Dinitrile complexes with a rare cis-diphosphine rhenium(I) centre: syntheses, properties and cis- to trans-isomerization

Activation of organonitriles toward beta-electrophilic attack. Synthesis and characterization of methyleneamide (azavinylidene) complexes of rhenium

Treatment of the nitrile complexes cis-[ReCl(NCR)(dppe)(2)] (R = aryl; dppe = Ph(2)PCH(2)CH(2)PPh(2)) with [Et(2)OH][BF(4)] or SiMe(3)CF(3)SO(3) in CH(2)Cl(2) led to the formation of the methyleneamide (alkylideneamide or azavinylidene) compounds cis-[ReCl[NC(E)C(6)H(4)X-4](dppe)(2)]Y [E = H; X = OMe (1b), Me (1c), H (1d), F (1e), or Cl (1f), Y = BF(4); E = SiMe(3), X = Me (1c'), Y = CF(3)SO(3)] and trans-[ReCl[NC(H)C(6)H(4)X-4](dppe)(2)][BF(4)] [X = NEt(2) (2a), OMe (2b), H (2d), F (2e), or Cl (2f)]. They were characterized by multinuclear NMR spectrometry and X-ray crystallography (2e) which shows that the methyleneamide ligand exhibits linear (three-electron donor) geometry and behaves as a strong pi-electron acceptor. The complex (31)P[(1)H] and (1)H [NC(H)C(6)H(4)X-4] NMR patterns for the cis isomers were analyzed as ABCD and ABCDX (X part) spin systems, respectively. Complexes 1 and 2 undergo deprotonation by base to form the trans isomers of the corresponding nitrile complexes, trans-[ReCl(NCC(6)H(4)X-4)(dppe)(2)] [X = NEt(2) (3a), OMe (3b), H (3d), F (3e), or Cl (3f)] whose spectroscopic data are also presented and which on protonation give the corresponding trans isomers of the methyleneamide complexes (2). Reactions of cis-[ReCl(NCR)(dppe)(2)] with [Et(3)O][PF(6)] resulted in their oxidation and isomerization to afford trans-[ReCl(NCC(6)H(4)X-4)(dppe)(2)][PF(6)] [X = Me (4c), H (4d), or Cl (4f)].

Iminoacylation. 1. Addition of Ketoximes or Aldoximes to Platinum(IV)-Bound Organonitriles

The metal-mediated iminoacylation reaction of ketoximes or aldoximes upon treatment with the organonitrile platinum(IV) complexes trans-[PtCl(4)(RCN)(2)] proceeds under relatively mild conditions in acetonitrile (R = Me) or in chloroform (R = CH(2)Ph, Ph) to give trans-[PtCl(4)(NH=C(R)ON=CR(1)R(2))(2)] (R(1) = R(2) = Me; R(1)R(2) = C(4)H(8), R(1)R(2) = C(5)H(10), R(1)R(2) = (H)Ph, R(1)R(2) = (H)C(6)H(4)(OH)-o; 1-14) in 90-95% yield. All these compounds were characterized by elemental analyses (C, H, N, Cl, Pt), FAB mass spectrometry, and IR and (1)H, (13)C{(1)H}, and (195)Pt NMR spectroscopies. X-ray structure determinations of [PtCl(4)(NH=C(Me)ON=CMe(2))(2)] (1) and [PtCl(4){NH=C(Me)ON=C(C(5)H(10))}(2)] (3) disclosed their overall trans-configuration and the amidine one-end rather than N,N-bidentate coordination mode of the N-donor ligands. The iminoacyl species are in E-conformation which is held by a rather weak N-H.N hydrogen bond between the amidine =NH atom and the oxime nitrogen with the following observed distances and angles for 1 and [3]: N(1).N(2), and N(1)-H, N(1)H.N(2) are 2.605 [2.592], 0.74 [0.71], and 2.20 [2.25] Å; N(1)-H.N(2) is 115 degrees [111 degrees ]. No evidence of the Z-conformation in solution was obtained by NMR spectroscopy. Compounds trans-[PtCl(4)(NH=C(R)ON=CR(1)R(2))(2)] are unexpectedly stable toward hydrolysis both in the solid state and in solutions.