Nicholas C. Payne

Chelating diamide complexes of titanium: new catalyst precursors for the highly active and living polymerization of α-olefins

Abstract The reaction of RHN(CH 2 ) 3 NHR ( 1a , b ) ( a , R=2,6- i Pr 2 C 6 H 3 ; b , R=2,6-Me 2 C 6 H 3 ) with 2 equiv of BuLi followed by 2 equiv of ClSiMe 3 yields the silylated diamines R(Me 3 Si)N(CH 2 ) 3 N(SiMe 3 )R ( 3a , b ). The reaction of 3a , b with TiCl 4 yields the dichloride complexes [RN(CH 2 ) 3 NR]TiCl 2 ( 4a , b ) and two equiv of ClSiMe 3 . An X-ray study of 4a (P2 1 /n, a =9.771(1) A, b =14.189(1) A, c =21.081(2) A, β =96.27(1)°, V =2905.2(5) A 3 , Z =4, T =25°C, R =0.0701, R w =0.1495) revealed a distorted tetrahedral geometry about titanium with the aryl groups lying perpendicular to the TiN 2 -plane. Compounds 4a , b react with 2 equiv of MeMgBr to give the dimethyl derivatives [RN(CH 2 ) 3 NR]TiMe 2 ( 5a , b ). An X-ray study of 5b (P2 1 2 1 2 1 , a =8.0955(10) A, b =15.288(4) A, c =16.909(3) A, V =2092.8(7) A 3 , Z =4, T =23°C, R =0.0759, R w =0.1458) again revealed a distorted tetrahedral geometry about titanium with titanium–methyl bond lengths of 2.100(9) A and 2.077(9) A. These titanium dimethyl complexes are active catalysts for the polymerization of 1-hexene, when activated with methylaluminoxane (MAO). Activities up to 350,000 g of poly(1-hexene)/mmol catalyst·h were obtained in neat 1-hexene. These systems actively engage in chain transfer to aluminum. Equimolar amounts of 5a or 5b and B(C 6 F 5 ) 3 catalyze the living aspecific polymerization 1-hexene. Polydispersities ( M w / M n ) as low as 1.05 were measured. Highly active living systems are obtained when 5a is activated with {Ph 3 C} + [B(C 6 F 5 ) 4 ] − . A primary insertion mode (1,2 insertion) has been assigned based on both the initiation of the polymer chain and its purposeful termination with iodine.

Preparation and 31P NMR studies of platinum complexes of some chiral, bidentate phosphines

Abstract Two chiral diphosphines of formula RN(P(C 6 H 5 ) 2 , S -peap and S -alap, have been prepared from S -α-phenethylamine and the ethyl ester of S -alanine, respectively. Their syntheses, and the preparation of the achiral diphosphine beap, N , N ′-bis(diphenylphosphino)- N , N ′-dibenzylethylenediamine, are described. Platinum complexes of these bidentate ligands of formula Pt(chelate)CH 3 Cl and [Pt(chelate)CH 3 (X)]ClO 4 (X  acetone; p -YC 5 H 4 N, when Y  CH 3 , C 2 H 5 , CHO, CO 2 CH 3 , H and N(CH 3 ) 2 ; and a series of monodentate, Group V donor ligands, P(C 2 H 5 ) 3 , P(C 3 H 7 ) 3 , P(C 8 H 17 ) 3 , PCH 3 (C 6 H 5 ) 2 , P(CH 3 ) 2 C 6 H 5 , P(C 6 H 5 ) 3 , P(C 6 H 11 )(C 6 H 5 ) 2 , P(C 6 H 11 ) 2 C 6 H 5 , P(C 6 H 11 ) 3 , P(C 6 H 5 ) 2 N(C 2 H 5 ) 2 , As(C 6 H 5 ) 3 and Sb(C 6 H 5 ) 3 ) have been prepared and their 1 H and 31 P NMR parameters recorded. The cationic pyridine complexes show a correlation of the ϱ values of the para substituent to some of the 31 P chemicals shifts and coupling constants. The steric and electronic properties of the diphosphine ligands have been investigated by comparing their 31 P NMR parameters with those of analogous complexes containing (+)-diop and S , S -chiraphos.

Studies on metal–acetylene complexes. VII. The molecular structure of bis(tricyclohexylphosphine)(hexafluorobut-2-yne)platinum(0)

The acetylene complex Pt(P(cyclo-C6H11)3)2 (F3CC≡CCF3) crystallizes in the monoclinic space group P21/c with four formula units in a cell of dimensions a = 10.902(2),b = 21.766(3), c = 19.808(3) A, and β = 116.52(1)°. Three-dimensional X-ray data were collected on a four circle automatic diffractometer using Cu radiation. The structure was solved by the heavy atom method, and refined by full-matrix least-squares methods on F. A conventional agreement factor of 0.062 was achieved, employing 6678 observations for which I > 0. The coordination geometry at the platinum atom is essentially planar, for the acetylene triple bond makes an angle of 6.5(5)° with the plane formed by the Pt and the two P atoms. The triple bond length is 1.260(10) A. The acetylene adopts a cis-bent geometry, with a mean bend-back angle of 45.5(8)°. The ligand is considerably perturbed upon coordination to the Pt atom, as is evident from the Δv(C≡C) value of 578 cm−1.

Preparation and spectroscopic studies of five-co-ordinate β-diketonatotri(organo)tin compounds. Crystal structure of (1,3-diphenylpropane-1,3-dionato)triphenyltin(IV)

A series of new five-co-ordinate complexes, R3SnL [R = Me. (I)–(III) or Ph, (IV)–(VI); L = anions of acetylacetone (acac), benzoylacetone (bzac), or dibenzoylmethane (bzbz)], has been prepared and characterized by i.r., n.m.r. and Mossbauer spectroscopy. Compounds (I)–(III) have large quadrupole splittings (3·69–3·86 mm s–1), while those of (IV)–(VI) are much smaller (1·38–2·25 mm s–1). By use of partial quadrupole splittings these splittings are shown to be consistent with the mer-structure for compounds (I)–(III), and the all-cis-structure for (IV)–(VI). The all-cis-structure has been confirmed for (VI), [Ph3Sn(bzbz)], by a single-crystal X-ray diffraction study. Crystals are monoclinic, space group P21/c, with Z= 4 in a unit cell of dimensions: a= 13·216(5), b= 9·443(4), c= 22·344(9)A, and β= 109·42(2)°. The structure was solved by the heavy-atom method from intensity data collected by diffractometric methods, and refined by full-matrix least-squares methods to R 0·051 for 2328 observed reflections. The co-ordination about the Sn atom is essentially a distorted trigonal bipyramid. The phenyl groups occupy one axial and two equatorial co-ordination sites with the chelating ligand bonded to one equatorial and one axial site. Sn–C(eq) Bond lengths are 2·149(7) and 2·181(6), and Sn–C(ax) 2·180(6)A. The Sn–O(ax) distance [2·276(7)A] is significantly longer than Sn–O(eq)[2·094(7)A].

Studies on metal—acetylene complexes : VI. Crystal and molecular structure of [diethylbis(1-pyrazolyl)borato]methyl(1-phenylpropyne)-platinum(II), [(C2H5)2B(N2C3H3)2](CH3)Pt(C6H5CCCH3)

Abstract The crystal and molecular structure of [diethylbis(1-pyrazolyl)borato]methyl(1-phenylpropyne)platinum(II), ([(C2H5)2B(N2C3H3)2](CH3)Pt(C6H5CCCH3)), has been determined by a single crystal X-ray diffraction study using diffractometer techniques. The compound crystallizes in the monoclinic space group P21/c with a = 13.239(6), b = 11.077(5), c = 15.619)7) A and β = 114.53(2)°. The observed density of 1.71(2) g cm−3 agrees well with the calculated value, 1.687 g cm−3, assuming four molecules in the cell. A conventional agreement factor of 0.036 was obtained by least-squares refinement on F using 3289 observations and 194 variables. The coordination about the platinum atom is square planar, if the acetylene is assumed to occupy one coordination site. The substituents of the acetylene are cis-bent away from the Pt atom, the methyl substituent by 17.7(1.0)°, and the phenyl substituent by 21.2(9)°. The coordinated triple bond length is 1.227(10) A. These results indicate that the acetylene is moderately perturbed on coordination, consistent with the observation that Δν(CC) is 211 cm−1. The conformation of the ring formed by the bidentate polypyrazolylborate ligand is that of a “shallow” boat. One of the methylene H atoms on the ethyl substituents on the polypyrazolylborate ligand when placed in an idealized position is 2.65 A distant from the Pt atom.

Studies on metal-acetylene complexes

Abstract The acetylene complex (P(C 6 H 5 ) 3 ) 2 Pt(C 6 H 5 CCCH 3 ) crystallizes in the monoclinic space group P 2 1 with a = 14.840(4), b = 9.558(3), c = 13.553(4)A and β = 102.74(2)°. The observed density of 1.47(2) g cm -3 agrees with the value of 1.480 g cm -3 , calculated for M = 835.8 and Z = 2. Three dimensional X-ray diffraction intensity data were collected on an automatic four circle diffractometer using Mo radiation. The structure was solved by the heavy atom method and refined by Fourier and full matrix least-squares techniques on F . The final conventional agreement factor for the converged model is 0.042, using 2843 observations with I >3σ( I ). The coordination geometry about the Pt atom is essentially trigonal, if the coordinated triple bond of the acetylene is assumed to occupy one coordination site. The acetylene ligand adopts a cis -bent configuration, with a mean departure from linearity of 40(1)°. The coordinated triple bond length is 1.277(25) A. The plane of the phenyl substituent of the acetylene is inclined at an angle of 10.4° with the plane of the acetylene ligand. The mean Pt-(acetylene) distance is 2.029(15) A. The structural results indicate that the acetylene is considerably perturbed on coordination, consistent with the observation that Δν(C≡C) is 478 cm -1 .

The crystal and molecular structure of trans-[methyl- (2-oxacyclopentylidene)bis(dimethylphenylphosphine)- platinum(II)] hexafluorophosphate

The carbene complex trans-[CH3(CH2 COCH2 CH2)Pt{P(CH3)2 C6 H5}2]PF6 crystallizes in the centrosymetric orthorhombic space group Pcca (D82h) with a = 15.503(7), b = 18.81(1), c = 17.66(1) A. The measured density of 1.81(1) g cm−3 agrees with d(calc) = 1.81 g cm−3 for M = 703.41 and Z = 8. Three dimensional X-ray diffraction data were collected on an automatic four circle diffractometer using Mo radiation. The structure was solved by a combination of Patterson, Fourier and least-squares refinement techniques. The final conventional agreement factor for the converged model is R1 = 0.044, calculated on 1763 observations for which I > 3σ(I), with 160 variables. The anion lies on a crystallographic two-fold axis of symmetry, and is disordered. The coordination geometry is essentially square planar about the platinum atom. The cyclic carbene ligand is almost planar and is coordinated approximately perpendicular to the Pt square plane. The mean PtP distance is 2.305(5), the PtC(sp3) bond length is 2.080(18) and the C(sp2) atom lies 2.00(2) A away from the platinum atom. The structure is discussed in terms of the trans-influences of the ligands, and the character of the PtC(sp2) bond.

Studies in enantiomeric discrimination : I. Chiral phosphine complexes of platinum

Diastereomeric Pt complexes of formula [Pt(P-P)CH 3 (P ★ )]ClO 4 , where P-P is bis(diphenylphosphino)ethane or a chiral bidentate phosphine, one of 2 S -3 S -bis((diphenylphosphino)butane, (+)-2-3- O -isopropylidene-2,3-dihydroxy-1,4-bis(diphenylphosphino)butane, S-N,N -bis(diphenylphosphino)-1-phenylethylamine and S-N,N -bis((diphenylphosphino)alanine ethyl ester, and P ★ is a chiral monodentate phosphine of formula PC 6 H 5 R′R″, have been prepared. In the presence of an excess of the racemic modification of the monodentate ligand, varying degrees of stereoselective binding to the metal complex containing the chiral chelate ligand were observed. A partial resolution of several chiral monophosphines was thus achieved in situ, monitored by 31 P NMR and optical rotary dispersion spectra. The configuration of the preferentially bound enantiomer was investigated using single crystal X-ray techniques, and identified by optical rotary dispersion spectra. The factors affecting the degree and nature of the enantioselectivity are discussed.

The crystal and molecular structure of trans-[(methyl)(methylmethoxycarbene)bis(dimethylphenylphosphine)platinum(II)] hexafluorophosphate, [CH3{CH3C(OCH3)}Pt{P(CH3)2(C6H5)}2]PF6.

Abstract The crystal and molecular structure of trans-[(methyl)(methylmethoxycarbene)bis(dimethylphenylphosphine)platinum(II)] hexafluorophosphate has been determined from three dimensional X-ray data collected on an automatic four circle diffractometer using Mo radiation. The complex crystallizes in the orthorhombic system, space group Pnma, Z = 4, and unit cell dimensions a = 15.361(7), b = 15.180(7) and c = 10.933(6) ». Full-matrix least-squares refinement on F gave a final conventional R factor of 0.047 for 1714 reflections for which the observed intensity I > 3σ(I). Both ions have crystallographic site symmetry m. The coordination geometry about the platinum atom is approximately square planar. The platinum atom, the methyl-carbon atom, and the carbene ligand all lie on the mirror plane, while the two phosphine ligands are related by reflection in the mirror plane. The methylmethoxycarbene ligand adopts the trans configuration, and is disordered in the mirror plane. To account for this disorder, two carbene ligands have been refined as rigid groups, taking multiplicity factors into account. The two ligands are related by a 180° rotation about an axis passing approximately through the methyl-carbon atom and the platinum atom. The PtP bond distance is 2.283(3) », the PtCH3 bond length is 2.13(2) », and the PtC(sp2) of the carbene ligand mean bond length is 2.13(2) ».

Complexes of hybrid ligands. Synthesis of mixed-ligand, phosphino-alkoxide complexes of Pd2+: the crystal and molecular structure of the complex Ph2 PCH2C(CF3 )2OPdCl(PPh2Me)

Abstract The hybrid, bidentate, diarylphosphino-alkoxide ligand PPh 2 CH 2 C(CF 3 ) 2 O − , L 1 , gives the Pd 2+ bis- complex Pd(L 1 ) 2 , from which the chloride-bridged dinuclear complex [(L 1 )Pd(μ-Cl) 2 Pd(L 1 )] is made by reaction with PdCl 2 (PhCN) 2 . Cleavage of the dinuclear complex with monodentate ligands L 2 then gives Pd(L 1 )Cl(L 2 ) (L 2 =PPh 3 , PPh 2 Me, PPhMe 2 , PMe 3 , SMe 2 , or pyridine); NMR data show that PR 3 is cis to the phosphine site in L 1 in these complexes, but SMe 2 or pyridine are probably trans . A complete crystal and molecular structural determination has been made for cis -Pd(L 1 )Cl(PPh 2 Me). Crystals are monoclinic, space group P 2 1 / c , a = 10.821(1), b = 14.600(1), c = 18.674(2) A, β = 101.25(1)°, V = 2893 A 3 , Z = 4. Least-squares refinement on F of 361 variables using 3977 observations converged at a conventional agreement factor R = 0.025. The complex is square-planar, with the two phosphines cis ; the 5-membered chelate ring is in a dissymmetric envelope conformation. The PdP bonds differ in length, with that to the unidentate phosphine, 2.259(1) A, being significantly longer than that to the phosphine on the chelating ligand, 2.231(1) A.