Bond lengths carbyne complexes

A single crystal X-ray structure analysis of 8 (Fig. 4) confirms the molecular constitution of the compound deduced by spectroscopic methods and shows further structural details. The molecule is dimeric with a Mn-C15 ( -carbyne) bond length of 1.857(2) A and a Mn-Mn bond distance of 2.565(1) A the latter one is typical for a Mn-Mn single bond [13]. The Mn-C15 (carbyne) bond is short compared to known Mn-C single bonds, for example that in (OC)4Mn-C(C00Et)C(HgBr)C(0Et)0 is found to be 2.051(26) A [13b], For the acyclic carbyne complex [Cp(CO)2Mn = C-CH=CPh2]+ BF4 the MnC distance is 1.665(5) A [14] comparable values for... 

It is interesting to note that the decrease in metal electron density that accompanies the change from five- to six-coordinate geometry does not have a detectable effect on the metal-carbene carbon bond length in these complexes. The metal-carbyne carbon bond in several osmium carbyne... 

The osmium-carbyne carbon bond lengths for the three complexes do not differ significantly, and reference to Table IV indicates that these distances are distinctly shorter than the characterized metal-carbon double bonds of osmium carbene and carbonyl complexes. In both osmium alkylidene and carbyne complexes, then, the metal-carbon multiple bond lengths are largely insensitive to changes in the metal electron density (cf. Section IV,B). 

The X-ray structure determination of 107 reveals that the osmium-carbon bond length is increased by 0.07 A on going from the parent carbyne complex 79 to the silver adduct 107. This may be contrasted with the weaker interaction between the metal-carbon bond and the Aul fragment in Os(CH2AuI)Cl(NO)(PPh3)2 (see Section IV,C,1). 

In connection with carbene and carbyne complexes, an especially interesting tungsten compound is 18-C-XXV, which contains W=C, W=C, and W—C bonds, whose lengths are 1.79, 1.94, and 2.26 A, respectively. 

Early -block metal complexes containing one or two Qt-hydrogen atoms (see 24.47) may undergo a-hydrogen abstraction to yield carbene (alkylidene, 24.49) or carbyne alkylidyne, 24.50) complexes. The solid state structure of the product of reaction 24.45 confirms differences in the Ta—C bond lengths 225 pm for Ta—Caikyi and 205 pm for Ta Ccarbene-... 

Synthesis and characterisation of the first organometallic Tc(VIII) complex [MeTcOs] is described. Its reactions with alkenes and with aromatic amine bases are different to those of the analogous rhenium complex. 25 Terminal alkynes react with [Tc(Cl)(dppe)2] to form vinylidene complexes [Tc(=C=CHR)(Cl)(dppe)2] (R = Ph, Me, Bu ). Treatment of these complexes with acid yields the respective carbyne complexes [Tc( CH2R)(Cl)(dppe)2]. The Tc-C bond lengths in these complexes vary form 1.861(9) to 1.724(7) A, 26... 

TM compounds in high and low oxidation states with metal-carbon double and triple bonds have been the subject of a systematic theoretical study. Table 7 shows the calculated metal-ligand bond lengths of several tungsten carbene and carbyne complexes at the HF and MP2 levels of theory. The HF optimizations were carried out using two different basis sets. Basis set I has DZ quality at tungsten (no additional 6p... 

Table 7 Calculated Bond Lengths (pm) of Low- and High-valent Carbene and Carbyne Complexes ...

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