| Abstract |
Treatment of trans-[PtCl2(NCR)(2)] (1) \R = CH2CO2Me (1a), Ph (1b)\ with (R*)-camphor oxime (C9H16)C=NOH (2) gives access to the optically active mixed imine-nitrile complexes trans-(R*)-[PtCl2\NH=C(R)ON=C(C9H16)(NCR)] (4), which, on reaction with ketoximes (RRC)-R-1-C-2=NOH (3) \R-1 = R-2 =Me (3a), C4H8 (3b)\, give the chiral unsymmetric bis(imine) complexes trans-(R*)-[PtCl2\NH=C(R)ON=C(C9H16)\NH = C(R) - ON = (CRR2)-R-1\] (6) in moderate yields. An alternative route involves the reaction on the starting complexes 1 with ketoximes 3 to give the mixed imine-nitrile complexes trans-[PtCl2\NH=(CR)ON=(CRR2)-R-1\(NCR)] (5), followed by reaction of the latter with (R*)-camphor oxime (2) to afford products 6 in similar yields. Treatment of complexes 1 or 4 with two or one equivalent of 2, respectively, gives the symmetrical bis-(imine) complexes trans-[PtCl2\NH=C(R)ON=C(C9H16)\(2)] (7) These reactions are accelerated by microwave irradiation to afford, in better yields (71-50\%), the same products. The new optically active diimine compounds NH = C(R)ON=C-(C9H16) (8) are quantitatively liberated upon reaction of complexes 7 with a diphosphane. The chiral diimino ester 8a (R = CH2CO2Me) acts as a protic nucleophile and efficiently couples with the coordinated nitrile in 4 to give the new optically active, mixedm unsymmetric imine-1,3-diaza-1,3-diene complexes trans-(R*, R*)-[PtCl2(NH=C(R)ON=C(C9H16) \NH = C(R)N=C(CH2CO2Me)ON=C(C9H16)\] (9). Diimino ester 8a with an acidic alpha-methylene group also reacts with acyclic nitrones -O+N(Me)=C(H)R (10) to afford stereoselectively the (E)-cyanoalkenes (N C)C(CO2Me)=C(H)R (11) \R = 4-MeC6H4 (11a), 2,4,6-Me3C6H2 (11b)\. All of these compounds were characterised by IR and NMR (H-1, C-13, and Pt-195 for metal complexes) spectroscopy, ESI-MS or FAB-Ms, elemental analysis, and X-ray diffraction analysis (for 5C and 7b). ((C) Wiley-VCH Verlag GmbH \& Co.H=KGaA, 69451 Weinheimm Germany, 2008). |
