Preparation of chiral diimino- and diaminodiphosphine ligands and their CuI and AgI complexes. X-ray crystal structures of [Cu(1S,2S-cyclohexyl-P2N2)][PF6] and [Ag(1R,2R-cyclohexyl-P2N2H4)][BF4]

Abstract

The interaction of optically pure 1R,2R-diammoniumyclohexane mono-(+)-tartrate and 1S,2S-diammoniumcyclohexane mono-(-)-tartrate with 2 equiv. of o-(diphenylphosphino)benzaldehyde in the presence of 2 equiv. of potassium carbonate in a refluxing ethanol/water mixture gave the optically pure condensation products N,N′-bis[o-(diphenylphosphino)benzylidene]-1R,2R-diiminocyclohexane [1R,2R-cyclohexyl-P2N2, (R,R)-I] and N,N′-bis[o-(diphenylphosphino)benzylidene]-1S,2S-diiminocyclohexane [1S,2S-cyclohexyl-P2N2, (S,S)-I], respectively, in good yield. Reduction of optically pure (R,R)-I and (S,S)-I with NaBH4 in ethanol gave the optically pure reduced products N,N′-bis[o-(diphenylphosphino)benzylidene]-1R,2R-diaminocyclohexane [1R,2R-cyclohexyl-P2N2H4, (R,R)-II] and N,N′-bis[o-diphenylphosphino)benzylidene]-1S,2S-diaminocyclohexane [1S,2S-cyclohexyl-P2N2H4, (S,S)-II], respectively, in good yield. The coordination behaviour of I and II toward salts of CuI and AgI have been examined. The interaction of [Cu(CH3CN)4][X] (X = ClO- 4, PF- 6) with 1 equiv. of optically pure L4 [L4 = (R,R)-I, (S,S)-I, (R,R)-II and (S,S)-II] gave the corresponding optically pure [CuL4][X] complexes, III-VI [IIIa, L4 = (R,R)-I, X = PF- 6, IIIb, L4 = (R,R)-I, X = ClO4, IV, L4= (S,S)-I, X = PF- 6; Va, L4 = (R,R)-II, X = PF- 6, Vb, L4 = (R,R)-II, X = ClO- 4, VI, L4 = (S,S)-II, X = PF- 6], in good yield. For the CuI complexes, the L4 ligand acted as a tetradentate ligand. However, a variable-temperature 31P [1H] NMR study of IIIb shows that at ambient temperature one of the imino groups of the tetradentate ligand undergoes rapid dissociation to form a tridentate ligand. The interaction of AgBF4 with 1 equiv. of optically pure L4 [L4 = (R,R)-I, (S,S)-I, (R,R)-II and (S,S)-II] gave the corresponding optically pure [AgL4][BF4] complexes, VII-X [VII, L4 = (R,R)-I; VIII, L4 = (S,S)-I; IX, L4 = (R,R)-II; X, L4 = (S,S)-II], in good yield. For the AgI complexes, the L4 ligand acted as a tetradentate ligand with the two amino groups coordinated unsymmetrically to the silver. A variable temperature 31P [1H] NMR study of VII suggests that at high temperature the complex exists as a tri-coordinated complex. The structures of IV and IX were established by X-ray diffraction studies. Copyright © 1996 Elsevier Science Ltd.