Reaction of bis(diisopropy1amino)phosphenium triflate (l[CF3S03]) with silver salts AgY [Y-= CF3C0, (Za), CF:{-SO, (2b), CH3C0y (2c)l affords neutral complexes [[(iPr,N),(Y)P) Ag(OS02CF3)] (3a-c). While 3a, c are stable up to ambient temperature, 3b is only stable at low temperature and in equilibrium with the cation 1. The constitution of 3a-c was derived from multinuclear (IH, I3C, "P, ""Ag) NMR spectra. Compound 3a was further studied by X-ray single-crystal diffractommetry which showed the presence of dimeric units with p2-bridging triflate ligands and three-coordinate silver atoms with a planar T-shaped coordination geome try. Reaction of 4 -chloro-l ,3-bis (2,6-dime thylphenyl) -1,3,2-diazaphospholenium triflate (4[CF3S03]) with 2a, c affords equilibrium mixtures whose 31P-and IogAg-NMR spectra suggested the presence of silver complexes 5a, c with constitutions similar to those of 3a, c besides unreacted cation 4. No reaction was observed between 4[CF,SO,] and 2b. A common mechanism accounting for the different outcome of the individual reactions will be discussed.The ability of phosphenium ions RZP+ to form stable cationic transition-metal complexes of type I has long been recognised[ll. Considering that the free cations are isoelectronic and isolobal with neutral carbenes, the complexes I share the same relation with the carbene complexes I1 which are of considerable importance in organic and organometallic chemistry[2].Scheme 1 However, whereas carbene complexes are known for most d-block transition metals, examples of phosphenium complexes have hitherto been restricted mainly to group 6 (Mo, w) and group 8 (Fe) metals; lately, a single nickel phosphenium complex was reported [?]. The recently renewed interest in carbene complexes of the coinage m e t a l~[~~~] stimulated us to investigate if similar phosphenium complexes of these metals can be obtained. Knowing that many phosphorus ligands form stable coordination compounds with Ag+, we studied the reactivity of stable diaminophosphenium and 1,3,2-diazaphospholenium cationsL61 (which can be regarded as the isolobal and isoelectronic counterparts to the stable imidazoyl carbenesf71) towards silver salts AgY (Y-= CF3SOT. CF,CO,, CH3CO;).
ReactionsReaction of bis(diisopropy1amino)phosphenium triflate (1[CF3S03]) [s] with one equivalent of CF3C02Ag (2a) in CH2C12 afforded according to an "P-NMR spectroscopic assay a single product which was isolated in moderate yield as colourless, air-and moisture-sensitive crystals. The product was identified by NMR spectroscopy and by X-ray crystal structure analysis as the phosphane complex 3a featuring a four-coordinate phosphorus centre, rather than an anticipated three-coordinate phosphenium complex. In contrast to the known behaviour of phosphanes and p h o s p h i t e~ [~~~~] , no evidence for the formation of complexes of the type [Ag(PR3),]+ (pz > 1) was obtained when 3a was treated with an excess of phosphenium salt. Similar reactions as with CF3C02Ag were observed with 1[CF3S03] and C F 3 S 0 3 h g (2b) or CH...
