Stereochemical investigation of the addition of primary and secondary aliphatic amines to the nitrile complexes cis- and trans-[PtCl2(NCMe)2].: X-ray structures of the amidine complexes trans-[Pt(NH2Pri)2{Z-N(H)=C(NHPri)Me}]Cl2•4H2O and trans-[PtCl2(NCMe){E-N(H)=C(NMeBut)Me}]

The reactions of cis-[PtCl2(NCMe)(2)] with a fivefold excess of the primary aliphatic amines RNH2 (R = Me, Et. Pr', Bu-t) in CH2Cl2 at - 10 degreesC afford in high yield the bis-amidine complexes cis-(PtCl2{Z-N(H)=C(NHR)Me}(2)], where both amidine ligands assume the Z configuration. The corresponding reactions of trans-[PtCl2(NCMe)(2)] with RNH2 (R = Me, Et, Bu-t) give a mixture of the bis-amidine trans-[PtCl2{Z-N(H)=C(NHR)Me}(2)] and the mono-amidine trans -[PtCl2(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-[PtCl2(NCMe)(2)] with a 50-M excess of Pr'NH2 affords the bis-amidine bis-amine dicationic complex trans-[Pt(H2NPri)(2) {Z-N(H)=C(NHPr')Me}(2)]Cl-2, which has been characterized also by X-ray diffraction analysis. The reactions of cis- and trans-[PtCl,(NCMe)21 with the secondary aliphatic amines R'R"NH yield the bis-amidine complexes cis- and trans-[PtCl2 {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-[PtCl2(NCMe){E-N(H)=C(NMeBut)Me] has been characterized by single crystal X-ray diffraction. All the complexes have been characterized by IR, H-1 and C-13 NMR spectroscopies. The Z or E configuration of the amidine ligand can be readily deduced by H-1 NMR data. (C) 2002 Elsevier Science B.V. All rights reserved.