Synthesis and Resolution of (R,R)-(±)-1,1,4,7,10,10-Hexaphenyl-1,10-diarsa-4,7-diphosphadecane:  New Ligand for the Stereoselective Self-Assembly of Dicopper(I), Disilver(I), and Digold(I) Helicates

• Published in: Inorganic chemistry Vol. 41; no. 7; pp. 1897 - 1906
• Main Authors: Cook, Vernon C, Willis, Anthony C, Zank, Johann, Wild, S. Bruce
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 08-04-2002
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/ic010988d

Diphenylvinylarsine oxide reacts with 1,2-bis(phenylphosphino)ethane in the presence of potassium tert-butoxide to give the anti-Markovnikov product (R*,R*)-(±)/(R*,S*)-1,1,4,7,10,10-hexaphenyl-1,10-diarsa-4,7-diphosphadecane dioxide-1AsO,10AsO, which, upon reduction with HSiCl3/NEt3 in boiling acetonitrile, affords in 84% overall yield the di(tertiary arsine)−di(tertiary phosphine) (R*,R*)-(±)/(R*,S*)-diphars. After separation of the diastereomers by fractional crystallization, the (R*,R*)-(±) form of the ligand was resolved by metal complexation with (+)-di(μ-chloro)bis[(R)-1-[1-(dimethylamino)ethyl]-2-phenyl-C 2,N]dipalladium(II):  (R,R)-diphars, mp 87−88 °C, has [α]D 21 = −18.6 (c 1.0, CH2Cl2); (S,S)-diphars has [α]D 21 = +18.4 (c 1.0, CH2Cl2). The crystal and molecular structures of the complexes (M)-[M2{(R,R)-diphars}2](PF6)2 (M = Cu, Ag, Au) have been determined:  [M-(S Cu,S Cu)]-(−)-[Cu2{(R,R)-diphars}2](PF6)2, orthorhombic, P212121 (No. 19), a = 16.084(3) Å, b = 18.376(3) Å, c = 29.149(6) Å, Z = 4; [M-(S Ag,S Ag)]-(+)-[Ag2{(R,R)-diphars}2](PF6)2, triclinic, P1, a = 12.487(2) Å, b = 12.695(4) Å, c = 27.243(4) Å, α = 92.06°, β = 95.19°, γ = 98.23°, Z = 2; [M-(S Au,S Au)]-(−)-[Au2{(R,R)-diphars}2](PF6)2, orthorhombic, P212121 (No. 19), a = 16.199(4) Å, b = 18.373(4) Å, c = 29.347(2) Å, Z = 4. In the copper(I) and gold(I) helicates, each ligand strand completes 1.5 turns of an M helix in a parallel arrangement about the two chiral MAs2P2 stereocenters of S configuration. The unit cell of the silver(I) complex contains one molecule each of the parallel helicate of M configuration and the conformationally related double α-helix of M configuration in which each ligand strand completes 0.5 turns of an M helix about two metal stereocenters of S configuration. Energy minimization calculations of the three structures with use of the program SPARTAN 5.0 gave results that were in close agreement with the core structures observed.