The syntheses of a number of rhenium(I) tris(acetylene) compounds are
presented, including an improved synthesis of ReI(RC=CR)3 (1a, R = Me;
lb, R = Et). Reaction of the low-valent oxo anions NaRe(O)(RC=CR)2 wi
th Me3SiCl in the presence of RC=CR yields Re(OSiMe3)-(RC=CR)3 (2). Co
lorless 2a crystallizes in the tetragonal space group I4(1)/a, with a
= 27.631(3) A, c = 9.699(1) A, and Z = 16. The structure is similar to
those of isoelectronic tungsten(0) tris(acetylene) complexes such as
W(CO)(PhC=CPh)3. Compounds 2 react readily with acids and acidic alcoh
ols to form Re(OR)(RC=CR)3 (HOR = acetic acid, p-toluenesulfonic acid,
phenol, (CF3)2CHOH); reaction with HCI (g) yields ReCl(RC=CR)3. In ad
dition, the Lewis acids Me3SiCl and Me3SiOTf and 2 form ReCl(RC=CR)3 a
nd Re(OTf)(RC=CR)3 (3), along with (Me3Si)20 (OTf = CF3SO3, triflate).
Compounds 3 can also be synthesized from 1 and AgOTf or by addition o
f 2 equiv of Me3SiOTf to NaRe(O)(RC=CR)2. The triflate ligand appears
to be covalently coordinated from IR and F-19 NMR spectroscopy, but it
is readily displaced by better ligands (L = PMe3, OPMe3, CH3CN, pyrid
ine, pyridine N-oxide) to give [Re(L)(R=CR)3]OFt complexes. Weakly coo
rdinating ligands form equilibrium mixtures (e.g., 3 + H2O reversible
[Re(H2O)(RC=CR)3]OTf (4)). Reactions of 3 with NaOMe in MeOH/C6H6 yiel
d methoxide complexes, Re(OMe)(RC=CR)3(5). Re(OMe)(EtC=CEt)3(5b) react
s with 2-butyne by acetylene exchange. The reaction occurs within 2 da
ys at 25-degrees-C and appears to be first order in 5b and zero order
in 2-butyne, consistent with a dissociative pathway. The rates of acet
ylene exchange for Re(OR')(RC=CR)3 Vary widely in the order OMe almost
-equal-to OSiMe3 > OPh >> OAc, OTf, paralleling the basicity of the an
ionic ligands. Unlike the related hydroxide compound,10 the methoxide,
phenoxide, and acetate complexes do not rearrange to the stable oxo-a
lkyl or oxo-acyl compounds Re(O)R'(RC=CR)2 (R' = Me, Ph, C(O)Me), eith
er thermally or photochemically.