Binary carbonyls

Another interpretation of the 2045 cm" peak is the multiple bonding species formation. This frequency is comparable to the vibrational frequency of terminally-bonded CO in platinum carbonyl binary complexes Pt-(CO)n (n=l,2,3,4) synthesized by Ozin et al. by co-condensation of platinum atoms with carbon monoxide molecules in an argon matrix at very low temperature [22]. We prefer the assignment of this peak to the multiple bonded platinum carbon monoxide... 

Perhaps because of inadequate or non-existent back-bonding (p. 923), the only neutral, binary carbonyl so far reported is Ti(CO)g which has been produced by condensation of titanium metal vapour with CO in a matrix of inert gases at 10-15 K, and identified spectroscopically. By contrast, if MCI4 (M = Ti, Zr) in dimethoxy-ethane is reduced with potassium naphthalenide in the presence of a crown ether (to complex the K+) under an atmosphere of CO, [M(CO)g] salts are produced. These not only involve the metals in the exceptionally low formal oxidation state of —2 but are thermally stable up to 200 and 130°C respectively. However, the majority of their carbonyl compounds are stabilized by n-bonded ligands, usually cyclopentadienyl, as in [M(/j5-C5H5)2(CO)2] (Fig. 21.8). 

Figure 25.11 Metal frameworks of some high-nuclearity binary carbonyl and carbonylate clusters of osmium (a) Os5(CO)i6 (trigonal bipyramid) (b) Os6(CO)ig (bicapped tetrahedron, or capped trigonal bipyramid) (c) [Os6(CO)ig] (octahedron) (d) Os7(CO)2i (capped octahedron) (e) [Osg(CO)22] (bicapped octahedron) (f) [Osi7(CO)36] (3 shaded atoms cap an Osu trigonal bipyramid).

Thermolysis of binary carbonyls or of their partially substituted derivatives, either under vacuum or in solutions, has been used to produce carbonyls and carbonylate anions with an unparalleled range of structures (Fig. 25.11). The Ru chemistry, though less well developed, mostly parallels that of These compounds... 

Because they possess an odd number of valence electrons the elements of this group can only satisfy the 18-electron rule in their carbonyls if M-M bonds are present. In accord with this, mononuclear carbonyls are not formed. Instead [M2(CO)s], [M4(CO)i2] and [M6(CO)i6] are the principal binary carbonyls of these elements. But reduction of [Co2(CO)g] with, for instance, sodium amalgam in benzene yields the monomeric and tetrahedral, 18-electron ion, [Co(CO)4] , acidification of which gives the pale yellow hydride, [HCo(CO)4]. Reductions employing Na metal in liquid NH3 yield the super-reduced [M(CO)3] (M = Co, Rh, Ir) containing these elements in their lowest formal oxidation state. 

Apart from matrix-isolated binary carbonyls stable only at low temperatures, Ag(CO)B(OTeF5)4 (i (C-O) 2204 cm- ) has been isolated as a crystalline solid, as has [Ag(CO)2]+[B(OTeF5)4]- (linear C-Ag-C, Ag-C 2.14 A). 

A84. L. H. Jones, Inorganic Vibrational Spectroscopy, volume 1. Dekker, New York, 1971. Chapters Metal carbonyls, pp. 141-161 (38). Discussion of carbonyl stretching frequencies, force constants, etc., for binary carbonyls. 

C. H. Langford and M. Parris Reactions of Inert Complexes and Metal Organic Compounds, pp. 1-52 (170) see especially sections 6 and 7, complexes with B class ligands the binary carbonyls, and the substituted carbonyls. 

Complexes with B class ligands the binary carbonyls... 

It has been pointed out that the types of solvents which are used here, are not generally such as would enter into strong association with the substrate. The molecularity of the substitution reaction may then stand more chance of being an operational concept. Amongst the binary carbonyls, the only systems which have been extensively studied have been nickel tetracarbonyl and the hexacarbonyls of group VI. For the former, the observation of a first-order rate is at least consistent with a rate-determining dissociation of one carbonyl ligand followed by reaction of the intermediate with whichever nucleophile should be available. 

RATES OF THERMAL SUBSTITUTION IN SOME BINARY CARBONYLS... 

In the present study, we synthesized in zeolite cavities Co-Mo binary sulfide clusters by using Co and Mo carbonyls and characterized the clusters by extended X-ray absorption fine structure (EXAFS), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and high resolution electron microscopy (HREM). The mechanism of catalytic synergy generation in HDS is discussed. 

In contrast to the vast number of mono- and multinuclear binary carbonyl complexes of the transition metals, no isolable binary carbonyls of titanium, zirconium, or hafnium have been reported. 

Two U.S. patents issued to the Barium Steel Corporation in 1957 claim the formation of the heptacarbonyls M(CO)7 (M = Ti, Zr, Hf) as intermediates for the purification of these metals (9,10). In this described refining process, the finely divided metal is treated with CO at 300-400°C and 4-8 atm. The resulting liquid heptacarbonyl compound is then thermally dissociated to the pure metal and CO. The alleged existence of these binary carbonyls seems highly unlikely without supporting evidence. 

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