Ivor Wharf

Mesitylpseudohalogermanes Mes2Ge(CN)2 and Mes3GeX (X=CN, NCS, N3, NCO and OH; Mes=2,4,6-trimethylphenyl): syntheses, crystal and molecular structures

Abstract The crystal and molecular structures of the mesitylpseudohalogermanes, Mes2Ge(CN)2 (Mes=2,4,6-trimethylphenyl) and Mes3GeX (X=CN, NCS, N3, NCO, or OH), have been determined by X-ray diffraction methods; the isocyanate and hydroxide crystallise as a 1:1 hydrogen-bonded complex. All are covalent monomers free from pseudohalogen bridging, and all except the cyanides and hydroxide are N-bonded to germanium. Each Ge atom is four-coordinate in a distorted tetrahedral geometry, as evident from (mes)Ge(mes) angles between 112 and 120°, which are attributed to the sterically demanding mesityl groups. The greatest distortion is displayed by Mes2Ge(CN)2, for which the NCGeCN angle of 97.8(3)° and (mes)Ge(mes) angle of 119.8(3)° are also consistent with the bulky mesityl groups and the small steric requirements of the cyano groups. The GeNY angles show a distinctive trend, decreasing from 173.3(5)° for the isothiocyanate (Y=CS), through 153.5(5)° for the isocyanate (Y=CO), to 119.0(7)° for the azide (Y=NN), an effect attributed to differences in electronic structure of the pseudohalo ligands. The geometries of the compounds examined here are compared with those of some other tri- and dimesityl-Group 14 metal derivatives as well as related phenylgermanium compounds.

Crystal and molecular structures of some tri-aryltin isothiocyanates (Ar3SnNCS; Ar = C6H5, p-CH3C6H4, o-CH3C6H4, o-CH3OC6H4) and of the adduct hexamethylphosphoamide (N-thiocyanato) tris (o-tolyl) tin

Abstract Full crystal structures are reported for several tri-aryltin isothiocyanates. Ar3SnNCS [Ar  Ph (A), p-Tol (B), o-Tol (C), o-CH3OC6H4 (D)], as well for the adduct (o-Tol)3SnNCS·HMPA (E) (HMPA = hexamethylphosphoramide). Compound B like A has bridging thiocyanates with five-coordinate tin but C and D are the first accurately characterised monomeric Ar3SnNCS, with four-coordinate tin. The adduct has unambiguously five-coordinate tin even with the ortho-methyls present. The small but significant changes in thiocynate bond lenghts correlate with changes in the geometry at tin, and these changes confirm that ν(CN) values do indeed accurately monitor trends in modes of thiocynate bonding when involving coordination to the same type of Lewis acid environment.

STUDIES IN ARYLTIN CHEMISTRY. PART XIV. CRYSTAL AND MOLECULAR STRUCTURES OF TRIS(O-METHOXYPHENYL)TIN(IV) CHLORIDE, FLUORIDE AND OXIDE

Full crystal structures are reported for the tris( o -methoxyphenyl)tin compounds, ( o -CH 3 OC 6 H 4 ) 3 SnX [X=Cl ( A ), F ( B )] and [( o -CH 3 OC 6 H 4 ) 3 Sn] 2 O ( C ), together with both solid-state and solution (CDCl 3 ) 119 Sn NMR data for B and C as well as (Mes) 3 SnF and [( o -Tol) 3 Sn] 2 O. Compound B like A is monomeric with a similar but not identical arrangement of aryl groups around the tin while NMR data indicate that B has almost the same geometry in solution as in the solid state. The anomalously lower frequency δ ( 119 Sn) value for B is consistent with the more ionic character of the SnF bond compared with other SnX (X=Cl, Br, I) bonds. Compound C is the first (Ar 3 Sn) 2 O with an SnOSn bond angle between 140 and 180°. The comparison of solid-state with solution 2 J ( 119 Sn, 119 Sn) values for C and [( o -Tol) 3 Sn] 2 O suggests that the solid state favours structures having larger SnOSn angles. Reacting C with water gives ( o -CH 3 OC 6 H 4 ) 3 SnOH only in solution, identified by its 13 C and 119 Sn NMR spectra.

The crystal and molecular structures of diphenyldi(isothiocyanato)- bis(hexamethylphosphoramide)-tin(IV) and -lead(IV)

The compound diphenyldi(isothiocyanato)bis(hexamethylphosphoramide)tin(IV) is triclinic, space group P1, a 9.832(3), b 11.401(12), c 16.735(17) A, α 89.46(7), β 76.59(6), γ 85.81(5)° and Z  2. The structure was refined on 3741 nonzero Mo-Kα reflections collected at 173 K to R  0.036. The analogous lead(IV) compound is also triclinic, space group P1, a 10.031(1), b 12.427(2), c 15.292(5) A, α 86.97(2), β 77.78(2), γ 85.66(1)°, Z = 2. This structure was refined on 2886 Mo-Kα reflections collected at room temperature to R  0.031. These two compounds are isomorphous with unit cells containing two symmetry-independent Ph2M(NCS)2 · 2HMPA (M = Sn or Pb; HMPA = hexamethylphosphoramide) molecules occupying crystallographic inversion centers. The two molecules have very similar geometries, with an all-trans arrangement of ligands around the metal.

A fast atom bombardment mass spectrometry study of the hexamethylphosphoramide adducts of phenyltin(IV) and phenyllead(IV) halides

Abstract The fast atom bombardment (FAB) mass spectra of a series of hexamethylphosphoramide (HMPA) adducts of phenyltin(IV) halides [Ph 3 SnX · HMPA (X = Cl, Br, I); Ph 2 SnX 2 · HMPA (X = Br, I); Ph 2 SnX 2 · 2HMPA (X = Br, I)] and phenyllead(IV) halides [Ph 3 PbX · HMPA (X = Cl, Br, I); Ph 2 PbX 2 · HMPA (X = Br, I) and Ph 2 PbX 2 · 2HMPA (X = Cl, Br, I)] in a glycerol/HMPA matrix have been investigated, and compared with their electron impact (EI) spectra. No parent ions are observed in either FAB or EI, but in the FAB spectra there is a much higher proportion of metal-containing ions which also have and HMPA molecule attached. This is the case even in a HMPA-free matrix such as p -nitrophenyloctyl ether (NPOE). The main difference in the FAB spectra is the preferential loss of halide compared to phenyl, the reverse of that observed in the EI spectra. The same trend is observed for the IE and FAB spectra of the uncomplexed organometallics. Diphenyltin dihalide · HMPA adducts in the glycerol/HMPA matrix form Ph 3 Sn species which are absent when NPOE is used as the matrix liquid.

Synthesis and vibrational spectra of some tri- and di-phenylhaloplumbates

Abstract Phenylhaloplumbate salts of the type [Et 4 N][Ph 3 PbXY] (X or Y = Cl, Br, I), [Et 4 N][Ph 6 Pb 2 X 2 Y] (X or Y=Cl, Br), [Et 4 N][Ph 2 PbX 3 ] (X = Cl, Br, I), and [Me 4 N] 2 [Ph 2 PbX 4 ] (X = Cl, Br) have been prepared and characterised in the solid state by infrared and Raman spectroscopy over the range 250–80 cm −1 . Similar vibrational data are reported for [Me 4 N][Ph 3 PbX 2 ] (X = Cl, Br) and [Me 4 N][Ph 2 PbCl 3 ] as well as new data for Ph 3 PbX and Ph 2 PbX 2 (X = Cl, Br, I). These infrared and Raman data are consistent with 5-coordinate, approximately trigonal-bipyramidal structures for triphenyllead systems (except Ph 3 PbI) and 6-coordinate, approximately octahedral structures for diphenyllead systems (except Ph 2 PbI 2 ), the required degree of coordination being achieved by halogen bridges where necessary. Stretching modes associated with halogen bridges are observed as strong, broad infrared bands only weakly Raman active, characteristics which suggest that these bonds have high ionic character.

Synthesis and spectroscopic and X-ray structural characterisation of some para-substituted triaryltin(pentacarbonyl)manganese(I) complexes

Abstract A series of para-substituted triaryltin(pentacarbonyl)manganese(I) compounds [(p-XC6H4)3SnMn(CO)5: II, X=CH3; III, X=CH3O; IV, X=CH3S; V, X=F; VI, X=Cl; VII, X=CH3S(O2)] is reported for comparison with the known phenyl analogue I. IR data [ν(CO)] as well as complete 119Sn/55Mn/13C solution NMR results are given for I–VII. Chemical shifts, 119Sn versus 55Mn, except I, correlate well, but have differing single parameter (SP) correlations, 119Sn versus σI and 55Mn versus σ°p. These results are compared with previous SP studies of the 119Sn solution NMR spectra of the series, (p-XC6H4)4Sn and (p-XC6H4)3SnY (Y=Cl, Br, I). Full crystal structures are reported for compounds II–VI. All are similar to that of I, with the Mn(CO)5 moiety being a distorted tetragonal pyramid, and having a quasi-mirror plane through the central C4MnSnC3 skeleton. The Ar3Sn are distorted trigonal propellers with ring torsion angles in the range 30–80°, the exception being IV with one torsion angle of 22°.

Chlorotris(2,4,6-trimethylphenyl)tin(IV) and its ethanol hemisolvate

Chlorotris(2,4,6-trimethylphenyl)tin(IV), crystallizes from ethanol as solvent-free needles, [Sn(C(9)H(11))(3)Cl], (I), and as the hemisolvate, [Sn(C(9)H(11))(3)Cl].0.5C(2)H(6)O, (II). The asymmetric unit in (I) has three independent molecules, whereas in (II), there are two [Sn(C(9)H(11))(3)Cl] molecules together with one ethanol molecule. In the unit cell of (II), the ethanol molecules lie in channels between stacks of (Mes)(3)SnCl molecules (Mes is 2,4,6-trimethylphenyl) and each ethanol molecule is disordered (0.50:0.50) over two positions. A comparison of the structures of the title compounds and other (Mes)(3)SnX (X = F, Br or I) systems with those of the triphenyltin analogues shows that the steric requirements of the o-CH(3) groups are met by a flattening of the SnC(3) skeleton and increases in the average Sn-X and Sn-C values. Comparing Sn-X data for (Mes)(3)SnX (X = F, Cl, Br or I) systems with values for the tris(o-methoxyphenyl)tin analogues suggests that the Sn-F distance of 1.961 A in (Mes)(3)SnF may well be characteristic of sterically unhindered four-coordinate Ar(3)SnF systems.

Pressure-tuning infrared and Raman spectroscopy of Group 14 tetraphenyl compounds

The effect of high external pressures on the vibrational spectra of the tetraphenyl Group 14 compounds, Ph4M (M = Si, Ge, Sn, Pb), were examined between ambient pressure and 40 kbar with the aid of a diamond-anvil cell. The four compounds displayed similar behaviour as the pressure was increased and a structural transition at approximately 15 kbar, most probably associated with a phenyl ring rotation, was identified in each case. The pressure dependencies of selected vibrational modes were obtained.

Studies in Aryltin Chemistry. Part 15. The Sulphur Effect in the EI and Positive-ion FAB Mass-spectra of Some p-Methylthiophenyltin Compounds

Electron-impact (EI) and fast-atom bombardment (FAB) mass-spectra (MS), the latter in a m-nitrobenzyl alcohol (NBA) matrix, are reported for Ar„SnPh(4.n) (Ar = /?-CH3SC6H4; η = 1-4) and Ar3SnX (X = CI, Br, I). In both EIand FAB-MS for ArnSnPh(4.n) significant molecular ion (M x ) intensity ( 10-12%) is present regardless of the number of CH3S groups present. In contrast to Ph4Sn, no (OE x + ) (ArPh)2Sn x + ions are observed. ΕΙ-MS data for Ar3SnX (X = CI, Br, but not I) vary with the probe temperature, suggesting the sample undergoes disproportionation before ionisation, the effect being greater with X = Br. FAB-MS (NBAmatrix) data for Ar3SnX show much less sign of this effect.