| Research Abstract |
Avariety of low-valent transition metal complexes of crown thioethers such as 1,4,8,11-tetrathia- cycloteetradecane ([14]aneS_4), its 6,6,13,13-tetramethyl analogue (Me_4[14]aneS_4), 1,5,9,13-terathiachclo-hexadecane ([16]aneS_4), and its 3,3,7,7,11,11,15,15-octamethy analogue (Me_8[16]aneS_4) have been prepared. They are RhL^+ (L=R_4[14]aneS_4, R_8[16]aneS_4), cis- and trans-RuCl_<>L (L=R_4[14]aneS_4,R_8[16]aneS_4), trans-RuH(C1)L (L=Me_4[14]aneS_4,Me_8[16]aneS_4), trans-RuH(BH_4,Ru_2H(C1)(<nu>-H) [Me_4[14]aneS_4]_2^+, and trans-MoL_2Me_8[16]aneS_4 (L'=Cl, Br, N_2, CO, HC<congruent>CH, PhC<congruent>CH, CH_2=CH_2). The elctrochemical, spectral, and x-ray structural studies of these complexes as well as extended Huckel MO calculations on the models, RH(SH_2)_4)^+ and trans-Mo(N_2)_2(SH_2)_4 revealed that the crown thioethers behave as p_<<pi>> donor ligand. this eelctronic feature of the crown thioether was further verified by the facile oxidative addition of CH_2Cl_2 to give trans-RHCl(CH_2Cl)L^+ and also by an unpercedented direct arylation of the coordinated N_2 molecule in trans-Mo(N_2)_2Me_8[16]aneS_4 with PhX under ambient conditions affording trans-MoX(N_2Ph)Me_8[16]-aneS_4 (X=Br, I). The chemical properties of the above complexes are found to be affected by the ring size of the macrocycles and the geometry of the complexes. For example, a reaction of cis-RuCl_2R_4[14]-aneS_4 with Al_2Me_6 in aromatic hydrocarbons proceeds through an intermolecular C(sp^2)-H bond activation to give trans-RuCl(Ar)R_4[14]aneS_4 (Ar=Ph, tolyl), while a similar reaction of trans-isomer afforded trans-MoCl(Me)Me_4[14]aneS_4. By contrast, cis-RuCl_2Me_8[16]aneS_4 gave an expected RuCl(Me_8[16]aneS_4. It is to be noted that trans-Mo(N_2)_2Me_8[16]aneS_4 represents the first example of dinitrogen complex containing only sulfur ligand which has been long desired to prepared as a chemical model to mimic the function of nitrogenase.
|
