Alan J. Welch

Synthesis of mono- and polynuclear perhalophenyl palladium-platinum acetylide complexes. Molecular structure of (NBu4)2[Pt2Ag2(C6F5)4(CCPh4] · 4CH2Cl2

Abstract The reaction between [Ag(CCR)]n (R = tBu, Ph) and the appropriate mononuclear palladium or platinum substrate affords mononuclear derivatives of the type [M(C6F5)(CCR)L2] (M = Pd, Pt; R = tBu, Ph; L = PPh3, dppe). Polynuclear (NBu4)2[Pt2Ag2(C6F5)4(CCPh)4] (X = F, Cl; R = Ph, tBu) complexes are obtained by reaction between (NBu4)2[Pt2(μ-X′)2(C6X5)4] (X′ = Cl, X = F; X′ = I, X = Cl) and [Ag(CCR)]n (Pt:Ag ratio 1:2). Similar heterometallic derivatives Q2[Pt2M2(C6F5)4 (CCR)4] (Q = PMePh3, NBu4; M = Ag, Cu; R = Ph, tBu) can be prepared by reaction of Q2[cis-Pt(C6F5)2(CCR)2] with AgCl or CuCl (Pt:M ratio 1:1). The structure of (NBu4)2[Pt2Ag2(C6F5)4 (CCPh)4]·4CH2Cl2 has been determined by X-ray diffraction.

The chemistry of monoanionic carbaborane ligands. Synthesis, and molecular and electronic structure of [3,3,3-(CO)3-4-SMe2-3,1,2-MnC2B9H10], and order-of-magnitude improved structure of (η-C5H5)Mn(CO)3

Abstract The synthesis, and spectroscopic and structural characterisation of a transition metal complex of, formally, a monoanionic carbaborane ligand are described. Two molecules of [3,3,3-(CO)3-4-SMe2-3,1,2-MnC2B9H10] crystallise in the triclinic space group P 1 , with a 7.154(4), b 8.7890(21), c 13.366(3) A, α 91.438(19), β 101.21(3), γ 110.69(3)°, at 185 ± 1 K. R = 0.0352 for 3859 observed reflections. The carbamanganaborane has an essentially icosahedral polyhedral geometry, and the pendant SMe2 unit is oriented such that the S lone pair…H(1)δ+ interaction is maximised. The average OCMnCO angle is 89.91°. A redetermination of the structure of the known species CpMn(CO)3 affords molecular parameters of high precision. Space group P21/a with a 11.941(7), b 6.981(5), c 10.798(7) A, β 117.97(5)°, Z = 4, R = 0.0418 for 1960 significant reflections measured at 185 ± 1 K. In this compound OCMnCO is wider, average 92.14°. Charge iterated EHMO calculations suggest that the anionic carbaborane ligand may be represented by a form in which a charge of −1.5 e on the five facial atoms is partially offset by a charge of +0.3 e on the pendant S atom. EHMO/FMO calculations confirm that the carbaborane is a better electron donor than the Cp ligand to the {Mn(CO)3} unit, and indicate that the additional electron density on Mn resides in fragment orbitals that are antibonding between C and O. In particular, CO → Mn σ donation is restricted in the carbaborane compound relative to the Cp compound. Consistent with the results of these calculations, ν(CO) values of the former compound are measurably lower than those of the latter species.

Steric effects in heteroboranes. Part 7: The synthesis and characterisation of arene-ruthenium complexes of C-substituted carbaboranes. Molecular structures of 1-Ph-3-(mes)-3,1,2-closo-RuC2B9H10 (mes = C6H3-1,3,5) and 1-Ph-2-Me-3-(p-cym)-3,1,2-closo-RuC2B9H9 (p-cym = C6H4Me-1-iPr-4), the latter showing an incipient deformation

Abstract The synthesis and characterization of Tl 2 [7-Ph-7,8- nido -C 2 B 9 H 10 ], 3-( p -cym)-3,1,2- closo -RuC 2 B 9 H 10 ( 1 ), 1-Ph-3-(mes)-3,1,2- closo -RuC 2 B 9 H 10 ( 2 ), 1-Ph-3-( P -cym)-3,1,2- closo -RuC 2 B 9 H 10 ( 3 ) and 1-Ph-2-Me-3-( p -cym)-3,1,2- closo -RuC 2 B 9 H 9 ( 4 ) are reported. The ruthenium-containing species are obtained from the reactions between the appropriate [(arene)RuCl 2 ] 2 and either Tl 2 [7,8- nido -C 2 B 9 H 11 ], Tl 2 [7-Ph-7,8- nido -C 2 B 9 H 10 ] or Tl 2 [7-Ph-8-Me-7,8- nido -C 2 B 9 HP 9 ]. Crystallographic studies on 2 and 4 reveal that whereas the former contains an essentially undistorted {RuC 2 B 9 } framework, there is some indication that in the latter, a polyhedral deformation from closo towards pseudocloso has just begun. This idea gains support from comparison of the 11 B NMR shifts for 1 , 3 and 4 with those for reference carbaboranes.

Asymmetrically bonded π ligands: I. Hinging away from metal of substituted allyls: Syntheses of 1-syn-methyl and -phenyl complexes, and the molecular structures of (η-1-Ph-C3H4)Pd(tmeda)]BF4, [(η-C5H5)Pd(η-1-Ph-C3H4)], and [(phen)Mo(CO)2(NCS)(η-1-Ph-C3H4)] at 185 K

Abstract Seven new complexes of (η-1-Me-C3H4) and (η-1-Ph-C3H4) with symmetric metal ligand backbones have been synthesised and spectroscopically characterised. Crystals of three of them, [(η-1-Ph-C3H4)Pd(tmeda)]BF4 (4), [(η-C5H5Pd(η-1-Ph-C3H4)] (5), and [(phen)Mo(CO)2(NCS)(η-1-Ph-C3H4)] (8), were suitable for X-ray diffraction studies. 4 is orthorhombic, Pca1, with four ion pairs in a cell of dimensions a 11.326(4), b 16.048(5), and c 9.950(3) A. Using 4431 data measured at 185 K, R converged at 0.0311. Crystals of 5 are monoclinic, P21/c, with a 14.2255(19), b 5.8203(11), c 13.837(5) A, and β 91.287(21°) at 185 K, Z = 4. 3064 amplitudes have been used to afford R = 0.0267. For 8 the monoclinic cell is a 15.658(4), b 9.473(3), c 15.666(6) A, and β 113.95(3)°, P21/a, Z = 4. Low temperature (185 K) data were collected, and 3734 used to refine the structure to R = 0.0362. The molecular structures of 4, 5, and 8 all reveal an η-1-syn-Ph-C3H4 ligand that is asymmetrically bonded to the metal atom, such that M-C(l) > M-C(3). Analysis of intra- and intermolecular contacts strongly suggests that, at least for 5, the distortion in the metal-allyl bonding is electronic in origin.

31P and 195Pt NMR studies on the clusters [Pt4(μ2-CO)5L4]. L=PEt3, PMe2Ph, PMePh2, PEt2But: the molecular structure of a monoclinic modification of [Pt4(μ2-CO)5(PMe2Ph)4]

Abstract Several clusters complexes of composition [Pt4(μ2-CO)5L4] have been synthesized and characterized, using 31P and 195Pt NMR. L = PEt3, PMe2Ph, PMePh2, PEt2But. The molecular structure of a new monoclinic modification of the PMe2Ph derivative has been determined: space group P21/n with a = 19.698(4), b = 10.9440(20), and c = 21.360(6) A, β = 112.432(18)°, Z = 4. Using 4751 reflections measured at 290 ± 1 K on a four-circle diffractometer the structure has been refined to R = 0.0846. The molecule has no imposed symmetry, but the central Pt4(CO)5P4 core has the approximate C2v architecture established for the previously known orthorhombic modification. The Pt4 unit is thus a highly distorted, edge-opened (3.3347 A) tetrahedron, with five edge-bridging carbonyl and four terminal phosphine ligands. In contrast to the crystallographic results 31P and 195Pt NMR spectra reveal equivalent 31P and 195Pt spins, which can be interpreted in terms of a tetrahedral arrangement of platinum atoms. It is suggested that this equivalence arises from time-averaging of all possible isomeric edge-opened tetrahedra.

Sterically-induced low temperatur polyhedral rearrangements of carbaplatinaboranes: Synthesis and crystal structures of 1-Ph-3,3-(PMe2Ph)2-3,1,2-PtC2B9H10, 1-Ph-3,3-(PMe2Ph)2-3,1,11-PtC2B9H10, 11-Ph-3,3-(PMe2Ph)2-3,1,11-PtC2B9H10 and 1,11-Ph2-3,3-(PMe2Ph)2-3,1,11-PtC2B9H9

Abstract Reaction of cis-Pt(PMe2Ph)2Cl2 with Tl2[7-Ph-7,8-nido-C2B9H10] affords 1-Ph-3,3-(PMe2Ph)2-3,1,2-PtC2B9H10, mild thermolysis (55°C) of which yields 1-Ph-3,3-(PMe2Ph)2-3,1,11-PtC2B9H10 and 11-Ph-3,3-(PMe2Ph)2-3,1,11-PtC2B9H10. Both of the latter compounds are produced by the microwave irradiation of a mixture of cis-Pt(PMe2Ph)2Cl2 and [HNMe3][7-Ph-7,8-nido-C2B9H11]. When cis-Pt(PMe2Ph)2Cl2 is allowed to react with Tl2[7,8-Ph2-7,8-nido-C2B9H9] at room temperature the only isolable species is 1,11-Ph2-3,3-(PMe2Ph)2-3,1,11-PtC2B9H9. The generation of rearranged products with 3,1,11-PtC2B9 architectures is inconsistent with a diamond-square-diamond mechanism for the isomerisation of icosahedral heteroboranes.

Polynuclear homo- or heterometallic palladium(II) - platinum(II) pentafluorophenyl complexes containing bridging diphenylphosphido ligands. Synthesis and crystal structure of [(C6F5)2Pt(μ-PPh2)2Pt(phen)]

Abstract The binuclear anionic derivatives (NBu 4 ) 2 [(C 6 F 5 ) 2 M(μ-PPh 2 ) 2 M′(C 6 F 5 ) 2 ] (M = M′ = Pd, 1 ; M = M′ = Pt, 2 ; M = Pd, M′ = Pt, 3 ) have been obtained by treating either (NBu 4 ) 2 [(C 6 F 5 ) 2 M(μ-X) 2 M′(C 6 F 5 ) 2 ] (X = Cl, Br) with LiPPh 2 ( 1,2 ) or [ cis - M(C 6 F 5 ) 2 (PPh 2 ) 2 ] 2− with M′(C 6 F 5 ) 2 (THF) 2 ( 1,2,3 ). These binuclear derivatives react with HCl yielding the tetranuclear complexes (NBu 4 ) 2 [(C 6 F 5 ) 2 M(μ-PPh 2 ) 2 M′(μ-Cl) 2 M′(μ-PPh 2 ) 2 M(C 6 F 5 ) 2 ] ( 7 : M = M′ = Pt; 8 : M = M′ = Pd; 9 : M = Pt, M′ = Pd). However, 2 and 3 react with HCl in the presence of PPh 3 to yield the binuclear asymmetric complexes (NBu 4 )[(C 6 F 5 ) 2 M(μ-PPh 2 ) 2 M′(C 6 F 5 )(PPh 3 )] ( 10 : M = M′ = Pt; 11 : M = Pt, M′ = Pd). The tetranuclear complexes 7, 8 , and 9 react with bidentate ligands yielding the neutral asymmetric binuclear complexes [(C 6 F 5 ) 2 M(μ-PPh 2 ) 2 M′(LL)] ( 5 : M = M′ = Pt; LL = dppm; 12 : LL = phen; 13 : M = M′ = Pd, LL = bipy). The salts Li 2 [M(C 6 F 5 ) 2 (PPh 2 ) 2 ] (M = Pd, Pt) react with PtCl 2 (dppm), [Pt(μ-Cl)(C 6 F 5 )(tht)] 2 or PtCl 2 to yield [(C 6 F 5 ) 2 M(μ-PPh 2 ) 2 Pt-(dppm)] ( 4 : M = Pd; 5 : M = Pt), (NBu 4 )[(C 6 F 5 ) 2 Pt(μ-PPh 2 ) 2 Pt(C 6 F 5 )(tht)] ( 6 ) or (NBu 4 ) 2 [(C 6 F 5 ) 2 Pt(μ-PPh 2 ) 2 Pt(μ-Cl) 2 Pt(μ-PPh 2 ) 2 Pt(C 6 F 5 ) 2 ] ( 7 ), respectively. These complexes have been characterized by IR and 19 F and 31 P NMR spectroscopy, the latter indicating that in all cases no metal-metal bonds are present. The molecular structure of [(C 6 F 5 ) 2 Pt(μ-PPh 2 ) 2 Pt(phen)] has been established by an X-ray diffraction study. The Pt…Pt distance (3.5711(9) A) confirms that there is no PtPt bond.

Synthesis of anionic pentafluorophenyl platinum-silver acetylide complexes. Molecular structures of (NBu4[Pt(C6F5) 2(μ-CCPh)2Ag(PPh3)] and (NBu4)2[{Pt(C6F52(μ-CCPh)2Ag}2(μ-dppe)]

Abstract Heterobinuclear alkynyl-bridged complexes (NBu 4 )[Pt(C 6 F 5 ) 2 (μ-CCR) 2 AgL] (R=1cr;Ph or t Bu; L=1cr;PPh 3 or PEt 3 ) ( 1 - 4 ) are obtained by treating the anionic tetranuclear platinum-silver derivatives (NBu 4 ) 2 [Pt 2 Ag 2 (C 6 F 5 ) 4 (CCR) 4 ] (R=1cr;Ph or t Bu) with PPh 3 or PEt 3 (molar ratio 1:2 or 1:4), whereas treatment with the bidentate 1,2-bis(diphenylphosphino) ethane (dppe) (molar ratio 1:1) gives tetranuclear complexes (NBu 4 ) 2 [{Pt(C 6 F 5 ) 2 (μ-CCR) 2 Ag} 2 (μ-dppe)] (R=1cr;Ph 5 ; R=1cr; t Bu 6 ). The structures of (NBu 4 )[Pt(C 6 F 5 ) 2 (μ-CCPh) 2 AgPPh 3 ]( 1 ) and (NBu 4 ) 2 [{Pt(C 6 F 5 ) 2 (μ-CCPh) 2 A} 2 (μ-dppe)] ( 5 ) have been established by singlecrystal X-ray diffraction studies. In the solid state, the structure of the anion of complex 1 reveals that the two metal atoms [Pt⋯Ag 3.059(1) A] are asymmetrically bridged by two phenylacetylide groups, each of which forms a σ-bond to platinum and a side-on π-bond to silver. The anion of compound 5 , which possesses an inversion centre, is formed by two identical {Pt(C 6 F 5 ) 2 (μ-CCPh) 2 Ag} units connected through a dppe ligand. Each silver atom is asymmetrically π-bonded to each acetylide group and completes their trigonal coordination by bonding to a phosphorus atom of the dppe. 1 H, 19 F, 31 P NMR data indicate that all complexes exhibit dynamic behaviour in solution.

Sterically induced opening of a closo carbametallaborane: synthesis and characterisation of 1,2-Ph2-3-(η-C5Me5)-3,1,2-pseudocloso-RhC2B9H9

The structure of the cage in 1,2-Ph2-3-Cp★-3,1,2-RhC2B9H9 is distorted from icosahedral by repulsion between the two phenyl rings, forced to lie nearly coplanar by the presence of the Cp★ ligand. Thus the C(1) ⋯ C(2) distance is 2.51 A and B(6) approaches to within 2.92 A of Rh(3). The nature of the distortion, which engenders the description pseudocloso for the RhC2B9 polyhedron, is discussed in relation to 11B NMR chemical shifts and to recent controversy over iso-closo versus hyper-closo descriptors.

Synthesis and reactivity of mixed pentafluorophenylpalladium(I)-platinum(I) derivatives molecular structure of ClPt(μ-dppm)2 Pd(C6F5)

Abstract XPt(μ-dppm) 2 Pd(C 6 F 5 ) (X  Cl (I), Br (II), C 6 F 5 (III) have been prepared by treating PdX(C 6 F 5 )(η 1 -dppm) 2 with Pt(COD) 2 or Pt(PPh 3 ) 4 . Substitution reactions of I yield neutral (SCN) or cationic (PPh 3 , py) derivatives. The species R 2 N + , SO 2 or RCCR (R  COOMe) insert into the PdPt bond of I to give A-frame Pd II -Pt II complexes, but reaction with SnCl 2 gives the SnCl 3 − derivative. The reactions of X-Pt(μ-dppm) 2 Pd(C 6 F 5 ) (X  Cl (I), C 6 F 5 (III)) with isonitriles RNC (R  p -Tol, Cy, t-Bu) has been studied; the nature of the products obtained depends on the starting material, the isonitrile, and the reaction conditions. The molecular structure of ClPt(μ-dppm) 2 Pd(C 6 F 5 ) has been established by a single crystal X-ray study.