Glucopyranoside-incorporated silver(I) bis(carbene) complexes have been prepared through the reactions of silver oxide with related imidazolium salts. The palladium(II) bis(carbene) complexes were synthesized from their corresponding silver(I) complexes via the technique of transmetalation. In solution, both trans-anti and trans-syn rotamers are observed for these square-planar Pd(II) complexes. In the solid state, the complex [1-methyl-3-(methyl 2,3,4-tri-O-benzoyl-6-deoxy-R-Dglucopyrano-6-yl)imidazol-2-ylidene] 2 PdBr 2 adopts a trans-anti conformation, while the complexesPdBr 2 adopt a trans-syn conformation. The steric congestion between the two glucopyranoside groups in the last two trans-syn compounds are perhaps relaxed through tilting of the imidazole rings and rotation of the flexible CH 2 spacer, which connects the imidazole ring and the glucopyranoside group. The palladium(II) complexes were further hydrolyzed to produce water-soluble hydrolysates. Preliminary catalytic studies show that these hydrolyzed palladium precatalysts are efficient in the Suzuki-Miyaura coupling reaction between phenylboronic acid and a hydrophilic substrate, 2-chlorobenzoic acid, in aqua medium. In the presence of tetra-n-butylammonium bromide (TBAB), these precatalysts also display efficient catalytic properties in the reaction of phenylboronic acid with both the hydrophilic substrate 1-chloro-3-nitrobenzene and the hydrophobic substrate 2-chlorophenol. In all cases, the catalytic systems are stable, which allow them to be reused for at least three cycles. This catalytic system also facilitates the separation of products from the catalyst and, therefore, is environmentally benign.

Intramolecular alkoxycarbonylation of tungsten-propargyl compounds proceeds with excellent diastereoselectivities to form η 3 -δ-and --lactones but for γ-lactones. With OSi(t-Bu)Me 2 substituted for an R-hydroxy group , η 3 -γ-lactones are stereoselectively formed with syn stereoselection . An optically active tungsten η 3 -γ-lactone is prepared from D-(+)-xylose to illustrate the stereochemical effect of OSi(t-Bu)Me 2 . All these η 3 -γ-, -δ-, and --lactones are converted to allyl anions that react in situ with aldehydes and ketones to produce various β-(hydroxylalkyl)-R-methylene-γ-lactones with good diastereoselectivity. This reaction is also applied to the synthesis of chiral R-methylene butyrolactones. Organic carbonyls add to the π-allyl groups of η 3 -γ-and -δ-lactones opposite the tungsten fragment, whereas additions occur from the metal side for η 3 --lactones. The stereochemical courses of these reactions are discussed in detail. These two tungsten-promoted reactions efficiently effect stereoselective transformation of chloroalkynols to complex R-methylene-γ-lactones, which are useful materials for syntheses of trisubstituted 1,3-, 1,4-, and 1-5-diols.

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In reactions of zirconocene dichloride, Cp(2)ZrCl(2), with 1 equiv and an excess amount of LiBH(3)CH(3), the methyltrihydroborate complexes, Cp(2)ZrCl[(mu-H)(2)BHCH(3)], 1, and Cp(2)Zr[(mu-H)(2)BHCH(3)](2), 2, were isolated. The reaction of titanocene dichloride, Cp(2)TiCl(2), with an excess amount of LiBH(3)CH(3) produced the monosubstituted methyltrihydroborate complex, Cp(2)Ti[(mu-H)(2)BHCH(3)], 3. The titanium was reduced from Ti(IV) to Ti(III), producing a 17-electron, paramagnetic titanocene complex. Under a dynamic vacuum at room temperature, compound 2 decomposed and produced the zirconium hydride compound Cp(2)ZrH[(mu-H)(2)BHCH(3)]. Single crystal X-ray structures of 1, 2, and 3 were determined. Crystal data for 1: space group P2(1)/c, a = 13.7921(3) A, b = 13.4227(3) A, c = 13.0868(3) A, beta = 91.6448(12) degrees, Z = 8. Crystal data for 2: space group Pna2(1), a = 15.2949(4) A, b = 9.3417(2) A, c = 9.3211(2) A, Z = 4. Crystal data for 3: space group Fmm2, a = 9.1795(3) A, b = 13.0993(5) A, c = 8.8520(3) A, Z = 4.