Elusive Scorpionates: C₃-Symmetric, Formally Dianionic, Facially Tridentate Ligands

Abstract

The reaction of AlCl with [(2-HO-3,5-tBuCH)P] (H[OP]) results in AlCl[OPH] ([OPH] = [(2-O-3,5-tBuCH)PH]), which is a zwitterionic molecule containing an unprecedented C-symmetric but formally dianionic chelate. Derivatization of [OPH] gives [OPR] (R = hydrocarbon), demonstrating the development of a novel class of long elusive scorpionates.

Facile synthesis of zwitterionic organoaluminum complexes containing formally dianionic homoscorpionate ligands

“…All solvents were reagent grade or better and purified by standard methods. Compounds tris(3,5‐di‐ tert ‐butyl‐2‐hydroxyphenyl)phosphine (H 3 [O 3 P]) and 1 were prepared following reported procedures. ε‐CL was dried over CaH 2 (1 wt %) at 80°C for 0.5 hr and distilled under reduced pressure.…”

“…with AlCl 3 in THF at 25 C (Scheme 1). [11] Complex 1 is zwitterionic and can be further derivatized to afford AlMe [O 3 PMe] (2, [O 3 PMe] 2− = [(2-O-3,5-tBu 2 C 6 H 2 ) 3 PMe] 2− ) by sequential deprotonation at phosphonium with MeLi, nucleophilic methylation at aluminum with MeLi, and electrophilic methylation at phosphine with MeOTf. These zwitterionic complexes represent the first examples of homoscorpionate derivatives bearing a formally dianionic, C 3 -symmetric, facially tridentate ligand.…”

“…The solid thus obtained was washed with pentane (2 mL × 3) and dried in vacuo to afford the product as an off-white solid; yield 103.9 mg (83%). Colorless crystals were grown from a concentrated diethyl ether solution at −35 C. 1 T A B L E 2 Selected bond distances (Å) and angles (deg) of 2, 3, 7, 8, 9, and 11 in comparison with those of 1 [11] and {Li(DME) 3 }{AlMe[O 3 P]} [11] Compound 2 3 7 8…”

“…Formally dianionic homoscorpionates, however, are rare. We reported recently the serendipitous synthesis of AlCl[O 3 PH] ( 1 , [O 3 PH] 2− = [(2‐O‐3,5‐ t Bu 2 C 6 H 2 ) 3 PH] 2− ) from the reaction of (2‐HO‐3,5‐ t Bu 2 C 6 H 2 ) 3 P (H 3 [O 3 P]) with AlCl 3 in THF at 25°C (Scheme ) . Complex 1 is zwitterionic and can be further derivatized to afford AlMe[O 3 PMe] ( 2 , [O 3 PMe] 2− = [(2‐O‐3,5‐ t Bu 2 C 6 H 2 ) 3 PMe] 2− ) by sequential deprotonation at phosphonium with MeLi, nucleophilic methylation at aluminum with MeLi, and electrophilic methylation at phosphine with MeOTf.…”

A dianionic C3-symmetric scorpionate: synthesis and coordination chemistry

“…15 Variation of the bridging atom allowed to further tune electronics and charge of the scorpionate ligands, thus influencing coordination behavior and solubility of their complexes. Reported systems include CH/COH, 9 CH 3 /C 6 H 5 -Si, 16 N, 9a P, 8,9,17 [R-P] + , 18 PvO, 9b,19 As, 9a AsvO, 9b 22 Si-, 23 Ge − , Sn − , 24 Pb − . 20 † Electronic supplementary information (ESI) available: Synthetic and characterization data for all new compounds, additional figures.…”