Chui Fan Liu's research while affiliated with University of Illinois at Chicago and other places

2,2′-Diaminobiphenyl-R,R-trans-1,2-diaminocyclohexaneplatinum(II) Chloride Trihydrate, (R,R-chxn)(dabp)Pt]Cl2·3H2O, crystallizes in the space group p212121 (D24, No. 19) with a = 6.219(4) Å, b = 17.633(2) Å, c = 21.523(3) Å, V = 2,360.4(8) Å3, ϱcalcd = 1.739 g cm−3, ϱmeasd = 1.74 g cm−3, and Z = 4. Diffraction data were collected with a Picker FACS-1 four-circle diffractometer. The structure was solved by the heavy atom method and refined by least-square calculations to residuals R = 0.0586 and weighted R = 0.0668. The 2,2′-diaminobiphenyl ligand exhibits complete stereospecificity in its coordination to platinum(II) ion with λ chiral conformation.

Substitution reactions of Δ-cis-α-[Rh(SS-EDDP)Cl2]− (SS-EDDP = ethylenediamine-N-N′ -di-S-α-propionate) with R-alanine, S-alanine, R,S-alanine, and glycine yielded the corresponding amino acid rhodium(III) complexes of SS-EDDp with retention of configuration. Substitution reactions of Δ-cis-β-[Rh(SS-EDDp)Cl2]− with amino acids, however, resulted in isomerization to the Δ-cis-α- product or retention of configuration depending on the reaction condition. Electronic absorption, circular-dichroism, optical-rotatory-dispersion, and proton nuclear magnetic resonance spectra of those substitution products are reported.

The decarboxylation reaction of δ -cis-β-[Co(L1)(pdH)] complex yielded δ -cis-β-[Co(L1) (R-pro)], while the δ -cis-β-[Co(L2) (S-pro)] was obtained from the reaction of δ -cis-β-[Co(L2) (pdH)], where L1 is (3R)3-methyl-1, 6-bis[(2S)-pyrrolidin-2-yl]-2, 5-diazahexane, L2 is (3S) 3-methyl-1, 6-bis-[(2S)-pyrrolidin-2-yl]-2, 5-diazahexane, and pdH is the pyrrolidine-2, 2-dicarboxylate ion. The asymmetrically synthesized prolines were isolated via the decomposition of the decarboxylated complexes. The proline isolated from δ -cis-β-[Co(L1) (R-pro)] showed a specific rotation of +12.0, representing a 24% excess of R-proline over S-proline, while the proline isolated from δ -cis-β-[Co(L2) (S-pro)] showed a specific rotation of -10.0, indicating a 20% excess of S-proline over R-proline.

Upon decarboxylation Λ-cis-β-[COL1(amm)]2+ yielded Λ-cis-β-[CoL2(R-alaO)]2+, while Δ-cis-β-[CoL2(amm)]2+ gave Δ-cis-β-[CoL2(S-alaO)]2+; where L1=(3R)-3-methyl-1,6-bis[(2S)-pyrrolidin-2-yl]-2,5-diazahexane, L2=(3S)-3-methyl-1,6-bis[(2S)-pyrrolidin-2-yl]-2,5-diazahexane, amm =α-amino-α-methylmalonate and alaO = alaninate. The asymmetrically synthesized alanines were isolated but with extensive racemization via the decomposition of the decarboxylated complexes.

Ethylenediamine rhodium(III) complexes of ethylenediamine-N,N′-di-S-α-propionate have been prepared and the absolute configurations of these complexes have been assigned based on pmr and CD data.

The preparation and characterization of four complexes containing equimolar platinum(II) and (S)-methionine S-oxide are reported. The crystal and molecular structure of bis[μ-[(2S,SS)-2-amino-4-(methylsulfinyl)butanoato(2-)-S,O,μ-N]]- diplatinum(II), [Pt2{(2S,SS)-methionine S-oxide(2-)}2], Pt2[C5H9NO3S]2, is reported from single-crystal three-dimensional X-ray data collected by counter methods. The dinuclear complex crystallizes as rhombic prismatic crystals in space group P21 (C22; No. 4). Cell constants are a = 11.4826 (15) Å, b = 12.5007 (19) Å, c = 5.5839 (9) Å, and β = 96.684 (12)°. For Z = 2 this gives dcalcd = 2.99 g cm-3; dobsd = 2.97 (2) g cm-3. There were 2826 independent measurements, and the structure was refined to an R value of 0.0257. The complex has two bridging imido nitrogens (ionized α-amino groups from the amino acid) that link the platinum(II) centers in a four-membered ring. Each four-coordinate platinum atom is surrounded by nearly coplanar N, S, and O atoms from one methionine S-oxide ligand and the bridging imido nitrogen from the other. The two planes of coordination meet at the bridging imido groups at an angle of 129.59 (3)°. The molecule lacks C2 symmetry in the crystal lattice because of quite dissimilar hydrogen bonding arrangements involving the two imido nitrogen atoms and different oxygen atoms of a neighboring molecule in the crystal. The (2S,RS)-diastereomeric dimer is concluded to be similar in molecular structure by comparison of analyses, circular dichroism spectra, infrared spectra, and titration data. Comparison is also made with the structure and properties of the corresponding dichloromononuclear complexes.

The compounds (3R)3-methyl-1,6-bis[(2S)-pyrrolidin-2-yl]-2,5-diazahexane (L1) and (3S)3-methyl-l,6 bis[(2S)-pyrrolidin-2-yl]-2,5-diazahexane (L2) have been synthesized, together with their cobait(III) complexes, cis- and trans-[CoCl2L]+ and cis-[CoL(NO2)2]+ and cis-[CoL(C2O4)]+. The optically active quadridentate ligands co-ordinate stereospecifically in both the cis and trans complexes: in the cis geometry, L1 and L2 give stereo-specifically the Λ-cis-β and Δ-cis-β configurations, respectively; in the trans geometry, both ligands give optically active trans configurations. Electronic-absorption, circular-dichroism, and optical-rotatory-dispersionspectra are reported and used, together with chemical data, to assign the absolute configurations of the complexes.

The reaction of K 2PtCl 4 with L-2,3-diaminopropionic acid gives dichloro(L-2,3-diaminopropionic acid)platinum(II), which is oxidized by chlorine to tetrachloro(L-2,3-diaminopropionic acid)platinum(IV). Bis(ethylenediamine)(L-2,3-diaminopropionic acid)platinum(IV) chloride, [Pt(en) 2L-Dap]Cl 4, is obtained by reacting ethylenediamine with tetrachloro(L-2,3-diaminopropionic acid)platinum(IV). This complex is resolved into diastereoisomers through the d-tartrate salt. The resolved complex can be prepared directly from the reaction of L-2,3-diaminopropionic acid on optically active cis-dichlorobis(ethylenediamine)platinum(IV) chloride. Based on the known absolute configuration of (+) 365-cis-[Pt(en) 2Cl 2]Cl 2, it is proposed that the absolute configuration of (+) 312-[Pt(en) 2L-Dap]Cl 4 is Δ(λ enλ enλ Dap) and that of (-) 320-[Pt(en) 2L-Dap]Cl 4 is Λ(δ enδ enλ Dap). ORD, CD, and proton NMR spectra of the two diastereoisomers are discussed.