TRANSITION-METAL STANNYL COMPLEXES .5. SYNTHESIS OF ANIONIC STANNYL COMPLEXES K[(PI-AROMATE)(CO)2CRSNPH3] AND REACTION WITH ORGANOTIN HALIDES TO BIS(STANNYL) COMPLEXES (PI-AROMATE)(CO)2CR(SNPH3)(SNR3) (PI-AROMATE=C6H6-NMEN)

The anionic stannyl complexes K[(pi-arene)(CO)2CrSnPh3] (pi-arene = C6H6, 1,3,5-C6H3Me3, 1,2,4,5-C6H2Me4, C6Me6) were prepared by deprotonation of the corresponding hydrido stannyl complexes (pi-arene)(CO)2Cr(H)SnPh3 with KH. Cyclovoltammetric investigations showed that the anionic complexes are reversibly oxidized and that the oxidation potential increases from pi-arene = benzene (E1/2 = -0.481 V) to pi-arene = C6Me6 (E1/2 = -0.677 V). The influence of the electronic and steric properties of the pi-arene ligand and the halide on the ratio between substitution and redox reaction was investigated by reaction with different organotin halides. With Me3SnCl or Me2SnCl2 the anionic stannyl complexes exclusively give the substitution products (pi-aromat)(CO)2Cr(SnPh3)-(SnMe2X) (X = Me, Cl). Upon reaction with Ph3SnCl or Ph2SnCl2, oxidation becomes increasingly competitive when the pi-arene ligand is successively substituted by methyl groups; for pi-benzene only formation Of (pi-C6H6)(CO)2Cr(SnPh3)(SnPh2X) (X = Me, Cl) is observed, for pi-C6Me6 only oxidation. Products arising from both substitution and oxidation are found for pi-C6H3Me3.