Synthesis and characterization of metal (M = Al or Ga) 2-phosphino(phenolate/benzenethiolate) complexes and their electrochemical behavior in the presence of CO₂

Article type: Research Article

Authors: Bruggen, Jessica A.^a | Feller, Keyton D.^a | Schickel, Henry I.^a | Tuleushova, Nazym^c | Zhukush, Medet^c | Lam, Kevin^{b; c} | Barry, Brian M.^{a; *} | Kemp, Richard A.^{d; e}

Affiliations: [a] Department of Chemistry, University of Wisconsin-Platteville, Platteville, WI, USA | [b] Department of Pharmaceutical, Chemical and Environmental Sciences, Faculty of Engineering and Science, University of Greenwich, Central Avenue, Chatham Maritime, Chatham, Kent, UK | [c] Department of Chemistry, Nazarbayev University, Astana, Republic of Kazakhstan | [d] Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, NM, USA | [e] Advanced Materials Laboratory, Sandia National Laboratories, Albuquerque, NM, USA

Correspondence: [*] Corresponding author: Dr. Brian M. Barry (Chemistry, 216 Ottensman Hall), 1 University Plaza, Platteville, WI 53818, USA. Tel.: +1 608 342 7377; E-mail: barryb@uwplatt.edu.

Abstract: A series of Group 13 complexes MLX2 (M = Al or Ga, L = SC6H4-2-PtBu2 or OC6H4-2-PtBu2, X = Me or C6F5) have been synthesized and characterized by multinuclear NMR spectroscopy and single crystal X-ray diffraction. Reactions of Me3Al or Me3Ga with an equivalent of either 2-tBu2P(C6H4)OH (1) or 2-tBu2P(C6H4)SH (5) resulted in the formation of four new (2,3,6, and 7), 4-coordinate dimethyl chelate (S,P or O,P) complexes via methane elimination. The dimethyl gallium complexes (3 and 7) underwent a further reaction with excess B(C6F5)3, and through ligand exchange (methyl/pentafluorophenyl), resulted in the disubstituted bis(pentafluorophenyl) analogs (4 and 8). Cyclic voltammetry (CV) experiments for all compounds in the presence of and the absence of (1–8) CO2 were performed. For compounds showing cathodic reduction waves under CO2 (2,3,4, and 6), bulk electrolysis experiments were performed. Electrochemical studies indicate that, for several compounds, a transient CO2 adduct is formed which undergoes a one-electron, irreversible (or partially irreversible) reduction to form an unstable radical anion.

Keywords: Carbon dioxide, main-group complex, cyclic voltammetry, X-ray crystallography, phosphinophenolate, phosphinobenzenethiolate, frustrated Lewis pair

DOI: 10.3233/MGC-170245

Journal: Main Group Chemistry, vol. 16, no. 4, pp. 307-319, 2017