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Mixed Chloride/Phosphine Complexes of the Dirhenium Core. 3. Novel Structures with Diethylphosphido-bridges and
F. Albert Cotton1, Evgeny V. Dikarev, Marina A. Petrukhina
1Laboratory for Molecular Structure and Bonding, P.O. Box 300012, Department of Chemistry, Texas A&M University, College Station, Texas 77842-3012.
Abstract:
The interaction between octachlorodirhenium anions and diethylphosphine 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 [Re(2)Cl(8)](2)(-) with an excess of PEt(2)H in dichloromethane or acetonitrile led to the first example of a face-sharing complex of rhenium(IV) with three phosphido-bridges, namely [Bu(n)(4)N][Re(2)(&mgr;-PEt(2))(3)Cl(6)] (1). The unusual edge-sharing Re(2)(&mgr;-PEt(2))(2)Cl(4)(PEt(2)H)(4) (2) complex of rhenium(III) with C(i)() core symmetry, containing both terminal phosphines and phosphido-bridges, has been obtained by carrying out the reaction with an excess of PEt(2)H in a benzene (or propanol) - HCl mixture at room temperature. A new example of the 1,2,7,8-type of dirhenium(II) complex, Re(2)Cl(4)(PEt(2)H)(4) (3), having diethylphosphine ligands located cis on each Re atom, has been isolated from the reaction of [Re(2)Cl(8)](2)(-) with PEt(2)H in an ethanol-HCl medium. The solid-state structures of complexes 1-3 have been investigated by X-ray crystallography. Complexes 1 and 2 both crystallized in two forms: [Bu(n)(4)N][Re(2)(&mgr;-PEt(2))(3)Cl(6)] 1a, P2(1)/n with a = 10.482(1) Å, b = 16.512(2) Å, c = 23.986(2) Å, beta = 93.637(8) degrees, and Z = 4; [Bu(n)(4)N][Re(2)(&mgr;-PEt(2))(3)Cl(6)].1.5 C(7)H(8) 1b, C2/c with a = 38.746(9) Å, b = 10.322(2) Å, c = 27.277(3) Å, beta = 110.35(1) degrees, and Z = 8; Re(2)(&mgr;-PEt(2))(2)Cl(4)(PEt(2)H)(4) 2a, P2(1)/n with a = 11.081(3) Å, b = 11.029(3) Å, c = 15.627(2) Å, beta = 90.05(1) degrees, and Z = 2; 2b, P2(1)/c with a = 16.094(3) Å, b = 15.193(3) Å, c = 15.548(3) Å, beta = 100.98(3) degrees, and Z = 4. X-ray data for complex Re(2)Cl(4)(PEt(2)H)(4) 3 are as follows: P2(1)/n with a = 10.445(2) Å, b = 10.113(3) Å, c = 13.473(2) Å, beta = 102.17(2) degrees, and Z = 2. Three bridging &mgr;-PEt(2) groups in the face-sharing complex 1 span a short metal-metal distance of 2.4060(6) Å, averaged over 1a and 1b, with a small Re-PEt(2)-Re angle of 61.34(7) degrees. The rhenium-rhenium bond length in the edge-sharing complex 2 is 2.7545(7) Å, 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 phosphine ligands is 87.11(7) degrees. The Re-Re bond distance in 3, 2.2533(8) Å, is typical for triply bonded dirhenium complexes, and the P-Re-P angle for the cis phosphine groups is 93.12(6) degrees.