B. Cetinkaya

Carbene complexes: XXIII. Preparation, characterisation, and structures of the enetetramine-derived carbenerhodium(I) chloride complexes [RhCl(LR)3],trans-[RhCl(CO)(L2R′)], and [{RhCl(COD)}2{μ-L2(323)R}] [L2R or R′ = CN(R or R′)(CH2)2NR(or R′) (R CH2)Ph or Et, R′ Me) and L(323)R CN(R)(CH2)3N(CH2)2N(CH2)3N(R)C (R CH2Ph)]

From [{Rh(μ-Cl)COD)}2 and the enetetramine L2Me, L2Et, L2CH2Ph, or L(2323)CH2Ph) the crystalline complexes [RhCl(LR)3][R  CH2Ph (1) or Et (3)], [{RCl(COD)}2{μL2(323)CH2Ph}] (2), or trans-[RhCl(CO)(LR)2] [R  CH2Ph (4) or Me (5)] have been obtained in high yield [LR CN(R)(CH 2)2NR and L{(su323)R}  CN(R)(CH2)3N(CH2)2N(CH2)3N(R)C]. Complex 2 provides a rare example of a bridging bis(carbene) dimetal complex and the first for one derived from an enetetramine. The X-ray structures of1–5 show that (i) the mutually trans-RhCcarb bonds for 1 and 3 are longer than the cis-; (ii) the RhCl bond lengths range from 2.268(4) (5) to 2.464(6) (3)A; (iii) in the bis(carbene) complexes 4 and 5, as well as in 2, the five-membered almost planar Ccarb,NC2N ring (or fragment for 2) is approximately orthogonal to the plane containing Rh, Cl, and Ccarb, while in the tris(carbene) complexes 1 and 3 the mutually trans-carbene ligands are twisted from a parallel arrangement by 49°; and (iv) the sum of the bond angles at each Ccarb or N is close to 360°.

Transition-metal complexes of two valence tautomers of a bulky phenoxide, 2,6-Bu-t2-4-MeC6H2O− (ArO−); preparation and crystal and molecular structure of a phenoxytitanium(III) and a cyclohexadienonylrhodium(I) complex, [Ti(η-C5H5)2 OAr] and [Rh(ArO-η5)(PPh3)2]

Abstract The 2,6-di-t-butyl-4-methylphenoxo ligand (ArO−) is ambidentate, giving rise to the O-bonded 15-electron d1 [Ti(η-C5H5)2OAr] and the η5 -[C(2)-C(6)]-bonded 18-electron d8 complex [Rh(ArO-η5)(PPh3)2], obtained from [{Ti(η-C5H5)2Cl}2]-LiO Ar and [Rh{N(SiMe3)2}(PPh3)2]-ArOH, respectively; the average TiC(η) distance is 2.362(10) A, TiO 1.892(2) A, and O:C(of Ar) 1.352(3) A, and TiOC 142.3(2)°; in the RhI complex, C(2)C(6) are coplanar (with CC(av.) 1.38(2) A). C(1)O 1.28 A, and Rh to C(2) C(6) bond lengthsare in the range 2.19–2.65 A.

trans/cis-isomerism and isomerisation of PdII and PtII carbene complexes; The crystal and molecular structures of cis- and trans-PtCl2 [C(NPhCH2)2]PEt3

Abstract trans-PtII or trans-PdII carbene complexes are isomerised to the thermodynamically more stable cis compounds; cis- and trans-isomeric pairs are compared with respect to reactivity and physical properties, including spectroscopic and X-ray data.

Butyl metal aryloxides, arylamides, and sulphur and phosphorus analogues—II. Synthesis and characterization of novel bulky alkoxides and aryloxides of aluminium; X-ray structure of [Al(μ-OCH2Ar)Me2]2 (Ar = C6H2Bu3t-2,4,6)

Abstract The alkoxide, (2,4,6-tri-t-butylbenzoxo)dimethylaluminium, [Al (μ-OCH2Ar)-Me2]2 (Ar = C6H2Bu3t-2,4,6), (1), has been prepared from the corresponding benzyl alcohol ArCH2OH and trimethylaluminium in C6H14 at ca 25°C. Even using an excess of the alcohol, only one of the methyl groups of AlMe3 was replaceable under these conditions. By contrast, using the bulky phenol Ar′OH (Ar′= C6H3Bu2t-2,6) and an excess of AlMe3 yielded the bis-aryloxide, bis-[2,6-di(t-butyl) phenoxo]methylaluminium, AlMe(OAr′)2 (Ar′= C6H3Bu2t-2,6), (2). The less hindered phenol Ar″OH (Ar″ = C6H3Bu2t-2,4) and an excess of AlMe3 gave the expected aryloxide, (2,4-di-t-butylphenoxo)dimethylaluminium, AlMe2(OAr″) (Ar″ = C6H3Bu2t-2,4) (3). Compounds 1-3 have been characterized spectroscopically and in the case of the crystalline alkoxide 1, also by X-ray crystallography; some selected geometric parameters are: AlO 1.841(3) and 1.858(2), Al1.939(5) and 1.959(6), Al Al′ 2.84, O O2.37 A; OAlO′ 79.8(1), AlOAl′ 100.2(1)°. Complex 1 has the structure [AlMe2(μ-OCH2Ar)]2, both as the solid and at 30°C in C6D6 solution. Less complete data on the aryloxides 2 and 3 suggest that the former is a monomer, whereas the latter is a dimer, probably by virtue of OAr″-bridging.

Carbene complexes : IV. Far infrared and 31P NMR spectra of palladium and platinum carbene complexes

Abstract Infrared bands mainly associated with v (M—X 2 ) stretching modes (M = Pd or Pt, and X = Cl, Br, or P) have been identified in the spectra of 35 carbene complexes. Based on these results and on | 1 J | ( 31 P— 195 Pt) the trans -influence of the carbene ligands is assessed.

Carbene complexes. Part I. Electron-rich olefins as a source of carbene complexes of platinum(II) and palladium(II); and some experiments with (CF3)2CN2

The reactions of electron-rich olefins with di-µ-chloro-dichlorobis(phosphine)diplatinum(II)(and bromo-, arsine-, and PdII analogues) have been investigated. In general, the product is the trans-PtII or PdII carbene complex, or the cis-isomer, or a mixture of these compounds, depending on the reagents, solvent, and reaction conditions. The compounds are stable, crystalline, and monomeric. Bis(trifluoromethyl)diazomethane reacts with (i) di-µ-chloro-dichlorobis(triethylphosphine)diplatinum(II) to give the product of insertion only into the terminal Pt–Cl bonds, and (II) tris(triphenylphosphine)platinum(0) to furnish the adduct Pt[(CF3)2CN2·(CF3)2C](PPh3)2. Structures and mechanisms are discussed.

Synthesis and Properties of Chlorotris (1,3-Dibenzylimidazolidin-2-ylidene) Rhodium (I) and of Some Related Compounds

The electron-rich alkene Open image in new window (R = CH2Ph) has been used as a source of various carbenerhodium(I) complexes: [RhC](cod)(L)] (1), [RhCl(L)3] (2), [RhCl(CO)(h)3] (3), and trans-[RhCl(CO)(L)2] (4), and of the iridium(I) complex [IrCl(L)3] (5). Compounds (2) and (5) are of particular interest as they contain no other neutral ligand apart from the carbene: Open image in new window (R = CH2Ph); their chemistry is in many ways related to that of the well known complexes [MCl(PPh3)3] (M = Rh or Ir). Thus, compound (2) readily loses a carbene ligand upon treatment with either carbon monoxide [ultimately to lead to (4)], or O2 to yield a compound tentatively formulated as [RhCl(L)2(O2)] (6). The x-ray structures of complexes (2) and (4) have been determined.