Many of alkylureas (H 2 NCONHC n H 2n+1 , C n -U) exhibited phase transitions and those found for C 4, 8 -U had fairly large entropy of transition, indicating formation of quasiplastic phases. X-ray structure determinations of C 2, 5-14 -U revealed a characteristic common hydrogen bond network to result in the formation of two-dimensional, platelike supramolecules having crossed arrangement of alkyl groups. The crystal structures of C 2, 5-14 -U were found to be built by stacking the corresponding supramolecules along the a axis. The phase transitions of C 10, 13, 14 -U and those of C 8, 12 -U were found to accompany shifts of supramolecules along the crystal c axis and along both the b and c axes respectively. The transitions found for C 4 , 8 -U were proved to be of order-disorder type associated with the disordering of the alkyl groups. The transition of C 4 -U was found to be associated with a drastic twist of the plane of the NCON moiety. The transition temperatures of C 4 -U and C 8 -U were depressed significantly by doping C 3 -U

Tetrakis(triphenylphosphine)palladium(0) catalyzes the hydrostannylation of alkynes to give vinylstannanes in excellent yields. This reaction proceeds in syn manner.

Yamamura parameters for the nonhydrogen atoms using block-diagonal least squares with unit weights led to an R of 0.094 for the 1567 nonzero reflections observed.R e a c t i o n o f 7 with Hg(OAc)2 o r HgC12. The reaction was carried out in a manner identical with that described in the reaction of 1 with HgX2. The mercurials 8a (a, X = OAc) and 8b (b, X = C1) were readily crystallized from methanol. 8a: 60% yield; mp 116-117 "C; IR (Nujol)

Variable-temperature UV-vis, 13 C NMR and IR studies showed that proton-transferred complexes were formed between phenols and amines in apolar solvents at low temperature. Upon cooling a solution of pnitrophenol and diisopropylamine in toluene, the colour of the solution changed from colourless to yellow. This thermochromism was ascribed to the proton transfer in the hydrogen-bonding complex. Under UV-vis conditions, butylamine and imidazole also caused similar thermochromism upon complexation with p-nitrophenol, while triethylamine, quinuclidine and pyridine did not. The thermochromic behaviour was particularly dependent on the stoichiometry of the amine and the phenol: a solution of 3,3'-dibromo-5,5'-dinitro-2,2'-biphenyldiol and diisopropylamine with a molar ratio of 1:1 showed no thermochromism, while solutions with 1:2 or higher ratios showed thermochromism, indicating that excess amine is required to obtain the proton-transferred species. These results revealed that the proton-transferred species forms in apolar solvents at low temperature if an appropriate hydrogen-bonding network between the phenol and the amine can stabilize it.

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