ABSTRACT
It has been shown by IR and NMR spectroscopy that cyclic trimeric perfluoro-o-phenylenemercury (o-C6F4-Hg)3 (1) is capable of binding closo-[B10H10]2- and closo-[B12H12]2- anions to form complexes [[(o-C6F4Hg)3](B10-H10)]2- (2), [[(o-C6F4Hg)3]2(B10H10)]2-(3), [[(o-C6F4Hg)3](B12H12)]2- (4), and [[(o-C6F4Hg)3]2(B12H12)]2- (5). According to IR data, the bonding of the [B10H10]2- and [B12H12]2- ions to the macrocycle in these complexes is accomplished through the formation of B-H-Hg bridges. Complexes 2, 3, and 5 have been isolated in analytically pure form and have been characterized by spectroscopic means. X-ray diffraction studies of 3 and 5 have revealed that these compounds have unusual sandwich structures, in which the polyhedral di-anion is located between the planes of two molecules of 1 and is bonded to each of them through two types of B-H-Hg bridges. One type is the simultaneous coordination of a B-H group to all three Hg atoms of the macrocycle. The other type is the coordination of a B-H group to a single Hg atom of the cycle. According to X-ray diffraction data, complex 2 has an analogous but half-sandwich structure. The obtained complexes 2-5 are quite stable; their stability constants in THF/acetone (1:1) at 20 degrees C have been determined as 1.0 x 10(2)Lmol(-1), 2.6 x 10(3)L(2)mol(2), 0.7 x 10(2)Lmol(-1), and 0.98 x 10(3)L(2)mol(-2), respectively.
ABSTRACT
Although the two polymorphic modifications, (I) and (II), of the title compound, C(13)H(10)N(2)O, crystallize in the same space group (P2(1)/c), their asymmetric units have Z' values of 1 and 2, respectively. These are conformational polymorphs, since the molecules in phases (I) and (II) adopt different rotations of the phenyl ring with respect the central 2-cyanocarboxyaminoprop-2-enyl fragment. Calculations of crystal packing using Cerius(2) [Molecular Simulations (1999). 9685 Scranton Road, San Diego, CA 92121, USA] have shown that (I) is more stable than (II), by 1.3 kcal mol(-1) for the crystallographically determined structures and by 1.56 kcal mol(-1) for the optimized structures (1 kcal mol(-1) = 4.184 kJ mol(-1)). This difference is mainly attributed to the different strengths of the hydrogen bonding in the two forms.
Subject(s)
Alkynes/chemistry , Nitriles/chemistry , Crystallography, X-Ray , Hydrogen Bonding , Models, Molecular , Molecular ConformationABSTRACT
Two phenyl-substituted carboranes, 3-phenyl-1,2-dicarba-closo-dodecaborane(12), C8H16B10, (I), and 1-phenyl-1,7-dicarba-closo-dodecaborane(12), C8H16B10, (II), were found to be isostructural. Comparison of the bond angles at the ipso-C atoms of the phenyl substituent for (I) and (II) [117.71 (3) and 118.45 (10) degrees, respectively] indicates that electron donation of the carborane cage for B- and C-substituted carboranes is different.
ABSTRACT
Two new diterpenoids, sarcophytins B and C (1, 2), and the previously known sarcophytin (4) have been isolated from the Indian Ocean soft coral Sarcophyton sp. Structures of 1 and 2 were established by spectral data and supported by X-ray analysis of 1.
Subject(s)
Cnidaria/chemistry , Diterpenes/isolation & purification , Animals , Crystallography, X-Ray , Diterpenes/chemistry , Molecular Structure , Spectrum AnalysisABSTRACT
The title compound, C(10)H(8)N(2)O(3), has been prepared by condensation of 2-methoxybenzaldehyde and nitroacetonitrile in ethanol at room temperature. Its investigation has been undertaken as a part of search for new nonlinear optical compounds. The pi-conjugated molecule is almost planar. Molecules in the crystal are packed in stacks with antiparallel molecular orientation and slightly alternating distances between mean molecular planes.
