In the preceding papers 1) we reported new synthetic methods of some nitrogen-containing heterocyclic compounds, in which diaminocarbene palladium(I1) complexes generated from amines and PdC12(RNC)2 may be involved as key intermediates.
Here we wish to report the preparation of an imidazolidinylidene palladium(I1) complex (3_) by the intramolecular cyclization of a diaminocarbene palladium(I1) complex (2) which is prepared by the reaction of o!-aminoacetal (or D(-aminoketal) (L) with PdC12(RNC)2. Pd(II)C12(RNC)2 1 NH2tHy(OC2H5)2 J R'R" 1 Cl, _,,CNR $ /PdL /NHR Cl ':C -2C2H50H \NHfHf(OC2H5)2 2 R'R" (1) As shown in Table I, some diaminocarbene palladium(I1) complexes (2) were prepared by the reactions of c(-aminoacetals or ketal with PdC12(RNC)2 according to the reported procedure. 2) The structure of z2has been established by elemental analysis, IR, 3) NMR and molecular weight determination.3) Cyclization of the diaminocarbene palladium(I1) complexes (2) leading to the formation of imidazolidinylidene palladium(I1) complexes (2) was carried out as follows. A solution of 0.529 g (1 nol) of complex (2) and 0.344 g (2 mmol) of p-toluenesulfonic acid (or coned sulfuric acid (1 mmol)) in 9 ml of chloroform was stirred at room temperature under nitrogen for 24 hr. The chloroform solution was treated with Norit after aqueous work up and concentrated. The residue was triturated with ether-hexane (5:l) to precipitate imidazolidinylidene palladium(I1) complex (3&) in 82% yield. 2 : IR (KBr) 3430, 3200, 3100, 2218, 1573, 1450, and (nujol mull) 320, 292 cm-'; NMR (CDC13 with TMS) S 0.9Q2.5 (m, 20H), 3.6*4.3 (m, 2H)