TY - JOUR
T1 - Anionic amino acid [closo-1-CB 9H 8-1-COO-10-NH 3]- and dinitrogen acid [closo-1-CB 9H 8-1-COOH- 10-N 2] as key precursors to advanced materials
T2 - synthesis and reactivity
AU - Ringstrand, Bryan
AU - Kaszynski, Piotr
AU - Young, Victor G.
AU - Janoušek, Zbynek
PY - 2010/2/1
Y1 - 2010/2/1
N2 - Amino acid [closo-1-CB gH 8-1-COO-10-NH 3]- (4) was prepared by amination of iodo acid [closc-1-CB gH 8-1-COOH10-l]- (1) with LiHMDS in a practical and reproducible manner. The apparent dissociation constants, pK 2 = 5.6 and PK 1 > 11, were measured for 4[NMe 4] in 50% aq. EtOH. Diazotization of 4 with NO +PF 6- under mildly basic conditions afforded stable dinitrogen acid [closo-1-CB 9H 8-1-COOH-10-N 2] (5). Activation parameters (ΔH‡ = 33.9 ± 1.4 kcal mol -1 and ΔH‡ = 10 ± 3.5 cal mol -1 K -1) for thermolysis of its methyl ester [ctoso-1-CB 9H 8-I-COOMe-10-N 2] (11) in PhCN were established, and the heterolysis of the B-N bond is believed to be the rate-determining step. Electrochemical analysis showed a partially reversible reduction process for 11 (E 1/2 red = -1.03 V) and 5(E 1/21 red = -1.21 V), which are more cathodic than reduction of [closo-1-CB 9H 9-1-N 2] (17). The dinitrogen acid 5 was reacted with pyridine and N, N-dimethylthioformamide, to form pyridine acid 6 and protected mercapto acid 6, respectively, through a boronium ylide intermediate 18. Compound 7 was converted to sulfonium acid 8. The molecular and crystal structures for 5 [C 2H 9B 9N 2O 2 monoclinic, P2 1In, a = 7.022(2) ̊,D = 11.389(4) Å, c = 12.815(4) Å, β = 96.212(5)°; V = 1018.8(6) Å 3, Z= 4,], 6 [C 7H 14B 9NO 2, monoclinic, P2 1In, a = 14.275(4) ̊, b=12.184(3) Å, c = 30.538(8) Å, β = 95.377(4)°; V= 5288(3) ̊ 3, Z= 16], and 8 [C 7H 19B 9O 2S, monoclinic, P2 1/c a = 15.988(5) Å, b = 19.377(6) Å, c=9.655(3) A, β = 98.348(5)°; V= 2959.4(16) Å 3, Z= 8] were determined by X-ray crystallography and compared with results of density functional theory (DFT) and MP2 calculations. Electronic structures of 5, 6, and related species were elucidated with electronic spectroscopy and assessed computationally at the B3LYP/6-31 G(d, p), MP2/6-31G(d,p), and ZINDO//MP2 levels of theory.
AB - Amino acid [closo-1-CB gH 8-1-COO-10-NH 3]- (4) was prepared by amination of iodo acid [closc-1-CB gH 8-1-COOH10-l]- (1) with LiHMDS in a practical and reproducible manner. The apparent dissociation constants, pK 2 = 5.6 and PK 1 > 11, were measured for 4[NMe 4] in 50% aq. EtOH. Diazotization of 4 with NO +PF 6- under mildly basic conditions afforded stable dinitrogen acid [closo-1-CB 9H 8-1-COOH-10-N 2] (5). Activation parameters (ΔH‡ = 33.9 ± 1.4 kcal mol -1 and ΔH‡ = 10 ± 3.5 cal mol -1 K -1) for thermolysis of its methyl ester [ctoso-1-CB 9H 8-I-COOMe-10-N 2] (11) in PhCN were established, and the heterolysis of the B-N bond is believed to be the rate-determining step. Electrochemical analysis showed a partially reversible reduction process for 11 (E 1/2 red = -1.03 V) and 5(E 1/21 red = -1.21 V), which are more cathodic than reduction of [closo-1-CB 9H 9-1-N 2] (17). The dinitrogen acid 5 was reacted with pyridine and N, N-dimethylthioformamide, to form pyridine acid 6 and protected mercapto acid 6, respectively, through a boronium ylide intermediate 18. Compound 7 was converted to sulfonium acid 8. The molecular and crystal structures for 5 [C 2H 9B 9N 2O 2 monoclinic, P2 1In, a = 7.022(2) ̊,D = 11.389(4) Å, c = 12.815(4) Å, β = 96.212(5)°; V = 1018.8(6) Å 3, Z= 4,], 6 [C 7H 14B 9NO 2, monoclinic, P2 1In, a = 14.275(4) ̊, b=12.184(3) Å, c = 30.538(8) Å, β = 95.377(4)°; V= 5288(3) ̊ 3, Z= 16], and 8 [C 7H 19B 9O 2S, monoclinic, P2 1/c a = 15.988(5) Å, b = 19.377(6) Å, c=9.655(3) A, β = 98.348(5)°; V= 2959.4(16) Å 3, Z= 8] were determined by X-ray crystallography and compared with results of density functional theory (DFT) and MP2 calculations. Electronic structures of 5, 6, and related species were elucidated with electronic spectroscopy and assessed computationally at the B3LYP/6-31 G(d, p), MP2/6-31G(d,p), and ZINDO//MP2 levels of theory.
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U2 - 10.1021/ic9021323
DO - 10.1021/ic9021323
M3 - Article
C2 - 20043626
AN - SCOPUS:75649109251
SN - 0020-1669
VL - 49
SP - 1166
EP - 1179
JO - Inorganic chemistry
JF - Inorganic chemistry
IS - 3
ER -