C. Scott Browning

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.

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.

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.

SYNTHESIS, CHARACTERIZATION AND REACTIVITY OF BIS(DIPHENYLPHOSPHINO)AMINE NICKEL COMPLEXES

Abstract The binuclear Ni(0) complexes [Ni2(μ-CO)(CO)2(μ-L2)2 (3), where L2 is the bridging diphosphine ligand bis(diphenyl-phosphino)amine (1H) or bis(diphenylphosphino)methylamine (1Me), have been prepared by the reaction of [Ni(CO)4] and L2. The bridging CO ligands in complexes 3 are reversibly displaced by SO2 yielding [Ni2(μ-SO2)(CO)2(μ-L2)2] (4). The single crystal X-ray structure of the binuclear complex. [Ni2(μ-SO2)(CO2)(μ-(PPh2)2NH)2] (4H), is presented. [Ni2(μ-SO2)(CO)2(μ-(Ph2P)2−NH)2]·(C8H10) crystallizes in the monoclinic space group C2 c , Z=4 with lattice parameters a = 27.227(5), b = 9.543(2), c = 22.979(4) A and β = 113.26(3)° . Reaction of the complexes 3 with X2, where X = Cl or I, ultimately gives [NiX2L2] (5), although intermediates in the reactions are observed. 13PNMR and mass spectral data for teh complexes are reported. Attempts to react the binuclear complexes 3 with several other ligands were unseccesful.

Preparation, structure and cytotoxicity of cis-diammineplatinum(II) dinuclear complexes with 1-alkyluracil and imidate ligands ☆

Abstract A series of platinum dinuclear complexes with l-alkyluracil, cis -[Ph 2 (PtU) 2 (NH 3 ) 4 ] (NO 3 ) 2 , cis-[Pt 2 (n-BuU) 2 (NH 3 ) 4 ](NO 3 ) 2 , cis-[Ph 2 (BzlU) 2 (NH 3 ) 4 ](NO 3 ) 2 and cis-[Pt 2 (NaphCH 2 U) 2 (NH 3 ) 4 ](NO 3 ) 2 (head-to-head, where U=uracil), and with imide ligands, cis-[Ph 2 (SI 2 (NH 3 ) 4 ](NO 3 ) 2 (head-to-head), cis-[Pt 2 (DMGI) 2 (NH 3 ) 4 ](NO 3 ) 2 (head-to-head), cis-[Pt 2 (DMGI) 2 (NH 3 ) 4 ](NO 3 ) 2 (head-to-tail) and cis-[Pt 2 (DMGI) 2 (NH 3 ) 4 ] (NO 3 ) 2 (head-to-head, where SI = succinimidate, EMGI = 3-ethyl-3-methylglutarimidate and DMGi=3,3.dimethylglutarimidate) was synthesized, as well as platinum mononuelear complexes, cis-[PtCl(SI)(NH 3 ) 2 ] and cis- [Pt(SI) 2 (NH 3 ) 2 ]. The isomers of the dinuclear complexes (head-to-head and head-to-tail forms) were obtained separately by fractional recystallizations. Crystal structures of cis-[Pt 2 (SI) 2 (NH 3 ) 4 ](NO 3 ) 2 (head-to-head), cis-[Pt 2 (DMGI) 2 (NH 3 ) 4 ](NO 3 ) 2 (head-to-head) and cis-[Pt 2 (EMGI) 2 (NH 3 ) 4 ](NO 3 ) 2 (head-to-head) were determined by X-ray diffraction analysis. Cytotoxic activity was evaluated by the IC 50 value using mouse sarcoma S-180 cells. Most head-to-head complexes are considerably active, while the corresponding head-to-tail analogues are inactive. The active complexes, in general, release ligands in saline at 37°C, and a relationship between hydrophobicity of the complexes and the IC 50 value has been shown.

The preparation and structure of the bis-vinyl ether complex Pt(Ph 2PCH 2CH 2PPh 2)[(MeO 2C)CC(OMe)(CO 2Me)] 2

Abstract Reaction of the [Pt(dppe)] 2+ cation (where dppe = Ph 2 PCH 2 CH 2 PPh 2 ) with the activated acetylene dimethyl acetylenedicarboxylate in methanol solution results in the formation of the bis-vinyl ether complex Pt(dppe)[(MeO 2 C)C C(OMe)(CO 2 Me)] 2 . The compound is characterized by infrared, 1 H and 31 P( 1 H) NMR spectroscopy, elemental analysis and X-ray crystallography.

An ab initio study of the ligands diphosphinoamine and diphosphinomethane in the chelating and bridging geometries

Abstract A study of the energies of the model compounds diphosphinoamine (dpa) and diphosphino-methane (dpm) as a function of the P-E-P (E = N and C respectively) bond angle was conducted using ab initio methods at the MP4SDQ/6-31G∗//RHF/3-21G∗ level. Equilibrium structures of C2v and Cs, symmetry were obtained for both compounds. The compounds were found to exhibit a very similar angular dependence of their potential energy. The difference in destabilization between dpa and dpm as they are distorted from their equilibrium geometries to any angle o emanates from the difference in their equilibrium P-E-P bond angles.

Platinum(II) co-ordination chemistry of bis(diphenylphosphino)amine

A spectroscopic and structural examination of the platinum(II) co-ordination chemistry of bis(diphenylphosphino)amine (dppa) and bis(diphenylphosphino)methylamine (dppma) has been made. The complexes [Pt(dppa)Cl2], [Pt(dppma)Cl2], [Pt(dppa)(CN)2], [Pt(dppma)(CN)2], [Pt(dppa)2]2+ and [Pt(dppma)2]2+ as the chloride, iodide and tetrafluoroborate salts, [Pt(Ph2PNPPh2)2], trans-[Pt-(dppa-P)2(CN)2] and [Pt2(µ-dppa)2(CN)2] have been prepared. The solid-state structures of [Pt(dppa)2][BF4]2·MeCN,[Pt(dppma)2][BF4]2 and trans-[Pt(dppa-P)2(CN)2] have been determined by X-Ray crystallography. The crystallographic examination permits a critical evaluation of the nature of the strain in the four-membered rings formed by ligand chelation to a transition-metal centre. Structural and theoretical data suggest that bis(diphenylphosphino)amine chelate complexes should be more strained than the corresponding bis(diphenylphosphino)methane (dppm) complexes. The preference of PtII for binding to dppa rather than dppm implies the formation of a stronger Pt–P bond in complexes of the former ligand.