We have studied the reactivity of the complexes [Pd(C6H4X-2)Br(bpy)] (bpy = 2,2‘-bipyridine; X = C(O)Me (1a), CN (1b), CHO (1c)), [Pd{C6H4CHCH2-2}(PPh3)(bpy)](TfO) (TfO = CF3SO3; 2d), trans-[Pd(C6H4X-2)Br(PPh3)2] (X = C(O)Me (3a), CN (3b), CHCH2 (3d)), and [Pd(μ-Br)(C6H4X-2)(PPh3)]2(X = C(O)Me (4a), CN (4b)). Their reactions with XyNC (Xy = 2,6-dimethylphenyl) depend on the nature of X and the other ligands and on the reaction conditions. The products of these reactions are mono- and triinserted complexes. Among the former are [Pd{C(NXy)C6H4X-2}Br(L2)] (L2 = bpy, X = C(O)Me (5a), CN (5b); L = CNXy, X = C(O)Me (6a), CN (6b), CHCH2 (6d)) and trans-[Pd{C(NXy)C6H4CHCH2-2}(CNXy)2(PPh3)](TfO) (7d). The reaction of 1c with XyNC (1:5 molar ratio) gives 10, a product resulting after substitution of bpy, coordination of two molecules of XyNC, triinsertion of XyNC, and a cyclization resulting after the attack of the nitrogen of the first inserted molecule at the carbon atom of the formyl group. The complexes [Pd{κ2 C 1,N 3-C(NXy)C(NXy)C(NXy)C6H4X-2}Br(CNXy)] (X = C(O)Me (8a), CN (8b)) were obtained by reacting (i) 3a or 3b with XyNC (1:4 molar ratio) or (ii) Pd(dba)2 (dba = dibenzylideneacetone) with BrC6H4X-2 and XyNC (1:1:4 molar ratio). When this oxidative addition reaction was carried out with BrC6H4CHO-2, the resulting product decomposed to give the Pd(I) complex [Pd2Br2(CNXy)4] (9). Tl(TfO) was reacted with (i) 8a and 8b (1:1 molar ratio) to give the corresponding triflato complexes 11a and 11b, (ii) 4a (1:2 molar ratio) in the presence of moisture to give the cyclopalladated aquo complex [Pd{κ2 C,O-C6H4{C(O)Me-2}(OH2)(PPh3)](TfO) (12a), and (iii) 4b (3:1 molar ratio) to give [Pd(C6H4CN-2)(κ2 N,N- 4b)(PPh3)](TfO) (13b), in which 4b behaves as a ligand through the two cyano groups. The crystal structures of 5b, 6b, 7d, 8a,b, 9, 10, 11a,b, 12a, and 13b have been determined by X-ray diffraction studies.

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The complexes [Pd(C 6 H 4 X-2)BrL 2 ] (L 2 ) trans-(PR 3 ) 2 , R ) Ph, X ) CHdCH 2 (1a), CHO (1b), C(O)Me (1c), CN (1d) CN (2d′)) have been prepared by oxidative addition of the corresponding bromoarene BrC 6 H 4 X-2 to "Pd(dba) 2 " ()[Pd 2 (dba) 3 ]‚dba, dba ) dibenzylideneacetone) in the presence of the appropriate ligand. The compound [Pd{C 6 H 4 (CHdCH 2 )-2}(bpy)(PPh 3 )]TfO (3a; TfO ) CF 3 SO 3 ) has been obtained by reacting 1a with bpy in the presence of TlOTf. The cyclopalladated [Pd{κ 2 -C,O-C 6 H 4 {C(O)Me}-2}(bpy)]TfO (4c) has been prepared from 2c and TlOTf. The dimeric complexes [Pd(µ-Br) 5b′′), CN (5d′′)) have been synthesized by reacting complexes 1b-d with [PdCl 2 (NCPh) 2 ] in a 2:1 molar ratio or C 6 H 4 Br-1-X-2 with "Pd(dba) 2 " and P(o-To) 3 in 1:1:1 molar ratio. The latter method leads to the monomericThe complex 2c reacts with the alkyne PhCtCPh or EtCtCEt and TlOTf to give 1-methyl-2,3-diphenyl-1H-indenol (7) or 1-methyl-2,3-diethyl-1H-indenol (8), respectively. The crystal structures of complexes 1a‚2CH 2 Cl 2 , 1b‚CH 2 Cl 2 , 2b,d, and 6c′′ have been determined by X-ray diffraction studies. An interesting supramolecular layered structure is formed through CN‚‚‚H-C bpy and Br‚‚‚H-C bpy hydrogen bonds in complex 2d.

Two trinuclear iridium hydride clusters of the type [Ir3(μ3-H)(H)6(PHOX)3]X1X2 (X1 = PF6, X2 = OTf; X1 = X2 = PF6; X1 = X2 = OTf; PHOX = (S)-4-tert-butyl-2-[2-(di-o-tolylphosphinyl)phenyl]-4,5-dihydrooxazole, (S)-2-[2-(diphenylphosphinyl)phenyl]-4-isopropyl-4,5-dihydrooxazole) have been prepared and characterized by X-ray diffraction and multidimensional NMR. They contain a single bridging hydride in pseudo-trans position to the P-donors. The complexed PHOX ligands reveal a chiral pocket involving one pseudoequatorial P-aryl substituent and one pseudoaxial (proximate to the oxazoline substituent) P-aryl group. These trinuclear complexes are shown to be inactive as hydrogenation catalysts.

1H and (19)F pulsed gradient spin-echo (PGSE) diffusion studies on cationic mono- and trinuclear iridium complexes containing the PHOX chiral P,N-auxiliary (S)-4-tert-butyl-2-[2-(di-o-tolylphosphino)phenyl]-4,5-dihydrooxazole with the anions BF(4)(-), PF(6)(-), OTf(-), B(C(6)F(5))(4)(-), and BArF(-) in methanol, chloroform, methylene chloride, and 1,2-dichloroethane are reported. In chloroform, the anion and cation within each salt afford almost the same, relatively small, diffusion constant (D-value) suggesting strong ion-pairing. In methanol, the D-value for the cation is the same in the five mononuclear salts, suggesting that the cation is moving independently of the anion (no ion-pairing). In methylene chloride and 1,2-dichloroethane the diffusion data suggest a mixed picture for the five anions. While the smaller BF(4)(-), PF(6)(-), and OTf(-) anions do not affect the translation of the cations, the larger boron-based anions B(C(6)F(5))(4)(-) and BArF(-) clearly slow the motions of the cations. However, it would seem that for all five anions there is some--but not complete--ion pairing in these two solvents.

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o-Formylaryl)palladium complexes [Pd{C 6 H(CHO)-6-R 3 -2,3,4}X(N-N)] [R ) OMe; X ) Cl; N-N ) bpy (2,2′-bipyridine) (1a), tmeda (N,N,N′,N′-tetramethylethylenediamine) (1b). R ) H; X ) Br; N-N ) bpy (2a), tmeda (2b)] react with ylides PhCHdPPh 3 , pyCHdPPh 3 (py ) 2-pyridyl), or ClCHdPPh 3 to give the (o-alkenylaryl)palladium derivatives [Pd{C 6 -The compounds 3a, 4, and 6a,b are obtained as mixtures of E and Z isomers, whereas the formation of 3b and 5 is stereoselective (E isomer). The reaction of the (o-acetylaryl)palladium complexes [Pd{C 6 HC(O)Me-6-(OMe) 3 -2,3,4}Cl(tmeda)] ( 7) and [Pd{C 6 H 4 (C(O)Me)-2}Br(bpy)] (8) with bases results in the formation of the 3-palladaindan-1-ones [Pd(κ 2 -{C 6 HC(O)CH 2 -6-(OMe) 3 -2,3,4})(tmeda)] (9) and [Pd(κ 2 -{C 6 H 4 C(O)CH 2 -2}(bpy)] (10). Complexes 3b and 6a,b react with alkynes RCtCR′ to give indenylpalladium complexes [Pd{η-C 9 HBn-1-R-2-R′-3-(OMe) 3 -5,6,7}(tmeda)]TfO [Bn ) benzyl, TfO ) CF 3 SO 3 , R ) R′ ) Me (11); R ) C(O)Me, R′ ) H (12)] and [Pd{η-C 9 H 4 Bn-1-R-2-R′-3}(N-N)]TfO [R ) R′ ) H, N-N ) bpy (13a), tmeda (13b); R ) R′ ) Me, N-N ) bpy (14a), tmeda (14b); R ) R′ ) Et, N-N ) bpy (15a), tmeda (15b); R ) R′ ) Ph, N-N ) bpy (16a), tmeda (16b); R ) Ph, R′ ) H and R ) H, R′ ) Ph, N-N ) bpy (17a); R ) H, R′ ) Ph, N-N ) tmeda (17b); R ) Ph, R′ ) Me, N-N ) bpy (18a), N-N ) tmeda (18b)]. Complex 3b reacts with Me 2 CdCdCH 2 , CS 2 , or MeNdCdS to give [Pd(η 3 -CMe 2 C{C 6 H(E-CHdCHPh)-6-(OMe) 3 -2,3,4}CH 2 )(tmeda)]Tf O (19), [Pd(S 2 C{C 6 H-(E-CHdCHPh)-6-(OMe) 3 -2,3,4})(tmeda)]TfO (20), or [Pd(SC(NMe){C 6 H(E-CHdCHPh)-6-(OMe) 3 -2,3,4})(tmeda)]TfO (21). The crystal structures of 12, 17b, and 18a have been determined; the hapticities of the indenyl five-membered rings are intermediate betwen η 3 and η 5 .

The problems associated with low-temperature pulsed-gradient spin-echo (PGSE) NMR diffusion measurements are discussed. The influence of convection is overcome by employing a coaxial insert inside a normal 5 mm NMR tube. By means of this configuration, correct diffusion constants and temperatureindependent hydrodynamic radii can be obtained. Introduction. ± There are increasing numbers of applications of pulsed-gradient spin-echo (PGSE) NMR diffusion measurements [1] [2] in inorganic and organometallic chemistry [3 ± 15]. The calculated diffusion coefficient D can be used to estimate molecular volumes (the larger the molecule, the slower it diffuses).In recent PGSE diffusion studies, the potential of this technique for the study of ion pairing has been emphasized [16 ± 19]. Through a separate analysis of the translational properties of cation and anion, it is possible to gain insight into whether these charged species move independently or as a single unit in solution. Solvents with a relatively low dielectric constant, such as CHCl 3 , favor the formation of tight ion pairs [18] [19]. In these solvents, both cation and anion have been found to show the same, relatively small, diffusion coefficient as they move together as a relatively large unit. In morepolar solvents, such as MeOH, the cation and anion are usually not associated and show different and mutually independent D-values. In CH 2 Cl 2 , we have observed an intermediate situation, where there is partial but usually not complete ion pairing [18] [19]. The translational properties of the cation will then be affected by the anion, and vice versa. For salts of transition metals, the PGSE diffusion methodology, frequently in combination with NOE data, offers a unique structural approach to this problem. By means of these methods, the relative anion-dependent activity of the Ir phosphinooxazoline (PHOX) complexes 1 in the catalytic hydrogenation of olefins in CH 2 Cl 2 can be explained [6] [19] [20].When no