MIXED CHLORIDE PHOSPHINE COMPLEXES OF THE DIRHENIUM CORE - 3 - NOVEL STRUCTURES WITH DIETHYLPHOSPHIDO-BRIDGES AND TERMINAL DIETHYLPHOSPHINES/

The interaction between octachlorodirhenium anions and diethylphosphin e has been shown to strongly depend on reaction conditions, mainly the nature of the solvent and the amount of phosphine, As a result, novel dirhenium products with oxidation states ranging from Re-II to Re-IV have been obtained. The reaction of [Re2Cl8](2-) with an excess of PEt 2H in dichloromethane or acetonitrile led to the first example of a fa ce-sharing complex of rhenium(IV) with three phosphido-bridges, namely [(Bu4N)-N-n] [Re-2(mu-PEt2)(3)Cl-6] (1). The unusual edge-sharing Re- 2(mu-PEt2)(2)Cl-4(PEt2H)(4) (2) complex of rhenium(III) with C-i core symmetry, containing both terminal phosphines and phosphidobridges, ha s been obtained by carrying out the reaction with an excess of PEt2H i n a benzene (or propanol) - HCl mixture at room temperature. A new exa mple of the 1,2,7,8-type of dirhenium(II) complex, Re2C14(PEt2H)4 (3), having diethylphosphine ligands located cis on each Re atom, has been isolated from the reaction of [Re2Cl8](2-) with PEt2H in an ethanol-H Cl medium. The solid-state structures of complexes 1-3 have been inves tigated by X-ray crystallography. Complexes 1 and 2 both crystallized in two forms: [(Bu4N)-N-n] [Re-2(mu-PEt2)(3)Cl-6] 1a, P2(1)/n with a = 10.482(1) Angstrom, b = 16.512(2) Angstrom, c = 23.986(2) Angstrom, b eta = 93.637(8)degrees, and Z = 4; [(Bu4N)-N-n][Re-2(mu-PEt2)(3)Cl-6]. 1.5 C7H8 1b, C2/c with a = 38.746(9) Angstrom, b = 10.322(2) Angstrom , c = 27.277(3), beta = 110.35(1)degrees, and Z = 8; Re-2(mu-PEt2)(2)C l-4(PEt2H)(4) 2a, P2(1)/n with a = 11.081(3) Angstrom, b = 11.029(3) A ngstrom, c = 151627(2) Angstrom; beta = 90.05(1)degrees, and Z = 2; 2b , P2(1)/c with a = 16.094(3) Angstrom, b = 15.193(3) Angstrom, c = 15. 548(3) Angstrom, beta = 100.113(3)degrees, and Z = 4. X-ray data for c omplex Re2Cl4(PEt2H)(4) 3 are as follows: P2(1)/n with a = 10.445(2) A ngstrom, b = 10.113(3) Angstrom, c = 13.473(2) Angstrom, beta = 102.17 (2)degrees, and Z = 2. Three bridging mu-PEt2 groups in the face-shari ng complex 1 span a short metal-metal distance of 2.4060(6) Angstrom, averaged over la and Ib, with a small Re-PEt2-Re angle of 61.34(7)degr ees. The rhenium-rhenium bond length in the edge-sharing complex 2 is 2.7545(7) Angstrom, averaged over 2a and 2b, while the bridging Re-PEt 2-Re angle is 72.16(6)degrees, and the P-Re-P angle for the terminal p hosphine ligands is 87.11(7)degrees. The Re-Re bond distance in 3, 2.2 533(8) Angstrom, is typical for triply bonded dirhenium complexes, and the P-Re-P angle for the cis phosphine groups is 93.12(6)degrees.