Alan T. Hutton

The infrared spectra of pyridine N-oxide complexes of transition metal perchlorates in relation to their structures

Abstract The infrared spectra of the complexes [M(pyO) 6 ](ClO 4 ) 2 (pyO = pyridine N -oxide; M = Mn, Fe, Co, Ni, Zn) are discussed. Assignments of v (M-O) and other significant vibrations are based on the band shifts induced by deuteration of the heterocyclic ring and the effects of metal ion substitution. Earlier spectroscopic evidence suggesting distortion from regular octahedral site symmetry is discounted by the far-infrared spectra. In agreement with recent crystallographic evidence for O h site symmetry in these complexes, one infrared-active v (M-O) band is expected and observed. The effects on the spectra of structural distortion in the 6-coordinate Cu II complex [Cu(pyO) 6 ](ClO 4 ) 2 , reduced coordination number in the 4-coordinate complex [Cu(pyO) 4 ](C1O 4 ) 2 , and increased cationic charge in the Ga III complex [Ga(pyO) 6 ](C1O 4 ) 3 are discussed.

The infrared spectra (500-150 CM−1) of the complexes cis- and trans-[Pt(pyridine)2X2] (X = Cl, Br, I, SCN)

Abstract The IR spectra of cis - and trans -[Pt(pyridine) 2 X 2 ] (X = Cl, Br, I, SCN) are discussed. Distinction between the v Pt—N and v Pt—X bands is based on their relative sensitivities to 15 N -labelling and deuteration of the pyridine ring, to halogen substitution and to 15 NCS-labelling. Two v Pt—N and two v Pt—X bands are observed in the cis -complexes as required for C 2v symmetry. The D 2h symmetry of the trans -complexes requires one v Pt-N and one v Pt—X band but additional bands are observed and are ascribed to coupling between v Pt—N and v Pt—X.

Irregular three-coordination in mercury: structures of phenyl- and methylmercury(II) dithizonate

[Hg(C6Hs)(CI3HIlN4S)] crystallizes in the monoclinic space group P2Jc with a = 5.991 (3), b = 20.68 (1), c = 17.129 (9) A,/~= 99.40 (5) °, Z = 4. [Hg(CH3)(CI3HIIN4S)] crystallizes in the triclinic space group Pl with a = 14.866 (7), b = 11.194 (6), c = 4.557 (3) A, a = 89.30 (5),/~= 95.85 (5), y= 97.62 (5) °, Z = 2. Final R = 0.058 and 0.061 respectively. In both structures the Hg atom exhibits planar, irregular three-coordination, the geometry at the Hg atom being approximately T-shaped, with the dithizone residue (C 13HllN4S-) acting as a bidentate ligand coordinating through S and N. The imino proton participates in a weak intramolecular hydrogen bond which stabilizes the N-N-C-N-N chain in an anti,s-trans configuration relative to the formal C=N double and C-N single bonds.

Bimetallic systems. Part 6. Chromium(0)–, molybdenum(0)–, or tungsten(0)–platinum(II) acetylide complexes containing bridging Ph2PCH2PPh2, including their efficient formation from platinum–silver complexes by transmetallation. Crystal structure of [(p-MeC6H4CC)-Pt(µ-CCC6H4Me-p)(µ-Ph2PCH2PPh2)2W(CO)3]

Treatment of trans-[Pt(CCR)2(dppm-P)2](dppm = Ph2PCH2PPh2) with [W(CO)3(NCMe)3] gave [(RCC)Pt(µ-CCR)(µ-dppm)2W(CO)3](R = Ph, p-tolyl, or Me) accompanied by [Pt2(CCR)4-(µ-dppm)2] and other products. Treatment of trans-[Pt(CCPh)2(dppm-P)2] with [Mo(CO)4-(1,5-cod)](1,5-cod = cyclo-octa-1,5-diene) or with [Mo(CO)3(cht)](cht = cyclohepta-1,3,5-triene) gave [(PhCC)Pt(µ-CCPh)(µ-dppm)2Mo(CO)3], in 20—25% yield, but the corresponding chromium compound could not be made in this way. However, treatment of the readily available complexes [(RCC)2Pt(µ-dppm)2AgX](X = Cl or l) with [W(CO)3(NCMe)3] or [Mo(CO)3(cht)] gave the above mentioned platinum–tungsten or –molybdenum complexes with displacement of silver halide (transmetallation), usually in good yield and without formation of the diplatinum complexes. Purple [(PhCC)Pt(µ-CCPh)(µ-dppm)2Cr(CO)3] was made similarly but not isolated. 1H-{31P} N.m.r. studies at different temperatures showed the complexes to be fluxional, corresponding to rapid terminal–bridging CCR interchange with inversion of the Pt(µ-dppm)2M boat-shaped eight-membered rings. The complexes [(RCC)Pt(µ-CCR)(µ-dppm)2W(CO)3](R = Me or Ph) were rapidly and reversibly protonated by CF3CO2H to give [(RCC)Pt(µ-CCHR)(µ-dppm)2W(CO)3]+, isolated as the PF6– salts; preliminary studies suggested that the molybdenum complexes could also be protonated. Phosphorus-31 and 1H n.m.r. data are given and discussed. With the Pt(µ-Ph2PCH2PPh2)2M moieties, platinum-195 was observed to be quite strongly (magnetically) coupled to one of the methylene hydrogens, that which was pseudo-equatorial, but coupling to the pseudo-axial hydrogen was not observed. Crystals of the title compound are monoclinic, space group P21, with a= 11.847(3), b= 16.023(4), c= 18.351 (4)A, β= 116.23(1)°, and Z= 2; final R factor 0.026 for 4 043 observed reflections. The structure shows that the two metal centres [Pt ⋯ W 3.037(1)A] are asymmetrically bridged by one of the p-tolylacetylide groups such that the Pt–C and W ⋯ C distances are 2.094(9) and 2.398(9)A, respectively, with the CC vector perpendicular to the PtP4W plane.

Bimetallic systems. Part 11. Heterobimetallic and unsymmetrical diplatinum complexes from cis-[PtR2(dppm-P)2](dppm Å Ph2PCH2PPh2; R = Me, 1 -naphthyl, or C6H4Me-o): crystal structure of [(C6H4Me-o)2Pt(µ-dppm)2PtMe2]

Treatment of cis-[Pt(C10H7)2(dppm-P)2](dppm = Ph2PCH2PPh2, C10H7= 1-naphthyl)(syn-anti mixture) with [Rh2Cl2(CO)4] gave [(C10H7)2Pt(µ-dppm)2RhCl(CO)] which showed a complex 31P-{1H} n.m.r. spectral behaviour with temperature. The analogue [(C6H4Me-o)2Pt(µ-dppm)2RhCl(CO)] was prepared in solution and behaved similarly. Treatment of cis-[Pt(C6H4Me-o)2(dppm-P)2] with [PtMe2(cod)](cod = cyclo-octa-1,5-diene) gave in solution a slowly equilibrating mixture of the syn- and anti-isomers of cis,cis-[(C6H4Me-o)2Pt(µ-dppm)2PtMe2], (4a) and (4b), respectively of which the minor (syn) isomer (4a) crystallized out and whose crystal structure has been determined. Treatment of [PtMe2(dppm-PP′)] with dppm at –30 °C gave cis-[PtMe2(dppm-P)2]in situ which on treatment with [{AgI(PPh3)}4], [AuCl(PPh3)], or AgPF6gave, respectively, [Me2Pt(µ-dppm)2AgI], [Me2Pt(µ-dppm)2Au]Cl, or [Me2Pt(µ-dppm)2Ag] PF6, all fully characterized. Solution 31P-{1H} n.m.r. studies showed that treatment of [PtMe2(dppm-P)2] with [MCl(Me)(cod)] gave the donor-acceptor cations [Me2Pt(µ-dppm)2MMe]+(M = Pt or Pd) in high yield. Crystals of the title compound are monoclinic, space group P21/n, with a= 12.371(2), b= 21.368(5), c= 21.917(5)A, β= 92.84(2)°, and Z= 4; the final R factor was 0.063 for 4 506 observed reflections. The structure confirms the cis square-planar co-ordination at both platinum atoms and shows the eight-membered Pt2P4C2ring in a twist saddle conformation with a Pt ⋯ Pt separation of 4.91 A. In the crystals used for data collection the o-tolyl groups adopt a syn configuration, which is shown to constitute the minor isomer in chloroform solution.

Bimetallic systems. Part 12. Mixed rhodium(I)–platinum(II) acetylide complexes containing bridging Ph2PCH2PPh2. Crystal structures of [(MeCC)Pt(µ-dppm)2(σ,η-CCMe)Rh(CO)]PF6 and of [ClPt(µ-dppm)2(σ,η-CCMe)Rh(CO)]PF6

Treatment of [Pt(CCMe)2(dppm-P)2] with [Rh2Cl2(CO)4] gave [(MeCC)Pt(µ-dppm)2(σ,η-CCMe)Rh(CO)]Cl readily converted into the corresponding PF6– salt (1b) the crystal structure of which was determined. Other complexes of the type [(RCC)Pt(µ-dppm)2(σ,η-CCR)Rh(CO)]Cl were made similarly; with R = Ph, p-tolyl, CH2CH2Ph, or C(Me)CH2. The complexes are fluxional with the low-temperature limiting 1H-{31P} n.m.r. spectrum showing non-equivalent pseudoequatorial and pseudo-axial CH2 protons, He coupled to 195Pt and Ha not. The fluxional process corresponds to interchange of He and Ha and interchange of terminal and bridging CCR. When heated in toluene for 3 h, [(RCC)Pt(µ-dppm)2(σ,η-CCR)Rh(CO)]Cl (R =p-tolyl or Ph) was converted into [(RCC)Pt(µ-dppm)2(σ,η-CCR) RhCl]. With CO, [(p-MeC6H4CC)Pt(µ-dppm)2(σ,η-CCC6H4Me-p)RhCl] rapidly gave back [(p-MeC6H4CC)Pt(µ-dppm)2(σ,η-CCC6H4Me-p)Rh(CO)]Cl. Treatment of [Pt(CCR)2(dppm-P)2] with [Rh2Cl2(C8H14)4](C8H14= cyclo-octene) also gave [(RCC)Pt(µ-dppm)2(σ,η-CCR)RhCl](R =p-tolyl or Ph) but the complexes were not isolated pure. Treatment of [(PhCC)2Pt(µ-dppm)2HgCl2] with [Rh2Cl2(CO)4] caused rapid and complete displacement of HgCl2, giving [(PhCC)Pt(µ-dppm)2(σ,η-CCPh)Rh(CO)]+; similarly treatment of [(PhCC)2Pt(µ-dppm)2AgCl], [(PhCC)2Pt(µ-dppm)2Cul], or [(PhCC)2Pt(µ-dppm)2Au]Cl with [Rh2Cl2(CO)4] gave [(PhCC)Pt(µ-dppm)2(σ,η-CCPh)Rh(CO)]+. Treatment of [Cl(RCC)Pt(µ-dppm)2AgCl] with [Rh2Cl2(CO)4] gave [ClPt(µ-dppm)2(σ,η-CCR)Rh(CO)]+(R = Me, Ph, or p-tolyl) isolated as PF6– or AgCl2– salts. These complexes could also be made in ‘one-pot’ syntheses, viz. successive treatment of [Pt(dppm-PP′)2]Cl2 with AgO2CMe–PhCCH followed by treatment with [Rh2Cl2(CO)4], without isolation of the intermediate platinum–silver complex. The crystal structures of [(MeCC)Pt(µ-dppm)2(σ,η-CCMe)Rh(CO)]PF6(1b) as the dichloromethane solvate and of [ClPt(µ-dppm)2(σ,η-CCMe)Rh(CO)]PF6(5a) were determined. Crystals of (1b) are orthorhombic, space group Pbca, a= 19.212(7), b= 27.364(6), c= 21.468(5)A, and Z= 8; those of (5a) are orthorhombic, space group Pn21a, a= 43.39(1), b= 25.178(9), c= 10.164(6)A, and Z= 8. Final R factors were 0.088 for 4 500 and 0.058 for 6 320 observed reflections, respectively. In each complex cation the two metal centres [Pt ⋯ Rh 3.099(2) for (1b) 3.066(2) and 3.086(2)A for (5a)] are bridged by a methylacetylide group σ-bonded to Pt and π-bonded in an unsymmetrical side-on fashion to Rh [mean Rh–CPt 2.24(2), mean Rh–CMe 2.44(2)A], giving rise to an A-frame structure.

Studies on the existence of a tautomeric equilibrium in solutions of the analytical reagent dithizone

Abstract The traditional view that solutions of dithizone in organic solvents comprise equilibrium mixtures of thiol and thione forms which are individually responsible for the characteristic strong visible absorption bands around 440 and 620 nm is examined critically. Fourier transform 1H and 13C NMR spectroscopic measurements on dithizone, seven of its alkyl-substituted homologues, and on its 13C- and 15N-labelled analogues point to the existence of only a single molecular species in chloroform, benzene or acetone. The marked solvatochromism, however, has yet to be explained. Modifications to established synthetic routes are reported which are especially suitable for the small-scale preparation of isotopically-labelled dithizone analogues.

Synthesis of [M(CO)4(Ph2PCHRPPh2)](M = Cr, Mo, or W; R = COPh or COC6H4Me-p) and photochemically induced reactions of the complex [W(CO)4{Ph2PCH(COPh)PPh2}]: crystal structures of the complexes [W(CO)4{Ph2POC(Ph)CHPPh2}] and [W(CO)4(PPh2OH)(PPh2CH2COPh)]

Compounds of type [[graphic omitted]Ph2)](M = Cr, Mo, or W) are deprotonated by LiBun and the resultant carbanions are acylated by RCOCl (R = Ph or C6H4Me-p) to give the complexes [[graphic omitted]Ph2}]. These acylated complexes react with NaOMe, reversibly, to give enolate anions [[graphic omitted]Ph2}] or with RCOCl/pyridine to give the complex [[graphic omitted])2CCR(OCOR)}]. Irradiation of [[graphic omitted]Ph2}] gives, initially, the six-membered-ring chelate complex [[graphic omitted]Ph2}](3a), which is in turn converted into [W(CO)4(PPh2OH)(PPh2CH2COPh)](4a) in the presence of light and traces of water. Crystals of both (3a) and (4a) are monoclinic, space group P21/c, with Z= 4. Those of (3a) have a= 17.013(3), b= 10.454(2), c= 19.723(3)A, and β= 114.23(1)°. Those of (4a) have a= 18.629(3), b= 9.931 (1), c= 18.182(4)A, and β= 94.58(1)°. Final R factors were 0.030 for 3 634 and 0.068 for 4 027 observed reflections, respectively.

Bimetallic systems. Part 4. Synthesis and characterisation of mixed copper(I)–, silver(I)–, or gold(I)–platinum(II) acetylide complexes containing bridging Ph2PCH2PPh2

The bis(monodentate dppm)diacetylide complexes of type trans-[Pt(CCR)2(dppm-P)2](dppm = Ph2PCH2PPh2; R = Ph, p-tolyl, Me, etc.) react with silver nitrate or silver hexafluorophosphate to give mixed platinum–silver salts of the type [(RCC)2Pt(µ-dppm)2Ag]X (X = NO3– or PF6–) or with [{AgX(PPh3)}4](X = Cl or I) to give neutral platinum–silver complexes, [(RCC)2Pt(µ-dppm)2-AgX](X = Cl or I), in excellent yield. The salts and neutral complexes can be interconverted, e.g. the nitrate salt with NaI gives the neutral platinum–silver iodide complex and when the neutral platinum–silver chloride complex [(PhCC)2Pt(µ-dppm)2AgCl] is treated with [NH4][PF6] in acetone the corresponding [PF6]– salt is formed. A more convenient method of synthesis of the complex [(PhCC)2Pt(µ-dppm)2AgX] is to treat [Pt(dppm-PP′)2]X2(X = Cl or I) with two equivalents of AgO2CMe + PhCCH. Treatment of [Pt(dppm-PP′)2]X2 with one equivalent of AgO2CMe + RCCH gives platinum–silver monoacetylides of type [(RCC)ClPt(µ-dppm)2AgCl](R = Ph, p-tolyl, Me, CH2CH2Ph, or CMeCH2). In ‘one-pot’ reactions PtCl2(or K2[PtCl4]) was treated with two equivalents of dppm followed by one equivalent of AgO2CMe + PhCCH to give the complex [(PhCC)ClPt(µ-dppm)2AgCl] in 71% overall yield. This chloro-complex, when treated with LiBr or NaI in dichloromethane–acetone, gave the corresponding bromo- or iodo-complexes [(PhCC)XPt-(µ-dppm)2AgX](X = Br or I) in ca. 90% yields. Treatment of [Pt(CCC6H4Me-P)2(dppm-p)2] with [AuCl(PPh3)] gave the platinum–gold complex salt [(p-MeC6H4CC)2Pt(µ-dppm)2Au]Cl. Treatment of [Pt(dppm-PP′)2]Cl2 with Li[Cu(CCPh)2] gives [(PhCC)2Pt(µ-dppm)2CuCl], which in acetone solution + Na[BPh4] gives the corresponding salt [(PhCC)2Pt(µ-dppm)2Cu][BPh4]. All of the complexes were characterised by microanalysis, solution conductivity measurements, i.r. spectroscopy, and particularly 31P-{1H} and 1H-{31P} n.m.r. spectroscopy. The variable-temperature 1H-{31P} and 31P-{1H} n.m.r. spectra of the complexes are discussed.

Examination of the ratio. nu. /sup D//. nu. /sup H/ for infrared bands assigned to the C--H(D) and ring vibrations in metal complexes of quinoline, pyridine, aniline, and their fully-deuterated analogues

The infrared spectra of sixteen metal complexes comprising the ligands quinoline, pyridine, aniline and their fully-deuterated analogues have been examined in order to determine the ratio D v/H v f...