Walter S. McDonald

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.

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.

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. Part 54. Complexes of palladium, platinum, rhodium, and iridium with But2PCH2CHMe(CH2)3PBut2. Crystal structures of [PdCl(But2PCH2CHMeCHCH2CH2PBut2)] and [IrH(Cl)(But2PCH2CHMeCHCH2CH2PBut2)]

The new diphosphine But2PCH2CHMeCH2CH2CH2PBut2(L) is shown to have 13C n.m.r. shifts which can be calculated empirically from the 13C n.m.r. shifts of related diphosphines. It reacts with [PdCI2(NCPh)2] to give the cyclometallated complex [[graphic omitted]But2)](1c), with the 2-methyl group in a pseudo-equatorial position, as shown by the crystal structure. With [PtCl2(NCBut)2] it gives [Pt2Cl4L2] as a complex mixture of isomeric 16-atom ring chelates, which, on treatment with CF3COOH followed by LiCl, gives [[graphic omitted]But2)]; this was not isolated pure but probably has a structure similar to (1c). Compound L also reacts with [Ir2Cl2(C8H14)4](C8H14= cyclo-octene) to give the cyclometallated hydride complex [[graphic omitted]But2)](2c) with an equatorial methyl group. Some of the isomer with a pseudo-axial methyl group was also formed but it slowly, but completely, isomerises to (2c) in solution. Compound (2c) does not lose dihydrogen to give a carbene on heating, in contrast to [[graphic omitted]But2)]. Compound L reacts with [Rh2Cl2(C8H14)4] to give [[graphic omitted]But2)](2e), but with RhCl3·3H2O it also gives two other species, probably rhodium(I)–olefinic diphosphine complexes. Compound (2e) with sodium propan-2-oxide and CO gives [[graphic omitted]But2)]. Proton, 13C, and 31P n.m.r. and i.r. data are given. Cell dimensions: (1c)a= 1.1907(3), b= 1.6466(4), c= 1.3537(4) nm, and β= 103.99(2)°; (2c)a= 1.1954(4), b= 1.6509(5), c= 1.3665(5) nm, and β= 104.18(3)°.

Facile thermally-induced cluster oxidations in metallaborane chemistry: arachno→nido→closo reaction sequences exhibited by iridanonaboranes and iridadecaboranes, and the stabilization of the iridium(V) oxidation state

Iridanonaboranes and iridadecaboranes which have adjacent open-face bridging H atoms and terminal Ir–H atoms readily lose H2 in formal cluster oxidations which involve stable isolable iridium (V) species.

Heterobimetallic complexes of platinum with silver, gold, mercury, or cadmium bridged by Ph2PCH2PPh2: crystal structure of [(PhCC)2Pt(µ-Ph2PCH2PPh2)2AgI]

The η1-Ph2PCH2PPh2(dppm) complexes [Pt(CCR)2(η1-dppm)2](R = Ph, p-tolyl, or Me) are used to give high-yield syntheses of heterobimetallic complexes with AgI, AuI, HgII, or CdII, in which the d10-metal can be 2-, 3-, or 4-co-ordinate.

Transition metal–carbon bonds. Part 53. The further chemistry of cyclometallated complexes formed from But2P(CH2)5PBut2 and PtCl2 : crystal structure of [PtCl{But2PCH2CH2CCHCH2PBut2}]

The cyclometallated complex [[graphic omitted]But2}](1a) reacts with CO, CNMe, or CNBut(Y) in the presence of NaBPh4 to give the salts [[graphic omitted]But2}][BPh4](2). The carbonyl complex when treated with NaOMe gives the hydride [[graphic omitted]But2}]. We have previously reported that [PtCl2(NCBut)2] reacts with But2P(CH2)5PBut2 to give a number of species, including (1 a) inseparably mixed with another complex. We have now separated this complex and identified it as [[graphic omitted]But2}](3). The compound Ph3C+BF4– converts (1a) into the olefin complex [[graphic omitted]But2}][BF4](5). Attempts to deprotonate (5) and other complexes with various bases, to give (3), were unsuccessful; various products were formed for which some structures are suggested. Crystals of (3) are monoclinic, space group P21/c, with a= 1.2319(3), b= 1.4370(4), c= 1.4693(3) nm, and β= 104.58(2)°. The structure was determined from 2 457 Fo and refined to R= 0.049. The molecule is disordered.

The chemistry of isomers of icosaborane(26), B20H26: synthesis and nuclear magnetic resonance study of various isomers of platinahenicosaboranes and diplatinadocosaboranes, and the X-ray crystal and molecular structures of 7,7-bis(dimethylphenylphosphine)-nido-7-platinaundecaborane and 4-(2′-nido-decaboranyl)-7,7-bis(dimethylphenylphosphine)-nido-7-platinaundecaborane

An improved synthesis of the known compound [(PMe2Ph)2(PtB10H12)] has been developed by deprotonation of B10H14 with NNN′N′-tetramethylnaphthalene-1,8-diamine followed by treatment with cis-[PtCl2(PMe2Ph)2]. This reaction has been applied to the 2,2′, 2,6′, and 1,5′ isomers of (B10H13)2 to prepare various isomeric platinahenicosaborane clusters [(PMe2Ph)2(PtB10H11–B10H13)] which differ either in the position of the conjuncto-linkage or the site of the platinum atom in the cluster. Appropriate modification of the reaction stoicheiometry in the case of 2,2′-(B10H13)2 led to the isolation of cisoid and transoid diplatinadocosaboranes [{(PMe2Ph)2(PtB10H11)}2]. The X-ray crystal structure of [(PMe2Ph)2(PtB10H12)] showed it to contain a platinaundecaborane cluster in which the tetrahapto B10H12 group is twisted by ca. 20° with respect to the PtP2 plane. Similarly, the molecular structure of the isomer of [(PMe2Ph)2Pt(η4-B10H11–B10H13)] obtained from 2,2′-(B10H13)2 is distorted by a twist of ca. 8°. A detailed n.m.r. study of a number of these clusters has been made, using the resonances of 1H, 11B, 31P, and 195Pt. In addition to permitting structural assignments, the data reveal a novel mutual pseudo-rotation of the η4-B10H11X group (X = H or B10H13) and the (PMe2Ph)2 grouping about the central Pt atom. For [(PMe2Ph)2(PtB10H12)] the two sets of 1H-{31P} methyl resonances at 100 MHz coalesce at 71.5 °C with an implied activation energy ΔG‡ of 79 ± 5 kJ mol–1 for the fluxional process. Similar activation energies were deduced for the various isomers of [(PMe2Ph)2(PtB20H24)].

Molecular structure of the 17-vertex conjuncto-platinaheptadecaborane [(PMe2Ph){PtB16H18(PMe2Ph)}]: a 16-vertex η6-hexadecaboranyl ligand

The compound [7-(PMe2Ph){7-PtB16H18-9′-(PMe2Ph)]} is a complex of a macropolyhedral 16-vertex borane ligand based on the structure of an as yet unknown B6–B10conjuncto-borane; it is the first example of a contiguous 17-vertex cluster species, and has a number of other interesting features.

Transition-metal–carbon bonds. Part 46. Cyclopalladation and cycloplatination of N-alkyl-N-nitrosoanilines

N-methyl-N-nitrosobenzylamine (Q) is not cyclo-(ortho-)palladated by Na2[PdCl4] but gives a complex of type [PdCl2O2]. In contrast N-Methyl-N-nitrosobenzylamine is readily ortho palladated to give the chloro-bridged complex [[graphic omitted]6H4}CI2](4a). This was converted into a mononuclear acetylacetonate (5a) and into species [[graphic omitted]6H4}ClL], L = PPh3( crystal structure determined), PMe2Ph, or pyridine, (6a), (6b), or (6c) respectively. With two moles of PPh3 per palladium the Pd–NO bond is broken giving the σ-aryl species [Pd{C6H4N(NO)CH3}Cl(PPh3)2](7a), the crystal structure of which has also been determined. With 1,2-bis(diphenylphosphino)ethane (dppe), (4a) gives the ion [[graphic omitted]6H4}(dppe)]+ isolated as its tetraphenylborate salt (8a). Some palladated derivatives of N-ethyl-N-nitrosoaniline and (4-methoxy)-N-methyl-N-nitrosoaniline were made similarly. With K2[PtCl4]N-methyl-N-nitrosoaniline gives a red material which was not obtained pure but which gave a mononuclear acetylacetonate [[graphic omitted]6H4}(acac)](5c) and bis-phosphine complex [Pt{C6H4N(NO)CH3}Cl(PPh3)2](7d) analogous to the palladium complex. N-Ethyl-N-nitrosoaniline reacted similarly. Crystals of (6a) are triclinic, space group P, with a= 9.990(2), b= 15.195(3), c= 9.276(2)A, α= 104.05(2), β= 97.92(2), γ= 89.47(2)°, and Z= 2. Those of (7a) are monoclinic, space group P21/c, with a= 12.047(2), b= 21.794(4), c= 16.402(2)A, β= 108.54(1)°, and Z= 4. Both compounds crystallise with a molecule of CH2Cl2. Least-squares refinements gave final R values of 0.089 for (6a) and 0.083 for (7a).