Reactivity of 2-(2-hydroxyphenyl)benzoxazole and 2-(2-hydroxyphenyl)benzothiazole towards group 10 transition metals. Evaluation in palladium catalyzed Suzuki?Miyaura C?C couplings

Published Date

24 May 2015, Vol.431:222–229, doi:10.1016/j.ica.2015.03.012

Advances in Transition Metal Catalysis

Title 

Reactivity of 2-(2-hydroxyphenyl)benzoxazole and 2-(2-hydroxyphenyl)benzothiazole towards group 10 transition metals. Evaluation in palladium catalyzed Suzuki–Miyaura C–C couplings

• Author 

• Hugo Valdés ^a
• Reyna Reyes-Martínez ^a
• J. Roberto Pioquinto-Mendoza ^a
• Alcives Avila-Sorrosa ^b
• Rubén A. Toscano ^a
• Simón Hernández-Ortega ^a
• David Morales-Morales ^a,,

• aInstituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior s/n, Ciudad Universitaria, C.P. 04510, Mexico
• bDepartamento de Química Orgánica, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional, Carpio y Plan de Ayala S/N, Colonia Santo Tomás, Mexico DF 11340, Mexico

Received 3 January 2015. Revised 8 March 2015. Accepted 10 March 2015. Available online 21 March 2015.

Highlights

• •
  A series of group 10 metal complexes with HPBO and HPBT were synthesized in a facile manner in moderate to high yields.
• •
  The palladium derivative of HPBO exhibited good catalytic activity in Suzuki–Miyaura couplings.
• •
  Depending on the metal the ligand HPBT exhibited up to four different coordination modes.
• •
  Depending on the metal the ligand HPBT may produce either coordination or organometallic species.
• •
  Studies in the solid state reveal important non-covalent interactions.

Abstract

A series of group 10 transition metal complexes based on 2-(2-hydroxyphenyl)benzoxazole (HPBO) and 2-(2-hydroxyphenyl)benzothiazole (HPBT) have been prepared. Reactions of nickel or palladium acetates with HPBT and HPBO produce chelate N–O coordinated compounds respectively. Whilst reaction of [K₂PtCl₄] with HPBT affords organometallic species product of a C–H bond activation of the phenolic moiety at room temperature. The molecular structures of the three complexes were unambiguously determined by means of single crystal X-ray diffraction analyses. The nickel compound [{Ni(κ²-N,O-HPBT)}₂(μ²-O-HPBT)₂(μ²-OOCCH₃)] (1) showing to be binuclear with the nickel ions found in six-coordinated distorted octahedral environments. Conversely, compound [Pd(κ²-N,O-HPBO)₂] (2) is a tetracoordinated monomer with the Pd center having a slightly distorted square planar geometry. Similarly, platinacycle [Pt(κ¹-N-HPBT)(κ²-N,C-HPBT)Cl] (3) shows the Pt center into a slightly distorted square planar geometry, exhibiting ligand HPBT in two different coordination modes, as single κ¹-N coordinated and as κ²-N-C metalated chelate bidentate ligand, completing the coordination sphere with a chloride ligand. The catalytic activity of the palladium complex (2) was evaluated in Suzuki–Miyaura cross couplings, showing good activity.

Graphical abstract

Group 10 metal complexes of 2-(2-hydroxyphenyl)benzoxazole (HPBO) and 2-(2-hydroxyphenyl)benzothiazole (HPBT) were prepared. Reactions with nickel or palladium acetates produce chelate N–O coordinated complexes and reaction of [K₂PtCl₄] with HPBT affords organometallic species via C–H bond activation. Crystal structures of the complexes were determined. The palladium complex was employed in Suzuki–Miyaura couplings.

Keywords

• 2-(2-Hydroxyphenyl)benzoxazole
• 2-(2-Hydroxyphenyl)benzothiazole
• Crystal structures
• Suzuki–Miyaura couplings
• C–H activation
• Catalysis

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Scheme 1.

Scheme 2.

Fig. 1.

Fig. 2.

 Table 1

Table 1.

 Table 2

Table 2.

Scheme 3.

Fig. 3.

Scheme 4.

Fig. 4.

Fig. 5.

 Table 3

Table 3.

 Table 4

Table 4.

 Table 5

Table 5.

• ZIP (218K)

Supplementary data 1

• ZIP (117K)

Supplementary data 2

• ZIP (138K)

Supplementary data 3

• DOCX (600K)

Supplementary data 4

• ⁎ 
  Corresponding author. Tel.: +52 55 56224514; fax: +52 55 56162217.

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