Electrochemical and spectroscopic studies of (P)Rh(R)(L) and ((P)Rh(L)/sub 2/)/sup +/ where P is the dianion of octaethyl- or tetraphenylporphyrin, R is a sigma-bonded alkyl group, and L is triphenylphosphine or dimethylphenylphosphine

Journal Article · Fri Jul 01 00:00:00 EDT 1988 · Organometallics; (United States)

DOI:https://doi.org/10.1021/om00097a022· OSTI ID:6929616

Kadish, K M; Araullo, C; Yao, C L

The electrochemistry and spectroelectrochemistry of (P)Rh(R), (P)Rh(R)(L), and ((P)Rh(L)/sub 2/)/sup +/ where P is the dianion of octaethylporphyrin (OEP) or tetraphenylporphyrin (TPP), R is CH/sub 3/, C/sub 2/H/sub 5/, or C/sub 4/H/sub 9/, and L is triphenylphosphine or dimethylphenylphosphine are reported. At polarographic concentrations of (P)Rh(R) (approx.10/sup -3/ M), the binding of one triphenylphosphine ligand and the formation of (P)Rh(R)(PPh/sub 3/) are observed. This contrasts to lower porphyrin concentrations where the bis(triphenylphosphine) adduct ((P)Rh(PPh/sub 3/)/sub 2/)/sup +/ is formed in solution. Formation constants for the conversion of (P)Rh(R) to (P)Rh(R)(PPh/sub 3/) were calculated by using electrochemical and spectroscopic methodologies and varied between 1.0 and 4.0 x 10/sup 3/ depending upon the porphyrin macrocycle (OEP or TPP), the specific R group, and the solvent (methylene chloride or benzonitrile). The electroreduction of (P)Rh(R)(PPh/sub 3/) initially leads to a porphyrin ..pi.. radical and the transient formation of ((P)Rh(R)(PPh/sub 3/))/sup -/ was spectrally characterized on the thin-layer electrochemical time scale. The formation of a porphyrin ..pi.. radical is also observed after reduction of ((TPP)Rh(PPhMe/sub 2/)/sub 2/)/sup +/. This reaction was characterized by thin-layer spectroelectrochemistry and provides the first example for reduction of a non-sigma-bonded Rh(III) porphyrin at the porphyrin ..pi..-ring and provides the first example for reduction of a non-sigma-bonded Rh(III) porphyrin at the porphyrin ..pi..-ring system.

• Research Organization: Univ. of Houston, TX (USA)
• OSTI ID: 6929616
• Journal Information: Organometallics; (United States), Journal Name: Organometallics; (United States) Vol. 7:7; ISSN ORGND
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400400* -- Electrochemistry
ALKANES
CARBOXYLIC ACIDS
CHEMICAL REACTIONS
CHEMISTRY
DATA
ELECTROCHEMISTRY
EXPERIMENTAL DATA
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
HYDROCARBONS
INFORMATION
NUMERICAL DATA
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PHOSPHINES
PHOSPHORUS COMPOUNDS
PORPHYRINS
REDUCTION
SPECTROSCOPY