177°) with Fe-N bond length of 1.93 similar to that of the TPPFe -azide complex (1.953 A). 

Also from Jacobsen s lab comes a clever application of chiral recognition to drive regioselective and stereospecific ring opening of epoxides. When an optically pure non-symmetrical 1,2-disubstituted epoxide (e.g., 11) is treated with a chiral (salen)chromium(III) azide complex, only one approach results in a chiral match , thus azide is delivered selectively to one position. Using this protocol, (/5, 25)-norpseudoephedrine (74) was synthesized in three steps with 42% overall yield and > 99% ee <01SL1013>. 

This is also the case for the kinetically inert octahedrally coordinated chromium(III) centre (d ) found in a salene chromium(III) complex with an organoazide in close proximity to the metal site (Figure 12.10). Salene chromium(II) complexes are known to catalyze the enantioselective opening of prochiral epoxides with TMS-N3. The organoazide derivative was obtained by stoichiometric azide transfer from an azido chromium(III) salene complex to epoxycyclopentane. 

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