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Review of Atomic and Molecular Structure Introduction Atomic and Molecular Structure Bonding Review Problems Alkanes and Friends: Structure, Bonding, Properties, and Nomenclature Introduction Hybridization in Methane, Ammonia, and Water Drawing Molecules Introduction to Alkanes Stability, Strain, and Properties of Alkanes and Cycloalkanes Review Problems Alkenes, Alkynes, and Aromatic Compounds Alkenes Aromatic Hydrocarbons Alkynes: Hydrocarbons Containing Triple Bonds Resonance Review Problems Heteroatom-Containing Functional Groups Compounds Containing sp3 Nitrogen Atoms Molecules Containing sp2 Nitrogen Atoms Molecules with sp-Hybridized Nitrogen Compounds Containing sp3 Oxygen Compounds Containing sp2 Oxygen Priorities in Nomenclature Structure and Bonding in Some Highly Reactive Species More Resonance Review Problems More Challenging Problems Purification and Identification of Organic Compounds 1 Introduction Purification of Organic Compounds Mass Spectrometry UV/Visible Spectroscopy Infrared Spectroscopy Review Problems More Challenging Problems Identification of Organic Compounds 2: Nuclear Magnetic Resonance Spectroscopy Introduction Chemical Shifts Spin-Spin Coupling Protons Attached to Oxygen and Nitrogen 13C NMR Spectroscopy Review Problems More Challenging Problems Stereochemistry Introduction Conformations of Alkanes Cycloalkanes Chirality Fischer Projections Review Problems More Challenging Problems Introduction to Mechanism Introduction Studying Organic Reaction Mechanisms Classification of Reactions Acids and Bases Tautomers: A Slight Digression Writing Mechanisms Using Curly Arrows Review Problems More Challenging Problems Nucleophilic Substitution at Saturated Carbon Introduction Mechanistic Types Stereochemical Implications Effect of Nucleophile Effect of the Leaving Group Effect of Substrate Structure Effect of Solvents Competing Reactions Competition between SN1 and SN2 Processes Applications and Scope of the Reaction Neighboring Group Participation and Intramolecular Reactions Review Problems More Challenging Problems Elimination Reactions Introduction Mechanisms Stereochemistry Regiochemistry Effect of Substrate Substitution versus Elimination Carbocation Rearrangements Examples and Applications Elimination to Give Alkynes Other Elimination Reactions Review Problems More Challenging Problems Addition Reactions Introduction Electrophilic Reactions Radical Addition Reactions Multicenter Processes Hydrogenation Review Problems More Challenging Problems Electrophilic Aromatic Substitution Introduction Electrophiles Orientation Effects Reactions of Polycyclic Aromatic Compounds Heterocyclic Aromatic Compounds Review Problems More Challenging Problems Nucleophilic Aromatic Substitution and Synthesis of Aromatic Compounds Introduction Unimolecular Nucleophilic Substitution of Aromatic Compounds: The Reactions of Diazonium Salts with Simple Nucleophiles Azo Coupling Reactions Nucleophilic Substitution of Aryl Halides, SN2Ar Substitution of Haloheterocycles Substitution via Benzyne and Related Intermediates Reactions in Side Chains of Aromatic Compounds Reduction of Benzene Rings Carbon-Aryl Bond Formation Aromatic Synthesis Review Problems More Challenging Problems Addition to Carbon-Heteroatom Double Bonds Introduction and Review Mechanism of Addition Reactions Reversible Addition Reactions Irreversible Addition Reactions Review Problems More Challenging Problems Substitution of Carbonyl Compounds: Carboxylic Acids and Their Derivatives Introduction: Review of Nomenclature Substitution Reaction Oxygen Nucleophiles Nitrogen Nucleophiles Synthesis of Acid Chlorides Hydride as Nucleophile Carbon Nucleophiles Review Problems More Challenging Problems Lipids and Carbohydrates Introduction Lipids Carbohydrates Review Problems More Challenging Problems Substitution alpha and ss to Carbonyl Groups Introduction Formation of Enols and Enolates Isomerizations Involving Enols and Enolates Reactions of Enols and Enolates with Electrophiles Two Useful Reactions of Nonenolizable Carbonyl Compounds Reactions at the ss-Position of alpha,ss-Unsaturated Carbonyl Compounds and Other Electron-Poor Alkenes Review Problems More Challenging Problems Rearrangement Reactions Introduction Migration to Electron-Deficient Carbon Migration to Electron-Deficient Nitrogen Migration to Electron-Deficient Oxygen: The Baeyer-Villiger Oxidation Anionic Rearrangements Neutral Rearrangements Review Problems More Challenging Problems Synthesis 1: One-Group Disconnections Introduction Simple Disconnections and the Retrosynthetic Approach One-Group Disconnections Review Problems More Challenging Problems Synthesis 2: Two-Group Disconnections and Protecting Groups Introduction to Two-Group Disconnections 1,2-Difunctionalized Compounds 1,3-Difunctionalized Compounds 1,4-Difunctionalized Compounds 1,5-Difunctionalized Compounds Robinson Annulation 1,6-Difunctionalized Compounds Pericyclic Disconnections Protecting Group Further Reading Review Problems More Challenging Problems More Challenging Problems Polymeric Materials Introduction Polymer Structures Preparation of Addition or Chain-Growth Polymers Preparation of Step-Reaction Polymers Unusual Biopolymers Review Problems More Challenging Problems Amines, Alkaloids, Amino Acids, Peptides, and Nucleic Acids Synthesis of Amines Alkaloids Amino Acids Peptides Nucleic Acids Review Problems More Challenging Problems Catalysis of Organic Reactions Introduction Catalysis by Acids and Bases Lewis Acid Catalysis Phase-Transfer Catalysis Reactions Catalyzed by Metal Surfaces Reactions Catalyzed by Transition Metal Complexes Organocatalysis Enzyme Catalysis Review Problems More Challenging Problems Organic Chemistry in Industry Introduction Process Chemistry versus Research Chemistry Pharmaceutical Industry Agrochemicals Dyes and Colorants Review Problems Further Reading Organic Chemistry and the Environment Introduction Pesticides Endocrine Disruptors Chlorofluorocarbons and Their Replacements Polycyclic Aromatic Hydrocarbons Plastics: Recycle, Degrade, or Burn? Is "Green Chemistry" the Future? Review Problems Further Reading Organic Chemistry in Forensic Science Introduction Drugs of Abuse Poisons and Poisoning Testing for Blood Dyes, Inks, and Paper Trace Evidence Visualization of Fingerprints Review Problems Appendix A: Glossary of Abbreviations and Acronyms Appendix B: Some Common/Trivial Names You Need to Know

Mononuclear palladium-hydroxo complexes of the type [Pd(N–N)(C6F5)(OH)][(N–N) = 2,2′-bipyridine (bipy), 4,4′-dimethyl-2,2′-bipyridine (Me2bipy), 1,10-phenantroline (phen) or N,N,N′,N′-tetramethylethylenediamine (tmeda) react with phenols ArOH in tetrahydrofuran giving the corresponding aryloxo complexes [Pd(N–N)(C6F5)(OAr)]. Elemental analyses and spectroscopic (IR, 1H and 19F) methods have been used to characterize the new complexes. The X-ray crystal structure of [Pd(tmeda)(C6F5)(OC6H4NO2-p)] has been determined. In the crystal packing the planes defined by two C6H4 rings show a parallel orientation. There are also intermolecular C–H···F and C-H···O hydrogen bonds.

Mononuclear palladium–hydroxo complexes of the type [Pd(N–N)(C6F5)(OH)] [(N–N = 2,2′-bipyridine (bipy), 4,4′-dimethyl-2,2′-bipyridine (Me2bipy), or N,N,N′,N′-tetramethylethylenediamine (tmeda) react with SO2 (1 atm) at room temperature in alcohol (methanol, ethanol, propanol or isopropanol) to yield alkyl sulfito palladium complexes [Pd(N–N)(C6F5)(SO2OR)] (R = Me, Et, Pr or iPr). Similar alkyl sulfito complexes [Pd(N–N)(C6F5)(SO2OR)] (N–N = bis(3,5-dimethylpyrazol-1-yl)methane); R = Me or Et) are obtained when [Pd(N–N)(C6F5)Cl] is treated with KOH in the corresponding alcohol ROH and SO2 is bubbled through the solution. The reaction of [Pd(bipy)(C6F5)(OH)] with SO2 in tetrahydrofuran gives [Pd(N–N)(C6F5)(SO2OH)]. The X-ray diffraction study of [Pd(tmeda)(C6F5)(SO2OPr)] has established the sulfur coordination of the propyl sulfito ligand.

The reaction of [NBu4]2[{M(C6F5)2(μ-OH)}2] (M=Pd, Pt) with amines R2NH in the presence of the heterocumulene phenylisocyanate, PhNCO, leads to the synthesis of the ureato(1−) complexes [NBu4][M(C6F5)2{PhNC(O)NR2}] (M=Pd, Pt). The single-crystal structure of [NBu4][(C6F5)2Pt{PhNC(O)NPri 2}] revealed the presence of a N,N′-chelating ureato(1−) with a N(1)PtN(2) bite angle of 64.0(3)°.

The growth of a large single crystal of the new non-linear optical salt morpholinium 4-hydroxybenzoate (M4HB) is reported. Growth of crystals from dry ethanol, or 2-propanol, yields the non-centrosymmetric form belonging to space group Cc (No. 9). This is the desirable structure since it exhibits second harmonic generation (SHG). Attempts to improve solubility by using a water : ethanol co-solvent result in the total loss of SHG activity due to the formation of morpholinium 4-hydroxybenzoate dihydrate in the centrosymmetric space group P2 1 /c (No. 14).

The synthesis of new mono- and bis(pentafluorophenyl) derivatives of palladium(II) with the mixed-donor bidentate ligands o-Ph2PC6H4–CHNR (RN–P) has been achieved. The new complexes of general formula [Pd(C6F5)2(RN–P)] [R=Me (1), Et (2), nPr (3) iPr (4), tBu (5), Ph (6), NH–Me (7)] and [Pd (C6F5)Cl(RN–P)] [R=Me (8), iPr (9), NH–Me (10)] have been, respectively, prepared by reaction between the labile precursors cis-[Pd(C6F5)2(PhCN)2] or [{Pd(C6F5)(tht)(μ-Cl)}2] (tht=tetrahydrothiophene) and the corresponding iminophosphines. Complex (9) undergoes metathetical exchange of chloride with anionic monodentate ligands when reacting with alkaline salts, giving the complexes of formula [Pd(C6F5)X(iPrN–P)] [X=Br (11), I (12), CN (13), SCN (14), SC6H5 (15), p-SC6H4Me (16), p-SC6H4NO2 (17), OMe (18)]. Furthermore, when the chloropentafluorophenyl complex (9) was treated with silver trifluoromethanesulfonate in the presence of tertiary phosphines, the cationic derivatives [Pd(C6F5)(L)(iPrN–P)](CF3SO3) [L=PEt3 (19), PMe2Ph (20), PMePh2 (21)] were obtained in good yield. The new complexes were characterized by partial elemental analyses and spectroscopic methods (IR, 1H, 19F and 31P NMR). The molecular structure of complex (15) has been determined by a single-crystal diffraction study, showing that the iminophosphine act as chelating ligand with coordination around the palladium atom slight distorted from the square-planar geometry.

The 3:2 phenol–triphenylphosphine oxide (phenol–TPPO) adduct was studied by means of X-ray diffraction together with high-resolution solid-state 31P NMR spectroscopy. The X-ray results showed that the crystalline structure, which belongs to the triclinic P[1 with combining macron] space group, involves disorder. There are two molecules of TPPO and three phenol molecules per unit cell. One of the latter is disordered across an apparent inversion centre. Analysis of NMR data in conjunction with the crystal structure allowed the origin of such disorder to be established, showing that it is dynamic in nature. Variable-temperature NMR experiments were performed and a coalescence temperature was found at 247 K. Spectra recorded below this temperature showed two phosphorus signals. The kinetics for the phenol residue exchanging between two different TPPO moieties (two-site exchange with equal populations) were determined. Thermodynamic parameters for the motion were calculated from Eyring plots. For temperatures ranging from 262.9 to 221.5 K, the bandshape analysis technique was used to derive the required data. For lower temperatures, the selective polarisation inversion experiment (SPI) was performed, whilst high temperature values were derived from variable-temperature T1ρ studies. The activation enthalpy (ΔH‡), calculated using the results obtained by bandshape analysis, T1ρ and SPI, was determined as 38 kJ mol−1, while the activation entropy (ΔS‡) was found to be −23 J mol−1 K−1 (assuming the transmission coefficient is ½). Phosphorus-31 shielding tensor anisotropies have been derived for this system by spinning sideband analysis at both fast and slow-exchange limits and it has been shown that the tensor is axially symmetric. Single-crystal experiments show that the symmetry axis of the tensor is along the P[double bond, length half m-dash]O bond (within experimental error).

[Rh(μ-OMe)(COD)]2 reacts with tris-ortho-tert-butylphenylphosphite in the presence of carbon monoxide to provide the first example of a stable dinuclear carbonyl-phosphite rhodium(0) complex with a metal–metal bond distance of 2.73(1) A. The geometry at the metals is different: square planar and distorted trigonal bipyramid. The crystallographic data indicate that two of the carbonyl ligands are semi-bridged between the two rhodium atoms.

The binuclear hydroxo complexes [Pd2(C,N)2(µ-OH)2] [C,N = 2-(dimethylaminomethyl)phenyl (dmba) or 2-(phenylazo)phenyl (az)] have been prepared by addition of 2 equivalents of NBu4OH to the corresponding di-µ-acetate complexes in acetone. The reactions of both hydroxo complexes with a number of nitriles, RCN, led to the formation of the carboxamide complexes [Pd2(C,N)2(µ-NHC(R)O)2] (R = Me, Ph or CH2CH) as well as the succinonitrile derivatives [(C,N)Pd{NHC(O)CH2CH2C(O)NH}Pd(C,N)]. The complexes [Pd2(C,N)2(µ-NHC(Me)O)2] can also be prepared by reaction of [Pd2(C,N)2(µ-OH)2] with acetamide. The hydroxo complex [Pd2(C6F5)4(µ-OH)2]2– reacted with nitriles in methanol or ethanol to give the imino ether complexes [Pd(C6F5)2{NHC(OR′)R}2] (R = Ph, R′ = Me or Et; R = Me, R′ = Me or Et) which in acetone solution are present as mixtures of EE, EZ and ZZ isomers. Similar reactions with 2-cyanopyridine and succinonitrile gave [Pd(C6F5)2{NC5H4C(OR′)NH-2}] and [Pd(C6F5)2{NHC(OR′)CH2CH2NH(OR′)}] (R′ = Me or Et) and the reaction with 2-cyanopyridine in acetone yielded [Pd(C6F5)2{NC5H4C(O)NH-2}]. The crystal structures of [Pd2(dmba)2(µ-NHC(Ph)O)2] and [Pd(C6F5)2{NHC(OMe)Me}2] have been determined by single-crystal X-ray diffraction.

The di-μ-hydroxo complexes [NBu4]2[{(C6X5)2M(μ-OH)2}2] (M=Pd or Pt; X=F or Cl) react with heterocyclic thiones H(LL′) (1:2 molar ratio) to give the heterocyclic-2-thiolate complexes NBu4][C6X5)2M(ν2-LL′)](LL′=pyridine-2-thiolate (pyS), pyrimidine-2-thiolate (ϱyrimS). 2,6-dimethyl-5-oxo-1,2,4,-triazine-3-thiolate (Me2tazS). 6-methyl-5-oxo-1,2,4,-triazine-3-thiolate (MetazS)) or [NBu4]2[{(C6F5)2M(μ-η2-MeimidS)}2] (MeimidS=methylimidazole-2-thiolate). The variable-temperature 1H NMR spectra of the complexes [NBu4]2[{(C6F5)2M(μ-ν2-MeimidS)}2] (M=Pd and Pt) suggest the existence of dynamic methylimidazole-2-thiolate complexes [NBu4][(C6X5)2M(ν2-LL′)] over the range −50 to +60°C are all static, but those of the chemical processes involving both dimeric and monomeric species. Crystallization of [NBu4]2[{(C6F5)2Pd(μ-ν2-MeimidS)}2] from wet dichloromethane-hexane-etherafforded the mixed complex [NBu4]2[{(C6F5)2Pd}2(μ-OH)(μ-ν2-MeimidS)]. The analogous mixed platinum complex [NBu4]2[{(C6F5)2Pt}2(μ-OH(μ-ν2-MeimidS)] was prepared by reaction of [NBu4]2[{(C6X5)2Pt(μ-OH)2}2] with the corresponding heterocyclic thione H(LL′) in 1:1 molar ratio. The crystal structure of [NBu4]2[{(C6F5)2Pd(μ-ν2-MeimidS)}2], determined by X-ray diffraction, confirmed the dimeric structure with a head-to-tail arrangement. C64H82F20N6Pd2S2, orthorhombic Pca2 1 , a=19.552(8), b=25.160(3), c=14.727(3) A , Z=4 .

A range of substituted oligothiophenes has been prepared and characterised. Crystal structures were determined for three substituted terthiophenes. Both in solution and in the solid state, syn-conformers were found to be populated to a greater extent than expected.

Reaction of [Pt(C2H4)(PPh3)2] with a range of alkenes gave the complexes [Pt(alkene)(PPh3)2], Complexes of alkenes bearing electron-withdrawing ligands were, predictably, more stable than those of electron-rich alkenes. The complexes were characterized by multinuclear (1H, 13C, 31P and 195Pt) NMR spectroscopy and the structures of the derivatives of trans-PhCHCHCHO and trans-PhCHCHCOMe were established by X-ray diffraction studies. The complexes reacted with PCy3 to give [Pt(alkene)(PCy)(PPh3], usually as a mixture of regioisomers.

Reaction of [Pt(C 2 H 4 )(PPh 3 ) 2 ] with propenoate or 2-methylpropenoate esters gave the complexes [Pt(propenoate)(PPh 3 ) 2 ] in good yield. These have been characterised by 1 H, 13 C, 31 P and 195 Pt NMR spectroscopy. The complex of benzyl propenoate has been characterised in a diffraction study. Reaction of the complexes produced with tricyclohexylphosphine, PCy 3 , gave [Pt(propenoate)(PCy 3 )(PPh 3 )]. The propenoate complexes were shown to be more stable than those of the 2-methylpropenoates.

Reaction of [Ir(cod)(py)2][PF6] with PPh3 or P(C6H4-4-F)3 gives the bis(phosphine) derivative [Ir(cod)L2][PF6], but with the poorly basic phosphine P(C6H4-4-CF3)3 or AsPh3 the mixed ligand complexes [Ir(cod)L(py)][PF6] are obtained. The synthesis of [Ir(AsPh3)(cod)(PPh3)][CF3SO3] is described, and the structures of this and of [Ir(AsPh3)(cod)(py)][PF6] determined by X-ray crystallography. The use of some of the complexes as catalysts for imine hydrogenation is described.

The reaction of the binuclear hydroxo complexes [NBu4]2[M(C6F5)2(μ-OH)2] (M = Pd or Pt) with alkyl or arylamines (RNH2) in the presence of dimethyl acetylenedicarboxylate (DMAD) yields the novel complexes [NBu4I(C6F2)2 M{N(R)C(CO 2 Me)CHC(O) -OMe}] (M = Pd, R = C6H5 (1), p-MeC6H4 (2), p-MeOC6H4 (3), p-ClC6H4 (4), Et (5), Pr (6), C6H5CH2 (7); M = Pt, R-p-MeC6H4 (8), p-MeOC6H4 (9). Similar reactions carried out with [PdR(PPh3)(μ-OH)2] yield the complexes [ PPh 3 )R Pd{N(R′)C(CO 2 Me)CHC(O) OMe }] (R  C6F5, R′  Me (10), Et (11), Pr (12), CH2C6H5 (13); RC6H5, R′Me (14), Et (15), Pr (16), CH2C6H5 (17). However, the reaction of [Pd(C6F5)(PPh3)(μ-OH)2] with PhNH2 and DMAD yields [Pd(C6F5)(PPh3)2(μ-OH)(μ-NHPh)]. The iminoenolate complex [( PPh 3 )( C 6 F 6 ) Pd{N(Ph)C(CO 2 Me)CHC(O) OMe }] (18) is obtained when the di-μ-hydroxo complex is treated with (18) is obtained when the di-μ-hydroxo complex is treated with HN(Ph)C(CO2Me)CHC(O)OMe. Protonation of complex 1 by HCl(aq) gives [NBu4]2[(M(C6F5)2(μ-Cl)2] and dimethyl N-phenylaminofumarate. [ NBu 4 ][( C 6 F 6 ) 2 Pd{N(Ph)C(CO 2 Me)CH 2 C(O) O }] (19) is obtained when complex 1 is treated with aqueous methanol. Conductivity measurements and spectroscopic (IR, 1H, 13C, 19F and 31P) methods have been used to characterize the complexes. The X-ray diffraction study of [ NBu 4 ][( C 6 F 6 ) 2 Pd{N(C 6 H 4 OMe-p)C(CO 2 Me)CHC(O) OMe} ] (3) has established that the coordination about palladium is approximately square planar and that there is substantial delocalization in the iminoenolate ligand.

Di-orthometalated iridium complexes of triaryl phosphites have been prepared and characterized. The synthesis of the triphenyl phosphite derivative [IrH(cod){P(OC6H4)2(OC6H5)}], 3, requires a circuitous route by treatment of [IrCl(cod){P(OPh)3}] with methyllithium and then methanol. However, with the hindered phosphites P(OAr)3 (Ar = C6H4-2-tBu or C6H3-2,4-tBu2) the di-orthometalated species 5a,b are readily obtained by reaction of the phosphite with [{Ir(μ-OMe)(cod)}2] or [Ir(cod)(py)2][PF6]. The mechanisms of these reactions have been investigated and are different. Both 5a and 5b are catalysts for imine hydrogenation. The complexes [IrH5{P(OAr)3}2] have been isolated from hydrogenation reactions and synthesized independently.

The hydroxo complexes [NBu4]2[{M(C6F5)2(μ-OH)}2] (M = Pd, Pt) react with phenols ROH (1:2 molar ratio) to give the bis(μ-aryloxo) complexes [NBu4]2[{M(C6F5)2(μ-OR)}2] (M = Pd, Pt; R = C6H5, p-MeC6H4, p-NO2C6H4, C6F5). The reaction of bis(μ-aryloxo) complexes with PPh3 (1:2 molar ratio) gives the aryloxo monomer complexes [NBu4][M(C6F5)2(OR)(PPh3)] (M = Pd, Pt; R = p-NO2C6H4, C6F5). The platinum monocarbonyl complexes [NBu4][Pt(C6F5)2(OR)(CO)] (R = p-NO2C6H4, C6F5) have also been prepared by reaction of the corresponding bis(μ-aryloxo) complexes with carbon monoxide at room temperature and normal pressure. [NBu4][Pd(C6F5)3(CO)] is isolated in low yield from the reaction of [NBu4]2[Pd(C6F5)2(μ-OC6H4NO2-p)] with CO in the presence of water. The identity of the isolated complexes has been established by partial elemental analyses, conductance measurements, and spectroscopic (IR, 1H, 19F, 31P) methods. A single-crystal diffraction study of [NBu4][Pt(C6F5)2(OC6H4NO2-p)(CO)] showed that coordination about platin...

The crystal structure of [Ir(cod)(L–L)]+3[cod = cycloocta-1,5-diene, L–L = 1-(diisopropylphosphino)-1′-(diphenylphosphino)ferrocene] can be related to those of the analogous complexes with L–L = 1,1′-bis(diphenylphosphino)ferrocene (dppf)1 and 1,1′-bis(diisopropylphosphino)ferrocene (disppf), 2, all the complexes being readily synthesized from [Ir(cod)(py)2]+(py = pyridine). An optimum diphosphine bite angle of approximately 99° is maintained in all three complexes by varying the twist of the ferrocene, which decreases with increasing steric profile of the phosphine, and by distortion of the geometry at the iridium atom away from square planar towards tetrahedral. The twist about the ferrocene moiety induces chirality at the iridium atom in all three complexes and the interchange of stereoisomers can be followed by variable-temperature 1H NMR spectroscopy. Application of the Eyring equation gave approximate values of ΔG‡ for this process of 36.1 ± 0.2, 39.3 ± 0.2 and 34.3 ± 0.2 kJ mol–1 for 1–3 respectively. The ligand disoppf also induces considerable distortion away from square-planar geometry in the complex [Rh(nbd)(disoppf)][BF4]4{nbd = norbornadiene (bicyclo[2.2.1]hepta-2,5-diene)}, as found in a crystal structure determination, which may account for the unusual lability of the chelating diphosphine. This is demonstrated by its reactions with Ph2P(CH2)nPPh2(n= 1 or 2) both of which give [Rh(L–L)2]+. More surprisingly, considering its lability in [Rh(nbd)(dppf)]+, dppf also readily displaced disoppf from 4, to give [Rh(nbd)(dppf)][BF4]5. The nbd ligand in this complex is not displaced by reaction with an excess of dppf.

The di-μ-hydroxo complexes [NBu 4 ] 2 [{MR 2 (μ-OH)} 2 ] (M = Pd or Pt; R = C 6 F 5 or C 6 Cl 5 ) and [{(C 6 F 5 )(PPh 3 )Pd(μ-OH)} 2 ] react with [NH 4 ] 2 [M′S 4 ] (M′ = Mo or W) in 1:1 molar ratio to yield the trinuclear complexes [NBu 4 ] 2 [{MR 2 } 2 (μ-M′S 4 )] and [{(C 6 F 5 )(PPh 3 )Pd} 2 (μ-M′S 4 )], respectively, with tetrathiomolybdate and tetrathiotungstate as bridging tetradentate ligands. Elemental analyses, conductance measurements and spectroscopic (IR, visible, 19 F, 31 P) methods have been used to characterize the new complexes. The X-ray crystal structure of [Bu 4 N] 2 [{Pd(C 6 F 5 ) 2 } 2 (μ-WS 4 )] has been established. Coordination at tungsten is tetrahedral and at palladium square, planar. The WPd distance indicates a metal-metal interacation.

The di-µ-carboxylato complexes [{Pd(CH2C9H6N)(µ-O2CR)}2](CH2C9H6N = 8-quinolylmethyl, R = Me or CF3) react in methanol with NaOH(aq)(1 : 1 molar ratio) to give the corresponding mixed hydroxo–carboxylato-bridged complexes [{Pd(CH2C9H6N)}2(µ-OH)(µ-O2CR)](R = Me 1 or CF32). The reactions of 1 or 2 with arylamines or thiols (1 : 1 molar ratio) yielded the corresponding amido- or thiolato-carboxylato complexes [{Pd(CH2C9H6N)}2(µ-O2CMe)(µ-NHR)](R = Ph 3, p-MeC6H44 or p-NO2C6H45) or [{Pd(CH2C9H6N)}2(µ-O2CR)(µ-SR′)](R = Me, R′= Et 6, But7, Ph 8 or p-MeC6H49; R = CF3, R′= But10). The 1H NMR data indicate a cis arrangement of the CH2C9H6N ligands. The crystal structure of complex 10 has been determined. It confirms the cis relationship of the CH2C9H6N ligands. The co-ordination at each palladium atom is approximately square planar and the oxygen atoms of the trifluoroacetate ligands are trans to carbon. The Pd2(µ-OCOCF3)(µ-SBut) core is quite bent with an angle of 55° between the two palladium co-ordination planes.

A range of mixed biphosphine complexes of palladium(0) has been prepared and characterized by 31P NMR spectroscopy. The complexes disproportionate in solution at rates which depend on the nature of the ligands. The structure of [Pd(dcpe)(dppe)] has been established in an X-ray diffraction study.

Addition of a dithiol ligand HS(CH2)nSH (n= 2–4) to [{Rh(µ-OMe)(cod)}2](cod = cycloocta-1,5-diene) afforded dithiolate-bridged complexes [{Rh2[µ-S(CH2)nS](cod)2}x](x= 1 or 2). These diene complexes react with carbon monoxide to give the binuclear tetracarbonyl complexes [Rh2{µ-S(CH2)nS}(CO)4]. The crystal structures of [Rh2{µ-S(CH2)nS}(cod)2](n= 2 or 3) have been determined by X-ray diffraction methods. A study of the electronic structure of the complexes by analysis of the topology of the charge density shows that in spite of a zero formal bond order between the rhodium atoms a direct metal–metal interaction may be characterized.

Rhodium(I) complexes of the ligands adamantyldiaziridine and 4-t-butylcyclohexyldiaziridine have been prepared and characterised. The structure of [RhCl(cod)(4-t-butylcyclohexyldiaziridine)] has been established by an X-ray diffraction study. The rhodium is coordinated to the equatorial nitrogen atom of the diaziridine. The complexes are rather poor catalysts for hydrogenation or hydroformylation of alkenes.

C 8 H 10 O 3 S cristallise dans P2 1 /c avec a = 5,638, b = 7,828 et c = 20,045 A, β = 95,05 °, Z = 4; affinement jusqu'a R = 0,041. C 7 H 8 O 2 S cristallise dans P2 1 /c avec a = 8,172, b = 9,095 et c = 10,844 A, β = 111,66 °, Z = 4; affinement jusqu' a R = 0,045.

C 8 H 10 O 3 S cristallise dans P2 1 /c avec a = 5,638, b = 7,828 et c = 20,045 A, β = 95,05 °, Z = 4; affinement jusqu'a R = 0,041. C 7 H 8 O 2 S cristallise dans P2 1 /c avec a = 8,172, b = 9,095 et c = 10,844 A, β = 111,66 °, Z = 4; affinement jusqu' a R = 0,045.

Rhodium(I) and iridium(I) complexes of the ligand bis(diphenylphosphino)methane disulphide (dppmS 2 ) have been prepared and characterised. The structures of [Rh(dppmS 2 )(cod)][ClO 4 ] and [Rh(dppmS 2 (CO) 2 ][ClO 4 ] were established in diffraction studies, the latter complex adopting an interesting pseudo-dimeric structure in the solid state.

The reaction of aryl(methoxy)diazirines with [M2(η5-C5Me5)2(µ-CO)2](M = Rh or Co) affords the µ-carbene complexes [M2(η5-C5Me5)(CO)2{µ-CR(OMe)}](R = aryl) in excellent yield. The carbonyl groups are terminal in the rhodium complexes, as demonstrated conclusively in an X-ray diffraction study, but bridging for the cobalt complex. Thermolysis of the rhodium complexes results in loss of CO and the formation of [Rh2(η5-C5Me5)2(µ-CO){µ-CR(OMe)}]. Protonation of either the mono- or di-carbonyl rhodium complex with HBF4 led to the formation of a stable cationic carbyne complex, [Rh2(η5-C5Me5)2(µ-CO)(µ-CR)][BF4]; the structure of the related [BPh4]– salt was established in a diffraction study. Dynamic processes in the complexes were investigated by variable-temperature NMR spectroscopy.

The enantioselective alkylation of a range of aldehydes by diethylzinc in the presence of N-isopropylephedrine has been investigated. Both the yield and the enantioselectivity of the reaction was found to depend on the ratio of Et 2 Zn to the aldehyde.

Heating a suspension of the monomeric hydroxo palladium complex of the type [Pd(N-N)(C(6)F(5))(OH)](N-N = bipy, Me(2)bipy, phen or tmeda) in methylketone (acetone or methylisobutylketone) under reflux affords the corresponding ketonyl palladium complex [Pd(N-N)(C(6)F(5))(CH(2)COR)]. On the other hand, the reaction of the hydroxo palladium complexes [Pd(N-N)(C(6)F(5))(OH)](N-N = bipy, phen or tmeda) with diethylmalonate or malononitrile yields the C-bound enolate palladium complexes [Pd(N-N)(CHX(2))(C(6)F(5))](X = CO(2)Et or CN), and the reaction of [Pd(N-N)(C(6)F(5))(OH)](N-N = bipy or phen) with nitromethane gives the nitromethyl palladium complexes [Pd(N-N)(CH(2)NO(2))(C(6)F(5))]. [Pd(tmeda)(C(6)F(5))(OH)] catalyses the cyclotrimerization of malononitrile. The crystal structures of [Pd(bipy)(C(6)F(5))(CH(2)COMe)].1/2Me(2)CO, [Pd(tmeda)(C(6)F(5))[CH(CO(2)Et)(2)]], [Pd(tmeda)(C(6)F(5))[CH(CN)(2)]] and [Pd(tmeda)(C(6)F(5))(CH(2)NO(2))].1/2CH(2)Cl(2) have been established by X-ray diffraction.

Mononuclear palladium hydroxo complexes of the type [Pd(N[bond]N)(C(6)F(5))(OH)] [(N[bond]N = 2,2'-bipyridine (bipy), 4,4'-dimethyl-2,2'-bipyridine (Me(2)bipy), 1,10-phenanthroline (phen), or N,N,N',N'-tetramethylethylenediamine (tmeda)] have been prepared by reaction of [Pd(N[bond]N)(C(6)F(5))(acetone)]ClO(4) with KOH in methanol. These hydroxo complexes react, in methanol, with CO (1 atm, room temperature) to yield the corresponding methoxycarbonyl complexes [Pd(N[bond]N)(C(6)F(5))(CO(2)Me)]. Similar alkoxycarbonyl complexes [Pd(N[bond]N)(C(6)F(5))(CO(2)R)] (N[bond]N = bis(3,5-dimethylpyrazol-1-yl)methane); R = Me, Et, or (i)Pr) are obtained when [Pd(N[bond]N)(C(6)F(5))Cl] is treated with KOH in the corresponding alcohol ROH and CO is bubbled through the solution. The reactions of [Pd(N[bond]N)(C(6)F(5))(OH)] (N[bond]N = bipy or Me(2)bipy) with CO(2), in tetrahydrofuran, lead to the formation of the binuclear carbonate complexes [(N[bond]N)(C(6)F(5))Pd(mu-eta(2)-CO(3))Pd(C(6)F(5))(N[bond]N)]. Complexes [Pd(N[bond]N)(C(6)F(5))(OH)] react in alcohol with PhNCS to yield the corresponding N-phenyl-O-alkylthiocarbamate complexes [Pd(N[bond]N)(C(6)F(5))[SC(OR)NPh]]. Similarly, the reaction of [Pd(bipy)(C(6)F(5))(OH)] with PhNCO in methanol gives the N-phenyl-O-methylcarbamate complex [Pd(bipy)(C(6)F(5))[NPhC(O)OR]]. The reactions of [(N[bond]N)Pd(C(6)F(5))(OH)] with PhNCS in the presence of Et(2)NH yield the corresponding thioureidometal complexes [Pd(N[bond]N)(C(6)F(5))[NPhCSNR(2)]]. The crystal structures of [Pd(tmeda)(C(6)F(5))(CO(2)Me)], [Pd(2)(Me(2)bipy)(2)(C(6)F(5))(2)(mu-eta(2)-CO(3))].2CH(2)Cl(2), and [Pd(tmeda)(C(6)F(5))[SC(OMe)NPh]] have been determined.

The complex cis,trans,cis-[PtCl(2)(OAc)(2)NH(3)(c-C(6)H(11)NH(2))] (JM-216) is currently undergoing clinical evaluation as an antitumor agent. In support of characterization and analysis of this complex a study of its isomers and other complexes [PtCl(m)()(OAc)((4)(-)(m)()())NH(3)(c-C(6)H(11)NH(2))] (m = 0-4) has been undertaken. The complexes have been obtained by a variety of synthetic routes which now extend the scope for the preparation of platinum(IV) antitumor complexes. As platinum(IV) complexes are very stable to substitution in the absence of catalysis, use has been made of both light and base catalysis to promote substitution. Oxidative addition to platinum(II) using hypervalent iodine reagents has also been used. The stereochemistry of the complexes has been confirmed by spectroscopic studies, primarily NMR including natural abundance (15)N NMR spectroscopy.

It has been known for almost a century that certain microorganisms consume or produce hydrogen. Activation of molecular hydrogen in biological systems is catalysed by the enzyme hydrogenase. By definition, hydrogenase enzymes (EC class 1.12) are able to catalyse both the forward and reverse reactions of equation 7.1.

The subject of supported metal complexes as catalysts was reviewed by Hartley in a book published in 1985 [1], and hydrogenation was extensively treated. Supported metal complexes as hydrogenation catalysts were also reviewed by Yermakov and Arzamaskova in 1986 [2], and enantioselective versions of the reaction by Hetflejs in the same year [3]. Therefore account will focus on work published since 1984.

A wide variety of soluble transition metal complexes are known to act as hydrogenation catalysts under very mild conditions. This field has been surveyed comprehensively in recent reference books [1] and review articles [2]. Since 1965, most reports on homogeneous hydrogenation have involved complexes of the platinum group metals with phosphine ligands, and there has been intense activity in this area.

Throughout the history of organometallic catalysis, water has been generally regarded as a medium which should be strictly avoided. Ironically, the history of organometallic chemistry started with the discovery of a water soluble complex [PtCl3(C2H4)]3− (Zeise’s salt, 1827) and there have been also other exceptions to the rule that organometallic compounds are moisture sensitive. The ability of [HCo(CO)4] and [HCo(CN)5]3− to catalyse hydrogenation was first reported fifty years ago; both are rather soluble in water, which is in fact the only suitable solvent for hydrogenations catalysed by the latter complex. So whilst it is still true that most organometallic compounds are best handled in a moisture-free environment, there is no a priori reason to exclude water as solvent for hydrogenation reactions.

Homogeneous hydrogenation reactions have been used widely in organic synthesis, both of the industrial and laboratory scale. [1–5]. Early workers used the reactions in the most obvious sense, to remove unwanted carbon-carbon double bonds, but recent years have seen much more interesting developments, particularly in the areas of diastereoselective and enantioselective reductions, and in stereoselective reduction of carbonyl groups. In research applications the platinum group metals have provided most of the catalysts, but in considering larger scale applications of the reactions it will be necessary in future to be aware of cost, particularly in view of the very large fluctuations in the price of rhodium over recent years.

The preceeding chapter described many homogeneous reductions involving molecular hydrogen (hydrogenation reactions). However, there is an alternative type of reduction reaction where the hydrogen is supplied by a donor molecule, DH2, which itself undergoes dehydrogenation during the course of the reaction (equation 3.1).