David H. Farrar

Synthesis and electrochemical study of cobalt carbonyl complexes of trimethylsilyl-substituted 1,3,5-triethynylbenzene

Treatment of 1,3,5-tris(trimethylsilylethynyl)benzene or 1,3,5-triethynylbenzene with Co 2 (CO) 8 or Co 2 (CO) 6 (dppm) produced the formation of substituted ethynylcobalt complexes with one, two or three Co 2 (CO) 6 or Co 2 (CO) 4 (dppm) units, [{X 3 (Co 2 (CO) 6 )C 2 } n (XCC) m (1,3,5-C 6 H 3 )] (X=H or SiMe 3 ) ( n =1, 2 or 3; m =3− n ) and [{SiMe 3 (Co 2 (CO) 4 dppm)C 2 } n (SiMe 3 CC) m (1,3,5-C 6 H 3 )] ( n =1 or 2; m =3− n ), in a high yield. Desilylation of the non-metallated alkynes in [{SiMe 3 (Co 2 (CO) 4 dppm)C 2 }(SiMe 3 CC) 2 (1,3,5-C 6 H 3 )] occurred on treatment with KOH. Electrochemical results provide evidence for communication between the C 2 Co 2 centres. Crystals of [{SiMe 3 (Co 2 (CO) 4 dppm)C 2 } 2 (SiMe 3 CC)(1,3,5-C 6 H 3 )] suitable for single-crystal X-ray diffraction were grown and the molecular structure of this compound is discussed.

Synthesis, characterization and reactivity of binuclear palladium(I)bis(diphenylphosphino)amine complexes

Abstract The binuclear Pd(I) complex [Pd 2 (μ-dppa) 2 (CH 3 CN) 2 ][BF 4 ] 2 ( 1 ), where dppa is the bridging diphosphine ligand bis(diphenylphosphino)amine, was prepared by the reaction of [Pd(dppa) 2 ][BF 4 ] 2 and 1 2 equiv. of [Pd 2 (dba) 3 ]. The acetonitrile ligands in complex 1 are readily displaced by other ligands. Substitution of one or both of the acetonitrile ligands of the dimer 1 with Cl − , Br − , I − , (CN) − and PPh 3 is described. 31 P NMR and mass spectral data for the complexes are reported. The single crystal X-ray structures of the binuclear complexes, [Pd 2 (μ-dppa) 2 (PPh 3 )(THF)][BF 4 ] 2 ·4THF, [Pd 2 (μ-dppa) 2 (PPh 3 ) 2 ][BF 4 ] 2 ·THF·H 2 O and [Pd 2 (μ-dppa) 2 Cl 2 ]·3CH 3 CN have been determined. Attempts to react the binuclear complex [Pd 2 (μ-dppa) 2 I 2 ] with ligands capable of bridging the PdPd bond (CO, SO 2 and HgCl 2 ) were unsuccessful.

Reactions of 2-indolylphosphines with Ru3(CO)12: cluster capping with μ3, η2-indolylphosphine as an anionic six-electron P, N-donor ligand

Stepwise bidentate coordination of the novel indolylphosphine ligands HL (1, HL = P(C(6)H(5))(2)(C(9)H(8)N)(diphenyl-2-(3-methylindolyl)phosphine); 2, HL = P(C(6)H(5))(C(9)H(8)N)(2)(phenyldi-2-(3-methylindolyl)phosphine); and 3, HL = P(C(6)H(5))(C(17)H(12)N(2))(di(1H-3-indolyl)methane-(2,12)-phenylphosphine)) to the ruthenium cluster Ru(3)(CO)(12) is demonstrated. Reactions of 1-3 with Ru(3)(CO)(12) led to the formation of Ru(3)(CO)(11)(HL) (4-6), in which HL is mono-coordinated through the phosphorus atom. The X-ray structures of 4-6 show that the phosphorus atom is equatorially coordinated to the triruthenium core. In all cases, gentle heating of Ru(3)(CO)(11)(HL) resulted in the formation of Ru(3)(CO)(9)(mu-H)(mu(3),eta(2)-L)(7-9) in which the NH proton of the indolyl substituent had migrated to the ruthenium core to form a bridging hydride ligand. The X-ray structure of Ru(3)(CO)(9)(mu-H)[mu(3),eta(2)-P(C(6)H(5))(2)(C(9)H(7)N)] (7) shows the deprotonated nitrogen atom of the indolyl moiety bridging over the face of the triruthenium core, bonding to the two ruthenium metal centers to which the phosphorus atom is not bound. The phosphorus atom is forced to adopt an axial bonding mode due to the geometry of the indolylphosphine ligand. Cluster electron counting and X-ray data suggest that the indolylphosphine behaves as a six-electron ligand in this mode of coordination. Compounds 4-9 have been characterized by IR, (1)H, (13)C and (31)P NMR spectroscopy.

SYNTHESIS AND CHARACTERIZATION OF NEW TRANSITION METAL DIYNYL COMPLEXES

The reaction of (η 5 -C 5 H 5 )Mo(CO)(dppe)Cl with LiCCCCSiMe 3 yielded (η 5 -C 5 H 5 )(CO)(dppe)MoCCCCSiMe 3 ( 1b ) and, as a by-product (η 5 -C 5 H 5 )Mo(CO)(dppe)Br ( 1a ). Treatment of 1b with 0.2 equivalents of tetrabutylammonium fluoride or (η 5 -C 5 H 5 )Mo(CO)(dppe)Cl with HCCCCH gave the terminal butadiyne complex (η 5 -C 5 H 5 )(CO)(dppe)MoCCCCH ( 2 ). Complex 2 was deprotonated with sec -BuLi or lithium diisopropylamide, and the resulting anion (η 5 -C 5 H 5 )(CO)(dppe)MoCCCCLi ( 3 ) was trapped with Me 3 SiCl to regenerate 1b . The synthesis of Co 2 (CO) 4 L 2 (μ-η 2 -Me 3 SiC 2 CCSiMe 3 ) (L 2 =dppa 4 , 2PPh 2 Me 5 ) compounds can be achieved by two methods: from Co 2 (CO) 6 (μ-dppa) by reaction with Me 3 SiCCCCSiMe 3 in 1:1 ratio to yield 4 , or from Co 2 (CO) 6 (μ-η 2 -Me 3 SiC 2 CCSiMe 3 ) by reaction with dppa (1:1 ratio) and PPh 2 Me (1:2 ratio) to yield 4 and 5 , respectively. When the Co 2 (CO) 4 (μ-dppa)(μ-η 2 -Me 3 SiC 2 CCSiMe 3 ) complex was treated with more Co 2 (CO) 6 (μ-dppa) the green di-substituted complex [Co 2 (CO) 4 (μ-dppa)] 2 (μ-η 2 :μ-η 2 -Me 3 SiC 2 C 2 SiMe 3 ) ( 6 ) was obtained. Desilylation of 4 with Bu 4 NF gave Co 2 (CO) 4 (μ-dppa)(μ-η 2 -Me 3 SiC 2 CCH) ( 7 ). All compounds synthesized have been characterized by analytical and spectroscopic data (IR, 1 H-, 31 P-, 13 C-NMR, MS). In addition, compounds 1a and 4 were characterized by X-ray structure analysis.

Reactivity of the P–N bond in the halide salts of bis[bis(diphenylphosphino)methylamine]platinum(II)

Conductivity measurements and 31P-{1H} NMR spectroscopy suggested that the chloride and iodide salts of bis[bis(diphenylphosphino)methylamine]platinum(II)[Pt(dppma)2]2+1 exist in solution equilibrium with the five-co-ordinate complexes [Pt(dppma)2X]+(X = Cl or I). The magnitude of the interaction of the iodide ion with 1 is greater than that of the chloride ion. The extent of formation of the halide-associated species is dependent upon the nature of the solvent. Association equilibrium constants Kassoc= 0.0718 and 0.315 mol dm–3 respectively were calculated for the chloride and iodide salts of 1 in MeNO2. Addition of trace quantities of water to solutions of the chloride or iodide salts of 1 effected cleavage of both P–N bonds of one of its dppma ligands giving [Pt(dppma){(Ph2PO)2H}]+2. The structure of the cation was investigated crystallographically as a mixture of the iodide and tetrafluoroborate salts of the form I0.21[BF4]0.79. The analogous reaction of the chloride salt of 1 with MeOH produces cleavage of only one P–N bond to give [Pt(dppma)(Ph2POMe)(Ph2PNHMe)]2+3 as the chloride salt. Phosphorus–nitrogen bond solvolysis of both ligands of 1 occurs to give the complex trans-[Pt(Ph2POMe)2(CN)2]4 upon addition of 2 equivalents of sodium cyanide to methanolic solvent mixtures of [Pt(dppma)2]X2(X = BF4, Cl or I). The product was characterised crystallographically. Possible mechanisms of formation of these complexes are discussed.

Ligand reactivity and resulting carbene formation in the complex Pt(π-CS)2(Ph3P)2

Abstract Electrophilic attack at both sulphur atoms in the complex Pt(π-CS2)(Ph3P)2 by methyl or ethyl iodide results initially in the formation of a cationic carbene complex [PtI(Ph3P)2(C(SR)2)]11 at 25°C. Subsequent reaction under reflux gives a neutral carbene complex with resultant loss of phosphine ligand.

Preparation, characterization and crystal structure of Fe((OPPh2)2N)3

Abstract White crystals of Fe((OPPh 2 ) 2 N) 3 were obtained from the reaction of a solution of Fe 2 (CO) 9 and excess (PPh 2 ) 2 NH, under an air atmosphere. This product does not form if the solvents are rigorously degassed and the reaction is performed under argon. The structure of the complex, as determined by single crystal X-ray crystallography, is an octahedral tris-chelate arrangement of the oxidized anionic ligand, [(O=PPh 2 ) 2 N] − coordinated to an Fe(III) center. The asymmetric unit of the unit cell also contains a disordered THF solvent molecule. The complex crystallizes in the triclinic space group P 1 , with Z = 2, a = 13.581(3), b = 13.886(8), c = 18.781(7) A , α = 95.48(4), β = 98.73(2), γ = 97.82(3)°, V = 3444(2) A 3 , M r = 1377, D x = 1.33 Mg m −3 , F(000) = 1434, T = 298 K and R = 0.086 for 5959 observed reflections. The magnetic moment of the compound Fe((OPPh 2 ) 2 N) 3 was found to be 5.4 BM, using the Gouy method. Reaction of the oxidized ligand, (OPPh 2 ) 2 NH, with Fe(III) salts, such as Fe(NO 3 ) 3 , produces Fe((OPPh 2 ) 2 N) 3 in high yields.

Reactions of the complexes Pt3(μ-CO)3L3 with SO2. Crystal structure of Pt3(μ-CO)3(PtBu2Ph)3•0.25(C4H8O)

Abstract Reactions of the complexes Pt3(μ-CO)3L3, where LPtBu3 (1a), PtBu2cPr (1b), PtBu2Ph (1c), PCy3 (1d) and PCy2Ph (1e), with SO2 have been examined. The complexes 1 may be divided into two classes: those complexes (1a, 1b and 1c) which fragment to yield a dimer Pt2(μ-SO2)(CO)2L2, where L=PtBu3 (2a), PtBu2CPr (2b), PtBu2Ph (2c), upon brief exposure to SO2 and those complexes (1d and 1e) which substitute CO ligands with SO2 ligands without a change in nuclearity to yield Pt3(μ-SO2)3L3, where L=PCy3 (3d) and PCy2Ph (3e). Traces of the complexes Pt3(μ-SO2)(μ-CO)2L3 (4) were observed after heating the complexes 2 under an SO2 atmosphere for 14 h. As formation of dimeric products appeared to be favoured by larger ligands L, a method of evaluating the non-bonding interactions between the ligands L and the cluster fragment Pt3(μ-CO)3 was used to evaluate the size to the phosphine ligands. The X-ray crystal structure of the complex Pt3(μ-CO)3(PtBu2Ph)3 (1c) is reported.

A reversible metal framework rearrangement in high-nuclearity osmium–platinum cluster compounds. X-Ray crystal structures of [Os6Pt(CO)17(µ3-NCMe)(C8H12)], [Os6Pt(CO)17(µ4-NCMe)(C8H12)](C8H12= cyclo-octa-1,5-diene), and [Os6(CO)19(µ3-NCMe)]: compounds with novel metal–acetonitrile bonding modes

The reaction of [Os6(CO)17(NCMe)] with [Pt(C8H12)2](C8H12= cyclo-octa-1,5-diene) results in the formation of [Os6Pt(CO)17(µ3-NCMe)(C8H12)](1). The geometry of (1) may be derived from that of [Os6(CO)18] by breaking one Os–Os edge and adding a terminal Pt(C8H12) fragment to one of the Os atoms constituting the central tetrahedron. Upon standing in CH2Cl2, cluster (1) isomerizes to a different geometry, [Os6Pt(CO)17(µ4-NCMe)(C8H12)](2). The isomerization process is first order with ΔH‡= 28.7 kcal mol–1 and ΔS‡= 13 cal K–1 mol–1. The structure of isomer (2) may be derived from its precursor (1) by breaking one more Os–Os edge and by moving the Pt(C8H12) unit into a bridging position. Substitution of the C8H12 ligand in (1) or (2) by 1,2-bis(diphenylphosphino)ethane or P(OMe)3 results in clusters having a metallic framework analogous to (1). The extrusion of the Pt moiety results from reaction of CO with either isomer giving a product characterized as [Os6(CO)19(µ3-NCMe)](3).

The structure and dynamic behaviour of disubstituted derivatives of [Rh6(CO)16] containing bidentate phosphorus ligands ☆

The solution structure and dynamic behaviour of [Rh6(CO)14(m,h 2 -dppm)] (1), [Rh6(CO)14(m,h 2 -dppe)] (2) and [Rh6(CO)14(m,h 2 dppe f )] (3) containing bridging diphosphine ligands have been examined using 1D 13 C, 31 P and 2D 13 C/{ 103 Rh}, 31 P/{ 103 Rh} HMQC and 13 C EXSY NMR techniques. It has been shown that the solid state structure of these clusters remains unchanged in solution, including the close non-bonding intramolecular interactions of the perfluorinated phenyl rings with adjacent terminal carbonyls. In solution, two different dynamic processes have been found: for 2 and 3, the P/CH2/CH2/P chain of the coordinated dppe and dppe f is non-rigid and this leads to the interchange of the two enantiomeric forms of the clusters through a ‘rocking’ motion of the bridging diphosphine; the rate of this exchange depends strongly on the non-bonding van der Waal’s interactions between the phosphorus substituents and adjacent carbonyl ligands which results in substantially slower dynamics for 3 because the steric requirements of the fluorinated phenyl rings considerably hinder this racemization. The second type of dynamics found in 1/3 involves exchange of terminal/face-bridging CO’s associated with the unsubstituted rhodium atoms. Regioselectivity of these exchanges is essentially similar for all three clusters, whereas the rates of these CO-exchanges are substantially higher in 3, which may be due to the lower net donicity of the per-fluorinated diphosphine. # 2003 Elsevier B.V. All rights reserved.