Wendy I. Cross

Synthesis and characterisation of mercaptoimidazole, mercaptopyrimidine and mercaptopyridine complexes of platinum(II) and platinum(III). The crystal and molecular structures of tetra(2-mercaptobenzimidazole)- and tetra(2- mercaptoimidazole)platinum(II) chloride

Abstract Reaction of K2[PtCl4] with 2-mercaptobenzimidazole (HL2) and 2-mercaptoimidazole (HL3) in aqueous ethanol afforded the new, crystalline, square-planar platinum(II) complexes [Pt(HL2)4]Cl2.EtOH (4) and [Pt(HL3)4]Cl2.2H2O (5), the crystal and molecular structures of which are reported. In both complexes the ligands are present in the thione form with coordination taking place through the sulphur atom only. The Pt–S bond lengths are 2.304(4) and 2.312(3) A in complex (4) and 2.314(12) and 2.317(12) A in complex (5). The S–Pt–S bond angles are 90.33(13) and 89.67(13)° in complex (4) and 94.46(4) and 85.54(4)° in complex (5). Reaction of the ligands 4-hydroxy-2-mercaptopyrimidine (HL4) and 2-mercaptopyridine (HL5) with K2[PtCl4] gave the new, dimeric platinum(III) complex [Pt2(L4)4Cl2] (6) and [Pt2(L5)4Cl2]·EtOH (7) which is similar to a previously reported complex prepared by a different method. In these complexes the organic ligands are bridging N, S donors, the chlorides are terminally coordinated to each platinum and there is a platinum–platinum bond. The reaction of 4-amino-2-mercaptopyrimidine (HL6) with K2[PtCl4] gave the monomeric platinum(II) complex cis-[Pt(HL6)2Cl2]·2H2O (8) in which each HL6 ligand is coordinated to the metal ion via the exocyclic amino group. Reaction of 4,6-dihydroxy-2-methylmercaptopyrimidine (HL7) with K2[PtCl4] gave the dimeric platinum(II) complex of formula [Pt2(L7)2(HL7)2]Cl2 (9), which is suggested to contain bridging L7 and HL7 ligands.

CFC replacement HCFC-133a (CF3CH2Cl) as a convenient precursor for the synthesis of chlorodifluorovinyl-metal derivatives of main group and transition metal elements: the first X-ray structural characterisation of chlorodifluorovinyl-containing organometallic complexes

Abstract The one-pot reaction of the CFC replacement 1-chloro-2,2,2-trifluoroethane (CF3CH2Cl, HCFC-133a) with two equivalents of butyllithium in diethylether at −78°C followed by the addition of main group or transition metal halides results in good yields of the metal-chlorodifluorovinyl-containing compounds R3Sn(CClCF2) {R=Me, Et, Bu}, Sn(CClCF2)4, Sb(CClCF2)3, Hg(CClCF2)nCl(2−n) (n=1,2), trans-[Ni(CClCF2)2(PBu3)2], trans-[Pd(CClCF2)2(PBu3)2] and [Au(CClCF2)(PPh3)]. The molecular structures of Hg(CClCF2)Cl, trans-[Pd(CClCF2)2(Bu3P)2] and [Au(CClCF2)(PPh3)] have been obtained from single crystal data; these are the first such structural data to be reported for any chlorodifluorovinyl-containing organometallic complexes. The molecular structure of [Au(CFCF2)(PPh3)], which was prepared using a similar method based on CF3CH2F (HFC-134a), is also reported and compared with that of the chlorodifluorovinyl analogue.

Single and double quantum transitions in the multi-frequency continuous wave electron paramagnetic resonance (cwEPR) of three six co-ordinate nickel(II) complexes: [Ni(EtL)2(Me5dien)] and [Ni(5-methylpyrazole)6]X2, X = (ClO4)− or (BF4)−. The single crystal X-ray structure at room temperature of [Ni(5-methylpyrazole)6](ClO4)2

Multi-frequency, variable temperature cw EPR powder spectra of [Ni(EtL)2(Me5dien)] (3) and [Ni(5-methylpyrazole)6]X2, X = (ClO4)− (1) or (BF4)− (2) are reported. The spectra of 1 and 2 show a temperature variation which is consistent with an increase in ∣D∣ as the temperature decreases. The changes in the spectra of 1 are irreversible. The low temperature spectra for each compound exhibit a double quantum transition whose powder dependence is the same as that for the single quantum transitions. The reasons for this behaviour, as well as the simulations of the whole spectra at various frequencies, is discussed. The single crystal X-ray structure of 1 at room temperature is reported, whilst it was found that these crystals disintegrated on cooling. This behaviour is consistent with the change in the EPR behaviour of this compound on cooling.

Azo-containing phosphine complexes of palladium(II) and platinum(II) and their effectiveness in the Heck reaction: crystal and molecular structure of [PdCl2{PPh2{1-(4-MeC6H4N2)-2-OC(O)MeC10H5}]·2EtOH

Abstract Reaction of Na[MCl4] (M=Pd or Pd) with the azo-containing phosphines Ph2P{1-(4-RC6H4N2)-2-OR′-C10H5} {R=Me (I), NMe2 (II); R′=C(O)Me} affords the complexes [MCl2L2] (1–4) in good yield. Complexes 1–4 have all been fully characterised by elemental analysis, 1H-, 13C{1H}-, and 31P{1H}-NMR spectroscopy and UV–visible spectroscopy. The use of 1 in the Heck reaction has been investigated and shown to effect up to 1000 turnovers.

The coordination chemistry of perfluorovinyl substituted phosphine ligands, a crystallographic and spectroscopic study. Co-crystallisation of both cis- and trans-isomers of [PtCl2{PiPr2(CFCF2)}2] within the same unit cell

The coordination chemistry of the perfluorovinyl phosphines PEt2(CF=CF2), P(i)Pr2(CF=CF2), PCy,(CF=CF2) and PPh(CF=CF2)2 to rhodium(I), palladium(II), and platinum(II) centres has been investigated. The electronic properties of the ligands are estimated based on v(CO) and 1J(Rh-P) values. X-Ray diffraction data for the square-planar Pd(II) and Pt(II) perfluorovinyl-phosphine containing complexes allow estimates of the steric demand for the series of ligands PPh2(CF=CF2), PEt2(CF=CF2), P(i)Pr2(CF=CF2), PCy2(CF=CF2) and PPh(CF=CF2)2 to be determined. The (CF=CF2) fragment is found to be more electron withdrawing than (C6F5) yet sterically less demanding. These ligands therefore provide a range of electron-neutral to phosphite-like electronic properties combined with a range of steric demands. This study also reveals that short intramolecular interactions from the metal centre to the beta-fluorine atom cis to phosphorus of the CF=CF2 groups are observed in all-trans square planar complexes of the ligands. Unusually, the complex [PtCl2{P(i)Pr2(CF=CF2)}2] crystallises with both cis- and trans-isomers present in the unit cell. It appears that co-crystallisation of both isomers occurs in order to maximise fluorous regions in the crystal packing, and the extended structure displays short fluorine-fluorine contacts. The generation of mixed geometries seems to be a phenomenon of crystallisation, as solution phase NMR studies reveal the presence of only the trans-isomer.

Azo-phosphine containing complexes of Group 6 metal carbonyls: crystal and molecular structure of [Mo(CO)5{1-(4-ethylphenylazo)-6-diphenylphosphino-naphthalen-2-ol}]

Abstract Treatment of the compounds [M(CO) 5 (NCMe)] (M=Cr, Mo, W) with the phenylazonaphthylphosphines 4-R–PhN 2 -1-C 10 H 5 -2-OR′-6-PPh 2 {R′=H, R=H ( I ), R=Me ( II ), R=Et ( III ), R=Pr i ( IV ) R=Bu t ( V ); R′=C(O)Me, R=Me ( VI )} afforded the mono-substituted products [M(CO) 5 (L)] ( 1 - 8 ) (M=Cr, L= II , 1 ; M=Mo, L= I – VI , 2 – 7 ; M=W, L= II , 8 ). Further reaction of cis -[Mo(CO) 4 (piperidine) 2 ] with the azo-phosphines I – V afforded the di-substituted complexes cis -[Mo(CO) 4 (L) 2 ] ( 9 – 13 ); whereas, reaction with VI afforded cis -[Mo(CO) 4 ( II ) 2 ] 10 rather than the expected compound cis -[Mo(CO) 4 ( VI ) 2 ] ( 14 ). 14 can, however, be prepared by esterification of 10 . The observed non-innocence of piperidene on displacement from cis -[Mo(CO) 4 (piperidine) 2 ] has been further investigated. Thus, treatment of 7 with piperidene yielded 3 as a result it becomes apparent that the potential reactivity of the displaced ligand needs to be considered carefully when carrying out simple substitution reactions. The molecular structure of 4 is also reported.

Synthesis and characterisation of cyclometallated orthoazobenzene complexes of Ru(II): crystal and molecular structure of [RuCl(CO)(η2-C,N-C6H4NNPh)(PPh3)2]·0.5CHCl3·0.5Et2O. Is there a similarity to the hydroxyazo/ketohydrazone tautomerisation in ortho-hydroxyazobenzenes?

Abstract Treatment of [RuHCl(CO)(PPh3)3] with Hg(o-C6H4NNC6H5)2 affords [RuCl(CO)(η2-C,N-o-C6H4NNC6H5)(PPh3)2] (1) in good yield, where the cyclometallated azobenzene ligand coordinates through an ortho-C and N to give a five-membered chelate ring. Reaction of 1 with AgNO3, followed by NaBr or NaI, affords the chloride exchanged products [RuX(CO)(η2-C,N-o-C6H4NNC6H5)(PPh3)2] (2 and 3), while reaction of 1 with AgOC(O)Me gives the monondentate acetate complex [Ru{η1-OC(O)Me}(CO)(η2-C,N-o-C6H4NNC6H5)(PPh3)2] (4), and reaction with NaS2CNEt2·2H2O gives the chelate complex [Ru(CO)(S2CNEt2)(η2-C,N-o-C6H4NNC6H5)(PPh3)] (5). The cationic complex [Ru (CO)(bipy)(η2-C,N-o-C6H4NNC6H5)(PPh3)][BF4] (6) is obtained on treatment of 1 with AgNO3, followed by bipy and NaBF4. In the solid-state structure of 1, significant changes in the bond lengths for the cyclometallated azobenzene ligand are observed and are discussed with the aid of a range of related examples, and compared with those observed in the well-known hydroxyazo/ketohydrazone tautomeric process in azodyes.

The synthesis and chemistry of fluorovinyl-containing phosphines and the single crystal X-ray structure of SPPri2[(CF=CF2)

The first perfluorovinyl alkyl-containing phosphines of the type PR2(CFCF2) (R = Et, iPr, Cy) are reported. The reactivity of these air- and moisture-stable materials has been explored, both at the phosphorus centre and at the fluorovinyl moiety. When PR2(CXCF2) (X = F, Cl) is reacted with LiAlH4 a mixture of PR2(CXCFH) isomers and other defluorinated materials are produced, but the reaction with LiAlH(OBut)3 affords the single products Z-PR2(CFCFH) or E-PR2(CClCFH), respectively, in high yields. Reaction of the fluorovinyl alkyl phosphines with hydrogen peroxide, elemental sulfur or selenium yields fluorovinyl-containing phosphine oxides, sulfides and selenides, respectively. The phosphine sulfide SPPri2(CFCF2) is the first perfluorovinyl phosphorus(V) compound to be characterised crystallographically and it exhibits an unusually short [1.9358(9) A] PS bond. Reaction of fluorovinyl phosphines with XeF2 results in compounds of the type F2PR2(CFCF2), identified on the basis of multinuclear NMR studies. These compounds decompose in the presence of moisture to yield the respective phosphine oxides. Reaction of OPPh2(CFCF2) with Br2 results in bromine addition across the double bond to give OPPh2(CFBrCF2Br).

Reaction of dimethylselenourea and selenourea with dibromine to produce selenourea–dibromine, the ‘T’-shaped 1:1 molecular adduct N,N-dimethyl-2-selenourea–dibromine, its solvent of crystallisation-containing analogue and the unusual ionic compound 5[(H2N)(Me2N)CBr]+[SeBr6]2–[Se2Br9]–2[Br3]–. A low temperature crystallographic reinvestigation of N-methylbenzothiazole-2-selone–dibromine

The reactions of the selenoamides N,N-dimethyl-2-selenourea, dmsu, selenourea, su and N-methylbenzothiazole-2-selone, mbts, with dibromine has been studied. In all reactions the bulk product formed is the 1∶1 T-shaped addition compound, selenoamide·Br2. The crystal structure of dmsu·Br2 1 has been determined and compared to its solvated analogue, dmsu·Br2·CH2Cl2. Despite the different crystal packing in these two adducts, an asymmetry in d(Se–Br) is exhibited by both, ruling out the possibility that differences in Se–Br bond lengths are attributed solely to crystal packing forces. Both structures are essentially zwitterionic, a negative charge resides on the SeBr2 moiety and the positive charge is supported by the two nitrogen atoms. The recently reported mbts·Br2, previously described as a carbene interacting with SeBr2, was reinvestigated. Considering findings from a low temperature X-ray study and the 13C NMR spectrum, this compound is in fact also best described as zwitterionic, analogous to 1 and previously described structures. An interesting minor product from the reaction of two equivalents of dibromine with dmsu has also been characterised crystallographically. This complicated ionic structure of formula 5[(H2N)(Me2N)CBr]+[SeBr6]2–[Se2Br9]–2[Br3]– illustrates the susceptibility of certain selenoamides to carbon–selenium bond cleavage when a dihalogen that is more strongly oxidising than I2 or IBr is treated with them in a stoichiometric ratio greater than 1∶1. This curious (and disordered) structure represents the first report of the anion [Se2Br9]–.

(Triphenylarsine)iodinemonobromine: a charge-transfer adduct in which arsenic selectively bonds to iodine

The title molecule, (iodobromo)triphenylarsenic(III), [As(BrI)(C6H5)3], has a dart shape, with the phenyl rings arranged in a propeller conformation [I—As—C—C 61.3 (4), 43.8 (4) and 54.1 (4)°]. There is no indication that the halogen atoms have mixed site occupancies. Packing forces displace the I atom away from one phenyl ring [I—As—C 117.3 (2)°] towards the other two [I—As—C 109.8 (2) and 108.3 (2)°] and produce an even more pronounced leaning of the terminal bromine [As—I—Br 174.78 (2)°].