Mirella Sansoni

2-Diphenylphosphino-2′-diphenylphosphinyl-1,1′-binaphthalene (BINAPO), an axially chiral heterobidentate ligand for enantioselective catalysis

Abstract Racemic 2-diphenylphosphino-2′-diphenylphosphinyl-1,1′-binaphthalene (BINAPO) 5 has been prepared in four steps from 1,1′-binaphthalene-2,2′-diol (BINOL) 1 and has been resolved with the aid of the C,N-cyclopalladated complex with N,N-dimethyl (S)-1-(1-naphthyl)ethylamine 6. P,O-chelate binding to palladium occurs in solution and this is confirmed in the solid state by X-ray analysis. (S)-BINAPO is an immediate precursor of (S)-BINAP and is itself an effective chiral inducer for the Pd-catalyzed asymmetric hydrosilylation of styrene (over 70% e.e.).

Synthesis and characterization of gold(III) adducts and cyclometallated derivatives with 6-benzyl- and 6-alkyl-2,2′-bipyridines

The reaction of a series of 6-substituted-2,2′-bipyridines HL (N2C10H7R, R = CH2Ph, CHMePh, CMe2Ph, CH2Me, CMe3 or CH2CMe3) with HAuCl4 or Na[AuCl4] has been investigated. Under different experimental conditions, salts [H2L][AuCl4], adducts [Au(HL)Cl3] or cyclometallated derivatives [Au(L)Cl][X](X = AuCl4, BF4 or PF6) have been isolated. The cyclometallated species arise from direct activation of a C–H bond either of a phenyl or a methyl substituent. The structures of an adduct [Au{N2C10H7(CHMePh)-6}Cl3] and two metallated species [Au{N2C10H7(CMe2C6H4)-6}Cl][AuCl4] and [Au{N2C10H7(CMe2CH2)-6}Cl][BF4]·0.5H2O have been determined by X-ray diffraction. In the adduct the gold atom is bonded to the nitrogen atom of the unsubstituted pyridine ring: a long-range interaction with the other nitrogen atom is observed, Au ⋯ N 2.758(4)A. In the two cyclometallated species the bipyridines act as tridentate N,N,C anions, giving a [5,6] and a [5,5]-fused ring system, respectively. In [Au{N2C10H7(CMe2C6H4)-6}Cl]+ the hexaatomic N,C ring adopts a boat-like conformation: the structure reveals a rather short interaction between one hydrogen of the Me group in axial position and the gold atom, Au ⋯ H 2.62 A. The pentaatomic N,C ring in [Au{N2C10H7(CMe2CH2)-6}Cl]+ is not planar: the co-ordination around the gold atom is essentially square planar. The new cyclometallated complexes [Au(N,N,C)Cl]+ are compared with those derived from similarly substituted pyridines described previously.

Crystal structure of [Me3NCH2Ph][Fe4(CO)13H]. A ‘butterfly’ metal cluster with an unusually bonded carbonyl group

A single-crystal X-ray analysis has shown the [Fe4(CO)13H]– anion to contain a butterfly arrangement of metal atoms; twelve carbonyl groups are terminally bonded, three to each iron atom, whereas the thirteenth carbonyl group interacts with all the four iron atoms and behaves as a four-electron ligand.

Iron, cobalt and nickel carbide-carbonyl clusters by CO scission

A new approach to the synthesis in good yields of known cobalt and iron carbidecarbonyl clusters by CO cleavage in mild conditions is reported. Cleavage of CO results from attaching an acetyl or benzoyl carbocation to the oxygen atom, and by transfer of electrons from an external source. This synthetic approach to carbide molecular clusters may be of some significance with respect to the formation of carbide atoms on to metal crystallites. Attempts to synthesize nickel carbide clusters with the same approach have only been partly successful. The new [Ni9C(CO)17]2~ and [Ni8C(CO)13]2~ have been obtained more conveniently from the reaction of [Ni6(CO)12]2- with CC14. The related reaction of [Ni6(CO)12]2- with Co3(CO)9CCl results in the formation of the mixed-metal carbide cluster [Co3Ni9C(CO)20]3_. This compound is degraded under a carbon monoxide and hydrogen mixture (25 °C, 1 atm) to Ni(CO)4, [Co(CO)4]~ and ethane. Intermediate formation of [Co3Ni7(C-C) (CO)15]3-, in which the two carbide atoms show an interatomic separation of 1.43 A, or of a related species, would provide a possible pathway for C-C bond formation.

Palladium(II) and platinum(II)-C( 3 )-substituted 2,2′-bipyridines

Reaction of Pd(OAc)2 with HL1 and HL2 (HL1=6-iso-propyl-2,2′-bipyridine; HL2=6-neo-pentyl-2,2′-bipyridine), followed by treatment with LiCl or KI, gives [PdCl(L1)]2, (1), [PdCl(L2)]2 (2), and [PdI(L2)]2 (3), respectively. The chloride bridge in complexes1 and2 is split by PPh3 to give the mononuclear species PdCl(L1)(PPh3) (4) and PdCl(L2)(PPh3) (5). Spectroscopic data provide evidence for coordination of the deprotonated ligands through a nitrogen and the C(3) atom of the 6-substituted pyridine. An analogous platinum complex PtCl(L3)(SMe2) (6) (HL3=6-tert-butyl-2,2′-bipyridine) was obtained from trans-PtClMe(SMe2)2 and HL3. The crystal structures of compounds1 and6 have been solved by X-ray diffraction analysis.

Synthesis and X-ray structure of [CuPPh3CCPh]4, an electron deficient molecule with μ-bridging phenylacetylide ligands

Abstract The [CuPPh3CCPh]4 tetramer, obtained by treatment of [Cu(PPh3)2BH4] with phenylacetylene and KOH (molar ratio 1/1/1) in 1/1 benzene/benzyl alcohol, consists of a tetrahedral skeleton of metal atoms bonded to four terminal phosphine molecules and to four μ-3 -bridging phenylacetylide ligands which behave essentially as 2e donors.

Metallation of unactivated methyl groups: platinum(II) derivatives with 6-alkyl-2,2′-bipyridines

The reaction of K 2 [PtCl 4 ] with three 6-alkyl-2,2′-bipyridines HL, (N 2 C 10 H 7 R; R = CH 2 Me, HL et ; CHMe 2 , HL ip ; CH 2 CMe 3 , HL np ) affords five- and six-membered cyclometallated complexes [Pt(L)Cl] where L is a terdentate N , N , C anionic ligand which originates from HL through direct activation of a C(sp 3 )−H bond. In the case of HL ip , metallation generates a stereogenic carbon atom β to the metal. Complex 5, [Pt(L np )Cl], having an uncommon six-membered ring containing a Pt−C(sp 3 ) bond, was studied in depth in solution, by means of 1- and 2- dimensional NMR spectroscopy, and in the solid state by X-ray diffraction. Differences are observed in the behaviour of these ligands: thus with HLet an adduct, [Pt(HL et )Cl 2 ], was also isolated and its structure was determined by X-ray diffraction. In the metallated species, the fourth ligand, Cl, can easily be substituted by neutral or anionic ligands (CO, PPh 3 , CN − ). The metallated species react with potentially bidentate ligands L′−L′′ [Ph 2 PCH 2 PPh 2 (dppm), Ph 2 P(CH 2 ) 2 PPh 2 (dppe), Ph 2 P(CH 2 ) 2 AsPh 2 (dppae)] to give, with different Pt:L ratios, mononuclear [Pt(L)(L′−L′′)] + or dinuclear [(L)Pt(μ−L′−L′′)Pt(L)] ++ cationic species. In the second case an uncommon unsupported L′−L′′ bridge is present. The cyclometallated species are stable in air and moisture, and the N , N , C system is rather robust.

New carbide clusters in the cobalt sub-group. Part 5. Crystallographic characterization of deca-µ-carbonyl-carbido-octacarbonyl-polyhedro-octacobaltate(2–) in its bis(benzyltrimethylammonium) salt

The title complex crystallizes in the triclinic space group P with unit-cell dimensions a= 19.02(2), b= 10.37(1),c= 12.81(1)A, α= 116.43(8), β= 88.90(8), γ= 95.53(8)°, and Z= 2. The structure has been determined by conventional methods from X-ray single-crystal counter data and refined by least-squares calculations to R 0.064 for 3 539 significant diffraction intensities. The [Co8C(CO)18]2– anion contains a deformed tetragonal antiprism of metal atoms (D2 idealized symmetry) with an average Co–Co distance of 2.52 A. The carbide atom occupies the centre of the cluster; two kinds of Co–C(carbide) distances are present (means 1.99 and 2.15 A). There are eight terminal carbonyl ligands, one per metal atom, and the other ten carbonyls range from partially bent to symmetrically edge-bridging.

Synthesis and X-ray structure of [Ni16(CO)23C4]4–: a tetracarbide anionic cluster containing two interstitial C2 fragments

Reaction of [Ni10(CO)16C2]2– with four equivalents of PPh3 in tetrahydrofuran quantitatively afforded the novel brown [Ni16(CO)23C4]4– tetra-anion, whose metal frame has been shown by X-ray diffraction studies to consist of a unique hexadecanuclear truncated ν2-octahedron caging two interstitial C2 moieties with a very short interatomic C-C separation of 1.38 A.

Synthesis, NMR, and structural characterization of the [Ni9Pt3(CO)21H4-n]n− (n = 4, 3, 2) anionic clusters

Abstract The preparations of bimetallic carbonyl clusters having the general formula [Ni 9 Pt 3 (CO) 21 H - n ] n − ( n = 4, 3, 2) are described. X-ray studies on [NEt 4 ] 3 [Ni 9 Pt 3 (CO) 21 H] show that it is isostructural with [Ni 12 (CO) 21 H] 3− , with the platinum atoms occupying the inner triangle of the central Ni 3 Pt 3 planar triangulated array. The interstitial coordination of the hydride atoms in these compounds is inferred from 1 H and 195 Pt NMR and X-ray data.