SELENIUM AND TELLURIUM DERIVATIVES OF A MONOCARBON PLATINACARBABORANECOMPLEX

The reaction between Na[Pt(PEt3)(2)(eta(5)-7-CB10H11)] 1 and PhSeCl in thf (tetrahydrofuran) afforded a mixture containing the isomeric spec ies [Pt(SePh)(PEt3)(eta(5)-n-SePh-7-CB10H10)] (n = 8 2a or 9 2b) and t he compound [Pt(SePh)(PEt3) {eta(5)-8-O(CH2)(4)Cl-7-CB10H10}] 3. The m olecular structures of complexes 2a and 3 were established by X-ray cr ystallography. Both molecules have Pt(SePh)(PEt3) groups with the plat inum atoms pentahapto co-ordinated by nido-7-CB10 cage frameworks. In 2a the cage substituted SePh group is attached to the boron atom in th e a site with respect to the carbon in the CBBBB ring ligating the pla tinum and this is true also of the O(CH2)(4)Cl substituent in 3. The i somers 2 are also formed when PhSeSePh is used instead of PhSeCl. Trea tment of the salt 1 with PhTeI in thf yielded a mixture of [Pt(PEt3)(2 ) {eta(5)-9-Te(Ph)CH2Cl-7-CB10H10}] 4 and Pt-2(TePh)(mu-TePh)(2)(PEt3) (2)(eta(5)-2-CB10H11)] 5. Single-crystal X-ray diffraction studies wer e employed to establish the formulations and molecular structures of b oth molecules. Compound 4 is a charge-compensated platinacarbaborane w ith a Pt(PEt3)(2) group and with the nido-7-CB10 framework carrying a Te(Ph)CH2Cl moiety at the boron vertex situated in the beta site with respect to the carbon in the CBBBB ring ligating the platinum. Complex 5 is a diplatinum species in which Pt(TePh)(PEt3) and Pt(PEt3)(eta(5) -2-CB10H11) units are bridged by two TePh groups. The X-ray study reve aled that in forming compound 5 from the reagent 1 the nido-7-CB10H11 cage system has undergone an unusual polytopal rearrangement to a nido -2-CB10H11 framework.