Search

Vierkantig-planêre chloried vir jodied stubstitusiereaksies trans ten opsigte van ‘n feniel σ-C binding is kineties ondersoek in chloroform vir ‘n reeks steries-gestremde platinum(II) komplekse van die vorm trans-[PtPh(L)2Cl] (L = PPh3, 1; PPh2Fc, 2; AsPh3, 3; SbPh3, 4). Die reaksies volg die normale assosiative aktivering, maar met ewewigte teenwoordig in alle stappe. Die tempokonstantes vir die direkte roete k12, is onderskeidelik (0.37 ± 0.03)x10-3 en 0 M-1 s-1 vir 1 en 2 by 40°C, en (1.6 ± 0.3)x10-3 en (143 ± 10)x10-3 M-1 s-1 vir 3 en 4 by 25°C. Die ooreenstemmende tempokonstantes vir die oplosmiddelroete, k13, is onderskeidelik (0.66 ± 0.03)x10-4 en (2.0 ± 0.2)x10-4 s-1 vir 1 en 2 by 40°C en (4.1 ± 0.6)x10-4 en (1105 ± 14)x10-4 s-1 vir 3 en 4 by 25°C. Die aktiveringsparameters vir 3 en 4 is bepaal as ∆H≠ = 99.8 ± 0.6 en 31 ± 1 kJ mol-1, met ∆S≠ = 36 ± 2 en -157 ± 4 J K-1 mol-1 vir die direkte roete, k12, en ∆H≠ = 45 ± 2 en 22.91 ± 0.11 kJ mol-1 en ∆S≠ = -181 ± 7 en -207.3 ± 0.4 J mol-1 K-1 vir die oplosmiddelroete, k13 onderskeidelik. Die kristalstrukture van trans-[PtPh(PPh2Fc)2Cl], trans-[PtPh(AsPh3)2Cl], trans-[PtPh(SbPh3)2Cl] en trans-[PtPh(SbPh3)2I] word gerapporteer. Struktuur- en reaktiwiteitsverwantskappe (van ongeveer vier ordegroottes) word bespreek, gebaseer op kinetiese data, multikern KMR-metings en die kristallografiese data.

Square-planar substitution reactions (chlorido for iodide, trans to methyl and hydrido as non-labile ligands) was kinetically investigated in chloroform solution in a series of platinum(II) trans-[PtRCl(L)2] complexes (R = Me: L = PPh3, 1; PPh2Fc, 2; P(NMe2)3, 3; AsPh3, 5; As(4-Me-Ph)3, 6; R = H: L = PPh3, 7) and cis-[PtMeCl(Ph2PFcPPh2)], 4. The reactions follow the normal associative mode of activation, but with equilibria present in all steps, with rate constants for the direct substitution pathway, k12, of (9.1 ± 1.0) × 10−4, 0, (1.389 ± 0.016)×10−2, (1.51 ± 0.15), (2 ± 4) × 10−3, (2.79 ± 0.04) × 10−2 and 0 mol−1 dm3 s−1 at 298 K for 1 to 7 respectively. The corresponding second order rate constants for the solvent assisted pathway, k13', were also determined. The activation parameters for the direct and solvent assisted pathways for 3 were determined as ΔH≠ = 60.4 ± 1.4 and 53.7 ± 0.3 kJ mol−1, and ΔS≠ = −78 ± 4 and −142 ± 1 J mol−1 K−1. A significant more than four orders-of-magnitude reactivity range was observed. Crystal structures of trans-[PtMeCl(PPh2Fc)2].2CHCl3.2H2O, trans-[PtMeCl{P(NMe2)3}2], cis-[PtMeCl(Ph2PFcPPh2)].2CHCl3 and trans-[PtHCl(PPh3)2].CH3OH are reported. This work is licensed under a Creative Commons Attribution 4.0 International License.

Hydrogenolysis reactions of cobalt acyl complexes, [Co(CO)3(L)(COR)] (L = phosphine, R = Me, nPr) have been monitored using in situ IR spectroscopy at moderate temperatures (

The isomorphous crystal structures of the title compounds, [Fe(2)M(C(5)H(5))(2)(C(17)H(14)P)Cl(CO)]·CH(2)Cl(2) or trans-[MCl(CO)(PPh(2)Fc)(2)]·CH(2)Cl(2) (M = Rh or Ir, and Fc is ferrocenyl), are reported. The data collection for M = Rh was performed at 293 (2) K, while the M = Ir data were collected at 160 (2) K. The compounds crystallize with two independent half-molecules in the asymmetric unit, both occupying inversion centres, and are accompanied by a single dichloromethane molecule on a general position. Due to the symmetry, there is 0.50/0.50 disorder present in the chloride and carbonyl positions. One molecule in each structure also has a second type of disorder in the chloride and carbonyl positions, which was refined over another two positions of equal distribution. The steric impact of the bulky PPh(2)Fc ligands was evaluated using the Tolman cone-angle model, resulting in an average value of 172° for the four molecules in both structures.

The substitution behaviour of [PtCl(R)(COD)] (R− = Me and Fc) complexes, by the stepwise addition of phosphine ligands, L (L = PPh3, PEt3 and P(NMe2)3), were investigated in situ by 1H and 31P NMR spectroscopy. Addition of less than two equivalents of the phosphine ligand results in the formation of dimeric molecules with the general formula trans-[Pt(R)(μ-Cl)(L)]2 for the sterically demanding systems where R− = Me/L = P(NMe2)3 and R− = Fc/L = PEt3, PPh3 and P(NMe2)3 while larger quantities resulted in cis- and trans mixtures of mononuclear complexes being formed. In the case of the relatively small steric demanding, strongly coordinating, PEt3 ligand the trans-[PtCl(R)(PEt3)2] mononuclear complexes were exclusively observed in both cases. The crystal structures of the two substrates, [PtCl(R)(COD)] (R− = Me or Fc), as well as the cis-[PtCl(Fc)(PPh3)2] substitution product are reported.

The synthesis and characterization of platinum(II) and palladium(II) complexes of the type [PtX2( n Pr-N(Ph2P)2)] (X = Cl, I) and [PdCl2(R-N(Ph2P)2)] {R = n Pr, p-OMe(C6H4)} containing aminodiphosphine P,P-bidentate ligands is described. Complexes of the type [PtCl2(R-N(Ph2P)2)] (where R = benzyl, 2-picolyl and n Pr) catalyzed the hydroformylation of 1-octene, albeit at low activities and slightly elevated regioselectivities toward the linear aldehyde, when compared with analogous compounds containing small bite angles.

Oxidative addition of SeCN(-) to tertiary phosphine ligands has been investigated in methanol at 298 K by use of UV-Vis stopped-flow and conventional spectrophotometry. In most cases k(obs) vs. [SeCN(-)] plots were linear with zero intercepts corresponding to a rate expression of k(obs) = k(1)[SeCN(-)]. Reactions rates are dependent on the electron density of the phosphorus centre with k(1) varying by five orders of magnitude from 1.34 +/- 0.02 x 10(-3) to 51 +/- 3 mol(-1) dm(3) s(-1) for P(2-OMe-C(6)H(4))(3) to PCy(3) respectively. Activation parameters range from 27 +/- 1 to 49.0 +/- 1.3 kJ mol(-1) for DeltaH(double dagger) and -112 +/- 9 to -140 +/- 3 J K(-1) mol(-1) for DeltaS(double dagger) supporting a S(N)2 mechanism in which the initial nucleophilic attack of P on Se is rate determining. Reaction rates are promoted by more polar solvents supporting the mechanistic assignment. Reasonable linear correlations were observed between log k(1)vs. pK(a), (1)J(P-Se) and chi(d) values of the phosphines. The reaction rates are remarkably sensitive to the steric bulk of the substituents, and substitution of phenyl rings in the 2 position resulted in a decrease in the reaction rate. The crystal structures of SePPh(2)Cy and SePPhCy(2) have been determined displaying Se-P bond distances of 2.111(2) and 2.1260(8) A respectively.

Reacting a series of the bicylic Phoban-Q (9-Q-9-phosphabicyclo[3.3.1]nonane and 9-Q-9-phosphabicyclo[4.2.1]nonane) derivatives (Q = alkyl, cyclo alkyl, aryl) with KSeCN results in the formation of the corresponding phosphine selenides. The first order phosphorus–selenium coupling constants, 1JP–Se, ranges from 682 to 689 Hz for the [3.3.1] isomers and from 703 to 717 Hz for the [4.2.1] isomers indicating the former to be significantly more electron rich. The crystal structures of Se = Phoban[3.3.1]-Q (Q = CH2CH3, C3H6Ph, Cy, and Ph) and Se = Phoban[4.2.1]-Q (Q = Cy and Ph) are reported and reveal P Se bond distances ranging from 2.1090(9) to 2.1245(7) A. For Q = Cy and Ph the two isomers ([3.3.1] and [4.2.1]) co-crystallise in the same crystal enabling the determination of the molecular structures for both from the same data collection. The cone angles for all ligand derivatives were determined according to the Tolman model but by using the actual P–Se bond distances and were found to be virtually identical ranging from 165° to 175°. Changes in the Q substituent have a minor effect on the overall steric and electronic properties of the Phoban family of ligands and can be used to manipulate physical properties without changing the chemical properties significantly.

Reaction of trans-[PtClMe(SMe2)2] with the mono anionic ligands azide, bromide, cyanide, iodide and thiocyanate result in substitution of the chloro ligand as the first step. In contrast the neutral ligands pyridine, 4-Me-pyridine and thiourea substitute a SMe2 ligand in the first step as confirmed by 1H NMR spectroscopy and the kinetic data. Detailed kinetic studies were performed in methanol as solvent by use of conventional stopped-flow spectrophotometry. All processes follow the usual two-term rate law for square-planar substitutions, kobs = k1 + k2[Y] (where k1 = kMeOH[MeOH]), with k1 = 0.088 ± 0.004 s−1 and k2 = 1.18 ± 0.13, 3.8 ± 0.3, 17.8 ± 1.3, 34.9 ± 1.4, 75.3 ± 1.1 mol−1 dm3 s−1 for Y− = N3, Br, CN, I and SCN respectively at 298 K. The reactions with the neutral ligands proceed without an appreciable intercept with k2 = 5.1 ± 0.3, 15.3 ± 1.8 and 195 ± 3 mol−1 dm3 s−1 for Y = pyridine, 4-Me-pyridine and thiourea, respectively, at 298 K. Activation parameters for MeOH, N 3 - , Br−, CN−, I−, SCN−, and Tu are ΔH≠ = 47.1 ± 1.6, 49.8 ± 0.6, 39 ± 3, 32 ± 8, 39 ± 5, 34 ± 4 and 31 ± 3 kJ mol−1 and ΔS≠ = −107 ± 5, −77 ± 2, −104 ± 9,−113 ± 28, −85 ± 18, −94 ± 14 and −97 ± 10 J K−1 mol−1, respectively. Recalculation of k1 to second-order units gives the following sequence of nucleophilicity: MeOH N 3 - Br - ∼ py 4 - Me - py ∼ CN - I - SCN - Tu (1:13:42:57:170:200:390:840:2170) at 298 K. Variation of the leaving group in the reaction between trans-[PtXMe(SMe2)2] and SCN− follows the same rate law as stated above with k2 = 75.3 ± 1.1, 236 ± 4 and 442 ± 5 mol−1 dm3 s−1 for X− = Cl, I and N3, respectively, at 298 K. The corresponding activation parameters were determined as ΔH≠ = 34 ± 4, 32 ± 2 and 39.3 ± 1.7 kJ mol−1 and ΔS≠ = −94 ± 14, −86 ± 8 and −68 ± 6 J K−1 mol−1. All the kinetic measurements indicate the usual associate mode of activation for square planar substitution reactions as supported by large negative entropies of activation, a significant dependence of the reaction rate on different entering nucleophiles and a linear free energy relationship.

Two key intermediates in the mechanistic cycle of cycloplatination of aryl oximes by PtII complexes were crystallographically characterized. trans-[PtCl2(SOMe2)(N-acetophenone oxime)] is an active precursor on the C–H cleavage reaction coordinate. The formation of trans-[PtCl2(N-benzaldehyde oxime)2] accounts for the rate retardation by excess oxime. DFT calculations support the crystallographic evidence that provides unequivocal proof for the electrophilic nature of cycloplatination. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

Reaction of [PtCl(PTA)3]+ (PTA = 1,3,5-triaza-7-phosphabicyclo[3.3.1.13,7]decane) with halides and pseudohalides gives [PtX(PTA)3]+ (X = Br−, and NCS−) in an equilibrium process. At 25°C, equilibrium constants are 3.3(7), 11(2) and 20(2) for Br−, and NCS−, respectively. Protonation of [PtCl(PTA)3]+ results in the formation of cis-[PtCl2(PTA)2]. Two pK a values pK a1 = 2.1(1) and pK a2 = 3.3(8) were obtained, corresponding to the protonation of [PtCl(PTA)3]Cl and cis-[PtCl2(PTA)2], respectively. From an aqueous reaction mixture of [PtCl(PTA)3]Cl and NCS−, crystals of {[Pt(NCS)(PTA)3]NCS}3·5H2O were isolated. The compound crystallizes in the triclinic space group P and its crystal structure has been determined. Three platinum cations, three thiocyanate counterions and five solvent water molecules are present in the asymmetric unit.

Reacting [PtCl(PTA)(3)]Cl (PTA = 1,3,5-triaza-7-phosphatricyclo[3.3.1.1(3,7)]decane) with KSeCN in aqueous or MeOH medium results in the abstraction of the PTA ligands to yield Se = PTA. The reaction also proceeds quantitatively by direct reaction of PTA and KSeCN in water or methanol. The methylated PTA ligand, [PTA-Me]I (1-methyl-1-azonia-3,5-diaza-7-phosphatricyclo[3.3. 1.1(3,7)]decane iodide), reacts accordingly with KSeCN, albeit significantly slower. The crystal structure of Se = PTA, 1, and [Se = PTA-Me]I - CH3OH, 2, revealed P = Se bond distances of 2.0991(19) and 2.100(2) angstrom, respectively. The first order phosphorous selenium coupling constants, (1)J(P-Se) (D2O), of 722 and 788 Hz for Se = PTA and [Se = PTA-Me]I, respectively, indicates the latter is significantly less electron rich. (Less)

The [Rh(acac)(CO)(L)] (acac = acetylacetonato; L1 = 1,3-bis-(2,6-diisopropylphenyl)imidazolinylidene and L2 = 1,3-bis-(2,4,6-trimethylphenyl)imidazolinylidene) complexes were prepared by the action of the parent carbene on [Rh(acac)(CO)2] in THF. The crystal structure characterisation of [Rh(acac)(CO)(L1)] revealed a slightly distorted square planar geometry with the carbene ligand orientated almost perpendicular to the equatorial plane; an elongated trans Rh–O bond of 2.0806(18) A reflecting the considerable trans-influence of the carbene ligand. By measuring the CO stretching frequencies in a range of [Rh(acac)(CO)(L)] complexes (L = CO, L1, L2, PPh3, PnBu3, P(O–2,4-tBu2–Ph)3) the following electron donating ability series was established: L1 ∼ L2 ∼ PnBu3 > PPh3 > P(O–2,4-tBu2–Ph)3 > CO; indicating the carbenes investigated in this study to have a similar electronic cis-influence as trialkyl phosphines. Both complexes do not display hydroformylation activity towards 1-hexene in the absence of added phosphine or phosphite ligands under the conditions investigated (P = 60; T = 85 °C). In the presence of a phosphine or phosphite ligand the resulting hydroformylation catalysis was identical to that observed for [Rh(acac)(CO)2] and the corresponding ligand and subsequent high-pressure 31P NMR studies confirmed substitution of the carbene ligand under these conditions.

The aqueous solution behaviour of the equilibrium related cis-[PdCl2(PTA)2] and [PdCl(PTA)3]Cl complexes has been investigated in the presence of acid and iodide ions. Several of the resulting species were identified and a reaction scheme accounting for identified complexes is proposed. The crystal structures of trans-[PdI2(PTA-H)2][PdI3(PTA)]2 · 2H2O (1) (PTA-H+ = protonated form of PTA) and trans-[PdI2(PTA)2] (2) are reported. The geometry around the Pd(II) metal centre in 1 (for both the cation and anion) and 2 is distorted square planar. The PTA ligands occupy a trans orientation in the cation of 1 and in complex 2. Compound 1 represents a rare example of a Pd(II) system wherein the cation:anion pair, in a 1:2 ratio, are both coordination complexes. It is the first d8 Ni-triad square planar complex containing only one PTA ligand and only the second platinum group metal complex. For the cation in 1, the bond distances and angles are Pd(1)–P(1) = 2.2864(16) A, Pd(1)–I(1) = 2.6216(7) A, P(1)–Pd(1)–P(1)′ = 180.00(7)° and P(1)–Pd(1)–I(1) = 87.62(4)°, while in the anion the bond distances are Pd(2)–P(2) = 2.2377(15) A, Pd(2)–I(4) = 2.5961(13) A, Pd(2)–I(2) = 2.6328(13) A, Pd(2)–I(3) = 2.6513(8) A, while the angles are P(2)–Pd(2)–I(4) = 90.00(5)°, P(2)–Pd(2)–I(2) = 89.69(5)°, I(4)–Pd(2)–I(2) = 179.57(2)°, P(2)–Pd(2)–I(3) = 175.19(4)°, I(4)–Pd(2)–I(3) = 90.29(4)° and I(2)–Pd(2)–I(3) = 90.05(4)°. Bond distances and angles of the coordination polyhedron in 2 are Pd–P = 2.327(3) A, Pd–I = 2.5916(10) A, P–Pd–I = 89.13(7)° and P–Pd–P = 180.00(13)°. The average effective- and Tolman cone angles for the two ligands, calculated from the crystallographic data, are 115° and 117° for PTA and PTA-H, respectively.

C52H43N2O3P2RhS, triclinic, P1̅ (no. 2), a = 10.6260(3) Å, b = 11.7305(3) Å, c = 19.6582(5) Å, α = 76.489(1)°, β = 82.027(1)°, γ = 64.848(1)°, V = 2154.4 Å3, Z = 2, Rgt(F) = 0.028, wRref(F2) = 0.0722, T = 100 K.

The cis effects of phosphine, arsine and stibine ligands have been evaluated by measuring the IR stretching frequency in dichloromethane of the carbonyl ligand in a series of Rh(I) Vaska-type complexes, trans-[RhCl(CO)(L)2]. These data were correlated with those obtained by Tolman for the electronic trans influences in the [Ni(L)(CO)3] complexes. The electronic contribution, χFc, of ferrocenyl was determined as 0.8 from these plots by evaluating PPh2Fc as ligand. In order to accommodate arsine and stibine ligands an additional correction term, to compensate for differences in the donor atom, was added to Tolman’s equation for calculation of the Tolman electronic parameter of phosphine ligands. In the resulting equation: ν(CONi)=2056.1+∑i=13χi+CL values for CL of CP=0, CAs=−1.5 and CSb=−3.1 are suggested for phosphine, arsine and stibine ligands, respectively. The crystal and molecular structures of trans-[RhCl(CO)(PPh2Fc)2] · 2C6H6, trans-[RhCl(CO){P(NMe2)3}2] and trans-[RhCl(CO)(AsPh3)2] are reported. The Tolman cone angles for PPh2Fc and P(NMe2)3 were determined as 169° and 166°, while the effective cone angles for PPh2Fc, P(NMe2)3 and AsPh3 were determined as 171°, 168° and 147°, respectively.

This paper deals with the synthesis of rhodium(I) Vaska-type complexes of the general form trans-[Rh(CO)X(PX3)] (X=halide, X aryl or alkyl substituent) when incorporating tertiary phosphine ligands and illustrates their simple application as probes to evaluate steric and electronic effects, specifically in tertiary phosphine ligands, analogous to the Tolman model. They are easy to prepare and do not exhibit the toxicity as the corresponding nickel complexes, while structural and infrared data can be conveniently utilised to estimate ligand properties with relative ease. These Vaska-type complexes are often obtained as by-products when reacting [Rh(μ-Cl)(CO)2]2 with bidentate ligands in non-stoichiometric amounts, thus yielding unreacted dimer, which, upon addition of the tertiary phosphine, quantitatively converts to the Vaska-type complex. A representative summary of rhodium(I) Vaska-type systems is reported and structures correlated with steric and electronic properties of related literature complexes. Selected aspects of reactions of the corresponding arsine and stibine analogues are illustrated and solvent effects on equilibrium behaviour as well as the iodomethane oxidative addition described.

A range of tertiary phosphine ligands derived from (R)-(+)-limonene was studied by HP-31P NMR, HP-IR, batch autoclave reactions and molecular modelling during the hydroformylation of 1-dodecene using a cobalt catalyst system and a metal ∶ ligand ratio of 1 ∶ 2. The phosphorus atom was incorporated in a limonene bicycle where the third substituent was systematically varied, Lim-R (R = (CH2)17CH3, (CH2)9CH3, (CH2)4CH3, (CH2)3CH3, (CH2)3C6H5, (CH2)3CN, (CH2)3OCH2C6H5, (CH2)2OCH2CH3). The activity and selectivity was, to a large extent, governed by the equilibria between the modified and unmodified cobalt catalytic species in the reaction. Linearity ranged from 54 to 71% with Lim-(CH2)3CN yielding the most branched product and Lim-(CH2)4CH3 the most linear product. The n ∶ iso ratio (ratio of linear to 2-methyl branched alcohol) also followed the same trend with a ratio of 2.6 for Lim-(CH2)3CN and 4.9 for Lim-(CH2)4CH3. The rate decreased as the linearity increased with pseudo k values of 0.5 to 1.1. Hydrogenation of the alkene varied within a narrow band from 5–6%.

Structural and mechanistic aspects of orthoplatination of acetophenone and benzaldehyde oximes by the platinum(II) sulfoxide and sulfide complexes [PtCl(2)L(2)] (2, L = SOMe(2) (a), rac-SOMePh (b), R-SOMe(C(6)H(4)Me-4) (c), and SMe(2) (d)) to afford the corresponding platinacycles cis-(C,S)-[Pt(II)(C(6)H(3)-2-CR'=NOH-5-R)Cl(L)] (3, R, R' = H, Me) have been investigated. The reaction of acetophenone oxime with sulfoxide complex 2a in methanol solvent occurs noticeably faster than with sulfide complex 2d due to the fact that the sulfoxide is a much better platinum(II) leaving ligand than the sulfide. Evidence is presented that the orthoplatination is a multistep process. The formation of unreactive dichlorobis(N-oxime)platinum(II) cations accounts for the rate retardation by excess acetophenone oxime and suggests the importance of pseudocoordinatively unsaturated species for the C-H bond activation by Pt(II). A comparative X-ray structural study of dimethyl sulfoxide platinacycle 3b (R = R' = Me) and its sulfide analogue 3e (R = H, R' = Me), as well as of SOMePh complex 3c (R = H, R' = Me), indicated that they are structurally similar and a sulfur ligand is coordinated in the cis position with respect to the sigma-bound phenyl carbon. The differences concern the Pt-S bond distance, which is notably longer in the sulfide complex 3e (2.2677(11) A) as compared to that in sulfoxide complexes 3b (2.201(2)-2.215(2) A) and 3c (2.2196(12) A). Whereas the metal plane is practically a plane of symmetry in 3b due to the H-bonding between the sulfoxide oxygen and the proton at carbon ortho to the Pt-C bond, an S-bonded methyl of SOMePh and SMe(2) is basically in the platinum(II) plane in complexes 3c and 3e, respectively. There are intra- and intermolecular hydrogen bond networks in complex 3b. An interesting structural feature of complex 3c is that the two independent molecules in the asymmetric unit of the crystal reveal an extremely short Pt-Pt contact of 3.337 A.

A series of structures of trans-[MX 2(PBz3)2] [M = Pt, X = Cl−; PBz3 = tribenzylphosphine (1), I−, trans-diiodobis(tribenzylphosphine)platinum(II) (2), and NCS−, trans-di(thiocyanate)bis(tribenzylphosphine)platinum(II) (3); M = Pd, X = I−, trans-diiodobis(tribenzylphosphine)palladium(II) (4)] have been characterized by X-ray crystallography. In all compounds each tribenzylphosphine has one benzylcarbon close to the coordination plane. In (1), (2) and (4) those (in-plane) C atoms, from the two different PBz3, exhibit an anti conformation along the P—P axis, while (3) has the gauche conformation. Root mean square (RMS) calculations and half-normal probability plots show that the complexes in (2) and (4) are very similar and the only significant differences between them are the M—P bonds, 2.354 (4) and 2.330 (5) Å, and the M—I bond distances, 2.604 (1) and 2.611 (2) Å, for Pd and Pt, respectively. Calculations of the steric demand of the PBz3 ligands based on the Tolman model gave values ranging from 155 to 178° for the effective and 156 to 179° for the Tolman angles, respectively.

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°.

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. (C) 2001 Elsevier Science B.V. All rights reserved. (Less)

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.

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.

The chloro-bridged dimeric complex, trans-[Pd(μ-Cl)(CH3)(PPh2Fc)]2, was prepared by reaction of [Pd(Cl)(CH3)(COD)] (COD = cis,cis-1,5-cyclooctadiene) with 1 equivalent of PPh2Fc (PPh2Fc = ferrocenyldiphenylphosphine) in acetone medium. The complex was characterized by 1H and 31P NMR spectroscopy and a single crystal X-ray diffraction study revealed a trans geometry. The compound crystallizes in the triclinic space group P1, a = 11.476(2) A, b = 14.059(3) A, c = 14.658(3) A and α = 82.34(3)°, β = 75.09(3)°, and γ = 68.48(3)° with Z = 2. Most important geometrical parameters include bond lengths Pd(1)–P(1) 2.2165(10), Pd(2)–P(2) 2.2290(10), Pd(1)–C(1) 2.157(3), Pd(2)–C(2) 2.079(4), Pd(1)–Cl(1) 2.4329(13), Pd(1)–Cl(2) 2.4106(11), Pd(2)–Cl(1) 2.4169(10), and Pd(2)–Cl(2) 2.4414(13) A and bond angles P(1)–Pd(1)–C(1) 87.47(8), P(1)–Pd(1)–Cl(2) 176.88(4), C(1)–Pd(1)–Cl(1) 173.93(7), P(2)–Pd(2)–C(2) 89.03(11), P(2)–Pd(2)–Cl(1) 174.18(4), and C(2)–Pd(2)–Cl(2) 173.50(11)°. The effective and Tolman cone angles for P(1) were calculated as 170 and 167° and that for P(2) as 179 and 177°, respectively.

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.

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.

The novel ligands N,N-diethyl-N′-(−)-(3R)-menthyloxycarbonylthiourea (HL3), N,N-diethyl-N′-(+)-(3R)-menthyloxycarbonylthiourea (HL4), N-(−)-(3R)-menthyloxycarbonyl-N′-morpholinothiourea (HL5) and N-(+)-(3R)-menthyloxycarbonyl-N′-morpholinothiourea (HL6) have been prepared and characterised. The molecular structure of HL3 has been confirmed by X-ray crystallography. The reaction of these N,N-disubstituted-N′-menthyloxycarbonylthiourea ligands with cis-[PtCl2(DMSO)2] in the presence of sodium acetate yields geometric isomers of the resultant [Pt(L)Cl(DMSO)] complexes, that is the DMSO is sulfur bonded to the platinum in either a cis-(S,S) or trans-(S,S) arrangement with respect to the sulfur donor atom of the chelated ligand. This is in contrast to the complexation reaction of cis-[PtCl2(DMSO)2] with N-benzoyl-N′,N′-diethylthiourea (HL1) or N-benzoyl-N′-morpholinothiourea (HL2) which yields only one [Pt(L)Cl(DMSO)] complex in which the DMSO is in a cis-(S,S) arrangement with respect to the sulfur donor atom of the chelated ligand. The molecular structures of cis-(S,S)-[Pt(L)Cl(DMSO)], where L = (L1)− or (L6)−, have been determined by X-ray crystallography. The difference in the coordination chemistry of the acylthiourea and alkoxycarbonylthiourea ligands has been examined further by treating the [Pt(L)Cl(DMSO)] complexes with PPh3 to give the corresponding mono- and bis-(phosphine) complexes, [Pt(L)Cl(PPh3)] and [Pt(L)(PPh3)2]+. The 31P NMR studies of these complexes reveal that the alkoxycarbonylthiourea ligands bind less strongly than the acylthiourea ligands, which is consistent with the crystallographic studies. The weaker binding properties of the alkoxycarbonylthiourea ligands might be a possible explanation for the observed geometric isomerisation of the complexes and that the mechanism could involve a chelate ring opening step.

The synthesis and characterisation of platinum(II) complexes, with the general formula [Pt(acylthioureato)Cl(RR′SO)], is reported. These complexes are readily formed by the reaction of [PtCl2(RR′SO)2] with the acylthiourea ligands, N,N-di(2-hydroxyethyl)-N′-benzoylthiourea (HL), N,N-diethyl-N′-benzoylthiourea (HL1) and N,N-adipoylbis(N′,N′-diethylthiourea) (H2L2) in the presence of sodium acetate. Variation of the sulfoxide ligand (RR′SO) enables preparation of achiral complexes when RR′SO is dimethylsulfoxide (DMSO) or methylphenylsulfoxide (MPSO), and chiral complexes when use is made of the chiral sulfoxides, such as (R)-methyl(p-tolyl)sulfoxide and (S)-methyl(p-tolyl)sulfoxide. The reaction also yields, as a minor product, the corresponding cis-bis(acylthioureato)platinum(II) complexes, which can be removed by chromatography. The molecular structures of the two products, [Pt(L1)Cl(MPSO)] and cis-[Pt(L1)2], were determined by X-ray crystallography. The sulfoxide of [Pt(L1)Cl(MPSO)] is sulfur bound, as expected, and cis to the sulfur atom of the acylthioureato ligand. All bond lengths and bond angles around the square planar platinum are normal, with the Pt–S bond trans to Cl being 2.257(4) A and the Pt–S bond trans to O 2.192(3) A in length. The Pt–O and Pt–Cl bonds are 2.016(9) and 2.334(3) A, respectively, and are within the expected ranges. Similarly, the bond lengths and bond angles around the coordination plane of cis-[Pt(L1)2] compare well with related complexes.

Phenyl migration and oxidative addition were observed in nitromethane containing solutions of trans-[RhCl(CO)(SbPh3)n] (n = 2 or 3) and free SbPh3. A Rh(III) product resulting from phenyl migration and oxidative addition to Rh(I), trans-mer-[Rh(Cl)2(Ph)(SbPh3)3], was characterised by X-ray crystallography.

The disproportionation of dicobalt octacarbonyl induced by the free carbene 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene (IMes) and the X-ray characterization of the cyclohexane solvate of the resulting cobalt carbonyl N-heterocyclic carbene salt, [Co(CO)3(IMes)2]+[Co(CO)4] -·1/4C6H12, is reported. The crystal structure represents the first example of a [Co(CO)3(L)2][Co(CO)4] disproportionate salt reported to date.

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.

Bridge splitting of trans- [PtCl2(C2H4)](2) by C2H4 in chloroform yields trans-[PtCl2(C2H4)(2)] which slowly isomerises to cis[PtCl2(C2H4)(2)] (crystal structure reported); the bridge-splitting equilibrium constant was determined as 6.8 +/- 0.6 mol(-1) dm(3) by the use of a combined NMR tube/spectrophotometric cell, enabling NMR and UV/vis measurements on the same closed system. (C) 2006 Elsevier B.V. All rights reserved.

The crystal structure of the title compound, trans-[Pt(C6H5)(NCS)(C18H15P)2], represents a typical example where steric crowding around the platinum metal centre induces N-coordination of the thio­cyanate ligand. The compound crystallizes on a twofold rotation axis. Selected geometrical parameters are Pt—C = 2.019 (6) A, Pt—P = 2.3007 (11) A, Pt—N = 2.052 (6) A, C—Pt—P = 92.47 (3)°, P—Pt—P′ = 175.06 (5)° and N—Pt—P = 87.53 (3)°. The compound represents a rare example of a trans bis­phosphine complex of platinum(II) containing the NCS− ligand.

The title compound, [RhCl(PBz3)2(CO)] [PBz3 = tri­benzyl­phosphine, P(C7H7)3], which is the first reported tri­benzyl­phosphine–rhodium(I) structure, has pseudo-square-planar coordination geometry, with Rh—P bond distances of 2.3164 (15) and 2.3156 (16) A. The Rh—Cl, Rh—C and C—O bond distances are 2.3654 (15), 1.783 (6) and 1.162 (6) A, respectively, and the angles P—Rh—P, P—Rh—Cl (2 occurrences) and C—Rh—Cl are 177.67 (6), 90.86 (5), 87.11 (5) and 178.55 (17)°, respectively. Effective cone angles for PBz3 are 170 and 172°, while the Tolman cone angles are 171 and 173°. Each tri­benzyl­phosphine has one benzyl C atom close to the coordination plane, with C—P—Rh—CO torsion angles of −1.6 (3) and −30.2 (3)°, and with the benzyl C atoms in a gauche conformation relative to the P⋯P axis. DFT (density functional theory) calculations, optimizing the geometry of the complex in the gas phase, approximately reproduce this conformation, showing that it is only slightly affected by the crystal-packing arrangement.

The title compound, [PdBr2(C6H12N3)2] or [PdBr2(PTA)2] (where PTA is 1,3,5-tri­aza-7-phosphaadamantane), was found to be isostructural with the previously reported trans-[PtI2(PTA)2]. The Pd atom lies on an inversion centre, resulting in a trans-square-planar geometry. Selected geo­metrical parameters are Pd1—P1 and Pd1—Br1 distances of 2.320 (1) and 2.427 (1) A, respectively, and a P—Pd—Br angle of 90.6 (3)°. The effective cone angle for the PTA ligands was calculated as 114.0°.

A series of phosphine ligands with different electronic and steric properties were evaluated at fully modified conditions in cobalt catalysed hydroformylation of 1-octene. The steric demand of the ligands was based on the Tolman cone angle model covering a range of 132-175°. The electron donating ability was evaluated through the first order Se-P coupling constants as determined from the corresponding phosphine selenides covering a range of 672-752 Hz. Crystal structures of three phosphine modified cobalt dimers, [Co(CO)(3)(L)](2) (L = PA-C(5), PCy(3) and PCyp(3) with PA-C(5) = 1,3,5,7-tetramethyl-8-pentyl-2,4,6-trioxa-8-phosphatricyclo[3.3.1.1(3,7)]decane), are reported. The Phoban and Lim ligands (Phoban = mixture of 9-phosphabicyclo[3.3.1 and 4.2.1]nonane, Lim = 4,8-dimethyl-2-phosphabicyclo[3.3.1]nonane) resulted in systems about twice as active as most of the other ligands investigated, these ligands have a high Lewis basicity with (1)J(Se-P) values from 684-687 Hz. The linearity of the alcohol product in general decreased for the less electron donating ligands while no clear relationship was evident as a function of steric size. The parallel competing hydrogenation of 1-octene to octane varied from 9-15% for a cone angle range of 132-172°, but a sharp increase of up to 40% was observed for PA-C(5), PCy(3) and PCyp(3), all with cone angles169°. The catalytic behaviour provides evidence that is contrary to the dissociative substitution of CO by an alkene as the rate limiting step in all cases. For large symmetrical ligands, such as PA-C(5), PCy(3) and PCyp(3) the rate limiting step may move within the catalytic cycle and may now be situated at the carbonylation step where the chemoselectivity is also determined. The lack of clear correlation between the steric and electronic effect of the ligands and all catalytic parameters may serve as additional proof that the same system, especially in terms of the rate determining step, is not operative in all cases. The Phoban and Lim systems are superior with the highest reactivity and lowest alkene loss through hydrogenation. The unsymmetrical nature of the Phoban and Lim ligands may provide flexibility to adopt geometries inducing both high and low steric crowding, which may be a reason for its beneficial catalytic properties.

Orange crystals of bis(acetonitrile-κN)bis[N,N-bis(diphenylphosphanyl)ethanamine-κ(2)P,P']iron(II) tetrabromidoferrate(II), [Fe(CH(3)CN)(2)(C(26)H(25)NP(2))(2)][FeBr(4)], (I), and red crystals of bis(acetonitrile-κN)bis[N,N-bis(diphenylphosphanyl)ethanamine-κ(2)P,P']iron(II) μ-oxido-bis[tribromidoferrate(III)], [Fe(CH(3)CN)(2)(C(26)H(25)NP(2))(2)][Fe(2)Br(6)O], (II), were obtained from the same solution after prolonged exposure to atmospheric oxygen, resulting in partial oxidation of the [FeBr(4)](2-) anion to the [Br(3)FeOFeBr(3)](2-) anion. The asymmetric unit of (I) consists of three independent cations, one on a general position and two on inversion centres, with two anions, required to balance the charge, located on general positions. The asymmetric unit of (II) consists of two independent cations and two anions, all on special positions. The geometric parameters within the coordination environments of the cations do not differ significantly, with the major differences being in the orientation of the phenyl rings on the bidentate phosphane ligand. The ethyl substituent in the cation of (II) and the Br atoms in the anions of (II) are disordered. The P-Fe-P bite angles represent the smallest angles reported to date for octahedral Fe(II) complexes containing bidentate phosphine ligands with MeCN in the axial positions, ranging from 70.82 (3) to 70.98 (4)°. The average Fe-Br bond distances of 2.46 (2) and 2.36 (2) Å in the [FeBr(4)](2-) and [Br(3)FeOFeBr(3)](2-) anions, respectively, illustrate the differences in the Fe oxidation states.

The crystal structure of the title compound, trans-[PtCl(2)(C(16)H(23)P)(2)], has been determined at 100 K. The Pt atom is located on a twofold axis and adopts a distorted square-planar coordination geometry. The structure is only the second example of a coordination complex containing a derivative of the 4,8-dimethyl-2-phosphabicyclo[3.3.1]nonane (Lim) phosphine ligand family. The ligand contains four chiral C atoms, with the stereochemistry at three of these fixed during synthesis, therefore resulting in two possible ligand stereoisomers. The compound crystallizes in the chiral space group P4(3)2(1)2 but is racemic, comprising an equimolar mixture of both stereoisomers disordered on a single ligand site. The effective cone angles for both isomers are the same at 146°.

The crystal structure of cis-[PtCl2(C6H15As)2], (I), is isostructural with a previously reported structure of cis-[PtCl2(C6H15P)2], (II). A new polymorph of (II) is also reported here. Selected geometrical parameters in the arsine complex are Pt-Cl 2.3412 (12) and 2.3498 (13), Pt-As 2.3563 (6) and 2.3630 (6) A, Cl-Pt-Cl 88.74 (5), As-Pt-As 97.85 (2), and Cl-Pt-As 171.37 (4) and 177.45 (4) degrees. Corresponding parameters in the phosphine complex are Pt-Cl 2.364 (2) and 2.374 (2), Pt-P 2.264 (2) and 2.262 (2) A, Cl-Pt-Cl 85.66 (9), P-Pt-P 98.39 (7), and Cl-Pt-P 170.26 (7) and 176.82 (8) degrees.

The square-planar RhI complex, [Rh(trop)(PFcPh2)(CO)] (tropH = 2-hydroxy-2,4,6-cyclo­heptatrienone, C7H6O2, and PFcPh2 = ferrocenyl­di­phenyl­phosphine, C22H19FeP), contains a five-membered chelate ring. The most important bond lengths and angles include Rh—O 2.0838 (14) A (trans to P) and Rh—O 2.0487 (14) A (trans to CO), Rh—P 2.2395 (5) A, Rh—C 1.803 (2) A, and O—Rh—O 77.56 (6)° and P—Rh—C 89.73 (7)°.

The crystal structure of the title compound, trans-[PdCl(CH3)(C18H15P)2], was found to be isomorphous with several related platinum(II) and palladium(II) complexes. The Pd atom has a slightly distorted square-planar geometry, with most important bond lengths and angles of Pd—P = 2.3289 (7) and 2.3224 (7) A, Pd—Cl = 2.4227 (6) A and Pd—C = 2.054 (2) A, and P—Pd—P = 177.38 (2)°, P—Pd—Cl = 88.97 (2) and 89.03 (2)°, and C—Pd—Cl = 175.23 (8)°.

The title compound, [RhCl(C(8)H(12))(C(14)H(12)N(2)OS)], is a rhodium(I) derivative with a functionalized thio-urea ligand. Despite the presence of several heteroatoms, the thio-urea ligand coordinates only in a monodentate fashion via the S atom. The geometry of the coordination sphere is approximately square planar about the Rh(I) atom, with two bonds to the π-electrons of the 1,5-cyclo-octa-diene ligand, one bond to the Cl(-) ligand and one bond to the S atom of the thio-urea ligand. The mol-ecular structure is stabilized by intra-molecular N-H⋯O and N-H⋯Cl hydrogen bonding. Inter-molecular N-H⋯O hydrogen-bonding inter-actions lead to the formation of layers extending parallel to (011).

The title compound, C(12)H(23)PSe, represents the first structure of a phosphine containing the bicyclic 2-phospha-bicyclo-[3.3.1]nonane (VCH) unit. It contains two chiral centres per mol-ecule which can be either R,R- or S,S and crystallizes as a centrosymmetric, racemic micture of the enanti-omers. The P-Se bond distance of 2.1360 (16) Å is typical for these compounds. The Tolman cone angle (2.28 Å from P) was calculated as 163°, and the effective cone angle (using the crystallographically determined P-Se bond distance) is 168°.

The title compound, [PtCl(2)(C(13)H(26)NP)(2)], is a rare example of a sterically bulky ligand adopting a cis geometry in a square-planar complex. It crystallizes on a twofold rotation axis which bisects the Pt centre and the P-Pt-P' and Cl-Pt-Cl' angles. The ligand exhibits a random packing disorder in the N,N-dimethylpropylamine substituent, with the two orientations refining to occupancies of 0.404 (15) and 0.596 (15). Weak intermolecular interactions between a Cl and a H atom of the ligand of a neighbouring molecule result in extended chains along the a axis. The effective cone angle for the dimethyl[3-(9-phosphabicyclo[3.3.1]non-9-yl)propyl]amine (Phoban[3.3.1]-C(3)NMe(2)) ligand was determined as being in the range 160-181 degrees , depending on the choice of atoms used in the calculations.

Reaction of [PtCl2(SMe2)2] or K2PtCl4 with two equivalents of the water soluble phosphine ligand, 1,3,5-triaza-7-phosphaadamantane (PTA), afforded crystals of {cis-[PtCl2(PTA)2]}2 · H2O, 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. 31P NMR shows that in aqueous solution an equilibrium exists between the cis bis isomer and [PtCl3 − n(PTA)1 + n] (n = 2,3) complexes.

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.

C25H30ClN2ORhS, monoclinic, C2/c (no. 15), a = 22.508(2) Å, b = 8.5005(7) Å, c = 24.884(2) Å, β = 93.551(4)°, V = 4751.7 Å3, Z = 8, Rgt(F) = 0.0355, wRref(F2) = 0.0767, T = 100 K.