Stepwise Synthesis of the Functionalized Metallatetrahedron Re2(AuPPh3)2(μ-PCy2)(CO)7X (X = Cl, Br, I)

In THF solution the dirhenium complex Re 2 (μ-H)(μ-PCy 2 )(CO) 8 ( 1 ) reacts with an equimolar amount of LiPh at −100 °C to afford after warming up to room temperature within 1 h the salt Li[Re 2 (μ-H)(μ-PCy 2 )(C(Ph)O)(CO) 7 ] ( Li [2] ). Through cation exchange of Li + against PPh 4 +, Li [2] gives the airstable solid PPh 4 [2] in 86% yield. The selectivity of the LiPh attack at one of the four axial carbonyls in 1 was proved by the chiral shift reagent Eu(hfac) 3 which was dissolved in a CDCl 3 solution of PPh 4 [2] . The 1 H and 31 P NMR spectra show the diastereomeric resolution of the respective peaks in an integral ratio of 1:1 e.g. Δδ(μ-P) 0.43. The anion [2 - ] generates with 2 equiv of XAuPPh 3 (X = Cl, Br, I) in THF at room temperature within 15 min under release of the leaving group PhCHO the yellow cluster complexes Re 2 (AuPPh 3 ) 2 (μ-PCy 2 )(CO) 7 X ( 4 a − c ). Their precursor complex anions [Re 2 (μ-AuPPh 3 )(μ-PCy 2 )(CO) 7 X] - ( 3 a − c ) are obtained from 1 and an equimolar amount of XAuPPh 3 or from the deauration by treatment of 4a (X = Cl) with 1 equiv of LiPh via a transmetalation reaction. Such anions are isolable as salts, N(PPh 3 ) 2 [3 a − c ] . All new cluster complexes are identified by means of 1 H NMR, 31 P NMR and ν(CO) IR spectroscopic measurements, Li [2] and 4a (X = Cl) additionally by means of X-ray single-crystal structure analyses. Li [2] crystallizes triclinic, space group P 1̄, Z = 2, a = 10.536(2) Å, b = 11.433(2) Å, c = 19.125(3) Å, α = 98.01(1)°, β = 89.94(1)°, and γ = 112.22(1)°; 4a crystallizes monoclinic, space group P 2 1 / c, with Z = 4, a = 18.615(5) Å, b = 13.606(2) Å, c = 24.223(6) Å, and β = 105.14(2)°. The molecular structure of Li [2] shows a μ-H-, μ-P-bridged Re−Re bond of 3.1667(7) Å, the one of 4a a tetrahedrally shaped Re 2 Au 2 core with a μ-P-bridged Re−Re edge of 3.2680(10) Å.