Mixed-transition-metal acetylides: synthesis and characterization of complexes with up to six different transition metals connected by carbon-rich bridging units

The synthesis and reaction chemistry of heteromultimetallic transition-metal complexes by linking diverse metal-complex building blocks with multifunctional carbon-rich alkynyl-, benzene-, and bipyridyl-based bridging units is discussed. In context with this background, the preparation of 1-{(eta(2)-dppf)(eta(5)-C(5)H(5))RuCtriple bond]C}-3-{(tBu(2)bpy)(CO)(3)ReCtriple bond]C}-5-(PPh(2))C(6)H(3)] (10) (dppf = 1,1'-bis(diphenylphosphino)ferrocene; tBu(2)bpy = 4,4'-di-tert-butyl-2,2'-bipyridyl; Ph = phenyl) is described; this complex can react further, leading to the successful synthesis of heterometallic complexes of higher nuclearity. Heterotetrametallic transition-metal compounds were formed when 10 was reacted with {(eta(5)-C(5)Me(5))RhCl(2)}(2)] (18), (Et(2)S)(2)PtCl(2)] (20) or (tht)AuCtriple bond]C-bpy] (24) (Me = methyl; Et = ethyl; tht = tetrahydrothiophene; bpy = 2,2'-bipyridyl-5-yl). Complexes 1-{(eta(2)-dppf)(eta(5)-C(5)H(5))RuCtriple bond]C}-3-{(tBu(2)bpy)(CO)(3)ReCtriple bond]C}-5-{PPh(2)RhCl(2)(eta(5)-C(5)Me(5))}C(6)H(3)] (19), {1-(eta(2)-dppf)(eta(5)-C(5)H(5))RuCtriple bond]C]-3-(tBu(2)bpy)(CO)(3)ReCtriple bond]C]-5-(PPh(2))C(6)H(3)}(2)PtCl(2)] (21), and 1-{(eta(2)-dppf)(eta(5)-C(5)H(5))RuCtriple bond]C}-3-{(tBu(2)bpy)(CO)(3)ReCtriple bond]C}-5-{PPh(2)AuCtriple bond]C-bpy}C(6)H(3)] (25) were thereby obtained in good yield. After a prolonged time in solution, complex 25 undergoes a transmetallation reaction to produce (tBu(2)bpy)(CO)(3)ReCtriple bond]C-bpy] (26). Moreover, the bipyridyl building block in 25 allowed the synthesis of Fe-Ru-Re-Au-Mo- (28) and Fe-Ru-Re-Au-Cu-Ti-based (30) assemblies on addition of (nbd)Mo(CO)(4)] (27), (nbd = 1,5-norbornadiene), or {Ti](mu-sigma,pi-Ctriple bond]CSiMe(3))(2)}Cu(Ntriple bond]CMe)]PF(6)] (29) (Ti] = (eta(5)-C(5)H(4)SiMe(3))(2)Ti) to 25. The identities of 5, 6, 8, 10-12, 14-16, 19, 21, 25, 26, 28, and 30 have been confirmed by elemental analysis and IR, (1)H, (13)C{(1)H}, and (31)P{(1)H} NMR spectroscopy. From selected samples ESI-TOF mass spectra were measured. The solid-state structures of 8, 12, 19 and 26 were additionally solved by single-crystal X-ray structure analysis, confirming the structural assignment made from spectroscopy.