Relationships between the carbon-oxygen stretching frequencies of carboxylato complexes and the type of carboxylate coordination

This critical review presents a comprehensive study of transition-metal carboxylate clusters which may serve as secondary building units (SBUs) towards construction and synthesis of metal–organic frameworks (MOFs). We describe the geometries of 131 SBUs, their connectivity and composition. This contribution presents a comprehensive list of the wide variety of transition-metal carboxylate clusters which may serve as secondary building units (SBUs) in the construction and synthesis of metal–organic frameworks. The SBUs discussed here were obtained from a search of molecules and extended structures archived in the Cambridge Structure Database (CSD, version 5.28, January 2007) which included only crystals containing metal carboxylate linkages (241 references).

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Secondary building units, nets and bonding in the chemistry of metal–organic frameworks

This paper reviews research into the mechanisms of action of the lubricating oil additive, zinc dialkyldithophosphate (ZDDP). The development of the use and research into ZDDP is first charted historically, starting with the additive's first introduction in engine oils in the late 1930s. Then our current state of knowledge of each of the main facets of ZDDP behaviour both in solution and at metal surfaces is identified and discussed. It is concluded that we now know a great deal about the properties and morphology of ZDDP antiwear films but still relatively little about the reaction pathways that lead to ZDDP film formation or about the kinetics of ZDDP film generation and removal.

The History and Mechanisms of ZDDP

Structural and functional evolution of metallacrowns.

Organotin assemblies containing SnO bonds

A re-examination of the reaction between diphenylantimony trichloride and methanol showed that the initial product is a methanol adduct of the monomethoxide, SbPh2Cl2(OMe), rather than the oxide (SbPh2Cl2)2O, which is a hydrolysis product formed during recrystallisation. The corresponding tribromide, and the mixed halides, SbPh2Br3–nCln where n= 1 or 2, react similarly with methanol, losing a bromine atom to give solvated monomethoxy products. X-Ray diffraction analysis revealed that SbPh2Br2(OMe) crystallises as a centrosymmetric dimer, incorporating two molecules of methanol, which are attached via strong hydrogen bonds to the oxygen atoms of the methoxy groups. Co-ordination of the methanol oxygen to a symmetry-related antimony atom completes the distorted-octahedral co-ordination about antimony and forms a central eight-atom ring system in the chair conformation. Two unusual features are the similarity of the two Sb–O distances [2.101(4) and 2.121(4)A], even though the former is formally a normal σ bond and the latter a donor linkage, and the presence of a weak π-arene ⋯ H–C hydrogen bond, which probably accounts for the orthogonality of the phenyl groups at antimony.

Reaction of methanol with diphenylantimony(V) trihalides: crystal structure of [SbPh2Br2(OMe)·MeOH]2

Dibromo(phenyl)stibine

Crystals of the title compound are monoclinic with a= 15·97, b= 9·27, c= 27·34 A and β= 102°, space group C2/c with Z= 8. The atomic positions have been determined by Patterson and Fourier methods and refined by least squares to R 0·046 (1640 reflexions) from X-ray data. The conformation of the eight membered ring is close to a saddle with a mean P–N ring bond length of 1·557 A. The PNP angles are in the range 132·7–137·4°. The dimethylamino-groups and fluorine atoms are arranged alternately above and below the mean ring plane with P–N (amine) bonds of 1·621 A and P–F bonds of 1·566 A. Possible factors influencing the ring conformation adopted in tetrasubstituted compounds of this type are discussed.

Crystal structure of 1, trans-3, cis-5, trans-7-tetrakis(dimethylamino)-1,3,5,7-tetrafluorotetraphosphonitrile

Chlorination of (AsPh 2 ) 2 O with either elemental chlorine or sulfuryl chloride leads to cleavage of the oxobridge. With an excess of chlorine, the oxidation products are diphenylarsenic(V) trichloride and dihydroxodiphenylarsonium chloride. Oxidation of (AsPh 2 ) 2 O with SO 2 Cl 2 in a 1:1 molar ratio on the other hand gives diphenylarsenic(III) chloride and dihydroxodiphenylarsonium chloride. With an excess of SO 2 Cl 2 , diphenylarsenic(V) chloride, AsPh 2 Cl 3 , and dihydroxodiphenylarsonium hydrogensulfate [AsPh 2 (OH) 2 ] [HOSO 3 ] are the products. X-ray crystallography shows the latter has a supramolecular structure based on centrosymmetric dimeric ([HOSO 3 ][AsPh 2 (OH) 2 ]} 2 units formed by hydrogen bonding between pairs of tetrahedral cationic [AsPh 2 (OH) 2 ] + and anionic [HOSO 3 ] - units, which are then cross linked by further hydrogen bonds.

D. Bryan Sowerby

Papers

Reaction of methanol with diphenylantimony(V) trihalides: crystal structure of [SbPh2Br2(OMe)·MeOH]2

Dibromo(phenyl)stibine

Crystal structure of 1, trans-3, cis-5, trans-7-tetrakis(dimethylamino)-1,3,5,7-tetrafluorotetraphosphonitrile

Chlorination of (AsPh2)2O: Supramolecular structure of dihydroxodiphenylarsonium hydrogensulfate [AsPh2(OH)2] [HOSO3]

Biphenyl-2,2′-diylphenylantimony dibromide; a new square pyramidal antimony(V) compound