Stefanus Otto

Steric effects induced by ferrocenyl in tertiary organophosphines: crystal structure of trans-chloromethylbis(ferrocenyldiphenylphosphine)palladium(II) benzene disolvate

Abstract The structure determination of the title compound, trans -[PdMeCl(PPh 2 Fc) 2 ]·2C 6 H 6 , (PPh 2 Fc=C 22 H 19 FeP) shows the Pd(II) moiety to have a square planar geometry with the bulky phosphine ligands in a trans orientation. The compound crystallises in the triclinic space group P 1 with 1 mole per unit cell accompanied by two benzene solvent molecules. A 50% statistical disorder was observed in the methyl and chloride positions. Bond distances and angles of the coordination polyhedron are PdP=2.3328(10) A, PdCl=2.378(3) A, PdC(10)=2.108(10) A, PPdCl=92.70(9)° and PPdC(10)=86.8(4)°. The structure is compared with the isomorphous trans -[Pt(Cl) 2 (PPh 2 Fc) 2 ]·2C 6 H 6 and other relevant structures of Pt(II) and Pd(II) described in the literature. The steric demand of the PPh 2 Fc ligand was estimated from all known structures to be approximately 155° using the Tolman model.

Synthesis and characterisation of ferrocene-containing β-diketonato complexes of rhodium(I) and rhodium(III)

Abstract The synthesis of new β-diketonato rhodium(I) complexes of the type [Rh(FcCOCHCOR)(CO) 2 ] and [Rh(FcCOCHCOR)(CO)(PPh 3 )] with Fc=ferrocenyl and R=Fc, C 6 H 5 , CH 3 and CF 3 are described. 1 H, 13 C and 31 P NMR data showed that for each of the non-symmetric β-diketonato mono-carbonyl rhodium(I) complexes, two isomers exist in solution. The equilibrium constant, K c , which relates these two isomers in an equilibrium reaction, are concentration independent but temperature and solvent dependent. Δ r G , Δ r H and Δ r S values for this equilibrium have been determined and a linear relationship between solvent polarity on the Dimroth scale and K c exists. The relationship between RhP bond lengths, d(RhP), and 31 P NMR peak positions as well as coupling constants 1 J ( 31 P 103 Rh) has been quantified to allow calculation of approximate d(RhP) values. Variations in d(RhP) for [Rh(RCOCHCOR′)(CO)(PPh 3 )] complexes have also been related to the group electronegativities (Gordy scale) of the terminal β-diketonato R groups trans to PPh 3 . A measure of the electron density on the rhodium centre of [Rh(RCOCHCOR′)(CO)(PPh 3 )] may be expressed in terms of the IR carbonyl stretching wave number, ν (CO), the sum of the group electronegativities of the R and R′ groups, ( χ R + χ R′ ), or the observed p K a ′ values of the free β-diketones RCOCH 2 COR ′ . An empirical relationship between ν (CO) and either p K a ′ or ( χ R + χ R′ ) has also been quantified.

Electron density manipulation in rhodium(I) phosphine complexes: structure of acetylacetonatocarbonylferrocenyl- diphenylphosphinerhodium(I)

Abstract The title complex [Rh(acac)(CO)(PPh2Fc)] (acac = acetylacetonato, PPh2Fc = ferrocenyldiphenylphosphine), was obtained in acetone by reaction of the tertiary phosphine with [Rh(acac)(CO)2] and was characterised by IR spectroscopy, 1H and 31P NMR and single crystal X-ray crystallography. This is a rare example illustrating the incorporation of the ferrocenyl moiety in a monodentate tertiary phosphine complex of rhodium(I). It crystallises in the triclinic space group P 1 with two independent molecules in the asymmetric unit and refined to R=2.40% from 5215 reflections. The independent molecules, showing the usual square planar geometry, differ mainly in the rotation mode of the asymmetric phosphine around the Rh-P bond and a slight deviation in the Rh-CO bond from linearity, which was correlated with IR data.

trans-Chloro(methyl)bis(tricyclohexylphosphine)platinum(II).

The crystal structure of the title compound, [PtCl(CH3)(C18H33P)2], is isostructural with various platinum(II) and palladium(II) complexes containing two bulky tricyclohexylphosphine ligands in a trans orientation. The Pt atom resides on an inversion centre, resulting in a 50% statistical disorder in the chloro and methyl positions. The most significant geometrical parameters are Pt-P 2.3431 (8), Pt-Cl 2.440 (4) and Pt-C1 2.179 (13) A, and P-Pt-P 180, P-Pt-Cl 89.15 (12) and 90.85 (12), and C-Pt-Cl 172.7 (5) degrees. The effective and Tolman cone angles for the tricyclohexylphosphine ligands were calculated as 160 and 162 degrees, respectively.

Bicyclic phosphines as ligands for cobalt-catalysed hydroformylation

A range of tertiary bicyclic phosphine ligands derived from cis, cis-1,5-cyclooctadiene (Phoban family) was studied by batch autoclave reactions during the hydroformylation of a mixture of linear internal decenes using a cobalt catalyst system. Comparative runs were performed with PBu(3) as representative of standard trialkyl phosphine behaviour. The Phoban ligands comprise of a cyclooctyl bicycle with a mixture of the [3.3.1] and [4.2.1] isomers where the third substituent was systematically varied, Phoban-Q (Q = CH(2)CH(3), (CH(2))(4)CH(3), (CH(2))(9)CH(3), (CH(2))(19)CH(3), (CH(2))(3)N(CH(3))(2), C(6)H(11) and C(6)H(5)). An increase in ligand concentration resulted in a decrease in the reaction rate while the selectivity towards the n-alcohol product increased in accordance with a move from more unmodified catalysis to more modified catalysis. Alcohol yields of 77-85% were obtained at rates of 1.8-2.4 h(-1) for highly modified catalysis. Under highly modified conditions the linearity of the alcohol ranges in a narrow band from approximately 85-90% from Phoban-Ph to Phoban-Cy respectively. Hydrogenation of the alkene substrate varied from approximately 9-15% for Phoban-Ph and Phoban-Cy respectively the least and most electron donating derivatives. The two phosphine isomers were separated for Phoban-C(2) and the hydroformylation activity were re-evaluated for each isomer. The less electron donating [4.2.1] isomer required slightly higher ligand concentrations to achieve fully modified catalysis and gave rates and linearities comparable to the [3.3.1] isomer but giving slightly higher yields due to less hydrogenation of the olefin. In comparison, at fully modified conditions, PBu(3) gave a rate of 0.6 h(-1), alcohol yield of 77%, linearity of 81% and 17% hydrogenation. The crystal structures of the cobalt dimers [Co(CO)(3)(Phoban[3.3.1]-C(2))](2), [Co(CO)(3)(Phoban[3.3.1]-C(5))](2), [Co(CO)(3)(Phoban[3.3.1]-C(3)NMe(2))](2), and [Co(CO)(3)(Phoban[3.3.1]-Cy)](2) have been determined and indicated very similar geometries with Co-Co and Co-P bond distances ranging from 2.6526(10)-2.707(3) and 2.1963(8)-2.2074(9) A respectively. The cone angles of the Phoban ligands were calculated from the crystallographic data, according to the Tolman model, and ranges from 159-165 degrees.

Synthesis and characterisation of water soluble Pt(II) complexes of 1,3,5-triaza-7-phosphaadamantane (PTA). Crystal and molecular structure of {cis-[PtCl2(PTA)2]}2 · H2O

Abstract Reaction of [PtCl 2 (SMe 2 ) 2 ] or K 2 PtCl 4 with two equivalents of the water soluble phosphine ligand, 1,3,5-triaza-7-phosphaadamantane (PTA), afforded crystals of { cis -[PtCl 2 (PTA) 2 ]} 2 · H 2 O, of which the solid state structure was determined by X-ray crystallography. This study describes the first crystallographic study of a cis PTA complex of Pt(II). It crystallizes in the triclinic space group P 1 with two crystallographically independent Pt(II) moieties in the asymmetric unit which are linked by strong hydrogen bonds via a common water molecule. The title compound exhibits the shortest PtP bonds (avg 2.2263(14) A) known to date. 31 P NMR shows that in aqueous solution an equilibrium exists between the cis bis isomer and [PtCl 3 − n (PTA) 1 + n ] (n = 2,3) complexes.

Quantifying the trans influence of triphenylarsine. Crystal and molecular structures of cis-[PtCl2(SMe2)(AsPh3)] and cis-[PtCl2(AsPh3)2]·CHCl3

Reaction between a mixture of cis-trans-[PtCl2(SMe2)(2)] and 1 eqiv. AsPh3 in chloroform gives Cis-[PtCl2(SMe2)(AsPh3)] crystallizing in P2(1)/n with a = 10.397(2), b = 14.876(3), c = 13.956(3) Angstrom, beta = 90.86(3)degrees and Z = 4. Selected geometrical parameters are Pt-As 2.3531(10), Pt-S 2.262(2), Pt-Cl (trans to S) 2.301(2), Pt-Cl (trans to As) 2.328(2) Angstrom and S-Pt-As 88.85(6), S-Pt-Cl(2) 90.77(8), As-Pt-Cl(1) 91.07(6) and Cl-Pt-Cl 89.42(7)degrees, cis-[PtCl2(AsPh3)(2)].CHCl3 crystallizes in P2(1)/c with a = 20.557(4), b = 9.5951(19), c = 20.147(4) Angstrom, beta = 96.77(3)degrees and Z = 4. Selected geometrical parameters are Pt-As(1) 2.3599(9), Pt-As(2) 2.3770(9), Pt-Cl(1) (trans to As(1)) 2.3515(18), Pt-Cl(2) (trans to As(2)) 2.3251(18) Angstrom and As-Pt-As 97.87(3), As(1)-Pt-Cl(2) 88.67(5), As(2)-Pt-Cl(1) 84.30(5) and Cl-Pt-Cl 89.32(7)degrees. By comparison with related structures from the literature the following trans influence series was established PMe2Ph > PPh3 > AsPh3 approximate to SbPh3 > Me2SO approximate to SMe2 approximate to SPh2 > NH3 approximate to olefin > Cl- > MeCN

Five co-ordination at platinum(II) in a water soluble tertiary phosphine complex: crystal structure of [Pt(PTA)3(I)2]CH3OH

Abstract A five co-ordinate platinum(II) complex containing the water soluble 1,3,5-triaza-7-phosphaadamantane ligand (PTA) [Pt(PTA)3(I)2] (1), was characterised in the solid state and aqueous solution. A re-calculation of the Tolman cone angle for the PTA ligand, as well as preliminary equilibrium constants for the formation of 1, is given.

trans-Di­chloro­bis­(tri­phenyl­phosphine-P)­platinum(II)

Two different crystals (A and B) were used to structurally characterize trans-[PtCl2(PPh3)2] and to study random and systematic errors in derived parameters. The compound is isomorphous with trans-[PdCl2(PPh3)2] and with one of the polymorphs of trans-[PtMeCl(PPh3)2] reported previously. Half-normal probability plot analyses based on A and B show realistic s.u.s and negligible systematic errors. R.m.s. calculations give very good agreement between A and B, 0.0088 A. Important geometrical parameters are Pt—P = 2.3163 (11) A, Pt—Cl = 2.2997 (11) A, P—Pt—Cl = 87.88 (4) and 92.12 (4)°. Half-normal probability plots and r.m.s. calculations were also used to compare the title compound with the palladium analogue, showing small systematic differences between the compounds. The torsion angles around the Pt—P bond were found to be very similar to those reported for isomorphous complexes, as well as to the torsion angles around the Pt—As bond in trans-[PtCl2(AsPh3)2]. The NMR coupling constants for the title compound are similar to Pt—P coupling constants reported for analogous trans complexes.

Equilibrium, solid state behavior and reactions of four and five co-ordinate carbonyl stibine complexes of rhodium. Crystal Structures of trans-[Rh(Cl)(CO)(SbPh3)2], trans-[Rh(Cl)(CO)(SbPh3)3] and trans-[Rh(I)2(CH3)(CO)(SbPh3)2]

Abstract The crystal structures of the four-coordinate trans -[Rh(Cl)(CO)(SbPh 3 ) 2 ] ( 1 ) and the five-coordinate trans -[Rh(Cl)(CO)(SbPh 3 ) 3 ] ( 2 ) are reported, as well as the unexpected oxidative addition product, trans -[Rh(I) 2 (CH 3 )(CO)(SbPh 3 ) 2 ] ( 3 ), obtained from the reaction of 2 with CH 3 I. The formation constants of the five-coordinate complex were determined in dichloromethane, benzene, diethyl ether, acetone and ethyl acetate as 163±8, 363±10, 744±34, 1043±95 and 1261±96 M −1 , respectively. While coordinating solvents facilitate the formation of the five-coordinate complex, the four-coordinate complex could be obtained from diethyl ether due to the favorable low crystallization energy. The tendency of stibine ligands to form five-coordinate rhodium(I) complexes is attributed mainly to electron deficient metal centers in these systems, with smaller contributions by the steric effects. The average effective cone angle for the SbPh 3 ligand in the three crystallographic studies was determined as 139° with individual values ranging from 133 to 145°.