Monomeric structures carbonyl complexes

Treatment of 4 with either PF3 or 13CO results in CO substitution believed to proceed via a dissociative process yielding Ti(CO)2(PF3)-(dmpe)2 (6) and Ti(13CO)3(dmpe)2. Structural characterization of 6 showed it also to be monomeric, but possessing a monocapped trigonal prismatic geometry. Complexes 4, 5, and 6 may be considered phosphine-substituted derivatives of the as yet unisolated Ti(CO)7, thus representing the only isolable titanium carbonyl complexes where the titanium atom is in the zero oxidation state. 

In contrast to the results described above, experiments with palladium atoms and SiO lead to a different behavior. It is clear that PdSiO is formed, but compared with monomeric SiO the corresponding stretching vibration of PdSiO is shifted to higher wavenumbers (1246 cm-1 in solid argon)118. With the aid of a normal coordinate analysis involving different isotopomers, a linear structure of PdSiO is deduced. Bonding in PdSiO is similar to that in typical transition metal carbonyl complexes. 

Rhodium gives characteristic carbonyl complexes with diphosphines R2P(CH2) PR2. Monomeric complexes with cw-arrangement are obtained only for n = 2. In other cases, the structures (2.115) are formed.The dinuclear complex... 

The presence of halides in the coordination sphere with aldehydes is important as zinc halides are typically used in organic synthesis as organic carbonyl activators. Large excesses of aldehydes and anhydrous zinc halides were necessary. Both monomeric and polymeric structures with halide bridges were observed. Tetrahedral geometries were observed for mixed ligand, aldehyde, and halide complexes.353... 

Our study on the synthesis, structure and catalytic properties of rhodium and iridium dimeric and monomeric siloxide complexes has indicated that these complexes can be very useful as catalysts and precursors of catalysts of various reactions involving olefins, in particular hydrosilylation [9], silylative couphng [10], silyl carbonylation [11] and hydroformylation [12]. Especially, rhodium siloxide complexes appeared to be much more effective than the respective chloro complexes in the hydrosilylation of various olefins such as 1-hexene [9a], (poly)vinylsiloxanes [9b] and allyl alkyl ethers [9c]. 

The complex [Rh(TPP)(C02Et)] (reaction 42) is diamagnetic and monomeric in dichloromethane.195 The presence of an ethoxycarbonyl ligand was supported by the strong carbonyl stretch at 1700 cm-1, and the regeneration of [Rh(TPP)Cl(CO)] and ethanol via treatment with HC1. Related metalloporphyrins of the type [RhL-(Me2NH)2] (L = TPP or etioporphyrin) have been synthesized, and their structures... 

The models become more complex when they take the structure of the base into account. A simple and very popular hypothesis was proposed for esters by Ireland and coworkers in pioneering work23. This model supposes that a monomeric LDA is the active species and that the lithium-carbonyl interaction leads to a six-membered cyclic Zimmerman-Traxler chair-like transition state24, at which a more-or-less concerted proton transfer occurs. The resulting preference for the E enolate observed in THF and the Z preference in THF-HMPA mixtures, an issue discussed in more detail below, could even be accounted through steric considerations (Scheme 4). 

The structure and composition of products of reactions between tellurophene and metal carbonyls depends on the nature of the metal <1999UK415>. A monomeric complex was obtained in 80% yield when treating tellurophene with Cr(CO)3(MeCN) in dibutyl ether solution at 50-60 °C (Equation 8) <1972JOMC87, 1981MCL3>. 

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