First silver complexes of tetrahydropyrimid-2-ylidenes

The syntheses and characterizations of homoleptic silver(I) carbene complexes of the type LAgCl (3) and [L2Ag](2)(+)[Pd2Cl6](2-) (4) (L = dime sityltetrahyd ropyrimid-2-ylidene) are described. 3 was obtained by reaction of the corresponding tetrahydropyrimidinium salt with silver(I) oxide. Subsequent reaction of 3 with Pd(CH3CN)(2)Cl-2 afforded complex 4. The crystal structure of 3 has been determined to be a monomer in the solid state. The C-13 NMR spectra of both 3 and 4 exhibit C-13-Ag-107,Ag-109 coupling in solution. Furthermore, both compounds show a downfield shift of the carbene carbon of about 20 ppm to about 205 ppm in the C-13 NMR compared to five-membered ring silver(I) carbene complexes. Unlike other silver-carbene complexes, 3 does not undergo ligand exchange and can thus not be used for carbene transfer to other metals. (C) 2004 Elsevier B.V. All rights reserved.