REACTIONS OF AZIRIDINE WITH PLATINUM(II) NITRILES - FORMATION OF (AZIRIDINO)AMIDINES AND 2-IMIDAZOLINES AND X-RAY STRUCTURE OF TRANS-[PTCL2(N(H)=C(PH)NCH2CH2)2]

The amidine complexes cis- and trans-[PtCl2{NH=C(R)NCH2CH2}2] (R = Me, Ph) (1-4) are prepared by reaction of the nitrile complexes cis- and trans-[PtCl2(NCR)2] with two to four equiv. of aziridine, HNCH2CH2, at room temperature. All complexes were characterized by their IR, H-1 a nd C-13 NMR spectra, and by their microanalytical data and mass spectr a. These complexes are all likely associated to form dimers either in the solid state and partially in solution as evidenced by molecular we ight measurements carried out for trans-[Pt-Cl2{NH=C(Ph)NCH2CH2}2] (3) , and on the X-ray structure investigation of this complex. Complex 3 crystallizes in the monoclinic system with P2(1)/n space group, with a = 11.039(3), b = 10.883(3), c = 34.349(5) angstrom, beta = 90.34(4)-d egrees, V = 4127(1) angstrom3, Z = 8. The structure was solved and ref ined to R = 0.025 and R(w) = 0.028 for 4748 reflections with I greater -than-or-equal-to 3sigma(I). Complex 3 consists of 'dimers' [Pt2Cl4L4] (L = HN = C(Ph)NCH2CH2) formed by two [PtCl2L2] units intermolecularl y associated through four N-H...Cl hydrogen bond interactions (H...Cl approximately 2.4 angstrom) involving the chlorines and the amidinic p rotons. The H-1 and C-13 NMR spectra of 1-4 show that there is relativ ely free rotation around the C-N(aziridine) bond and also that they ar e formed as a complex mixture of isomers arising either from restricte d rotation around the C=N bond or around the Pt-N(amidine) bond. Compl ex 3 reacts with two equiv. of cis-Ph2PCH=CHPPh2 to give [Pt(cis-PPh2P CH=CHPPh2)2](Cl2) and formation of the amidine NH=C(Ph)NCH2CH2 togethe r with 2-(phenyl)imidazoline, N=C(Ph)N(H)CH2CH2, which is the only iso lated product when the reaction mixture is heated at 90-degrees-C for a few hours or stirred for a few days at room temperature. A mechanism is proposed for the reactions of nitriles with aziridine and the conv ersion of amidines to 2-imidazolines.