Anthony B. Cornwell

Derivatives of divalent germanium, tin and lead : XV. Some reactions of dicyclopentadienyltin and bis(methylcyclopentadienyl)tin with metal carbonyl compounds☆

Abstract The addition of dicyclopentadienyltin or bis(methylcyclopentadienyl)tin to THF solutions of the complexes M(CO)5THF (M = Cr, Mo, W) yields the complexes R2Sn:M(CO)5 (R = C5H5, M = Cr, Mo, W; R = MeC5H4, M = Cr, W) as amorphous solids. Infrared spectral data confirm the retention of the pentahapto mode of bonding of the C5 rings to tin, whilst the drastic lowering of the tin-119m Mossbauer isomer shift from 3.74–3.83 mm s−1 in the free stannylene ligands to 1.86–2.00 mm s−1 in the complexes, which is also accompanied by an increase from ca. 0.8 mm s−1 to 2.51–3.13 mm s−1 in the quadrupole splitting, serves to demonstrate the presence of synergic tin → metal σ- and metal σ tin (d → p)π-bonding along the tinmetal axis. With ennecarbonyl diiron, dimeric, tetranuclear [R2SnFe(CO)4]2 complexes are formed, which now contain monohapto rings bound to tin. These complexes undergo ring fission in strong bases (B) affording the base stabilised B · R2SnFe(CO)4 species, which contain trigonal bipyramidally coordinated iron. Reaction of bis(methylcyclopentadienyl)tin with octacarbonyl dicobalt produces Sn[Co(CO)4]4 as the only identifiable product. The product of the reaction between dicyclopentadienyl-tin and (C5H5)W(CO)3H has been reformulated as the divalent tin derivative Sn[W(CO)3(C5H5)]2.

The interaction of divalent tin compounds with transition metal carbonyls

Abstract The reaction of tin(II) halides, cyclopentadienyls, and β-diketonates with Co 2 (CO) 8 , Fe 2 (CO) 9 , and Group VI metal carbonyls is described.

The oxidation of distannanes by the tetracyanoethylene and 7,7,8,8-tetracyanoquinodimethane

Abstract The reaction of tetracyanoethylene (TCNE) and 7,7,8,8-tetracyanoquinodimethane (TCNQ) with distannanes result in the formation of complexes of the types R3Sn(TCNE) and R3Sn(TCNQ) (R = Me, Bu). Hexaphenylditin and TCNQ give the complex (Ph3Sn)2 · (TCNQ).

Structural studies in main group chemistry : XIX. Organotin(IV) derivatives of tetracyanoethylene, 7,7,8,8-tetracyanoquinodimethane and 2,3,5,6-tetrachlorobenzoquinone. The isolation of stable organotin-substituted radicals☆

Abstract The reaction of organotin chlorides with the lithium salt of 7,7,8,8-tetracyanoquinodimethane (TCNQ) or hexaalkylditins with TCNQ yield stable organotin-substituted free radicals of the types R3SnTCNQ. (R = Me, n-Pr, n-Bu) and Me2Sn(TCNQ.)2. The reaction of hexaphenylditin with TCNQ yields a (σ → π) charge transfer complex of stoichiometry (Ph3SnSnPh3)·TCNQ, whilst [Me2SnCl(terpyridyl)+](TCNQ-·) was isolated from the reaction of [Me2SnCl(terpyridlyl)+][Me2SnCl3-] and LiTCNQ. The oxidation of hexaalkylditins by tetracyanoethylene (TCNE) yields stable free radicals of the type R3SnTCNE·, but treatment with 2,3,5,6-tetrachlorobenzoquinone yields either R3SnOC6Cl4O·-p (R = Me) or R3SnOC6Cl4OSnR3-p (R = n-Bu, Ph). Tin-119 Mossbauer spectroscopy shows that the derivatives R3SnTCNQ· and R3TCNE· have trigonally-bipyramidally coordinated tin with planar [SnC3] skeletons and bridging [TCNQ·] and [TCNE·] groups forming infinite one-dimensional chain structures. Me3SnOC6Cl4O·-p was inferred to possess a similar structure but with oxy bridges forming chains with a SnOSnO backbone. Me2Sn(TCNQ·)2 has a structure intermediate between tetrahedral and octahedral with a non-linear MeSnMe unit and anisobidentate chelation by two TCNQ groups. The TCNQ derivatives were of two types: (i) “green” or “brown”, indicative of delocalisation of the Ione electron over the cyanoquinone ligand, and (ii) a “blue” form in which spin-pairing of the Ione electron between adjacent organic groups takes place. Me3SnTCNQ· may exist in both forms depending upon the mode of preparation.

Derivatives of bivalent germanium, tin, and lead. Part XIX. Reactions of bis(β-ketoenolato)tin(II) compounds with metal carbonyls: the octa-carbonyldicobalt system

The reaction of bis(β-ketoenolato)tin(II) compounds, [SnX2], with octacarbonyldicobalt in benzene at room temperature yields products of composition [{Co(CO)4}2SnX2], [Co2(CO)7(SnX2)], or [Co(CO)4(SnX)] depending on the nature of the β-ketoenolato-residue X. Infrared data indicate that the β-ketoenolato-groups chelate tin in all cases, and also the presence of both terminal and bridging carbonyl groups in [Co2(CO)7(SnX2)]. Tin-119m Mossbauer data for [{Co(CO)4}2SnX2] are very similar to those of [Co2(CO)7(SnX2)], which have the same structure as that determined for [{Co(CO)4}2Sn(pd)2](pd = pentane-2,4-dronate), demonstrating that the tetra-carbonylcobalt groups occupy cis positions at octahedrally co-ordinated tin. The Mossbauer isomer shifts of [Co(CO)4(SnX)] fall in the range 3.35–3.68 mm s–1, above those of the corresponding [SnX2] compounds, and structures involving [Co(CO)4]– anions co-ordinated to [SnX]+ cations via the carbonyl oxygen atom are proposed. The mechanisms of formation of the complexes are discussed.

Derivatives of divalent germanium, tin, and lead. Part IX. Tin(II) derivatives of alkyl acetoacetates, 4-phenylbutane-2,4-dione, 1,3-di-phenylpropane-1,3-dione, cyclohexane-1,2- and -1,3-diones, and 2-hydroxycyclohepta-2,4,6-trien-1-one

Tin(II) derivatives of the title compounds have been synthesised by reaction of the dione with bis(methylcyclo-pentadienyl)tin(II). The low values of the carbonyl-stretching vibration in the i.r. region indicate that all the diones except cyclohexane-1,3-dione function as bidentate ligands towards tin. N.m.r. and tin-119m Mossbauer data have been recorded and interpreted in terms of pseudo-trigonal-bipyramidal co-ordination of SnII. Evidence for the occurrence of an exchange process in solution has been obtained for the 2-hydroxycyclohepta-2,4,6-trien-1-one derivative. This compound is unusually stable towards oxidation and the observation of [(H5C5)Sn]+ and [(HC2)-Sn]+ fragments in the mass spectrum indicates possible association of the metal with carbon rather than oxygen in the [(C7H5O2)Sn]+ ion. Mass spectra of the 4-phenylbutane-2,4-dione and 1,3-diphenylpropane-1,3-dione derivatives have also been recorded.

Derivatives of bivalent germanium, tin, and lead. Part XX. Complex formation between tin(II) compounds and tetracyanoethylene, 7,7,8,8- tetracyanoquinodimethane, and 2,3,5,6-tetrachlorobenzoquinone

Complexes of tin(II) halides and bis(β-ketoenolates), bis(cyclopentadienyi)tin(II), and triethylammonium trichlorostannate(II) with tetracyanoethylene (tcne), 7,7,8,8-tetracyanoquinodimethane (tcnq), and 2,3,5,6- tetrachlorobenzoquinone (tcbq) have been synthesised and examined by i.r. and tin-119m Mossbauer spectroscopy. Complexes of [Sn(C5H5)2] with tcne and tcnq are formulated as charge-transfer complexes involving the π-electron system of the cyclopentadienyl rings, whereas the complexes [SnX2(tcne)·thf](X = Cl, Br, or I) and [NEt3H][SnCl3(tcne)] are considered to contain a tin-substituted radical species. Linear chain structures in which theoraanicmolecule bridaes adiacenttin atoms are proposed for the complexes of tin(II) bis(β-ketoenolates) with tcne, tcbq, and tcnq.

Derivatives of bivalent germanium, tin, and lead. Part XIII. Dicarbonyl-(methylcyclopentadienyl)stanniomanganese complexes

Complexes of composition [Mn(C5H4Me)(CO)2(SnX2)](X = various β-diketonate ligands) have been synthesised by photolysis of [Mn(C5H3Me)(CO)] and the appropriate bivalent tin compound in tetrahydrofuran.

Derivatives of bivalent germanium, tin, and lead. Part XI. The interaction of tin(II) halides and bis(β-ketoenolates) with di-iron enneacarbonyl

Tin(II) halides and bis(β-ketoenolates) react with di-iron enneacarbonyl to give high yields of complexes [(X2Sn)-Fe(CO)4](X = Cl, Br, pd, tbd, bpd, pbd, or dpd). In chloroform solution (osmometry), the pentane-2,4-dionate (pd) is dimeric but the remainder are only partially associated. Nujol mull i.r. spectra of the halide derivatives are consistent with a dimeric structure, but some dissociation is apparent for the β-ketoenolates being essentially complete for the bulky 4-phenylbutane-2,4-and 1,3-diphenylpropane-1,3-dionate ligands. In pyridine solution all the complexes are completely dissociated into pyridine-stabilised monomeric [(X2Sn)Fe(CO)4]˙py species. Varying degrees of dissociation occur in less nucleophilic solvents such as tetrahydrofuran and acetonitrile. lron-57 Mossbauer spectra of all the solid complexes demonstrate complete association into dimers at 77 K, but in frozen pyridine solution rehybridisation at iron to give trigonal-bipyramidal geometry occurs. The very low values of the tin-119 isomer shifts in the base-stabilised monomer complexes indicate substantial synergic tin→iron σ and iron→tin (d→d)π bonding.

Derivatives of bivalent germanium, tin, and lead. Part VII. Chromium, molybdenum, and tungsten pentacarbonyl complexes of tin(II) bis(β-ketoenolates)

Bis(β-ketoenolato)tin(II)-metal pentacarbonyl complexes, [(O:CR′·CH:CR·O–)2SnM(CO)5](R = R′= Me or CF3; R = Me, R′= Ph or CF3; M = Cr, Mo, or W), have been synthesised by photolysis of the Group 6 metal hexacarbonyl and tin(II) bis(β-ketoenolate) in tetrahydrofuran (thf). The i.r. spectra indicate that chelation of the β-ketoenolate residues does not change significantly on complex formation. The complexes exhibit very low isomer shifts (1.80–2.11 mm s–1), usually assumed to be characteristic of tin(IV) compounds, and demonstrate the invalidity of the use of the isomer shift of β-tin (2.56 mm s–1) as the arbitrary dividing line between the two oxidation states. The n.m.r. and Mossbauer data have been interpreted in terms of synergic (σ+π) interaction along the tin-transition metal axis.