Synthesis and Reactivity of Indenyl Ruthenium(II) Complexes Containing the Labile Ligand 1,5-Cyclooctadiene (COD):  Catalytic Activity of [Ru(η⁵-C₉H₇)Cl(COD)]

Abstract

The treatment of [RuCl 2 (COD)] n with KC 9 H 7 in THF leads to the formation of [Ru(η 5 -C 9 H 7 )Cl(COD)] (1) (80% yield) in a one-pot synthesis. Complex 1 is also formed by the reaction of [RuCl 2 (COD)] n with NaC 9 H 7 in THF followed by treatment of the intermediate complex [Ru(η 5 -C 9 H 7 )(η 2 -η 3 -C 8 H 11 )] (2) with HCl. Substitution of the labile COD ligand by bulky phosphines PR 3 (R ) Cy, i Pr 3 ) can be achieved at room temperature in THF to give 16electron species [Ru(η 5 -C 9 H 7 )Cl(PR 3 )], which react with CO (1 atm) to afford complexes 5) have been similarly prepared by reaction with the bidentate ligands. [Ru(η 5 -C 9 H 7 )Cl(NBD)] (NBD ) norbornadiene) (6) has been prepared through an exchange reaction of 1 with NBD and characterized by X-ray diffraction. Neutral complexes [Ru(η 5 -C 9 H 7 )X-(COD)] (X ) FBF 3 (7), N 3 (8)) were prepared from complex 1 by metathesis reactions of the chloride ligand by AgBF 4 and NaN 3 respectively. The treatment of 7 in CH 2 Cl 2 with an excess of pyridine and acetonitrile gives cationic complexes [Ru(η 5 -C 9 H 7 )(COD)L][BF 4 ] in good yield (L ) py (9), CH 3 CN (10)). The structure of complex 9 has been determined by X-ray diffraction. Complex 1 catalyzes [2+2] and [4+2] cycloaddition reactions of norbornene and 1,5-cyclooctadiene with alkynes to give exotricyclic [4.2.1.0] coupling products and exotricyclo [4.2.2.0]dec-7-enes, respectively. These processes take place with high efficiency and selectivity. Complex 1 is also active in the catalytic hydration of terminal alkynes to afford ketones in high yield and selectivity.

Synthesis and reactivity of ruthenium(II) complexes with 1,5-cyclooctadiene and pyridine-2,6-dicarboxylato ligands

“…The RuAO (aqua) bond length of 2.177(1) Å in 2 is compared with that in the aqua complex [Ru(HB(pz) 3 )(COD)(H 2 O)]CF 3 SO 3 (pz = pyrazolyl, 2.140(4) and 2.161(4) Å) [26]. The RuAN(L) bond lengths are 2.154 (4), 2.1442(11), 2.1583(18) and 2.147(3) Å in 3, 4, 7ÁCH 3 OH, and 9Á2H 2 O, respectively, which are a little shorter than those in other related cationic ruthenium complexes such as [Ru(g 5 -C 9 H 7 )(py) (COD)]BF 4 (2.197(8) Å) [27], [L OEt (COD)Ru(NH 2 -t-Bu)]BF 4 (2.197 (6) Å) and [L OEt (COD)Ru(NH 2 C 6 H 4 Me-p)]BF 4 (2.174(5) Å) [21], but comparable to those in the neutral complex [RuHCl(COD)py 2 ] (2.167 and 2.153 Å) [28]. The two Ru-COD moieties in complex 9 adopt the stable trans-conformation which could be observed in Fig.…”

Indenylmetal Catalysis in Organic Synthesis

“…Indenyl complex 70 has also been studied by Alvarez et al for [2+ +2] and [4+ +2] cycloaddition reactions of alkynes (Scheme 26). [58] Fort he indenylruthenium-catalyzed [4+ +2] cycloaddition reaction, the authors noted astronger dependence of the electronics and steric properties of the alkyne on product yield. In previous work, Trost and co-workers have shown that CpRu(COD)Cl 71 provides much higher yields of the [4+ +2] cycloaddition products across ad iverse range of alkynes.…”

Dichlorido(η4-cycloocta-1,5-diene)bis(triphenylphosphine)osmium(II)

“…For general background to Ru II and Os II COD complexes, see: Bennett & Wilkinson (1959); Albers et al (1989); Cucullu et al (1999); Coalter & Caulton (2001); Alvarez et al (2001); Winkhaus et al (1966); Schrock et al (1974); Dickinson & Girolami (2006). For C C bond lengths for free olefinic double bonds, see: Orpen et al (1989).…”

“…The ruthenium polymer [RuCl 2 (COD)] x (COD = cycloocta-1,5-diene), which can be readily prepared in 30-40% yield from RuCl 3 .3H 2 O and COD in boiling ethanol (Bennett & Wilkinson, 1959;Albers et al, 1989), has proved to be a useful precursor for a wide variety of ruthenium compounds (Cucullu et al, 1999;Coalter & Caulton, 2001;Alvarez et al, 2001). Although the analogous osmium polymer [OsCl 2 (COD)] x is also known, its utility as a starting material has remained relatively unexplored partially due to the difficuly in its preparation (Winkhaus et al, 1966;Schrock et al, 1974;Dickinson & Girolami, 2006).…”