Ljubica Manojlović-Muir

The trans-influence of ligands in platinum(II) complexes. The significance of the bond length data

Abstract Bond lengths in electroneutral, monomeric chloroplatinum(II) complexes containing carbon-donor ligands indicate that there is a correlation between the extent of platinumcarbon multiple bonding and the length of the PtCl (trans to C) bond. A qualitative model is suggested to account for the trans-influence of both σ-donor and π-acceptor ligands on PtCl bonds.

Reactions of co-ordinated ligands. Part 24. The reaction of bis-(but-2-yne)carbonyl(η-cyclopentadienyl or η5-indenyl)molybdenum tetrafluoroborate with acetonitrile and phosphines; crystal structures of but-2-ynecarbonyl(η5-indenyl)(triethylphosphine)molybdenum tetrafluoroborate and but-2-yne(η5-indenyl)bis(trimethylphosphine)molybdenum tetrafluoroborate

Reaction of the compounds [Mo(CO)(RC2R1)2(η-C5H5 or η5-C9H7)][BF4] with refluxing acetonitrile in the presence of the respective acetylene affords the compounds [Mo(NCMe)(RC2R1)2(η-C5H5 or η5-C9H7)][BF4] where R = R1= Me; R = But, R1= H; R = Ph, R1= Me; R = Pr1, R1= H. Treatment of [Mo(CO)(RC2R1)2(η-C5H5 or η5-C9H7)][BF4] at room temperature in methylene chloride with PEt3, PPh3, or P(C6H11)3 gives the monoacetylene compounds [Mo(CO)L(RC2R1)(η-C5H5 or η5-C9H7)][BF4][L = PEt3, PPh3, P(C6H11)3; R = R1= Me; R = But, R1= H; R = Pri, R1= H; R = Ph, R1= Me; or R = R1= C6H4Me-4]. Reaction of the acetonitrile complexes with the phosphines PEt3, PMe3, PMePh2, Ph2PCHCHPPh2, (Ph2PCH2)2, or (Me2PCH2)2 results in the displacement of both the acetonitrile and one acetylene ligand to form complexes of the type [MoL2(RC2R1)-(η-C5H5 or η-5-C9H7)][BF4]. X-Ray single-crystal crystallographic studies were carried out on the compounds [Mo(CO)(PEt3)(MeC2Me)(η5-C9H7)][BF4] and [Mo(PMe3)2(MeC2Me)(η5-C9H7)][BF4]. Crystals of the former are monoclinic, space group P21/c, Z= 4, in a unit cell of dimensions a= 9.158(2), b= 14.726(2), c= 16.581(3)A, and β= 94.12(2)°. Crystals of the latter complex are also monoclinic, space group P21, Z= 2, in a unit cell of dimensions a= 8.661 (2), b= 10.293(2), c= 13.580(2)A, and β= 106.42(2)°. The structures have been refined to R 0.041 (R′ 0.045) and R 0.039 (R′ 0.048) for 4 329 and 2 052 respective reflections with I > 3σ(I). The molybdenum co-ordination in each cation may be described in terms of a pseudo-octahedral structure. The but-2-yne ligand adopts a similar conformation in both complexes lying approximately coplanar with either the Mo–CO or Mo–PMe3 bond. Variable-temperature 1H and 13C n.m.r. data are interpreted in terms of rotation of the acetylene. Examination of the 13C chemical shifts of the acetylene contact carbons suggests that in these complexes the acetylene ligand can act as a four-electron donor.

- and -influence of ligands in platinum(II) complexes. The crystal and molecular structure of -[PtCl2(PEt3)(CO)]

Abstract In the complexes cis -[PtCl2(PEt3L], where L = Cl−, C(NPhCH2)2, C(OEt)NHPh, CNPh, CO, PEt3, P(OPh)3 or PF3, ligands L exert cis -influence on the PtP bond lengths ( ca. 0.06A), which is almost as large as their trans -influence on the PtCl ( trans to L) bond lengths ( ca. 0.07A). The two effects are independent of each other and lead to different cis - and trans -influence series of L. The trend in PtCl( cis to L) distances, displaying a variation of about 0.03A, reflects the change in the length, and presumably strength, of the PtP bonds. The X-ray analysis of cis -[PtCl2(PEt3)(CO)] was based on diffractometric intensities of 1820 independent reflections. The crystal structure was solved by the heavy atom method and refined by full-matrix least-squares to R = 0.037. The crystals are orthorhombic, space group Pca 21, a = 12.777, b = 8.587, c = 11.424A, Z = 4. They are built of discrete monomeric molecules with cis -square planar geometry. Selected bond lengths are: PtC 1.855(14), PtP 2.265(3), PtCl( trans to C) 2.296(4) and PtCl( trans to P) 2.368(3)A.

The crystal structures of the complexes [M(C6H4NNPh)(η5-C5H5)], M = Ni, Pd and Pt

Abstract The compounds [M(C 6 H 4 NNPh)(η 5 -C 5 H 5 )] (M = Ni, 1a ; M = Pd, 1b ; M = Pt, 1c ) display the unexpected reactivity pattern Pd > Pt > Ni on treatment with monotertiary phosphines. Their structures, determined by X-ray diffraction, provide no help in explaining this reactivity pattern but do illustrate the effects of differing metal size and polarisability. In particular, 1b and 1c display highly distorted M-η 5 -C 5 H 5 geometries: MC(η 5 -C 5 H 5 ) distances range from 2.167(3) to 2.408(3) A for 1b and 2.153(7)-2.367(8) A for 1c . The NiC(η 5 -C 5 H 5 ) distances in 1a are more regular: 2.036(5)-2.148(5) A. 1a is monoclinic, space group P 2 1 / n , with a 9.502(1), b 16.155(2), c 18.659(3) A, β 99.16(1)°, Z = 8, R = 0.037 for refinement of 361 parameters using 3072 unique intensities. 1b is monoclinic, space group P 2 1 / a , a 7.046(1), b 14.897(2), c 13.709(2) A, β 101.66(1)°, Z =4, R 0.022 for refinement of 237 parameters from 3099 unique intensities. 1c is isomorphous and isostructural with 1b , a 6.993(2), b 14.846(3), c 13.709(4) A, β 101.92(2) °. R = 0.027 for refinement of 181 parameters from 2818 unique intensities.

Co-ordinated phospholes from the coupling of alkynes with bridging phosphido ligands: the crystal and molecular structures of [Co2{µ-η2:η2′-C4(CO2Me)4PPh2}(µ-PPh2)(CO)4], [Mn2(η4-C4H4PPh2)(µ-PPh2)(CO)6], and [Mn2(µ-η5-C4H4PPh2)(µ-PPh2)(CO)5]

Reaction of µ-phosphido complexes with alkynes can lead to complexes with quaternised phosphole ligands; by this means a cobalt complex, [Co2{µ-η2:η2′-C4(CO2Me)4PPh2}(µ-PPh2)(CO)4], and a manganese complex, [Mn2(η4-C4H4PPh2)(µ-PPh2)(CO)6], in which the phosphole adopts respectively a terminal and a bridging mode, have been prepared and characterised by X-ray analysis as has related manganese complex, [Mn2(µ-η5-C4H4PPh2)(µ-PPh2)(CO)5].

Conformations of diphosphinoamines; variable-temperature nuclear magnetic resonance and X-ray crystallographic studies

The variable-temperature 31P-{1H} n.m.r. spectra of a series of diphosphinoamines, X2PN(R)PX2(R = H, Me, Et, or Pri, X = Ph; R = Me, But, or CH2But, X = Cl; R = Me or But, X = F; R = Et, X = NMe2) have been studied. Complementary information on these compounds has been obtained from 1H, 13C, and 19F n.m.r., including double and triple resonance experiments. The coupling constant, 2J(PNP), covers the range –23.9 to 731.9 Hz, and its magnitude and sign can be related to the proportion of molecules in which the local symmetry of the P–N–P skeleton is C2v rather than CS. Diphosphinoamine conformers of the latter type have been clearly identified for the first time both in solution (for R = Et or Pri, X = Ph, and R = But or CH2But, X = Cl) and also in the solid phase. X-Ray analysis of Ph2PN(Pri)PPh2, based on 1 269 diffractometric intensities refined to R= 0.035, shows that the symmetry of the P–N–P skeleton is close to Cs in the solid, with P–N = 1.706(4) and 1.711(4)A, and PNP = 122.8(3)°.

A dinuclear hydride complex of platinum(I) containing both bidentate and monodentate bis(diphenylphosphino)methane ligands: the crystal structure of [Pt2H(Ph2PCH2PPh2)(μ-Ph2PCH2PPh2)2][PF6]

Abstract The crystal structure of the title compound has been determined from 6049 X-ray diffractometric intensities with I > 3σ(I), and refined by a least-squares procedure to R = 0.050. The crystals are monoclinic, space group P21/n, a = 13.702(2) b = 14.255(2), c = 39.556(6) A, β = 94.75(1)°, Z = 4. The structure of the cation displays two different coordination modes of the Ph2PCH2PPh2 ligands. Two of these are bidentate, bridging the Pt-Pt bond [2.769(1)A] to form a Pt2(μ-Ph2PCH2PPh2)2 nucleus, while the third acts as a monodentate two-electron donor. The hydrido ligand was not located, but its position is inferred from the coordination geometry of the platinum atom to which it is bonded. The metalligand distances are: Pt-P(trans to P) 2.248(3)–2.289(4) and Pt—P(trans to Pt) 2.347(4) A.

The mechanistic role of η2-vinyl complexes in metal-promoted alkyne oligomerisations. The crystal and molecular structures of [W{η5-C(CF3)C(CF3)C(CO2Me )C(CO2Me)C(CF3)C(CF3)SPri}(η5-C5H5)], [WF {η5-C(CF2)C(CF3)C( CO2Me)C( CO2Me)C(CF3)C(CF3)SPri}(η5-C5H5)], and [W{η4-C(CF3)C(CF3)C(Me)C(Me)SPri}(η2-CF3CCCF3)(η5-C5H5)]

Reactions of Alkynes RCCR (R = CF3, CO2Me, or Me) with η2-vinyl complexes [W{η2-C(CF3)C(CF3)SR′}(CF3CCCF3)(η5-C5H5)](R′= Et, Prn, or Pri) give isomeric products [W(CF3C2CF3)2(RC2R)SR′(η5-C5H5)] resulting from insertion of the incomingalkyne into the MC bond of the η2-vinyl and thus illustrate that η2-vinyls can act as intermediates in metal-promoted alkyne oligomerisation reactions.

Crystal and molecular structure, and 31P N.M.R. characteristics of di-μ-chlorodi(propionyl)bis(dimethylphenylphosphine)diplatinum(III). Trans-influence of ligands in binuclear complexes

Abstract The 31 P n.m.r. spectra of the cis and trans isomers of (Pt 2 (μ-Cl) 2 (COEt) 2 (PMe 2 Ph) 2 ] reveal 1 J(PtP) coupling constants of ca 5400 Hz. The crystal structure of the trans isomer has been determined by X -ray diffraction methods. The PtP and PtC bond lengths are 2.209(1) and 1.972(5) A. The μ-PtCl distances, 2.498(1) A trans to COEt and 2.393(1) A trans to PMe 2 Ph, suggest that, relative to phosphine, σ-carbon donor ligands exert a greater trans -influence in binuclear complexes than they do in mononuclear platinum(II) derivatives.

The di-µ-bis(diphenylphosphino)methane-µ-hydrido-bis[methylplatinum(II)] cation: synthesis, molecular structure, and chemical properties

The binuclear title complex [Pt2Me2(µ-H)(µ-dppm)2][PF6], dppm = Ph2PCH2PPh2, has been prepared and characterized by lH and 31P n.m.r. spectroscopy and by an X-ray structure determination. Crystals are monoclinic, with space group P21/c, a= 10.640(3), b= 20.341(3), c= 23.201(3)A, β= 91.88(2)° and Z= 4. The structure has been solved by the heavy-atom method and refined to R= 0.053 for 5 374 reflections withl 3σ(I). The cation has the ‘A-frame’ structure with a Pt–Pt separation of 2.932(1)A; a closed three-centre two-electron Pt2(µ-H) bonding system is proposed. The complex undergoes slow reductive elimination of methane induced by added PMe2Ph and is photochemically decomposed, but it has high thermal stability.