C ≡ N Frequency Shifts in Dinitrilo Complexes of Cd²⁺

Abstract

Reaction of CdCl., with NC (CIL) n CN, n -1, 3, 4 and 5 produced new complexes. The C = N frequency red and blue shifts were noticed in them. These are explained in terms of interaction between the 5pAO of Cd 2+ and the MOs of the C=N group.It is well known that the vibration frequency of a nitrilo group changes on its coordination to a metal 1 and increases on its hydrogen bridge formation with a proton donating species 2 . Both frequency shifts were attributed to two different kinds of coordination; (a) coordination to the N-lone pair orbital causing an increase in the vibration frequency; (b) ^-coordination to the C = N bond causing a decrease in the vibration frequency 3 . Recent measurements of the vibration frequencies of the C = N groups in alkyl dinitrile complexes showed the two types of shifts. It was noticed that if the ligand acts as a bridge between two metal ions and coordinates through the lone pair orbitals on the nitrogen atoms in the complex Ag 1+ , n = 1, 2) 5 -6 and (M (NC (CH2) ,,CN) CL4 , (M = Ti 4+ , Sn 4+ , n = 1-4) ; 6~8 an increase in the C = N frequency is observed. On the other hand in the complexes M (CO) 3 (NC (CH2) ,,CN) X where the dinitrile coordinates via the triple bond as a bidentate ligand, a decrease in the C = N frequency is observed, (M = Mn 1+ , Re 1+ ; n = 1 -3; X = Cl, Br) 9 ' 10 . We report here an extension of this study to the dinitrilo complexes of Cd 2+ and a theoretical explanation for the observed frequency shifts. Experimental PartThe infrared spectra were measured on a PerkinElmer model 137E infracord spectrophotometer using nujol mulls, and on a Perkin-Elmer spectrophotometer model 257 with a 2.5 fold wave number expansion. The C, H, N analyses were performed by the Alfred Bernhardt Microanalytisches Laboratorium-Mühlheim, West-Germany. Preparation of Bismalononitrile cadmium (II) chloride, hexahydrateTwenty mmoles of malononitrile dissolved in the least amount of isobutanol were added to 10 mmoles of cadmiumchloride dissolved in the least amount of isobutanol also. The mixture was refluxed for 10 hours during which its colour changed from colorless to yellow. After cooling, the formed yellow precipitate was filtered, washed with ethanol and ether and dried under vacuum. Anal, for Cd [ (NC -CH.> -CN).,] CU • 6 H.,0 Calc. C, 17.0 H, 3,7" N, 13,2 Found. C, 16.7 H, 1.25 N, 12.27 Preparation of Chlor ocadmium (II)-fi-glutaronitrile, chlor ocadmium (11) chlorideSixty mmoles of glutaronitrile dissolved in the least amount of isobutanol were added to 30 mmoles of cadmiumchloride dissolved in ethanol and then refluxed for 25 hours. The solvent was then evaporated under vacuum. The formed white precipitate was filtered, washed with ethanol and ether and dried over calciumchloride under vacuum. Preparation of Chlor ocadmium (II)-/n-adiponitrile, chlor ocadmium (II) chlorideFourty mmoles of adiponitrile dissolved in the least amount of isobutanol were added to a solution of 10 mmoles of eadmiumchlorid in a minimum amount of ethanol. The mixture was then refluxed for 24 ...

Reaction of Vanadyl Ions with Alkyl Dinitriles

“…Thus both ci -d donation and d -ti back donation of electron is much weaker than ti -p electron transfer 25 . The net result is then a transfer of electrons from rr-bonds of the C = N group to the patomic orbital of the ion, a decrease of the CN bond order and a red shift of its frequency.…”

Multifunctional Ligands. Phosphinimine-Substituted Cyanofluoroaromatics Including X-ray Molecular Structures of Three Representative Ligands 4,6-(CN)2C6F2-1,3-(NPPh3)2, 4,6-(CN)2C6F2-1,3-(NPPh2Me)2 and 4,6-(CN)2C6F2-1-(NPPh3)-3-(NPPh2Me). Formation of Rhodium(I) Complexes

“…Although rare, a few side-on coordination compounds have been reported. − When π or side-on coordination occurs, the CN stretching frequency is very substantially reduced as a result of the perturbation of the CN π-bond structure. Complexes of this type wherein this mode of bonding has been invoked show an average CN stretching frequency shift on complex formation of approximately −190 cm -1 …”