Stereochemical investigation of the addition of primary and secondary aliphatic amines to the nitrile complexes cis- and trans-[PtCl 2(NCMe) 2]. X-ray structures of the amidine complexes trans-[Pt(NH 2Pr i) 2{ ZN(H)C(NHPr i)Me}]Cl 2·4H 2O and trans-[PtCl 2(NCMe){ EN(H)C(NMeBu t)Me}

Abstract

The reactions of cis-[PtCl 2(NCMe) 2] with a fivefold excess of the primary aliphatic amines RNH 2 (R=Me, Et, Pr i, Bu t) in CH 2Cl 2 at −10 °C afford in high yield the bis-amidine complexes cis-[PtCl 2{ ZN(H)C(NHR)Me} 2], where both amidine ligands assume the Z configuration. The corresponding reactions of trans-[PtCl 2(NCMe) 2] with RNH 2 (R=Me, Et, Bu t) give a mixture of the bis-amidine trans-[PtCl 2{ ZN(H)C(NHR)Me} 2] and the mono-amidine trans-[PtCl 2(NCMe){ ZN(H)C(NHR)Me}] derivatives, which could be isolated as pure products operating with a platinum nitrile complex:amine molar ratio of 1:50 or 1:1, respectively. The reaction of trans-[PtCl 2(NCMe) 2] with a 50-M excess of Pr iNH 2 affords the bis-amidine bis-amine dicationic complex trans-[Pt(H 2NPr i) 2{ ZN(H)C(NHPr i)Me} 2]Cl 2, which has been characterized also by X-ray diffraction analysis. The reactions of cis- and trans-[PtCl 2(NCMe) 2] with the secondary aliphatic amines R′R″NH yield the bis-amidine complexes cis- and trans-[PtCl 2{ EN(H)C(NR′R″)Me} 2] (R′, R″=Et) and/or cis- and trans-[PtCl(NCMe){ EN(H)C(NR′R″)Me} 2] (R′, R″=Et; R′=Me, R″=Bu t), where the amidine ligands have the E configuration. The compound trans-[PtCl 2(NCMe){ EN(H)C(NMeBu t)Me}] has been characterized by single crystal X-ray diffraction. All the complexes have been characterized by IR, 1H and 13C NMR spectroscopies. The Z or E configuration of the amidine ligand can be readily deduced by 1H NMR data.