Bernard L. Shaw

Transition metal–carbon bonds. Part XLII. Complexes of nickel, palladium, platinum, rhodium and iridium with the tridentate ligand 2,6-bis[(di-t-butylphosphino)methyl]phenyl

The bulky diphosphine 1,3-[(di-t-butylphosphino)methyl]benzene undergoes metallation very readily to give a new type of tridentate chelating system, 2,6-bis[(di-t-butylphosphino)methyl]phenyl (pcp). Complexes prepared are of the types [MX(pcp)](M = Ni, Pd, or Pt; X = Cl, Br, H, C⋮CPh, or CN; M = Rh, X = CO), [MHCl(pcp)](M = Rh or Ir), and [IrHCl(CO)(pcp)]. [Ni(CO)(pcp)][BPh4] was also prepared. 1H- and 31P- n.m.r. data and i.r. data are given.

Transition metalcarbon bonds: XL. Palladium(II) complexes of [(dimethylamino)methyl]-ferrocene

C5H5FeC5H4CH2NMe2 reacts with sodium chloropalladate(II) in the presence of sodium acetate to give the internally metallated binuclear species [Pd2X2 {C5H5FeC5H3CH2NMe2}2] (X = Cl). The corresponding iodide was prepared as were mononuclear species [Pd(acac) {C5H5FeC5H3CH2NMe2}] and [Pd-{C5H5FeC5H3CH2NMe2}L] L = PMe2Ph, AsMe2Ph, P(OMe)3 or PPh3. 1H NMR data are given.

Rapid reversible fission of a C–H bond in a metal complex: X-ray crystal structure of [RhHCl(But2PCH2CH2CHCH2CH2PBut2)]

The occurrence and stereochemistry of a rapid reversible C–H fission in [[graphic omitted]But2)] is established by n.m.r. spectroscopy, including triple resonance INDOR, and by X-ray crystallography.

Complexes of platinum(II) and palladium(II) with hybrid phosphine-phosphine oxide ligands of type Ph2P(CH2)nP()Ph2 (n = 1, 2, 3, or 4)

Treatment of [PtCl2(NCBut)2] or [PtCl2(cyclo-1,5-octadiene)] with Ph2P(CH2)n P(O)Ph2 (n = 1, dppmO; n = 2, dppeO; n = 3, dpppO; n = 4, dppbO) gives complexes of the type cis-[PtCl2{Ph2P(CH2)nP(O)Ph2}2], independently of mole ratio. Treatment of cis-[PtCl2(dppmO)2] with LiBr or NaI gives [PtX2(dppmO)2] (X = Br, cis; X = I, cis/trans mixture) and on treatment with Hg(CCPh)2 in ethanol, trans-[Pt(CCPh)2(dppmO)2] is formed. Treatment of these ligands with [PtMe2(cyclo-octa-1,5-diene)] gives exclusively cis-[PtMe2{Ph2P(CH2)nP(O)Ph2}2]. Coordination of the PO group was achieved by treating [PtCl2{Ph2P(CH2)nP(O)Ph2}2] with either AgNO3 or TlPF6, whereupon cis-[Pt{Ph2P(CH2)nP(O)Ph2-P,O}2]2+ (n = 1, or 2) is formed: these cations were also synthesized by treating [PtMe2{Ph2P(CH2)nP(≈O)Ph2}2] with HBF4. Treatment of [PdCl2(NCPh)2] with dppmO gives trans-[PdCl2(dppmO)2] only and this reacts with AgNO3 or TlPF6 to form cis-[Pd(dppmO-P,O)2]2+. The complexes were characterized by microanalysis, IR and NMR spectroscopy.

Transition metal–carbon bonds. Part 52. Large ring and cyclometallated complexes formed from But2PCH2CH2CHRCH2CH2PBut2(R H or Me) and IrCl3, or [Ir2Cl4(cyclo-octene)4] : crystal structures of the cyclometallated hydride, [IrHCl(But2PCH2CH2CHCH2CH2PBut2)], and the carbene complex [IrCl(But2PCH2CH2CCH2CH2PBut2)]

Treatment of But2P(CH2)5PBut2, with iridium trichloride gives a mixture of the 16-atom ring dihydride [lr2H2Cl4{But2P(CH2)5PBut2}2], a co-ordinatively saturated cyclometallated hydride, [[graphic omitted]But2)])(1b), which is non-fluxional, and an unidentified complex. A better route to the cyclometallated hydride (1b) is to treat [Ir2Cl2(C8H14)4](C8H14= cyclo-octene) with the diphosphine. Complex (1b) takes up carbon monoxide to give the six-co-ordinate [[graphic omitted]But2)] and loses dihydrogen on heating [ca. 200 °C (15 mmHg)] to give the very dark carbene/ylide complex [[graphic omitted]But2)](3)/(4). This carbene/ylide complex takes up dihydrogen at 20 °C (1 atm) to give back (1b). The diphosphine But2PCH2CH2CHMeCH2CH2PBut2 reacts with IrCl3 to give the 16-atom ring chelate [Ir2H2Cl4(But2PCH2CH2CHMeCH2CH2 PBut2)2], no cyclometallated product being detected. However, the complex [[graphic omitted]But2)], can be prepared from [Ir2Cl2(C8H14)4] and the diphosphine. Hydrogen-1, 13C, and 31P n.m.r. and i.r. data are reported. The crystal structures of (1b) and of the carbene/ylide (3)/(4) have been determined. Cell dimensions are, for (1b), a= 1 231.8(3), b= 1 435.9(3), c= 1 485.4(3) pm, and β= 104.82(2)° and for (3)/(4), a= 1 232.6(3), b= 1 436.2(3), c= 1 480.7(3) pm, and β= 104.87(2)°. The structures are isomorphous, with space group P21/c and Z= 4.

Deprotonation and C-alkylation of Ph2PCH2PPh2-derivatives of chromium(0), molybdenum(0), tungsten(0), platinum(II) and palladium(II)

Abstract Ph2PCH2PPh2 derivatives of the Group VI metal carbonyls, [M(CO)4(Ph2PCH2PPh2], are deprotonated by LiBun or LiMe, acting as strong bases. The resultant carbanions or lithio-derivatives are readily alkylated (trimethylsilylated) when treated with MeI, EtI, PhCH2Br, CH2CHCH2Br or Me3SiCl to give [M(CO)4(Ph2PCHRPPh2) (R = Me, Et, CH2Ph, CH2CHCH2 or SiMe3. Treatment with excess of MeLi and MeI gives the dimethylderivatives [M(CO)4(Ph2PCME2PPh2)]. Treatment of [PtX2(Ph2(PCH2PPh2)] with the non-nucleophilic (very bulky) base LiN[SiMe3]2, followed by MeI, EtI, BrCH2Ph, Me3SiCl, gives the corresponding C-substituted products [PtX2(Ph2PCHRPPh2)] (X = Cl, Br or I) and two successive treatments with LiN[SiMe3]2/MeI gives [PtI2(Ph2PCMe2PPh2)]. [PdI2Ph2PCH2PPh2)] reacts with LiN[SiMe3]2/MeI to give a mixture of [PdI2(Ph2PCMe2PPh2)], [PdI2(Ph2PCHMePPh2)] and [PdI2(Ph2PCH2PPh2)]. NMR data are given.

Formation of large chelate rings and cyclometallated products from diphosphines of type But2P(CH2)nPBut2(n= 5–8) and Ph2P(CH2)5PPh2 with palladium and platinum chlorides: factors affecting the stability and conformation of large chelate rings

The new diphosphines But2P(CH2)nPBut2(n= 5–7) are described and the previously known Ph2P(CH2)5PPh2 characterized more fully. The compounds, But2P(CH2)nPBut2(n= 5–8) react with [PdCl2(NCPh)2] to give crystalline complexes of the type [{PdCl2[But2P(CH2)nPBut2]}x], where x= 2 for n= 5, 7, or 8 but unknown for n= 6. Also for n= 5 a volatile cyclometallated complex [[graphic omitted]But2)] is formed. With [PtCl2(NCPh)2] or [PtCl2(NCBut)2], But2P(CH2)5Pbut2 gives trans-[{PtCl2[But2P(CH2)5PBut2]}x](x is unknown) and a cyclometallated product [[graphic omitted]But2)](X = Cl) contaminated by a very similar species, possibly [[graphic omitted]But2)] from which it could not be separated. The complex [{PtCl2[But2P(CH2)5PBut2]}x] with CF3CO2H, however, gives pure [[graphic omitted]But2)](X = O2CCF3) in almost quantitative yield and other pure complexes of this type with X = Cl, Br, I, or H are readily prepared by metathesis. The compound But2P(CH2)6PBut2 with [PtCl2(NCPh)2] gives trans-[{PtCl2[But2P(CH2)6PBut2]}x](x is unknown) and the cyclometallated [[graphic omitted]But2)]. A remarkable difference in extent of deuteriation is observed on treating [[graphic omitted]But2)](X = Cl or Br) with CF3CO2D. The chloro-complex is not deuteriated but the bromo-complex is deuteriated in both t-butyl and methylene groups. Using 31P n.m.r. spectroscopy the large-chelate mixed compounds described in this and previous papers, containing PBut2 groups in ‘corner’ positions, are shown to be stable in solution relative to open-chain structures. The complexes trans-[Pd2Cl4{Ph2P(CH2)5PPh2}2] and cis-[Pt2Cl4{Ph2P(CH2)5PPh2}2] are described. The literature on large-chelate-ring compounds is surveyed. Factors affecting the stability and conformational homogeneity of carbocyclic and hetero-substituted rings, cyclic peptides, and depsipeptides, and cyclic monomer–polymer equilibria are discussed. Since the effects of sterically demanding substituents on the stability of purely organic rings (large and otherwise) has been explained purely in terms of bond lengths, angles, torsion angles, etc., sterically demanding substituents must have similar effects on chelate rings. Enthalpy and entropy factors affecting the stability of large chelate rings and their conformational homogeneity in solution are discussed from this point of view. Infrared, 1H, 13C, and 31P n.m.r., and mass spectral data are given and discussed.

Transition-metal–carbon bonds. Part 45. Attempts to cyclopalladate some aliphatic oximes, NN-dimethylhydrazones, ketazines, and oxime O-allyl ethers. Crystal structures of [Pd2{CH2C(CH3)2C(NOH)CH3}2Cl2] and [Pd{CH2C(NNMe2)C(CH3)3}(acac)]

E-Methyl t-butyl ketoxime, with sodium acetate and Na2[PdCl4] in methanol, cyclopalladates regiospecifically on a t-butyl methyl to give the chloride-bridged complex [Pd2{CH2C(CH3)2C(NOH)CH3}2Cl2](1a), the crystal structure of which has been determined (see below). The corresponding bromide and iodide complexes have been made, as have several mononuclear species by bridge-splitting reactions, e.g. of type [[graphic omitted]OH)CH3}X(L)](X = Cl or Br; L = CO, PMe2Ph, PPh3, or pyridine). The salts [Pd(CH2C(CH3)2C(NOH)CH3}(Ph2PCH2CH2PPh2)](X = l or BPh4) have also been prepared. E-Ethyl t-butyl and E-phenyl t-butyl ketoximes are similarly cyclopalladated, but oximes of other carbonyl compounds, e.g. trimethylacetaldehyde, methyl isopropyl ketone, di-isopropyl ketone, ethyl methyl ketone, or 2-methylcyclohexanone, give dark intractable products. In contrast, methyl t-butyl NN-dimethylhydrazone with Na2[PdCl4] and Na[O2CMe] cyclometallates regiospecifically on the single methyl group to give [Pd2{CH2C(NNMe2)But}2Cl2]. The corresponding bromide or iodide complexes have been made as have bridge-split derivatives (with PMe2Ph, PPh3, or pyridine) and also an acetylacetonate, [[graphic omitted]Me2)But}(acac)](6), the crystal structure of which has been determined. NN-Dimethylhydrazones of acetaldehyde, acetone, cyclohexanone, or 4-t-butylcyclohexanone cause decomposition on attempted cyclopalladation. Acetophenone NN-dimethylhdrazone cyclopalladates specifically on the 2 position of the benzene ring (i.e. not on the C-methyl group). Methyl t-butylketazine cyclopalladates specifically on a t-butyl methyl giving [Pd2{CH2C(CH3)2C(NNCMeBut)CH3}2Cl2]: dimetallation could not be effected. Acetoxime O-allyl ether in methanol is cyclopalladated with concomitant attack by OMe to give [[graphic omitted]C-(CH3)2}2Cl2]. The corresponding ethoxy-compound is formed in ethanol; cyclohexanone oxime O-allyl ether is similarly palladated. Crystal data are: (1a), Monoclinic, space group P21/c, a= 7.312(1), b= 8.539(2), c=28.478(4)A, β= 91.74(1)°, and Z= 4; (6), Triclinic, space group P, a= 9.573(3), b= 10.714(3), c= 8.983(2)A, α= 94.41(2), β= 113.76(2), γ= 104.65(2)°, and Z= 2.

Transition metal—carbon bonds: XLIV. Organo-transition metal complexes containing crown ether groups☆

Some benzo-crown ethers, substituted in the arene ring, are described e.g. 15-X substituted benzo-15-crown-5 ether(1,X = CCPh, CHCHCOOH, CHCHCOOMe, CHCHCOOEt, CHCHCOCl). 15-Iodo-benzo-15-crown-5 and 18-iodo-benzo-18-crown-6, oxidatively add to Pd(PPh3)4 to give trans-[PdIR(PPh3)2], R=(2) or(3)). [Pt(stilbene)(PPh3)2] reacts similarly with the aryl iodides to give trans-[PtIR(PPh3)2](R=(2), (3), (4)-dimethoxy-phenyl. The platinum complexes with R = (2), (3) or (4) appear to form adducts with sodium iodide in solution. trans-[PtIR(PPh3)2] was converted to the corresponding thiocyanate and chloride (via the nitrate). PhCCR (R = (2) or 3,4-dimethoxyphenyl) react with cis-[PtCl2(PPh3)2 in the presence of hydrazine to give [Pt(PhCCR)(PPh3)2] and PhCCR react with [CO2(CO)8] to give [Co2(PhCCR))CO)6], with Ni(C5H5)2 to give [Ni2(C5H5)2(PhCCR)] and with W(CO)6 in acetonitrile to give [W(CO)(PhCCR)3]; PMe2Ph displaces the CO from [W(CO)(PhCCR)3] to give [W(PMe2Ph)(PhCCR)3]. [Cr(CO)6] reacts with the benzo-crown ethers RH, R = (2),(3) or (4) or with 1,2-dimethoxybenzene to give yellow arenechromium tricarbonyl complexes of the type [Cr(CO)3(RH)]. [Cr(CO)3(benzo-15-crown-5) forms a green 11 adduct with NaSCN.

Complexes of an azine diphosphine with Group 6 metal carbonyls: crystal structures of Z,Z-PPh2CH2C(But)?N?N?C(But)CH2PPh2 and [Mo(CO)3(E,Z-PPh2CH2C(But)?N?N?(But)CCH2PPh2)]

Treatment of the azine MeC(But)NNC(But)Me with 2 equivalents of LiBun, followed by 2 equivalents of PPh2Cl, gives the azine diphosphine Z,Z-PPh2CH2C(But)N–N(But)CCH2PPh21. This new diphosphine was treated with H2O2 to give the corresponding diphosphine dioxide 2a and with monoclinic sulfur to give the diphosphine disulfide 2b. Treatment of [M(CO)3(η6-cht)](cht = cyclohepta-2,4,6-triene) with 1 gave the metal tricarbonyl fac-[[graphic omitted]Ph2}](M = Mo, 3a; W, 3b; or Cr, 3c) in which the azine diphosphine is bonded in the E,Z configuration. Complexes 3a and 3b were also made by treating the corresponding metal hexacarbonyls with the azine diphosphine 1. Treatment of [M(CO)4(nbd)](M = Mo, W, or Cr; nbd = norbornadiene) with 1 gave the tetracarbonyl complexes [[graphic omitted]Ph2}]4 with the E,Z-azine diphosphine acting as a bidentate ligand. On heating, these tetracarbonyl complexes 4 were converted into the tricarbonyl complexes 3. Treatment of either 3a or 4a with 1 mol equivalent of bromine gave the neutral molybdenum(II) complex [[graphic omitted]Ph2}]5, whereas the tungsten complexes 3b and 4b with bromine gave the cation [[graphic omitted]Ph2}]+ isolated as its BPh4– salt 6. Proton, 13C-{1H} and 31P-{1H} NMR and infrared data are given. Crystals of 1 are monoclinic, space group P21/n, with a= 1667.2(2), b= 572.85(6), c= 1811.0(2) pm, β= 111.595(8)° and Z= 2; final R factor 0.0519 for 2049 observed reflections. Crystals of 3a are monoclinic, space group P21/n, with a= 985.7(1), b= 1870.2(2), c= 2220.8(2) pm, β= 93.71(1)° and Z= 4, final R factor 0.0354 for 5219 observed reflections.