Azide complex, molecular

Tetranuclear Ni11 complexes (889), (890a), and (890b) with unusual /i3-l,l,3 and /r4-1,1,3,3 azide binding modes have been obtained from discrete pyrazolate-based dinuclear building blocks.2141 (890a) and (890b) represent the only known examples of such EE/EO /i4 coordination of azide in molecular compounds. 

Fig. 41. (Left) Molecular structure of the azide complex 81 in the crystal. (Right) Central N3Ni(g-S)2( i,3-N3)NiN3 core in 81. The figures were generated using data downloaded from The Cambridge Crystallographic Data Center (CCDC) and correspond to the structure originally reported in Ref. (242).

An organometallie azide complex was obtained by replacement of THF through the azide anion in Cp3Sm(THF) (Eq. 6) [74], The molecular structure exhibits different and comparatively large Sm-N-N angles of 134(1) and 151(1)°. The Sm-N bond lengths of 2.47(2) and 2.48(2) A are comparable to those of the inorganic azides. 

Zink has applied a molecular orbital approach to photochemical assignments of excited states of iridium(III) azide complexes. The observed products of 250-400 nm irradiation of [Ir(N3)(NH3)5] are [Ir(NH3)5(NH2Cl)] and N2, the same products expected on the basis of populating the LL (ligand-localized Jt o - n ) excited state. It was suggested, therefore, that the photoreaction originates in the LL excited state. The formation of a coordinated nitrene intermediate has been ascribed to a combination of LMCT and LL states rather than to the LL state alone. 

The most complex molecular ion observed by ESR in azides is a product of 7- or UV-irradiation at low temperature [29,32]. It is the N4 molecular ion and is observed only in KN3 and RbN3. It is believed to occupy either of the two crystallographically equivalent azide ion sites. The nine-line hyperflne pattern expected for an unpaired electron interacting with four equivalent nuclei of spin 1 is observed. It was postulated that satellite lines (Figure 3a), appearing between the nine principal hyperfine lines, are due to pairs of adjacent N4 molec-... 

The modification of polymers can be readily conducted by chemical coupling reactions when the chain to be modified possesses groups such as vinyl, hydroxyl, or azide [23], etc. The Diels-Alder reaction between a diene and a dienophile, discovered by Otto Diels and Kurt Alder in 1928 [24], is the most important example of click chemistry. These robust and efficient click coupling reactions have been widely exploited in the construction of tailor-made functional polymeric materials with complex molecular architectures... 

The photolysis of azide complexes induced by LMCT excitation leads to a variety of products depending on the specific complex and reaction conditions. The azide radical which is formed in the primary photochemical step is known to be very labile [105]. It eliminates nitrogen. The nitrogen atoms which are thus formed can be detected by ESR spectroscopy at low temperatures. In simple cases the photolysis of azide complexes yields only the reduced metal and molecular nitrogen, e.g., equation (14) ... 

Cu(I)-catalyzed 1,3 dipolar cycloaddition of terminal alkynes and azides has emerged as a promising tool for an efficient and easy access of complex molecular-level structures regioselectively in good yields. This coupling technique deals... 

Spectroscopic analysis revealed that the thermally initiated [3 + 2] polycycloaddition produced 1,4- and 1,5-substituted triazole isomers in an approximately 1 1 ratio. This ratio appears to be statistic and dependant on the bulkiness of the organic moieties. For example, hfr-r-P[30(4)-20] with butyl spacers contained slightly more 1,4-triazole isomers than did hb-r-P[30(6)-20] with hexyl spacers. This becomes clearer if we look at the proposed transition states a and b of the [3 + 2]-dipolar cycloaddition (Scheme 16). Because of their molecular orbital symmetry, the acetylene and azide functional groups arrange in two parallel planes, a so-called two-plane orientation complex [48], which facilitates a concerted ring formation. If the monomer fragment or the polymer branch ( ) attached to the functional groups are bulky, steric repulsion will come into play and transition state a will be... 

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