4-Thiolatobenzoato-Bridged Rhodium/Zirconium Complexes: 32-Membered Metallamacrocycles and Their Linear Dinuclear Counterparts

(μ-Di-tert-butyl-silanediolato)bis-[bis-(η5-cyclo-penta-dien-yl)methyl-zirconium]

The reaction of t-Bu2Si(OH)2 with two equivalents of Cp2Zr(CH3)2 produces the title t-Bu2SiO2-siloxide bridged dimer, [Zr2(CH3)2(C5H5)4(C8H18O2Si)] or [Cp2Zr(CH3)]2[μ-t-Bu2SiO2] (1), where one methyl group is retained per zirconium atom. The same product is obtained at room temperature even when equimolar ratios of the silanediol and Cp2Zr(CH3)2 are used. Attempts to thermally eliminate methane and produce a bridging methyl-ene complex resulted in decomposition. The crystal structure of 1 displays typical Zr-CH3 and Zr-O distances but the Si-O distance [1.628 (2) Å] and O-Si-O angle [110.86 (15)°] are among the largest observed in this family of compounds suggesting steric crowding between the t-Bu substituents of the silicon atom and the cyclo-penta-dienyl groups. The silicon atom lies on a crystallographic twofold axis and both Cp rings are disordered over two orientations of equal occupancy.

Synthesis of Carboxylate Cp*Zr(IV) Species: Toward the Formation of Novel Metallocavitands

With the intent of generating metallocavitands isostructural to species [(CpZr)3(μ(3)-O)(μ(2)-OH)3(κO,O,μ(2)-O2C(R))3](+), the reaction of Cp*2ZrCl2 and Cp*ZrCl3 with phenylcarboxylic acids was carried out. Depending on the reaction conditions, five new complexes were obtained, which consisted of Cp*2ZrCl(κ(2)-OOCPh) (1), (Cp*ZrCl(κ(2)-OOCPh))2(μ-κ(2)-OOCPh)2 (2), [(Cp*Zr(κ(2)-OOCPh))2(μ-κ(2)-OOCPh)2(μ(2)-OH)2]·Et2O (3·Et2O), [[Cp*ZrCl2](μ-Cl)(μ-OH)(μ-O2CC6H5)[Cp*Zr]]2(μ-O2CC6H5)2 (4), and [Cp*ZrCl4][(Cp*Zr)3(κ2-OOC(C6H4Br)3(μ3-O)(μ2-Cl)2(μ2-OH)] [5](+)[Cp*ZrCl4](-). The structural characterization of the five complexes was carried out. Species 3·Et2O exhibits host-guest properties where the diethyl ether molecule is included in a cavity formed by two carboxylate moieties. The secondary interactions between the cavity and the diethyl ether molecule affect the structural parameters of the complex, as demonstrated be the comparison of the density functional theory models for 3 and 3·Et2O. Species 5 was shown to be isostructural to the [(CpZr)3(μ(3)-O)(μ(2)-OH)3(κO,O,μ(2)-O2C(R))3](+) metallocavitands.