Two synthetic routes to compounds [(η 5 -C 5 H 4 SiMe 3 ) 2

Phenylpalladium(I1) complexes of the type PdIPh(N-N), with N-N = N,N,N',N'-tetramethylethylenediamine (tmeda) or 2,2'-bipyridyl (bpy), can be conveniently prepared in 70-95% yield by oxidative addition of iodobenxene to bis(dibenzylideneacetone)palladium(0) in the presence of the appropriate nitrogen donor ligand. The bromo analogues were obtained in only S-12% yield in this way. The complex PdIPh(tmeda) (la) reacts readily with MeLi to give PdMePh(tmeda) (3) in 88% yield, whereas PdIPh(bpy) (la) gives PdMePh(bpy) (4) and PdMe,(bpy) in varying ratios. The formation of PdMe,(bpy) was found to result from the synergistic action of lithium iodide and methyllithium. Pure PdMePh(bpy) (4) was obtained in 82% yield via ligand-exchange from PdMePh(tmeda) (3). The crystal structures of PdIPh(N-N) (la, 2a) and PdMePh(N-N) (3, 4) complexes were determined by X-ray diffraction studies. The results show that the phenyl group is always oriented perpendicular to the coordination plane aroutd palladium, with the largest deviation found for 3 (14.3(2)"). The Pd-N bond distances in the tmeda complexes (2.127(6)-2.210(3) A) are larger than those in the bpy-coordinated complexes (2.870(8)-2.144f8) A). Similarly, the Pd-CfMe) bond distances (2.5703(8) and 2.575(l) & are larger than the Pd-C(Ph) bond distances (1.985(3)-1.996tlO) A)>.

A new enantiomerically pure S,N-chelated zinc bis(aminoarenethiolate), (R,R)-Zn(SC 6 H 4 C-(Me)HNMe 2-2) 2 ((R,R)-3b), has been synthesized by the reaction of the (R)-trimethylsilyl aminoarenethiolate species (R)-2b with ZnCl 2 in a 2:1 molar ratio. (R,R)-3b is an efficient catalyst for the addition of dialkylzinc compounds to aliphatic and aromatic aldehydes to give the corresponding secondary alcohols in nearly quantitative yields with optical purities of 69-99% ee under mild reaction conditions. Although excellent selectivities were obtained with this simple ligand containing only one stereogenic (carbon) center, further modifications of the amino substituents were studied. Cyclic N(CH 2) 4 or N(CH 2) 5 amino-substituted aminoarenethiolate ligands considerably enhanced the reaction rates, resulting in shorter reaction times and higher ee's. The mechanism of these 1,2-addition reactions has the general characteristics as reported by Noyori et al. This conclusion is based on the synthesis, isolation, and characterization (X-ray, 1 H and 13 C NMR) of the enantiopure zinc bis-(aminoarenethiolate) and organozinc aminoarenethiolate intermediates and on monitoring of the reaction process. We present evidence for an interpretation of the binding in the product-forming key intermediate complex in terms of an organozinc cation/anion pair. The possibility that the very efficient transfer of chiral information in this compact complex may be due to a combination of the shortness of the Zn-N coordinate bonds with concomitant η 2 bonding of the aldehyde substrate is discussed. The solid-state structure of the zinc bis-(aminoarenethiolate) (R,R)-Zn(SC 6 H 4 C(Me)HNMe 2-2) 2 is reported.

Summary: The reaction of with 1 equiv of LiCsCR (R = SiMes (5a),, Ph ( 5~) ) affords the monomeric complexes [(r15-CgH4SiMe~zTi(C=CSiMed27CuC=CR (R = SiMe3 (3a),, Ph ( 3~) ) .Complexes 3 were independently prepared by starting from and 1 In [CuC=CRl,, (R = SiMe3 (2a),, Ph (2c)) and are the first examples of stable monomeric bis(r/2-alkyne)(V1-alkynyl)copper compounds. Reaction of 1 with 1 I4 Alkynylcopper(1) compounds are generally encountered as polynuclear species which exist either as discrete aggregates or as o1igomers.l In these species the alkynyl ligands are 0-and nbonded to copper(1) centers. Recently we showed that bis(alkyny1)titanocenes are very useful chelating ligands for the stabilization of mononuclear bis(q2-alkyne)(v1-aryl)copper and -silver compounds, where aryl is for example CsH~Me3-2,4,6.~ In order to study intramolecular us intermolecular alkyne to copper coordination, we are interested in the isolation of mononuclear bis(y2-alkyne)(l11-alkynyl)-copper(1) compounds, using the chelate effect of the alkynyl units in the bis(alkyny1)titanocene (q5-C5H4-SiMe3)2Ti(CWSiMe& (lL3 Addition of (v5-C5H4SiMe3)2Ti(C=CSiMe3)2 (l)3f to solutions or suspensions of alkynylcopper(1) compounds, [CUCECR], (R = SiMes (2a), t-Bu (2b), Ph (2c)),l in a 1:l molar ratio leads to the quantitative formation of the monomeric complexes An alternative preparative route is the trans-with the corresponding alkynyllithium compounds LiCECR (R = SiMe3 (5a), t-Bu Gb), Ph ( 5~) ) (see Scheme 1). Complexes 3 are stable in solution and in the solid state and can be isolated as orange crystalline solids by cooling their diethyl ether solutions to -30 "C. They are soluble in most organic solvents, and solutions of 3 can be handled safely in air for short periods of time. Crystals of 3 are stable to air for a few weeks.The presence of two different C z C stretching frequencies in the IR spectra of 3 indicates that besides an +bonded alkynylcopper unit, CUCGCR, y2-bonded disubstituted alkyne ligands are present. Through the q2-coordination of these alkyne moieties to the copper atom in 3, the v(CeC) vibration is shifted from 2012 cm-l in the parent compound 13f to 1896 in 3a, 1902 in 3b, and 1941 cm-l in 3c. The +bonded alkynyl group, CzCR, is found at v(C=C) 2035 in 3a, 2095 in 3b, and 2094 cm-l in 3c.The molecular structure of 3a was determined by a single-crystal X-ray diffraction a n a l y~i s .~ The molecular structure of 3a (see Figure 1) shows that 2Ti (C4XiMe3) Crystallogr. 1966,20, 502-508. (d) Chem. SOC. Jpn. 1993, 66, 429-431. (f) Lang, H.; Seyferth, D. 2. Naturforsch. 1990,45B, 212-220. (4) Single crystals of 3a were grown by cooling a saturated Et20 solution to -20 "C. Crystal data for 3a: C31H53CuSibTi, red crystal

COMMUNICATIONS('vo Adduct 4 . 4-(3-Furyl)pyridine hydrochloride (80 mg, 0.44 mmol) [14] was added to ii mlution of 4-(maleimidoinethyl)pyridine (80 mg, 0.43 inmol) in distilled ioliicnc ( I 0 mL). The auspension was stirred with potassium carbonate for 2 h at room reinperattire and tiltercd. The resulting solution of 2 and 3 was flushed with argon and heated :it 60 C in the dark for 5 d Thecrystala of LZ.IO adduct that formed theii collected by filtration. Yield: 65 mg (41 'YO) IH NMR (250 MHz. CDCI,): 5 = 3 02 id. J = 8 Hr.

No abstract

No abstract

No abstract