Cyanide ligand basicities in Cp{prime}M(L){sub 2}CN complexes (M = Ru, Fe). Correlation between heats of protonation and vCN
- Ames Lab., IA (United States)
Basicities of the cyanide ligands in a series of Cp{prime}M(L){sub 2}CN complexes were investigated by measuring their heats of protonation ({minus}{Delta}H{sub CNH}) by CF{sub 3}SO{sub 3}H in 1,2-dichloroethane solution at 25 C to give Cp{prime}M(L){sub 2}(CNH){sup +}CF{sub 3}SO{sub 3}{sup {minus}}, in which the N-H{sup +} group is probably hydrogen-bonded to the CF{sub 3}SO{sub 3}{sup {minus}} anion. Basicities ({minus}H{sub CNH}) of the CpRu(PR{sub 3}){sub 2}CN complexes increase from 20.5 (PPh{sub 3}) to 22.4 (PMe{sub 3}) kcal/mol with increasing donor abilities of the phosphine ligands. Basicities of all the Cp{prime}Ru(PR{sub 3}){sub 2}CN complexes, where Cp{prime} = Cp or Cp*, are linearly correlated with their vCN values; the nonphosphine complexes, CpRu(1,10-phen)CN and CpRu(COD)CN, do not follow the same correlation. For a large number of Cp{prime}M(L){sub 2}CN complexes (M = Ru, Fe, L{sub 2} = mono- and bidentate phosphines, CO, 1,10-phen, and COD), their vCN values parallel vCN values of their protonated Cp{prime}M(L){sub 2}(CNH){sup +} analogues. Also, {sup 31}P NMR chemical shifts of the unprotonated Cp{prime}M(PR{sub 3}){sub 2}-CN and protonated CpM(PR{sub 3}){sub 2}(CNH){sup +} complexes are linearly related. Despite the high basicity of Ru in Cp*Ru-(PMe{sub 3}){sub 2}Cl (30.2 kcal/mol), the CN{sup {minus}} in Cp*Ru(PMe{sub 3}){sub 2}CN (25 kcal/mol) is the site of protonation; factors that determine whether protonation occurs at the Ru or the CN{sup {minus}} are discussed.
- Sponsoring Organization:
- National Science Foundation, Washington, DC (United States); USDOE, Washington, DC (United States)
- DOE Contract Number:
- W-7405-ENG-82
- OSTI ID:
- 642374
- Journal Information:
- Inorganic Chemistry, Journal Name: Inorganic Chemistry Journal Issue: 8 Vol. 37; ISSN 0020-1669; ISSN INOCAJ
- Country of Publication:
- United States
- Language:
- English
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