Transition metal–carbon bonds. Part 49. The action of amines on cis-[PtCl2(PPrn3)(C3H4)]: crystal structures of the complexes [PtCl(PPrn3){C(CH2)CH2NHBut}](four-membered ring) and [Pt2Cl2(PPrn3)2{C(CH2)CH2NHMe}2](eight-membered ring)

Abstract

Addition of NR₃(R = Me or Et) to the allene complex cis-[PtCl₂(PPrⁿ₃)(C₃H₄)] rapidly gives the zwitterionic alkenyl complexes [PtCl₂(PPrⁿ₃){C(CH₂)CH₂NR₃}]. Addition of NH₂Bu^t to the allene complex at or below –20° C gives an analogous complex, viz.[PtCl₂(PPrⁿ₃){C(CH₂)CH₂NH₂Bu^t}], but this with base, i.e. an excess of NH₂Bu^t or preferably Na[OPrⁱ], immediately cyclizes to give [[graphic omitted]HBu^t}](5) the crystal structure of which has been determined and shown to contain a four-membered ring. Treatment of the allene complex with an excess of methylamine gives [[graphic omitted]HMe}₂](6a) the crystal structure of which has also been determined and shown to contain an eight-membered ring. Benzylamine gives an analogous complex. Proton, ³¹P, and ¹⁹⁵Pt n.m.r. data are given and discussed, as are i.r. data. Crystals of (5) are monoclinic, space group C2/c, with a= 19.653(3), b= 11.538(2), c= 18.785(2)Å, β= 107.10(1)°, and Z= 8; R= 0.036 for 2 300 independent reflections. The complex (6a) is monoclinic, space group P2₁/n, with a= 11.315(3), b= 13.782(2), c= 11.385(3)Å, β= 100.76(2)°, and Z= 2; R= 0.032 for 2 083 independent reflections.