The dibenzo[b,f]azepinate (DBAP) complexes (DBAP)Li·(THF)3, (DBAP)2Mg·(THF)2, and (DBAP)2Ca·(THF)3 could be isolated as highly air-sensitive compounds in yields of 93%, 72%, and 48%, respectively. Crystal structures of these THF adducts reveal monomeric complexes in which the degree of ring puckering depends on the nature of the metal. The most extreme deviation from planarity is found for the most covalent bound metal, Mg, but in all cases no interaction between the metal and the azepine C═C bond is observed. The THF-free complex [(DBAP)2Mg]2, which could be obtained in 77% yield, crystallizes as an unusual dimer with three bridging and one terminal DBAP ligand. The bridging DBAP ligands are highly bent and span a cavity in which a Mg2+ ion is bound through three alkene–Mg interactions with an average Mg···C distance of 2.794(3) Å. Theoretical calculations support these contacts. A combination of AIM and NPA analyses shows polarization of the alkene π-electron density toward the metal (vertical polarization) but also demonstrates a polarization of electron density toward the C atom closest to Mg (horizontal polarization). Such metal–alkene interactions and implicit C═C bond polarization are key features in main group metal catalyzed alkene conversions.

10-Phenyl-5H-dibenz[b,f]azepine (5) is synthesized by Suzuki cross coupling of the protected bromo alkene 4 with PhB(OH)2. 5 reacts with PCl3 to afford the dichlorophosphanyl-azepine 6 in >90% yield. Alkylation of 6 with 1 equiv of t-BuMgBr leads, after recrystallization in Et2O, to the diastereomerically enriched (dr > 98:2) chloride rac-7, which the crystal structure reveals to be the (pS,RP)/(pR,SP) pair. The fact that rac-7 crystallizes in the Sohncke space group P212121 opens up the possibility of a mechanical separation of the enantiomers. Methylation of rac-7 is perfectly stereoselective with inversion of configuration at the P atom to yield the new ligand rac-8 as the (R,R)/(S,S) pair. The corresponding BH3-protected diastereomer rac-9 (i.e., the (R,S)/(S,R) pair), is isolated after flash column chromatography in 73% yield. Compounds 5–9 are accessible in multigram quantities. X-ray crystal structures of Ru(II) complexes demonstrate the ambidentate nature of ligand rac-8: Complex 10 is exclusively P-coordinated, while in complex 11 two ligands bind Ru through their P donors and stabilize the 14-electron metal center with a double agostic interaction. In complex 12, the ligand coordinates in a κP,η2-alkene bidentate fashion.

The reactions of rac- and (S,S)-trans-9,10-dihydro-9,10-ethanoanthracene-11,12-diamine (ANDEN) with PClPh2 in the presence of NEt3 yield the chiral amino-phosphine ligands rac-6 and (S,S)-6, respectively, on multi-gram scales. Both forms of 6 react quantitatively with MgPh2 to afford the C2-symmetric, N-bound Mg amidophosphine complexes rac-7 and (S,S)-7. The former crystallizes as a racemic conglomerate, which is a rare occurrence. Mixing (S,S)- or rac-6 with [IrCl(COE)2]2 leads in both cases to the homochiral dinuclear chloro-bridged P-ligated aminophosphine iridium complexes (S,S,S,S)-9 and rac-9 in excellent yields. X-ray quality single crystals only grow as the racemic compound (or ‘true racemate’) rac-9 thanks to its lowered solubility. In the coordinating solvent CH3CN, rac-9 transforms in high yield into mononuclear Ir-complex rac-10. The crystal structures of compounds rac-6, (S,S)-7, rac-9, and rac-10 reveal the ambidentate nature of the P–N function: amide-coordination in the Mg-complex (S,S)-7 and P-chelation of the softer Ir(I) centres in complexes rac-9 and rac-10. Furthermore, the crystal structures show flexible, symmetry lowering seven-membered P-chelate rings in the Ir complexes and a surprising amount of deformation within the ANDEN backbone. The simulation of this deformation by DFT and SCF calculations indicates low energy barriers. (S,S)-7 and (S,S,S,S)-9 catalyze the intra- and intermolecular hydroamination of alkenes, respectively: 5 mol% of (S,S)-7 affords 2-methyl-4,4′-diphenylcyclopentyl amine quantitatively (7% ee), and 2.5 mol% of (S,S,S,S)-9 in the presence of 5.0 mol% co-catalyst (LDA, PhLi, or MgPh2) gives exo-(2-arylamino)bornanes in up to 68% yield and up to 16% ee.

Enantiomerically pure C1 and C2-symmetric bidentate N,N- and N,P-ligands are accessible from (+)-camphor in good yields (60–90%). Modified syntheses of precursors 1 and 2 are disclosed as well as the crystal structures of three hydroxy-pyrazoline intermediates. Ligands 3, 4, 6, and 11 were fully characterized including an X-ray crystal structure of C2-symmetric 6, which showed an E-configuration in the solid state. These ligands form complexes with Ni(II), Pd(II), and Rh(I) in good yields (84–96%); the X-ray crystal structures of complexes 12, 14, and 16 confirmed the bidentate coordination modes of ligands 4, 6, and 11 and distorted tetrahedral [for Ni(II)] and square planar [for Rh(I)] coordination geometries. Furthermore, the structure of the Rh(I) complex 16 revealed the presence of a Ph2PCl ligand, which, along with spectroscopic data, is proof of an almost quantitative P–N bond cleavage upon coordination of ligand 11 to [RhCl(COD)]2.(4S,7R)-7,8,8-Trimethyl-4,5,6,7-tetrahydro-4,7-methano-1-phenylindazol-3-carboxylic acidC18H20N2O2[α]D20 = +72.4 (c 1.021, CHCl3)Source of chirality: (1R)-(+)-CamphorAbsolute configuration: (4S,7R)(4S,7R)-7,8,8-Trimethyl-4,5,6,7-tetrahydro-4,7-methano-1-phenyl-indazol-3-carbonyl chlorideC18H19ClN2O[α]D20 = +59.1 (c 0.305, CHCl3)Source of chirality: (1R)-(+)-CamphorAbsolute configuration: (4S,7R)((4S,7R)-7,8,8-Trimethyl-4,5,6,7-tetrahydro-4,7-methano-1-phenyl-indazol-3-yl)(3,4,5-trimethyl-pyrazol-1yl)methanoneC24H28N4O[α]D20 = +46 (c 0.21, THF)Source of chirality: (1R)-(+)-CamphorAbsolute configuration: (4S,7R)((4S,7R)-7,8,8-Trimethyl-4,5,6,7-tetrahydro-4,7-methano-1-phenyl-indazol-3-yl)(3,5-di-tert-butyl-pyrazol-1yl)methanoneC29H38N4O[α]D20 = +47 (c 0.06, THF)Source of chirality: (1R)-(+)-CamphorAbsolute configuration: 4S,7R(+)-(1R,1′R)-3,3′-(1,2-Dihydroxyethane-1,2-diylidene)bis[(1,7,7-trimethyl-bicyclo[2,2,1]-heptan-2-one]C22H30O4[α]D20 = +520.8 (c 1.02, CHCl3)Source of chirality: (1R)-(+)-CamphorAbsolute configuration: (1R,1′R)(+)-(1R,1′R)-3,3′-Bi(1,1′-diphenyl-pyrazole-camphor)C34H38N4[α]D20 = +105.7 (c 1.01, CHCl3)Source of chirality: (1R)-(+)-CamphorAbsolute configuration: (1R,1′R)(+)-3,3′-[(4S,7R)-(1,2-Dihydroxyethane-1,2-diylidene)(1,7,7-trimethyl-bicyclo[2,2,1]-heptan-2-one)]-((4′S,7′R)-7′,8′,8′-trimethyl-4′,6′,7′-trihydro-5′-ol-4′,7′-methano-1′-phenyl-indazol)C28H36N2O3[α]D20 = +228.6 (c 1.01, CHCl3)Source of chirality: (1R)-(+)-CamphorAbsolute configuration: (4S,7R,4′S,7′R)(E)-3,3′-((4S,7R)-7,8,8-Trimethyl-4,6,7-trihydro-5-ol-4,7-methano-1-phenyl-indazol-hydroxymethylene)-((4′S,7′R)-1′,7′,7′-trimethylbicyclo[2′.2′.1′]-heptan-2′-one)C28H34N2O2[α]D20 = +252 (c 1.00, CHCl3)Source of chirality: (1R)-(+)-CamphorAbsolute configuration: (4S,7R,4′S,7′R)3,3′-((4S,7R)-7,8,8-Trimethyl-4,6,7-trihydro-5-ol-4,7-methano-1-phenyl-indazol)-((4′S,7′R)-7′,8′,8′-trimethyl-4′,5′,6′,7′-tetrahydro-4′,7′-methano-2′H-indazol)C28H36N4O[α]D20 = +215.3 (c 0.538, CHCl3)Source of chirality: (1R)-(+)-CamphorAbsolute configuration: (4S,7R,4′S,7′R)3,3′-((4S,7R)-7,8,8-Trimethyl-4,5,6,7-tetrahydro-4,7-methano-1-phenyl-indazol)-((4′S,7′R)-7′,8′,8′-trimethyl-4′,5′,6′,7′-tetrahydro-4′,7′-methano-2′H-indazol)C28H34N4[α]D25 = +170 (c 0.160, CHCl3)Source of chirality: (1R)-(+)-CamphorAbsolute configuration: (4S,7R,4′S,7′R)3,3′-((4S,7R)-7,8,8-Trimethyl-4,5,6,7-tetrahydro-4,7-methano-1-phenyl-indazol)-((4′S,7′R)-7′,8′,8′-trimethyl-4′,5′,6′,7′-tetrahydro-4′,7′-methano-2′-diphenylphosphine-indazol)C40H43N4P[α]D20 = +1.4 (c 0.512, THF)Source of chirality: (1R)-(+)-CamphorAbsolute configuration: (4S,7R,4′S,7′R)

Multigram quantities of the optically pure amino–bis-sulfoxide ligand (S,S)-bis(4-tert-butyl-2-(p-tolylsulfinyl)phenyl)amine ((S,S)-3) are accessible by in situ lithiation of bis(2-bromo-4-tert-butylphenyl)amine (1) followed by a nucleophilic displacement reaction with Andersen’s sulfinate 2. Deprotonation of (S,S)-3 with MgPh2 yields the magnesium amido–bis-sulfoxide salt (S,S)-4 quantitatively. Metathetical exchange of (S,S)-4 with [RhCl(COE)2]2 affords the optically pure pseudo-C2-symmetric Rh(I)–amido bis-sulfoxide pincer complex mer-(R,R)-[Rh(bis(4-(tert-butyl)-2-(p-tolylsulfinyl)phenyl)amide)(COE)] (mer-(R,R)-5). This complex reacts with 3 equiv of HCl to give the facial Rh(III) complex fac-(S,R,R)-[Rh(bis(4-(tert-butyl)-2-(p-tolylsulfinyl)phenyl)amine)Cl3] (fac-(S,R,R)-6), in which one of the sulfoxide functions has been reduced to the sulfide and in which the resulting sulfoxide–sulfide–amine ligand is facially coordinated. The same complexes 5 and 6 form in a 1:2 ratio in a disproportionation reaction when [RhCl(COE)2]2 is treated with 2 equiv of neutral ligand 3. N–H activation is directly observed in the reaction of [IrCl(COE)2]2 with 3, affording the amido–hydrido–Ir(III) complex [Ir(bis(4-(tert-butyl)-2-(p-tolylsulfinyl)phenyl)amide)(Cl)(H)(COE)] (8).

The solvent-less quaternization of N-phenyl-camphorpyrazole 4 with BrC4H9, IC2H4OCH3, and IC2H4OC2H4OC4H9 afforded the corresponding chiral pyrazolium halides 5a, 6a, and 7a in excellent yields. The anions were modified either by trihalide formation with Br2 and I2, or by salt metathesis with LiNTf2 and NaCo(CO)4. All pyrazolium salts bearing the di-ether side chain 7a–d were liquids at room temperature, while the X-ray crystal structure of the bis(trifluoromethylsulfonyl)amide salt of the corresponding mono-ether analogue 6c (mp 97 °C) revealed intermolecular H-bonding interactions. Furthermore, an improved protocol for the well-known but notoriously low-yielding synthesis of (+)-hydroxymethylenecamphor 3 is disclosed.(1R,4S)-3-(Hydroxymethylene)-1,7,7-trimethylbicyclo[2.2.1]heptan-2-oneC11H16O2[α]D25 = +76.5 (c 4.24, CHCl3)Source of chirality: the precursorAbsolute configuration: (1R,4S)(4S,7R)-7,8,8-Trimethyl-1-phenyl-2-butyl-4,5,6,7-tetrahydro-4,7-methanoindazolium tribromideC21H29Br3N2[α]D25 = +7.9 (c 5.40, EtOH)Source of chirality: the precursorAbsolute configuration: (4S,7R)(4S,7R)-7,8,8-Trimethyl-1-phenyl-2-butyl-4,5,6,7-tetrahydro-4,7-methanoindazolium bromideC21H29BrN2[α]D25 = +13.3 (c 2.70, EtOH)Source of chirality: the precursorAbsolute configuration: (4S,7R)(4S,7R)-7,8,8-Trimethyl-1-phenyl-2-butyl-4,5,6,7-tetrahydro-4,7-methanoindazolium bis(trifluoromethylsulfonyl)amideC23H29F6N3O4S2[α]D25 = +8.4 (c 1.06, EtOH)Source of chirality: the precursorAbsolute configuration: (4S,7R)(4S,7R)-7,8,8-Trimethyl-1-phenyl-2-methoxyethyl-4,5,6,7-tetrahydro-4,7-methanoindazolium iodideC20H27IN2O[α]D25 = 6.5 (c 3.10, EtOH)Source of chirality: the precursorAbsolute configuration: (4S,7R)(4S,7R)-7,8,8-Trimethyl-1-phenyl-2-(3′,6′-dioxadecyl)-4,5,6,7-tetrahydro-4,7-methanoindazolium iodideC25H37IN2O2[α]D25 = +5.7 (c 1.80, C2H5OH)Source of chirality: the precursorAbsolute configuration: (4S,7R)(4S,7R)-7,8,8-Trimethyl-1-phenyl-2-methoxyethyl-4,5,6,7-tetrahydro-4,7-methanoindazolium tetracarbonylcobaltateC29H37CoN2O6[α]D25 = +27.0 (c 0.18, EtOH)Source of chirality: the precursorAbsolute configuration: (4S,7R)(4S,7R)-7,8,8-Trimethyl-1-phenyl-2-methoxyethyl-4,5,6,7-tetrahydro-4,7-methanoindazolium bis(trifluoromethylsulfonyl)amideC22H27F6N3O5S2[α]D25 = +4.3 (c 1.03, EtOH)Source of chirality: the precursorAbsolute configuration: (4S,7R)(4S,7R)-7,8,8-Trimethyl-1-phenyl-2-(3′,6′-dioxadecyl)-4,5,6,7-tetrahydro-4,7-methanoindazolium triiodideC25H37I3N2O2[α]D25 = +3.5 (c 1.30, EtOH)Source of chirality: the precursorAbsolute configuration: (4S,7R)(4S,7R)-7,8,8-Trimethyl-1-phenyl-2-(3′,6′-dioxadecyl)-4,5,6,7-tetrahydro-4,7-methanoindazolium bis(trifluoromethylsulfonyl)amideC27H37F6N3O6S2[α]D25 = +2.1 (c 2.27, EtOH)Source of chirality: the precursorAbsolute configuration: (4S,7R)(4S,7R)-7,8,8-Trimethyl-1-phenyl-2-(3′,6′-dioxadecyl)-4,5,6,7-tetrahydro-4,7-methanoindazolium tetracarbonylcobaltateC29H37CoN2O6[α]D25 = +14.0 (c 0.18, EtOH)Source of chirality: the precursorAbsolute configuration: (4S,7R)

The reactions of rac- and (S,S)-trans-9,10-dihydro-9,10-ethanoanthracene-11,12-diamine (ANDEN) with PClPh2 in the presence of NEt3 yield the chiral amino-phosphine ligands rac-6 and (S,S)-6, respectively, on multi-gram scales. Both forms of 6 react quantitatively with MgPh2 to afford the C2-symmetric, N-bound Mg amidophosphine complexes rac-7 and (S,S)-7. The former crystallizes as a racemic conglomerate, which is a rare occurrence. Mixing (S,S)- or rac-6 with [IrCl(COE)2]2 leads in both cases to the homochiral dinuclear chloro-bridged P-ligated aminophosphine iridium complexes (S,S,S,S)-9 and rac-9 in excellent yields. X-ray quality single crystals only grow as the racemic compound (or ‘true racemate’) rac-9 thanks to its lowered solubility. In the coordinating solvent CH3CN, rac-9 transforms in high yield into mononuclear Ir-complex rac-10. The crystal structures of compounds rac-6, (S,S)-7, rac-9, and rac-10 reveal the ambidentate nature of the P–N function: amide-coordination in the Mg-complex (S,S)-7 and P-chelation of the softer Ir(I) centres in complexes rac-9 and rac-10. Furthermore, the crystal structures show flexible, symmetry lowering seven-membered P-chelate rings in the Ir complexes and a surprising amount of deformation within the ANDEN backbone. The simulation of this deformation by DFT and SCF calculations indicates low energy barriers. (S,S)-7 and (S,S,S,S)-9 catalyze the intra- and intermolecular hydroamination of alkenes, respectively: 5 mol% of (S,S)-7 affords 2-methyl-4,4′-diphenylcyclopentyl amine quantitatively (7% ee), and 2.5 mol% of (S,S,S,S)-9 in the presence of 5.0 mol% co-catalyst (LDA, PhLi, or MgPh2) gives exo-(2-arylamino)bornanes in up to 68% yield and up to 16% ee.