Conversion of Nitriles Into Delta-2-1,3-oxazolines In Platinum(II) Complexes - Crystal-structure of trans-[PtCl2(N=C(Bu(t))OCh2Ch2)2]

The reactions of cis- and trans-[PtCl2(NCR)2] (R = p-MeC6H4, p-CF3C6H4, o-MeC6H4, Et, Pr(n), Pr(i) or Bu(t)) complexes with 2 equivalents of -OCH2CH2Cl, generated by deprotonation of HOCH2CH2Cl with LiBu(n), afford in high yield the bis(DELTA2-1,3-oxazoline) derivatives cis-and trans-[PtCl2{N=C(R)OCH2CH2}2]. The complexes have been characterized by their elemental analyses, IR, H-1 NMR, C-13-{H-1} NMR and FAB mass spectra. The structure of trans-[PtCl2{N=C(But)OCH2CH2}2] was established also by X-ray crystallography: monoclinic, space group P2(1)/n, a = 11.233(2), b = 8.741(2), c = 9.394(2) angstrom, beta = 101.61(3)degrees and Z = 2; R = 0.038 (R' = 0.042) for 2514 measured reflections with I greater-than-or-equal-to 3sigma(I). The N-C(R) and (R)C-O bond distances of 1.284(5) and 1.335(5) angstrom suggest that there is extensive electron delocalization within the N-C(R)-O system. The co-ordination geometry around Pt(II) is planar and the oxazoline rings are only slightly twisted. The formation of DELTA2-1,3-oxazolines from platinum(II)-co-ordinated nitriles has also been examined using HOCH2CH2Cl in the presence of the weak base NEt3. These reactions proceed through the initial formation of the bis(imido ester) complexes [PtCl2{NH= C(R)OCH2CH2Cl}2], present as their (Z,Z), (EE) and (E,Z) conformers, which slowly convert to the final cyclic DELTA2-1,3-oxazoline derivatives.