Isomerization of the alkyl ligand in (Me[sub 2]NCS[sub 2])Pd(PR[sub 3])(alkyl) complexes. Influences of heteroatom substitutents in the alkyl group on the alkyl isomerization equilibria and stability of alkylmetal complexes

Journal Article · Tue Dec 01 04:00:00 EST 1992 · Organometallics; (United States)

DOI:https://doi.org/10.1021/om00060a054· OSTI ID:6443395

Reger, D L; Garza, D G; Lebioda, L ^[1]

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1. Univ. of South Carolina, Columbia (United States)

A series of complexes of unusually stable alkylpalladium complexes of the formula (Me[sub 2]NCS[sub 2])Pd(PR[sub 3])(alkyl) (R = Me, Et) have been prepared from the reaction of (Me[sub 2]NCS[sub 2])Pd(PR[sub 3])Cl and the appropriate alkyllithium or Grignard reagent. The substituted complexes (Me[sub 2]NCS[sub 2])Pd(PEt[sub 3])(CH[sub 2]CH[sub 2]CF[sub 3]) and (Me[sub 2]NCS[sub 2])Pd(PEt[sub 3])(CH[sub 2]CH[sub 2]CN) were prepared in similar reactions, and the isomer of the latter, (Me[sub 2]NCS[sub 2])Pd(PEt[sub 3])(CH(CN)CH[sub 3]), was prepared from the low-temperature, in situ reaction of (Me[sub 2]NCS[sub 2])Pd(PEt[sub 3])H and CH[sub 2]CHCN. The reaction of (Me[sub 2]NCS[sub 2])Pd(PEt[sub 3])Cl with Li[C(CH[sub 3])[sub 3]]CuCN gives a color change indicative of the formation of the alkylpalladium complex, but this tert-butyl compound decomposes above [minus]40[degrees]C with the formation of its isomer, (Me[sub 2]NCS[sub 2])Pd(PEt[sub 3])(CH[sub 2]CH(CH[sub 3])[sub 2]). With this one exception, all of these complexes are extremely stable, especially the substituted alkyl complexes, which can be heated over 100[degrees]C in solution for extended periods without noticeable decomposition. Heating the unsubstituted isomers at 75[degrees]C in solution leads to isomerization of the alkyl ligand. For example, heating either (Me[sub 2]NCS[sub 2])Pd(PEt[sub 3])(CH[sub 2]CH[sub 2]CH[sub 3]) or (Me[sub 2]NCS[sub 2])Pd(PEt[sub 3])(CH[sub 2]CH[sub 2]CH[sub 3]) or (Me[sub 2]NCS[sub 2])Pd(PEt[sub 3](CH(CH[sub 3])[sub 2])) leads to a 10:1.0 equilibrium mixture, respectively, of the two. An equilibrium mixture of 10:1.0 is found for the other alkyl ligands studied. This 1.6 kcal/mol difference between the isomers is proposed to be the difference in energy between secondary versus primary alkylmetal complexes in the absence of steric constraints imposed by other ligands in the coordination sphere. 34 refs., 1 fig., 5 tabs.

• OSTI ID: 6443395
• Journal Information: Organometallics; (United States), Journal Name: Organometallics; (United States) Vol. 11:12; ISSN ORGND7; ISSN 0276-7333
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ALKALINE EARTH METAL COMPOUNDS
ALKANES
CHEMICAL REACTIONS
COMPLEXES
DECOMPOSITION
EQUILIBRIUM
GRIGNARD REAGENTS
HYDROCARBONS
ISOMERIZATION
LIGANDS
MAGNESIUM COMPOUNDS
ORGANIC COMPOUNDS
ORGANOMETALLIC COMPOUNDS
PALLADIUM COMPLEXES
PHOSPHINES
PHOSPHORUS COMPOUNDS
TRANSITION ELEMENT COMPLEXES