N Bridging

Among the products of the reaction between sodium thiocyanate and [n-Bu4.N]3[Re2Cl8], a substance was found which was considered to involve CO ligands. X-Ray analysis later identified it to be [n-Bu4N]3[Re2(NCS)io].  

The anion in this compound consists of two distorted octahedra sharing an edge formed by the N atoms of two bridging NCS ions (Fig. 34). The virtual D2H symmetry of the inner Re2N o set of atoms implies that the unpaired electron in this formally mixed-valence Re(III)-Re(IV) complex is delocalized equally over both metal atoms. The Re— Re distance of 2.613(1) A and the bridging angles of 102.7(3)° for N— Re—N and 77.4(3)° for Re—N—Re clearly indicate direct bonding, but the exact bond order is not certain. 

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VI. Tellurium-Containing Heterocycles with N-Bridged Atoms... 

N-Bridged tellurium-containing heterocycles are exemplified by derivatives of l,4-tellurazine[2,3-g/i]carbazole 107 and heterocycle 108. One-pot reaction of A-propargylcarbazole with tellurium tetrahalides under conditions of the two-phase tellurohalogenation (Section n,B,l) leads to halogenomethylene derivatives 107 (90KGS126). The reaction proceeds as the spontaneous electrophilic cycliza-tion of initially formed tellurium trihalides 109. 

Triazole reveals the T) (C) carbene function, J.-ti (N, N ) bridges with subsequent coordination via the site, J.-ti (N, N ) bridges with subsequent coordination to the N" site. 

Among the less eommon features of eomplexes of group VII are the switeh of the eoordination mode from to upon photoehemieal deearbonylation and the stabilization of the /i-N=N bridge in the rhenium speeies. 

In 1% aqueous acetic acid, the peptides of the sequence (Ala-Gly-Pro)n, bridged with Lys-Lys and beginning with n = 8 show a cooperative transition, which was interpreted as a triple helix-coil transition (see Figs. 35, 36). 

Lotz, Simon, Van Rooyen, Petrus H., and Meyer, Rita, cr, n-Bridging... 

The influence of the electronic coupling on the electron transfer rate was determined by changing the length of the (A T)n bridge. As expected, the rate decreased as the number n of the A T base pairs between electron donor and electron acceptor increased [4, 7]. But, surprisingly, the exponential correlation of Eq. (1) between the rate kEr and the distance is not valid for short distances. The plots in Fig. 3 and Fig. 4 show that at 6 A the electron transfer rate /cEt is much faster than expected [4, 7]. 

Crystal structures of dinickel complexes with 0,0-bridging and 0,N-bridging (O-methylated) carbamate have been reported.2074,20 (874) produces one equivalent of ammonia upon heating in methanol/water solution.2082... 

We have reported that the reaction of 2,4,6-tri(chloro)borazine CI3B3N3H3 with three equivalents of tris(isopropylamino)borane B(NHPr )3 led to the formation of 2,4,6-tri[bis(isopropylamino)boryl(isopropyl)amino]borazine 11 [Fig. 5(a)] in quantitative yield.26,27 The subsequent polycondensation carried out in vacuo up to 150°C, led to the formation of the polymer 12 containing B3N3 rings linked either through direct B—N interring bonds (minor pathway) or three-atoms —N—B—N— bridges... 

Heterocyclic compounds Heterocyclic C=N systems, such as benzoxazole and related thia-zoles, react with complex 2b to yield the ring-expanded adducts, e. g. complexes 90 and 91, by formal C-X (X = O, S) bond cleavage and coupling with the alkyne. In the case of benzisoxazole, the alkyne is not coupled but eliminated, and ring-enlargement of the ben-zisoxazole leads to the N-bridged dimer 92 [48]. 

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