Binuclear Carbonyl Derivatives

2 Binuclear Carbonyl Derivatives.-An improved synthesis of Re2(CO)io has been 

Reaction of [Ru(C0)i,] with CO2 yields the new dianion [Ru2(C0)83 , which has a novel configuration (2) in which trigonal bipyramidal and pyramidal Ru C0) 

Mn2(CO)io + Re2(GO)io 2[MnRe(CO)io ] have b en measured. The enthalpy of the product over the temperature 

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THE DECOMPOSITION OF COBALT OCTACARBONYL AND SUBSTITUTED BINUCLEAR COBALT CARBONYL DERIVATIVES IN THE PRESENCE OF TRIPHENYL PHOSPHINE... 

In 1980 we published a survey (1) of our major results in this area as of late 1979. These results include extensive work on binuclear CF N PF complexes of cobalt (2,3,4,5) and nickel (6). This paper summarizes our more recent results in this area with particular emphasis on binuclear complexes of chromium, molybdenum, and tungsten as well as some new results on iron carbonyl derivatives. 

The mass spectra of binuclear cyclopentadienylmetal carbonyl derivatives of chromium and molybdenum provide useful indications of the relative strengths of the metal-metal bonds in various compound types. The mass spectrum of [C5H5Cr(CO)3]2 (S. M = Cr) exhibits no bimetallic ions but only monometallic ions such as CsHsC CO) (n = 3,... 

The structures of two binuclear carbonyls, Mn2(CO)i0 and Fe2(CO)9, are shown in Figure 10-2 note the carbonyl bridges in these molecules. In addition, the metal atoms in each molecule are close enough to each other so there is significant metal-to-metai bonding interaction. The stabilities of such binuclear carbonyls and similar but more complex carbonyl derivatives cannot be convincingly rationalized by the classical valence-bond approach. It is here that molecular orbital theory must be invoked. 

Tetracarbonylalkyl derivatives of cobalt(I) have low stability. As early as 1964 it had been noted that ketones are formed in the thermal decomposition of CoR(CO)4 (R = Me, Et) presumably involving a binuclear intermediate or an intermolecular mechanism. The mechanism of acetone formation was studied for other cobalt systems that are more easily handled, namely, Co(>/ -C5H5)Me2(PMe3) and Co2(ti -CsH )2Me2(fi2-CO)2 . Upon carbonylation, in the former case, the transient carbonyl derivative Co()j -C5H5)Me2(CO) was observed spectroscopically, whereupon it underwent carbon monoxide insertion to give an acetyl-methyl complex, followed by reductive elimination of acetone ... 

The second binuclear complex [Fe2(CO)7(C8H8)] is a black solid, and appears to be a derivative of Fe2(CO)9, as it shows bands due to bridging carbonyl groups in its infrared spectrum (152). 

The first six entries in this section of Table X (entries 93-98) relate to attempted insertion reactions of fluoroalkenes or fluoroalkynes into Si-Mn or Si-Fe bonds. Even in the successful cases, yields are generally low, and in some instances (e.g., entry 94) MesSiF is lost from the insertion product to leave a fluoroalkenyl manganese carbonyl. In the case of the iron hydrido compound in entry 98, there is formal loss of hydrogen to give the binuclear derivative [CljSiFelCO). ... 

The reaction of binuclear metal carbonyls with bases has been recognized (137, 229, 244) as producing cationic metal carbonyl species, although the earlier derivatives defied isolation. This has been classed as a base reaction (122). 

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