Martin N. Gibbons

Reactions of [SbR3X2]2O with carboxylates and the crystal structures of [SbPh3(O2CCF3)2]2O and [SbMe3(O2CCH3)2]2O

Abstract Reactions of [SbPh3Br]2O and [SbMe3Cl]2O with a number of carboxylates lead to halogen substitution and formation of either [SbR3(O2CR′)]2O or SbR3(O2CR′)2. X-ray structures for two of the products, [SbPh3(O2CCF3)]2O and [SbMe3(O2CCH3)]2O, show that the carboxylates are unidentate. From NMR spectroscopy, the oxygen bridged compounds are hydrolysed by adventitious water giving SbR3(O2CR′)OH in solution but when R=phenyl the original compounds can be recovered on crystallisation.

Oxidation of (AsPh2)2E(E=O or S); supramolecular hydrogen-bonded self-assembly of an unusual tetranuclear adduct and crystal structure of [AsPh2(O)OH · AsPh2(S)OH]2

Abstract Oxidation of (AsPh 2 ) 2 E(E = O or S) with tert-butyl hydroperoxide and sulfur in the ratios 1:1 and 1:2 has been investigated in an attempt to produce compounds of the type AsPh 2 (E)−E−AsPh 2 and [AsPh 2 (E)] 2 E. Although it has been possible to isolate all four compounds of the type AsPh 2 (E)−E-AsPh 2 , where E = O or S, the dioxidation produces are less stable and recrystallisation of the products from oxidation of (AsPh 2 ) 2 O with sulfur and (AsPh 2 ) 2 S with tert-butyl hydroperoxide leads to a mixed arsinic acid-monothioarsonic acid [AsPh 2 (O)OH · AsPh 2 (S)OH] 2 . This compound has an unusual tetranuclear structure, arising from simultaneous intermolecular hydrogen bond formation between the OH groups of the constituent acids and the oxygen of a centrosymmetrically related diphenylarsinic acid molecule.

The first oxygen-bridged diorganoarsenic(V) compound: the crystal structure of AsMe2(S)OAs(S)Me2

Abstract The oxidation of tetramethyldiarsinedisulfide, (AsMe 2 S) 2 , with t -BuOOH under anhydrous conditions leads to both AsMe 2 (S)SAs(O)Me 2 1 and AsMe 2 (S)OAs(S)Me 2 2 . The formation of the oxygen-bridged isomer 2 is unexpected and can be rationalised as resulting from either oxidation of the As(III)/As(III) form of the disulfide, (AsMe 2 SSAsMe 2 ), or by an oxotropic rearrangement of 1 via a cyclic As 2 OS transition state. RHF/3–21G ∗ ab initio calculations predict that the oxo-bridged species 2 is more stable than the thio-bridged form 1 . The molecular structure of 2 has been determined by single crystal X-ray diffraction.

Multiply Bridged Diantimony Compounds

Abstract Metathesis reactions between compounds containing either double, (Ph2SbBrO)2, or single, (Ph3SbBr)2O, Sb-O-Sb bridges and arsinates, phosphinates, phosphates and carboxylates have been used in attempts to form products containing, respectively, quadruple and triple bridges. Although triply bridged systems are obtained from (Ph3SbBr)2O and both the arsenic and phosphorus based ligands, only the former react with (Ph2SbBrO)2 to produce products with four bridges between the antimony atoms. Ligand bite is considered to be an important parameter in stabilising such products.

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

Abstract Reactions between three diorganodithiophosphinates and diphenylantimony(V) bromide oxide (SbPh2OBr)2, led to antimony reduction while dithiophosphinate oxidation followed a complex path varying in detail with the nature of the organic groups on dithiophosphinate. Antimony(III) dithiophosphinates, SbPh2(S2PR2) where R  Me, Et and Ph, have been isolated and characterised and an X-ray structure determination for the methyl derivative shows weakly associated dimers in the solid state, intermediate between those in (SbPh2S2PPh2)2 and [Sb(4-MeC6H4)2S2PEt]2.

Oxygen bridged hexa(organo)di-antimony compounds: Hydrolysis by traces of moisture and crystal structures of [SbR3Br]2O, where R = p- or o-tolyl

Abstract 1 H and 13 C NMR spectroscopy of four compounds of the type [SbR 3 X] 2 O, where X = Br and R = Ph, p -tolyl and o -tolyl or X = Cl and R = Me, have been interpreted as showing that unless stringent precautions are taken to exclude moisture there is cleavage of the oxygen bridge to give solutions which contain both the hydroxo species, SbR 3 (OH)X, and the original bridged compound. This is in agreement with earlier results from IR spectra of compounds of this type in the presence of water. Rigorous exclusion of moisture leads to NMR spectra of only the unhydrolysed compound and this is the only product isolated when NMR solutions showing the presence of both compounds are crystallised. On the other hand, a stable hydroxobromide, Sb(mesityl) 3 Br(OH), has been isolated from hydrolysis of Sb(mesityl) 3 Br 2 . Crystal structures are reported for the o - and p -tolyl isomers of [Sb(tolyl) 3 Br] 2 O; the latter has crystallographically imposed 3¯ symmetry with a linear Sb-O-Sb bridge but the two independent molecules of the o -tolyl derivative have bridge angles of 161.0(2) and 171.5(2)°, respectively.

Preparation and crystal structures of [μ-SbPh2]2[Mo(CO)2(η5-C5H5)]2·CHCl3 and SbPh[Fe(CO)2(η5-C5H5)]2

Antimony is reduced when [SbPh 2 BrO] 2 is treated with Na[Mo(CO) 3 ( η 5 -C 5 H 5 )] to produce [ μ -SbPh 2 ] 2 [Mo(CO) 2 ( η 5 -C 5 H 5 )] 2 . A structure determination shows diphenylstibido groups bridging between two Mo(CO) 2 ( η 5 -C 5 H 5 ) moieties giving a central ‘butterfly’ shaped Sb 2 Mo 2 ring. The cyclopentadiene rings are trans to each other and Mo–Sb and Sb–Sb separations are both short. An iron analogue could not be obtained from [SbPh 2 BrO] 2 and Na[Fe(CO) 2 ( η 5 -C 5 H 5 )] but a mixture of SbPh[Fe(CO) 2 ( η 5 -C 5 H 5 )] 2 and SbPh 2 [Fe(CO) 2 ( η 5 -C 5 H 5 )] was obtained using SbPh 2 Cl. An X-ray structure for SbPh[Fe(CO) 2 ( η 5 -C 5 H 5 )] 2 shows an open stibinidine structure.

Carboxylate Bridged Octaphenyltetra-antimony (V) ‘Cage’ Compounds; [(SbPh2)4(μ-O)4(μ-OH)2 (μ-O2CR)2 · HO2CR], where R = Me or t-Bu and the Crystal Structure of [(SbPh2)4(μ-O)4(μ-OH) (μ-OEt)(μ-O2CMe)2]

Reactions of [SbPh2BrO]2 with carboxylates did not give [SbPh2(O2CR[2, the expected substitution products, which are highly sensitive to hydrolysis by traces of moisture, and cage compounds containing an Sb4O6 unit were obtained instead. With silver acetate and sodium trimethylacetate the products were [(SbPh2)4(μ-O)4(μ-OH)2(μ-O2CR)2]·HO2CR, R = Me 1 and R = t-Bu 2, respectively. An unusual compound, [(SbPh2)4(μ-O)4(μ-OH)(μ-OEt(μ-O2CMe)2] 3, in which one of the bridging hydroxo groups in 1 is replaced by an ethoxo group, was also isolated and its crystal structure determined.

New square-pyramidal organoantimony(V) compounds; crystalstructures of (biphenyl-2,2′-diyl)phenylantimony(V)dibromide, dichloride and diisothiocyanate,Sb(2,2′-C12H8)PhX2(X = Br, Cl or NCS), and of octahedralSbPh(o-O2C6Cl4)Cl2·OEt2

Oxidative addition between (biphenyl-2,2′-diyl)phenylantimony(III), Sb(2,2′-C 12 H 8 )Ph 1 and Br 2 or SO 2 Cl 2 gave Sb(2,2′-C 12 H 8 )PhBr 2 2 and Sb(2,2′-C 12 H 8 )PhCl 2 3, respectively, while the corresponding fluoride Sb(2,2′-C 12 H 8 )PhF 2 4 and the thiocyanate Sb(2,2′-C 12 H 8 )Ph(NCS) 2 5 were obtained by metathesis reactions between 3 and KF and KSCN, respectively. Compounds 2 and 3 are isostructural but, in contrast to the closely related SbPh 3 X 2 species, individual molecules have square-pyramidal geometry. Again in contrast to SbPh 3 X 2 compounds, secondary antimony–halogen interactions trans to the apical carbon atom lead to solid-state dimers, implying Lewis acidity at antimony. Antimony in the thiocyanate 5 showed similar square-pyramidal geometry with N-bonded thiocyanate groups but bridging by one thiocyanate again gives dimers in the solid. Oxidative addition between SbPhCl 2 and tetrachloro-ortho-benzoquinone in ether solution gave the tetrachlorocatechol analogue of 3 as a six-co-ordinate ether solvate, SbPh(o-O 2 C 6 Cl 4 )·OEt 2 6. If the weak bond to ether is ignored, antimony again has square-pyramidal geometry but formation of the adduct again points to antimony Lewis acidity. A non-solvated substituted catecholate, SbPh(o-O 2 C 6 H 2 Bu t 2 -3,5)Cl 2 8, was also synthesized but crystals suitable for X-ray diffraction could not be obtained.

Multiply bridged organodiantimony(V) compounds; crystalstructures of[(SbR2)2(µ-O)2(µ-O2AsMe2)2] (R = Phor p-tolyl) and[(SbR3)2(µ-O)(µ-O2MR′2)2] (R = Ph,M = P, R′ = Me; R = Ph,M = As, R′ = Me or Ph;R = p-tolyl, M = P,R′ = Me)

A number of quadruply and triply bridged organodiantimony(V) compounds have been synthesized by reactions of [(SbR 2 BrO) 2 ] (R = Ph or p-tolyl) and [(SbR 3 X) 2 O] (R = Ph or p-tolyl, X = Br or Cl) with Na(O 2 AsMe 2 ), Na(O 2 AsPh 2 ) or Na(O 2 AsMe 2 ). The compounds have been characterised by a range of spectroscopic methods and crystal structures are reported for two quadruply bridged, [(SbPh 2 ) 2 (µ-O) 2 (µ -O 2 AsMe 2 ) 2 ] and [{Sb(p-MeC 6 H 4 ) 2 } 2 (µ-O) 2 (µ-O 2 AsMe 2 ) 2 ], and four triply bridged compounds, [(SbPh 3 ) 2 (µ-O)(µ-O 2 PMe 2 ) 2 ], [(SbPh 3 ) 2 (µ-O)(µ-O 2 AsMe 2 ) 2 ], [(SbPh 3 ) 2 (µ-O)(µ-O 2 AsPh 2 ) 2 ] and [{Sb(p-MeC 6 H 4 ) 3 } 2 (µ-O)(µ-O 2 PMe 2 ) 2 ]. Related trimethylantimony(V) compounds, i.e. [{SbMe 3 (O 2 PMe 2 )} 2 O] and [{SbMe 3 (O 2 AsPh 2 )} 2 O], which are highly moisture sensitive, have also been obtained.