Sciencemadness Discussion Board - [Re2Cl8] electron configuration

[Re2Cl8] electron configuration

morsagh - 23-9-2015 at 04:38

If Re(III) has 4f¹⁴ 5d⁴ than 4 free electrons from d orbital will make 4 M-M bond. According to Sidgwick´s rule there is free orbital s than p_x,y,z and one in d. To radon there are 10e^- missing. So why it is [Re2Cl8] and not [Re2Cl10] when 4 ligands can donate only 8 electrons to each Re³⁺?

blogfast25 - 23-9-2015 at 05:13

Quote: Originally posted by morsagh

If Re(III) has 4f¹⁴ 5d⁴ than 4 free electrons from d orbital will make 4 M-M bond. According to Sidgwick´s rule there is free orbital s than p_x,y,z and one in d. To radon there are 10e^- missing. So why it is [Re2Cl8] and not [Re2Cl10] when 4 ligands can donate only 8 electrons to each Re³⁺?

Did you mean [Re2Cl8]2- ?

According to 'Inorganic Chemistry' (Shriver and Atkins, third edition, p.302), there is indeed a quadruple σ2π4δ2 bond between the Re atoms.

Bond angle between the Cl-Re and Re-Re axis is 104 degrees.

I think the empty 6s and 6p orbitals hydridise to sp2 and then each Cl- donates one of its lone p electron pairs. Non-existence of such an anion with 10 Cl could be explained by excessive steric hindrance?

Note that Re(0) = [Xe] 4f14 5d5 6s2

[Edited on 23-9-2015 by blogfast25]

Ozone - 23-9-2015 at 11:06

Yes, it's typically prepared as the tetrabutylammonium salt. We made this in a senior/grad level lab. After the Chemist survives the HCl gas, the synthesis yields beautiful emerald-green crystals. A quadruple bond is evident in the UV-VIS spectrum.

See:

http://www.sigmaaldrich.com/catalog/product/aldrich/250201?l...