Experimental and theoretical investigations of the formation of the diazene PhSN=C(H)N=NC(H)=NsPh from HCN2(SPh)(3) by a thiyl-radical-catalyzed mechanism: Identification of the HC(NSPh)2(center dot) radical and X-ray structures of HCN2(SPh)(3) and PhSN=C(H)N=NC(H)=NSPh

被引:14
作者
Chivers, T [1 ]
McGarvey, B [1 ]
Parvez, M [1 ]
VargasBaca, I [1 ]
Ziegler, T [1 ]
机构
[1] UNIV WINDSOR, DEPT CHEM & BIOCHEM, WINDSOR, ON N9B 3P4, CANADA
关键词
D O I
10.1021/ic960317t
中图分类号
O61 [无机化学];
学科分类号
070301 ; 081704 ;
摘要
The reaction of HCN2(SiMe(3))(3) with benzenesulfenyl chloride in a 1:3 molar ratio produces HCN2(SPh)(3) (4) as thermally unstable, colorless crystals. The decomposition of (4) in toluene at 95 degrees C was monitored by UV-visible, H-1 NMR and ESR spectroscopy. The major final products of the decomposition were identified as PhSN=C(H)N=NC(H)=NSPh (5) and PhSSPh. The structures of 4 and 5 were determined by X-ray crystallography. The crystals of 4 are monoclinic, space group P2(1)/a, with a = 9.874(2) Angstrom, b = 19.133(2) degrees, c = 10.280(2) Angstrom, beta = 113.37(1)degrees, V = 1782.8(5) Angstrom(3), and Z = 4. The final R and R(w) values were 0.042 and 0.049, respectively. The crystals of 5 are monoclinic, space group P2(1)/n, with a = 5.897(6) Angstrom, b = 18.458(10) Angstrom, c = 7.050(8) Angstrom, beta = 110.97(5)degrees, V = 716(1) Angstrom(3), and Z = 2. The final R and R(w) values were 0.075 and 0.085, respectively. The diazene 5 adopts a Z,E,Z structure with weak intramolecular S ... N contacts of 2.83 Angstrom, giving rise to four-membered NCNS rings. During the thermolysis of 4 at 95 degrees C in toluene a transient species (lambda(max) 820 nm) was detected. It decomposes with second-order kinetics to give 5 (lambda(max) 450 nm). The ESR spectrum of the reaction mixture consisted of the superposition of a three-line 1:1:1 spectrum (g = 2.0074, A(N) = 11.45 G), attributed to (PhS)(2)N-., upon a doublet of quintets (1:2:3:2:1) with g = 2.0070, A(N) = 6.14 G, A(H) = 2.1 G assigned to the radical HCN2(SPh)(2)(.). Density functional theory (DFT) calculations for the models of the radical showed the E,Z isomer to have the lowest energy. Thermochemical calculations indicate that the decomposition of HCN2(SH)3 into the diazene (Z,E,Z)-HSN=C(H)N=NC(H)=NSH (and 2 HSSH) is substantially more exothermic (Delta H = -176.1 kJ mol(-1)) than the corresponding formation of the isomeric eight-membered ring (HC)(2)N-4(SH)(2) (Delta(H) = -40.6 kJ mol(-1)). These calculations also indicate that the diazene is formed by a mechanism in which the RS(.) radical acts as a catalyst.
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页码:3839 / 3847
页数:9
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