113089-43-3Relevant academic research and scientific papers
Diastereoselective arbuzov dealkylation and evidence for phosphorus-carbon bond activation of prochiral cobalt(III) phosphonite complexes
Boone, Brian J.,Jablonski, Chet R.,Jones, Peter G.,Newlands, Michael J.,Yu, Yongfei
, p. 3042 - 3050 (2008/10/08)
(Sc)-(η5-Cp)CoI2(PPh 2NHC*H(Me)Ph) reacts with 1 equiv of dimethyl tert-butyl- or ethylphosphonite in methylene chloride solution to give diastereomeric P-chiral phosphinate Arbuzov products (R,SCo;RP;SC)-(η 5-Cp)CoI(PPh2NHC*H(Me)Ph)(P(0)(OMe)(t-Bu)) (3a) and (R,SCo;R,SP;SC)-(η 5-Cp)CoI(PPh2NHC*H(Me)Ph)(P(O)(OMe)(Et)) (3b), respectively. Apparent phosphorus-carbon bond cleavage also occurs to give (R,SCo;SC)-(η5-Cp)CoI(PPh 2NHC*H(Me)Ph)(P(O)(OMe)2) (4), which was isolated in low yield after aerial workup. Two diastereomers of the tert-butyl series 3a and one diastereomer of the four isolated for the ethyl series 3b were characterized by single-crystal X-ray diffraction. (SCo;RP;SC)-3a-1 crystallizes in the space group P212121 with a = 9.815(4) A?, b = 14.314(6) A?, c = 21.120(9) A?, V = 2967(2) A?3, Z = 4, and RF = 2.83% for 5958 reflections (F > 4.0σ(F)) at 198 K. (ACo;SP;SC)-3a-2 crystallizes in the space group P21 with a = 13.073(5) A?, b = 8.731(2) A?, c = 13.537(5) A?, β = 106.49(3)°, V = 1481.5(9) A?3, Z = 2, and RF = 3.19% for 4846 reflections (F > 4.0σ(F)) at 198 K. (RCo;SP;SC)-3b-2 crystallizes in the space group P212121 with a = 8.7004(7) A?, b = 12.0769(18) A?, c = 27.490(3) A?, V = 2888.5(6) A?3, Z = 4, and RF = 4.4% for 3118 reflections (F > 2.5σ(F)) at 297 K. The absolute configurations of all diastereomers were assigned on the basis of crystallographic results, circular dichroism, and chemical cycles involving Co epimerization. P=O?H-N intramolecular hydrogen bonding establishes a chaise longue conformation with pseudoaxial η5-Cp and pseudoequatorial iodide in the solid state. Proton nuclear Overhauser difference (NOED) spectra show that the solid-state conformation is retained in solution. Optical yields increased with increasing steric demands of the prochiral phosphonite substituent. A model based on 1,3-diaxial steric interactions in the transition state leading to dealkylation is proposed to account for the observed Co→P chiral induction.
Optically active transition-metal Compounds.1,2 Preparation, structure, absolute configuration, and conformational analysis of chiral pseudooctahedral cobalt(III) phosphonato and phosphinato complexes. Optical induction in the transition-metal Arbuzov reaction
Brunner, Henri,Jablonski, Chet R.,Jones, Peter G.
, p. 1283 - 1292 (2008/10/08)
(S)-η5CpCoI2(PPh2NHCH(Me)Ph) reacts with 1 equiv of trimethyl phosphite or dimethyl phenylphosphonite in benzene or methylene chloride solution to give diastereomeric Arbuzov products (R,SCo,SC)-η5-CpCoI(PPh 2NHCH(Me)Ph)(P(O)(OMe)2) (6a,b) and (R,SCo,R,SP,SC)-η 5-CpCoI-(PPh2NHCH(Me)Ph)(PhP(O)(OMe)) (7a-d), respectively. Compounds 6a and 7a were characterized by X-ray diffraction, including determination of absolute configuration. 6a crystallizes in the space group P212121 with a = 9.470 (2) A?, b = 15.136 (3) A?, c = 19.562 (4) A?, and Z = 4 and was refined to R = 0.041 for 4721 reflections. 7a also crystallizes in P212121 with a = 9.995 (2) A?, b = 13.934 (2) A?, c = 22.422 A?, and Z = 4 and was refined to R = 0.058 for 3749 reflections. The absolute configuration of all diastereomers was established by a combination of crystallographic, circular dichroism, and epimerization studies. Conformational analysis on the basis of crystallographic data in the solid state and proton nuclear Overhauser difference (NOED) spectra in solution show a quasi-chair conformation determined by the presence of a strong intramolecular NH?O=P hydrogen bond. Initial substitution of diastereotopic iodide occurs with essentially zero optical yield; however, considerable chiral induction occurs in the subsequent Arbuzov dealkylation step leading to the phosphinato complexes 7.
