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 crystal structure determination showed that in diphenylbismuth thiocyanate the thiocyanate group bridges between pairs of bismuth atoms to give infinite chains in which alternate bismuth atoms are co-ordinated to either two nitrogen or two sulfur atoms. The conformation of the resulting chain is a ‘rectangular spiral’, in contrast to the ‘triangular spiral’ structure of the related diphenylantimony thiocyanate. Unstable diphenylantimony selenocyanate has also been prepared and the complexity in the C–N stretching region of the IR spectrum suggests a structure similar to that of the thiocyanate analogue. Diphenylarsenic thiocyanate is a liquid at room temperature and a conventional 1,3-thiocyanate-bridged structure is suggested from IR data.

Some Group 15 pseudo-halides and the crystal structure of diphenylbismuth(III) thiocyanate

The structures of two new difluorophosphates, Co(O2PF2)2·2MeCN and Cu(O2PF2)2, have been determined from single-crystal X-ray data. The former crystallises in the space group Cmca, Z= 4, with a= 9.227(4), b= 13.871(5), and c= 9.471(4)A, and the structure has been refined to R= 0.046 for 489 observed reflections. The compound is polymeric with bridging difluorophosphate groups, with the cobalt atom in octahedral co-ordination to four oxygen atoms and two nitrogen atoms from the traps oriented acetonitrile molecules. The copper compound belongs to the space group Fddd, Z= 48, with a=10.134(4), b= 24.495(9), and c= 34.058(10)A, and the refinement converged at R= 0.067 for 1 587 observed reflections. It also has a polymeric structure with two independent copper atoms and bridging difluorophosphate groups. Each copper atom has four near oxygen neighbours but distorted-octahedral co-ordination is completed by two longer contacts to oxygen atoms of symmetry-related difluorophosphate groups. This tridentate function for the difluorophosphate group has not previously been observed.

Crystal structures of the difluorophosphate complexes, Co(O2PF2)2·2MeCN and Cu(O2PF2)2

Tri- and di-arylantimony(V) thiocyanates and mixed halide thiocyanates; crystal structure of triphenylantimony(V) di-isothiocyanate

Crystal structures have been determined from X-ray diffraction data for [Hpy]2[Sb2OBrnCl6-n] where n= 0 (1), 2 (2), and 4 (3) and Hpy = pyridinium. The compounds are isostructural, crystallising in the monoclinic space group P21/c, with the following cell dimensions: a= 8.816(3), b= 8.61 5(3), c= 28.116(8)A, β= 112.73(5)° for (1); a= 8.91 9(3), b= 8.81 3(3), c= 28.21 8(8)A, β= 113.57(4)° for (2); and a= 8.982(3), b= 8.884(3), c= 28.343(8)A, β= 113.80(4)° for (3). The structures have been solved by Patterson and Fourier methods and refined by full-matrix least squares to R 0.074 (2 652 observed reflections) for (1), 0.075 (2 887) for (2), and 0.066 (2 706) for (3). The compounds all contain a discrete [Sb2OX6]2– anion in which the antimony atoms are triply bridged by one oxygen and two halogen atoms. Both (2) and (3) show halogen disorder. In the former, all six halogen positions are involved but the two bridging positions have ca. 53% occupancy by bromine; in (3) the disorder is between the two sets of terminal positions and the bridging positions are uniquely occupied by bromine. A major feature of the structures and probably a great contributor to the overall stability is a very strong hydrogen bond [2.68(1)A in (1) and 2.72(1)A in (2) and (3)] between the bridging oxygen and one of the pyridinium cations.

D. Bryan Sowerby

Papers

Some Group 15 pseudo-halides and the crystal structure of diphenylbismuth(III) thiocyanate

Crystal structures of the difluorophosphate complexes, Co(O2PF2)2·2MeCN and Cu(O2PF2)2

Tri- and di-arylantimony(V) thiocyanates and mixed halide thiocyanates; crystal structure of triphenylantimony(V) di-isothiocyanate

The crystal structures of [Hpy]2[Sb2O BrnCl6 –n] where n= 0, 2, and 4 and Hpy = pyridinium; stabilisation by very strong N–H ⋯ O hydrogen bonds

Reduction of antimony(V) by dithiophosphinates and the crystal structure of dimeric diphenylantimony(III) dimethyldithiophosphinate