1-triorganylstannyl-1,2,4-triphosphole: A versatile starting material for phosphorus-rich cage compounds and pi-complexes

The reaction of Na[3,5-di(tert-butyl)-1,2,4-triphospholyl] (Na-2) with R3Sn Cl (R = Ph, Me, nBu) affords the 1-triorganylstannyl-3,5-di(tert-butyl)-1,2 ,4-triphospholes 4a-4c in very good yields. A rapid suprafacial [1,5]-sigma -tropic shift of the SnPh3 group in 4a with Delta G(double dagger)=31.5 kJ mol(-1) indicates a labile P-Sn bond-one of the characteristic features of 4a-4c. Compound 4a provides access to the polycyclic organophosphorus cage compound C(4)tBu(4)P(5)-SnPh3 (6) in a high-yield chemoselective and diaste reospecific cycloaddition reaction; compound 4b transfers 1,2,4-triphosphol yl ligands quantitatively to Sn-II to form a hexaphosphastannocene derivati ve. Compound 4a displaces the ethene ligands in [CpCo(C2H4)(2)] to form the stannyltriphosphole complex [Cp(eta(4)-1,2,4-C(2)tBu(2)P(3)SnPh(3)) Co] (1 0). The absolute positive sign (reduced coupling constant K-1(Sn-119, P-31) < 0) of (1)J(Sn-119, P-31) = + 1611.7 Hz for 10 has been determined by C-1 3{H-1,P-31} heteronuclear triple-resonance experiments. Reaction of 10 with another equivalent of [CpCo(C2H4)(2)] breaks the Sn-P bond and replaces it with a Sn-Co bond to yield the extremely slipped 34 valence electron (VE) triple-decker sandwich complex [CpCo(mu,eta(5):eta(2)-3,5-di(tert-butyl)1,2 ,4-triphospholyl)Co(SnPh3)Cp] (11). The central ligand exhibits unique stru ctural features. Oxidation or thermolysis of 11 affords [Cp(1-phenyl-3,5-di (tert-butyl)-(eta(4)-1,2,4-triphosphole)Co] (12) by elimination of a [Cp(di phenylstannylene)Co] unit.