Rhenium‐containing metathesis catalysts are formed selectively and in good yields from Re2O7 according to (a) and (b). In the presence of SnMe4, all four complexes are catalytically active, while in the absence of SnMe4 only 3, the methyl‐richest compound, still catalyzes the metathesis. 2 is the only diamagnetic compound in the series R6–2nReOn; this can be attributed to spin‐pairing in the ReRe bond.
strengthens the Os-carbonyl bond opposite the donor atom (Rh). This effect has been observed previously in related dative-bonded c o m p o~n d s .~~~~~~~The Rh-Os separation of 2.8744 (3) 8, is typical of a single bond but is not a useful indication about the nature of this interaction, especially in the presence of the bridging alkyne. This Rh-Os bond is somewhat longer than that observed (2.758 (5) 8,) in the related compound [RhOsC1zBr(p-CO)(dppm)2] ,53 which in our interpretation would have an Os-Rh donor-acceptor bond accompanied by semibridging carbonyl groups. The significant difference in these two Rh-Os distances no doubt results from the very different bridging ligands involved, with the alkyne group causing greater separation of the metals in the present case. SummaryA series of low-valent, dppm-bridged complexes involving Rh and Os are readily obtained from [RhOsH-(CO),(dppm),]. Carbonyl substitution in [RhOs(CO),-( d p~m )~] + by the poorer n-acceptor but better o-donor tBuNC ligand occurs on Os opposite the metal-metal bond, supporting our arguments that the Os-Rh bonds in these species are best regarded as donor-acceptor interactions. Carbonyl loss from the saturated Os center in the com- pounds [Rh0~(C0),(p-CO)(p-RC=CR)(dppm)~] [BF,] isaccompanied by the unusual formation of a Rh+Os dative bond, regenerating coordinative saturation at Os. This may be viewed as an example of the neighboring-group effect, with Rh assisting in labilization of a carbonyl from Os. The presence of the coordinatively unsaturated Rh center in these compounds provides a route into chemistry involving the normally inert and coordinatively saturated Os center, and it is probable that substitution reactions occur by coordination at Rh, followed by facile rearrangement. This suggestion is supported by the reactions of [RhOs(CO),(cc-RC=CR)(dppm),] [BF,] with a series of neutral and anionic ligands, in which the incoming ligands are clearly shown to be bound to the Rh center. Acknowledgment.We thank the Natural Sciences and Engineering Research Council of Canada (NSERC) and the University of Alberta for support of this work and the NSERC for partial support of the diffractometer and for an Undergraduate Student Research Award to R.A.F. We also thank Professor J. Takats for a loan of 13CO-enriched O S~( C O )~~ and Professor R. G. Cave11 for supplying a sample of NaS,PMe2.2H20.Supplementary Material Available: Listings of anisotropic thermal parameters, positional and thermal parameters for the BF4anion and CH,Cl, molecules, additional bond lengths and angles, and hydrogen atom parameters for 12 and NMR data for 9-22 (11 pages); a listing of the observed and calculated structure factors for 12 (48 pages). Ordering information is given on any current masthead page.The title compound methyltrioxorhenium(VI1) reacts with catechols to yield complexes of the formula CH3Re(0),(1,2-02C6R4) ( ( 2)) that are fully characterized as pyridine adducts 3. Conducting these reactions in the presence of nucleophiles, e.g., halides, gives the hexa...
Methylrhenium(VII) oxide 1 is an excellent starting substance for the synthesis of rhenium complexes with π‐alkyne ligands. As depicted below, the oxygen‐abstracting effect of polymer‐bound triphenylphosphane ℗ can be exploited for the production of the new complexes. 2. According to theoretical studies the existence of such ReV compounds was highly improbable. Reduction of 2, R R′ Me, led to the first ReIV‐alkyne complex 3.
Water‐Soluble Metal Complexes and Catalysts, IV. — 2,2′‐Bipyridine‐5‐sulfonic Acid Synthesis, Purification, Derivatives and Metal Complexes The synthesis of 2,2′‐bipyridine‐5‐sulfonic acid (1a) is achieved by mercury(II)‐catalyzed sulfonation of 2,2′‐bipyridine in oleum (30% SO3) in 10‐50‐g amounts. The crude product is purified by extraction of 1a as tetra(n‐butyl)ammonium salt into dichloromethane and re‐extraction of the free acid with conc, hydrobromic acid. Melting of 1a together with potassium hydroxide gives 5‐hydroxy‐2,2′‐bipyridine (2). The salts 1b–d (Na+, [N(n‐C4H9)4]+, [P(C6H5)4]+) and sulfonamides 1f–h (tert‐butyl, benzyl, 2‐pyridylmethyl) of the acid 1a are ligands of different solubility. The coordination chemistry of these N,N‐chelating ligands is studied. The compounds 4–14 of chromium, molybdenum, tungsten, manganese, rhenium, and osmium containing carbonyl or oxo ligands are prepared as examples of chelate complexes with metals in low and high oxidation states. The solubility of the complexes is mostly determined by the cations: sodium salts are usually soluble in water and/or in short‐chained alcohols. Tetra‐n‐butylammonium and tetraphenylphosphonium salts and the sulfonamides are soluble in polar organic solvents. On the other hand, the distribution of charge has an influence on solubility. Increased polarity of the anion, caused by high oxidation states of the metals, decreases the solubility of the complex in organic solvents.
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