C-M bond distance

Fig. 5. M—C bond distances of analogously substituted Lewis acid-base adducts...

Adduct formation between group 13 compounds R3M and group 15 compounds ER 3 affect the geometry of both compounds. According to the VSEPR model, the C-M-C bond angles of the Lewis acid R3M should decrease (from 120° toward tetrahedral) and the M-C bond distances... 

Reasonably similar observations can be made for the complexes bis(2,3,4-trimethyl-pentadienyl)ruthenium and bis(2,4-dimethylpentadienyl)chromium, both of which contain metals larger than iron. Thus, in ruthenocene and chromocene the average M-C bond distances have been found to be 2.196(3) and 2.169(4) A, respectively, whereas for their open analogs, the distances are quite comparable, if not actually shorter, at 2.188(3) and 2.165(4) A, respectively. Thus it does seem that the Fe-C bond distances in Fe(2,4-... 

As is the case for transition-metal carbonyl complexes (754), the M-C bond distance should be a more sensitive structural indicator of the nature of the M-CCR bond than is the length of the multiple bond, because bond distances change more between bond orders I and 2 than between bond orders 2 and 3. As for the C=C bond lengths described earlier, classifying a M-CCR bond length as normal or short requires a reference point some approaches to this are described next. 

Increase of the M—Cl and M—C stretching force constants (accompanied by a corresponding decrease of the M—Cl and M—C bond distances) with increasing chlorine substitution across the series [(CH3)4 M C1 ] where n = 0 to 4, has been observed and rationalized as a combination of inductive and resonance effects. For instance, in the case of M = Ga the bond distances R Ga—C) in A and stretching force constants /(Ga—C) in md3m A for the [Me4, jGaCl ] series are ... 

The hexacarbonylniobate(—1) and hexacarbonyltanta-late(—1) anions are well established. The [Nb(CO)e] anion can be prepared at atmospheric pressure of CO from NbCR by using a prereduction step with alkali metal/naphthalene at low temperature, followed by carbonylation of the intermediate at low temperature in DME as solvent. Another method of preparation, also operating at atmospheric pressure of CO, uses the reduction of NbCls with Mg/Zn/pyridine at room temperature and gives yields as high as 48% of recrystallized Na(THF)[Nb(CO)e]. The alkali metal derivatives of [M(CO)6l , M = Nb, Ta, are rapidly oxidized by air the PPN derivatives are stable in air for short periods of time. PPN[Nb(CO)6l and PPN[Ta(CO)6l are isostructural the hexacarbonyl anions possess an almost exact octahedral geometry with the following M-C bond distances Nb-CO, 2.089 A Ta-CO, 2.083 A. 

An analysis of more than 20000 crystal structures of J-block metal carbonyl complexes confirms a clear correlation between C O and M-C bond distances, i.e. as the M-C bond distance decreases, the C bond distance (rfco) increases. Ninety per cent of the structural data fall into a region in which 117.0 pm > dco > 112.8 pm, and for these M-CO interactions, the M-C bonding contributions are approximately in balance. For 4%, w-bonding dominates and dco > 117.0 pm, while for 6%, cr-bonding and ionic contributions dominate and dco < 112.8 pm. 

Table 10.4. Hydrogen and methyl derivatives of the Group 2 and 12 metals M-C bond distances in gaseous, monomeric dialkyls MR2, and M-H bond distances in gaseous, monomeric dihydrides MH2 or diatomic radicals. MH. AU distances in pm. ...

M-C bond distances from reference [12], M-H bond distances in metal dihydrides from reference [11] M-H bond distances in monohydrides from reference [13]. In MH2. In.MH. 

Table 11.1. Gaseous, monomeric mono- and tri-chlorides of the Group 13 elements M-Cl bond distances, R (in pm), and bond energies, Dq or MBE (in kJ mol ). The Tl-Cl bond distance and the mean bond energy of TICI3 are unknown, presumably because of the low stability of the gaseous trichloride relative to the monochloride. Gaseous monomeric trimethyl derivatives M-C bond distances and mean bond energies. ...

Bond distances in the monochlorides from reference [1] bond distances in the trichlorides from reference [2] M-Cl bond energies calculated from data in reference [3] unless otherwise indicated M-C bond distances from reference [4] and M-C bond energies from reference [5] unless otha-wise indicated. Reference [6]. Reference [7]. 

The M-C bond distances in the trimethyl derivatives and the M-Cl bond distances in both trichlorides and monochlorides are displayed in Fig. 11.1. The M-C bond distances are seen to increase from B to Al, but to remain essentially constant from A1 to Ga. The unexpected shortness of the Ga-C bond reflects the d-block contraction. The break at Ga is followed by a normal increase from Ga to In and a smaller increase from In to Tl. The unexpected shortness of the Tl-C bond reflects the/-block contraction as well as relativistic effects. 

The variation of M-Cl distances in the trichlorides is very similar to the variation of M-C bond distances. To the extent that M-Cl bonds are shortened by polarity effects, the shortening appears to be nearly constant down the group. 

M-C bond distances in gaseous, monomeric dialkyls MR2, and M-H bond distances in gaseous, monomeric dihydrides MH2 or diatomic radicalsMH. 

M-Cl bond distances, R (in pm), and bond energies. Do or MBE. Gaseous monomeric trimethyl derivatives M-C bond distances and mean bond energies. 

The bands caused by M —C vibrations are less intense than v(CO) bands, but in general stronger than 5(MCO). The changes in the M —C bond distances have therefore less influence on the character of the M — C bond than the changes in the C — O bond distances. Consequently, the analysis of IR spectra in the v(CO) vibrational region furnishes valuable information concerning the electronic structure and symmetry of the carbonyls. 

The BAN rule is usually not applicable to complexes of early transition metals (Groups 3 and 4), /-elements and main-group metals, which have more ionic type of bonding. it-Complexes of typical r(-metals violating the BAN rule can exist but are less stable and have relatively longer M-C bond distances than those which conform to it. For sandwich complexes, this approach has been developed into the... 

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