Arylcalcium Hydrides as Precursors to Alkoxides and Aryloxides of Calcium

Abstract

AbstractCalcium atoms react with +I‐substituted benzene derivatives under cocondensation conditions to yield arylcalcium hydrides. With toluene, tert‐butylbenzene, and trimethyl(phenyl)silane the reaction showed no selectivity for C−H activation, resulting in the formation of each of the three possible isomers, while with m‐xylene the reaction resulted in selective activation of the bond meta to the CH3 groups. Treatment of (tert‐butylphenyl)calcium hydride with di‐ and trisubstituted phenols such as 2,6‐di‐tert‐butylphenol, 2,6‐di‐tert‐butyl‐4‐methylphenol, and 2,4,6‐tri‐tert‐butylphenol resulted in the formation of calcium aryloxides in yields > 95%. [Ca(2,4,6‐tBu3C6H2O)2(THF)3] crystallises from a THF solution as a distorted trigonal bipyramid, with two THF ligands in the trans‐axial positions and the third THF ligand and both aryloxide groups in equatorial positions. The Ca−OAryl bond length was found to average at 2.181(3) Å. The Ca−O−CAryl angles are almost linear, with Ca1−O1−C1 and Ca1−O2−C19 being 173.9(3)° and 178.8(3)°, respectively, while the O1−Ca1−O2 angle was determined as 152.04(12)°. A reaction between (tert‐butylphenyl)calcium hydride and triphenylmethanol resulted in the formation of the corresponding monomeric calcium bis(alkoxide) Ca(OCPh3)2(THF)4 in 95% yield. The structure was determined as a distorted octahedron with the alkoxide ligands in a cis‐equatorial arrangement. The Ca−O bond length was determined at 2.1609(17) Å. The Ca−O−CAryl angle of 177.46(16)° is almost linear, while the O1−Ca1−O1A angle was determined at 110.12(19)°. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)