THE SYNTHESES AND STRUCTURES OF SALTS OF THE OCTACHLORODIRHENATE(III)AND OCTACHLORODIOSMATE(III) ANIONS WITH THE 1,2-BIS(TRIPHENYLPHOSPHONIUM)ETHANE CATION

The reactions of cis-Re-2(O2CCH3)(2)Cl-4(py)(2) or (n-Bu4N)(2)Re2Cl8 w ith PR3 (R = Cy or Ph) in refluxing 1,2-dichloroethane afford the bis- phosphonium salts (R3PCH2CH2PR2)Re2Cl8; the crystal structure of the d erivative where R = Ph shows that this is only the second example of a salt of the [Re2Cl8](2-) anion in which a 3-fold orientational disord er of the Re-Re units is encountered. A cation exchange reaction betwe en (Ph3PCH2CH2PPh3)Cl-2 and (n-Bu4N)(2)Os2Cl8 affords (Ph3PCH2CH2PPh3) Os2Cl8, which possesses an Os-Os bond distance of 2.1896(3) Angstrom a nd is the second example of a crystal structure of a [Os2Cl8](2-) salt in which a fully staggered rotational geometry is present. (C) 1997 E lsevier Science Ltd.