Arylcalcium Hydrides as Precursors to Alkoxides and Aryloxides of Calcium

Calcium 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 CH 3 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‐ t Bu 3 C 6 H 2 O) 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−O Aryl bond length was found to average at 2.181(3) Å. The Ca−O−C Aryl 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(OCPh 3 ) 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−C Aryl 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)