MOLECULAR COCRYSTALS OF CARBOXYLIC-ACIDS PART-24 - COCRYSTALS INVOLVING TRIPHENYLPHOSPHINE OXIDE - STRUCTURES OF THE UNIQUE ADDUCT HYDRATESOF TRIPHENYLPHOSPHINE OXIDE WITH ADAMANTANE CARBOXYLIC-ACID AND TEREPHTHALIC ACID, AND THE ANHYDROUS ADDUCT WITH O-PHTHALIC ACID

The crystal structures of the adducts of triphenylphosphine oxide (TPP O) with the carboxylic acids adamantane carboxylic acid (ACA) (the 1:1 monohydrate, [(TPPO)(ACA)(H2O)1, (1)}, terephthalic acid (PPA) (the 4 .1 dihydrate, [(TPPO)(4)(PPA) (H2O)(2)], (2)} and o-phthalic acid (OPA ) {the 2:1 anhydrate, [(TPPO)(2)(OPA)], (3)} have been determined and refined to residuals 0.044, 0.040 and 0.064 for 2461, 3096 and 2227 ob served reflections, respectively. The adducts (1) and (2) represent th e first reported hydrated examples of TPPO-carboxylic acid adducts and in addition have, instead of the expected single directed hydrogen bo nd between the phosphoryl oxygen and the carboxylic acid proton [such as is found with (3)], unique three-centre interactions between the wa ter molecule, the carboxylic acid groups and either a single triphenyl phosphine oxide (the polymeric adamantane carboxylic acid structure, ( 1) [O-O, 2.654 Angstrom, 2.736 Angstrom, 3.000(5) Angstrom) or two tri phenylphosphine oxides (the monomeric terephthalic acid structure, (2) O-O, 2.567 Angstrom, 2.707 Angstrom, 2.721(5)Angstrom]}. In contrast, with (3), the two carboxylic acid groups are involved in separate dir ect interactions with the two TPPO molecules [O-O, 2.574 Angstrom, 2.6 25(8) Angstrom].