Pravat Bhattacharyya

Bis(bidentate) complexes of iminobis(diphenylphosphine chalcogenides)[M{N(XPPh2)2-X,X′}2](X = S or Se; M = Ni, Pd or Pt)

The compound NH(SePPh2)2 has been synthesised from NH(PPh2)2 and selenium in refluxing toluene. A range of complexes [M{N(XPPh2)2-X, X′}2](X = Se, M = Pt 1 or Pd 2; X = S, M = Pt 3, Pd 4 or Ni 5) of the monoanions derived from NH(SePPh2)2 and its sulfur analogue have been prepared. The new compounds have been characterised by microanalysis, NMR and IR spectroscopy. The crystal structures of NH(SePPh2)2, 1, 2 and 5 were determined. The neutral NH(SePPh2)2 crystallised as H-bonded dimer pairs with a noticeable difference in the hydrogen bonded and non-hydrogen bonded PSe bond lengths. The PSe groups are approximately anti. On complexation the anionic ligands are bidentate and in all cases the resulting MX2P2N rings are distinctly puckered.

Selenocarbonyl synthesis using Woollins reagent

Abstract [PhP(Se)(μ-Se)]2 selenates secondary and tertiary amides to the corresponding selenoamides in 30–70% yields at 130°C in toluene and indolizine-3-aldehydes to selenoaldehydes in 40–59% yield at 25°C.

The Reactivity of [PhP(Se)(μ‐Se)]2 and (PhP)3Se2 Towards Acetylenes and Cyanamides: X‐ray Crystal Structures of Some P‐Se‐C and P‐Se‐C‐N Heterocycles

Several unusual P-Se-C and P-Se-C-N heterocycles are formed by the reaction of [PhP(Se)(mu-Se)]2 or (PhP)3Se2 with alkynes or cyanamides, generated by the fragmentation of the organophosphorus-selenium compound and addition across the C identical to C or C identical to N triple bond of the organic substrate. X-ray crystallographic analysis reveals an unexpected diversity of structural motifs within these heterocyclic systems, including P2SeCN, P2C2Se and PC2Se2 rings.

Preparation and characterisation of [Pt{N(SePPh2)2-Se,Se′}(PR3)2]Cl (R = alkyl or aryl); crystal structure of [Pd{Ph2PNP(Se)Ph2-P,Se}{N(SePPh2)2-Se,Se′}]·0.5EtOH·0.3CH2Cl2

Reaction of NH(PPh2)2 with selenium gives Ph2P(Se)NHP(Se)Ph2 which may be deprotonated with KOBut to give K[Ph2P(Se)NP(Se)Ph2]. This can be treated with appropriate Group VIII metal complexes to give [Rh{N(SePPh2)2}(cod)](cod = cycloocta-1,5-diene), a series of complexes of formula [Pt{N(SePPh2)2-Se,Se′}(PR3)2]Cl (PR3= PMe3, PMe2Ph, PEt3, PPh3, 1//2NH(PPh2)2 or 1//2Ph2PCH2CH2PPh2) and [MCl{N(SePPh2)2-Se,Se′}(PMe2Ph)](M = Pt or Pd). The new compounds have been characterised by 31P and 195Pt NMR and IR spectroscopy, FAB+ mass spectrometry and microanalyses. Furthermore, a small quantity of a mixed-ligand complex [Pd{Ph2PNP(Se)Ph2-P,Se}{N(SePPh2)2-Se,Se′}]·0.5EtOH·0.3CH2Cl2 has been characterised by X-ray crystallography and 31P NMR spectroscopy. Its structure reveals an approximately planar five-membered PdSeP2N ring and a puckered six-membered PdSe2P2N ring. In the crystal the molecules pack with channels which contain the disordered CH2Cl2 molecules running down the a direction.

An alternative strategy to an electron rich phosphine based carbonylation catalystThis paper is dedicated to the memory of Prof. Noel McAuliffe in recognition of his contribution to phosphine chemistry and friendship.

The complexes [Rh(CO)Cl(2-Ph2PC6H4COOMe)], 1, and trans-[Rh(CO)Cl(2-Ph2PC6H4COOMe)2], 2, have been synthesized by the reaction of the dimer [Rh(CO)2Cl]2 with 2 and 4 molar equivalents of 2-(diphenylphosphino)methyl benzoate. The complexes 1 and 2 show terminal ν(CO) bands at 1979 and 1949 cm−1 respectively indicating high electron density at the metal centre. The molecular structure of the complex 2 has been determined by single crystal X-ray diffraction. The rhodium atom is in a square planar coordination environment with the two phosphorus atoms trans to each other; the ester carbonyl oxygen atom of the two phosphine ligands points towards the rhodium centre above and below the vacant axial sites of the planar complex. The rhodium–oxygen distances (Rh⋯O(49) 3.18 A; Rh⋯O(19) 3.08 A) and the angle O(19)⋯Rh⋯O(49) 179° indicate long range intramolecular secondary Rh⋯O interactions leading to a pseudo-hexacoordinated complex. The complexes 1 and 2 undergo oxidative addition (OA) reactions with CH3I to produce acyl complexes [Rh(COCH3)ClI(2-Ph2PC6H4COOMe)], 4, and trans-[Rh(COCH3)ClI(2-Ph2PC6H4COO-Me)(2-Ph2PC6H4COOMe)], 5, and the kinetics of the reactions reveal that the complex 1 undergoes faster OA reaction than that of the complex 2. The catalytic activity of the complexes 1 and 2 in the carbonylation of methanol were higher than that of the well known species [Rh(CO)2I2]− and the complex 1 shows higher activity than 2.

Bridge cleavage of [{PhP(Se)(μ-Se)}2] by 1,2-C6H4(EH)(E′H) (E, E′=O or NH). X-ray crystal structure of PhP(Se)(NHC6H4NH-1,2)

Abstract Treatment of [{PhP(Se)(μ-Se)} 2 ] ( 1 ), the oxidation product of (PhP) 5 with excess selenium, with 2-aminophenol, 1,2-phenylenediamine, catechol or 3,4-diaminotoluene leads to the rupture of the dimer giving PhP(Se)(NHC 6 H 4 O-1,2) ( 2 ), PhP(Se)(NHC 6 H 4 NH-1,2) ( 3 ), PhP(Se)(OC 6 H 4 O-1,2) ( 4 ) and PhP(Se)(NHC 6 H 3 (CH 3 -3)NH-1,2) ( 5 ), respectively. In the molecular structure of 3 , determined crystallographically, there are two independent molecules within the unit cell which are linked by PSe⋯HN hydrogen bonds, leading to chains of dimer pairs in the solid state.

N-Metallation of MS2N2 rings. X-ray crystal structures of [(η5-C5Me5)Ir(S2N2)Au(PPh3)][ClO4], [{(η5-C5Me5)Ir(S2N2)Au}2(μ2-dppm)][ClO4]2 and [Au(dppeS-P)Cl]2

Bimetallic complexes [(η5-C5R5)M(S2N2)Au(PPh3)][ClO4] and tetrametallic species [{(η5-C5R5)M(S2N2)Au}2(μ2-P^P)][ClO4]2 (R=H, M=Co; R=Me, M=Ir; P^P=dppm or dppe) can be prepared by treatment of [(η5-C5R5)M(S2N2)] with gold(I) electrophiles generated by chloride abstraction from [AuCl(PPh3)] or [(AuCl)2(μ2-P^P)]. X-Ray crystallography of [(η5-C5Me5)Ir(S2N2)Au(PPh3)][ClO4] and [{(η5-C5Me5)Ir(S2N2)Au}2(μ2-dppm)][ClO4]2 confirms auration of the metal-bound nitrogen atom of the MS2N2 ring. π-Stacking of theMS2N2 rings occurs within both structures.

Novel bimetallic lead(II) complexes of polydentate amine-phenol ligands

Abstract The polydentate amine-phenol ligands N(CH2CH2NHCH2C6H4OH-2)3 (H3L1) and (2-HOC6H4CH2NH)2C2H4-1,2 (H2L2) prepared by reduction of the Schiff bases H3saltren and H2salen react with lead(II) acetate trihydrate to form complexes 1 and 2 respectively, both of which are dimeric in the solid state and fluxional in solution at ambient temperatures. These complexes are characterised by IR, microanalysis and single crystal X-ray diffraction.

Heterocycle formation using [PhP(Se)(μ-Se)]2. The crystal structures of [PhP(Se)(μ-Se)]2, PhP(Se)Se2(C7H10) and PhP(Se)(μ-Se)(μ-NPh)P(Se)Ph

An X-ray crystallographic study of [PhP(Se)(μ-Se)]21, the oxidation product of the homocycle (PhP)5 with ten equivalents of selenium, revealed that the molecule is centrosymmetric with a planar central P2(μ-Se)2 core and trans disposition of exocyclic PSe bonds. In the reaction of 1 with norbornene (bicyclo[2.2.1]hept-2-ene), crystallographic analysis of the product 2 revealed exo addition of a PhP(Se)Se2 unit across the CC bond, giving a 1,2-diselena-3-phospholane (C2PSe2) ring. Norbornadiene (bicyclo[2.2.1]hepta-2,5-diene) reacts more slowly with 1, allowing the isolation of a 1,2-selenaphosphetane (C2PSe ring) in addition to a diselenaphospholane. The reaction of 1 with azobenzene proceeds with cleavage of the NN bond and substitution of a bridging selenium atom in 1 by an NPh unit, giving the first crystallographically characterised selenaazadiphosphetane (P2SeN) ring.

Monoxidised sulfur and selenium derivatives of bis(diphenyl-phosphino)amine: synthesis and co-ordination chemistry

The Complexes cis/trans-[M{Ph2P(E)NHPPh2}2] Cl2 and [M{Ph2P(E)NPPh2}2](M = Pd or Pt) E = S or Se have been prepared and characterised. The crystal structures of two representative examples, trans-[Pt{Ph2P(Se)NHPPh2}2] Cl2 and cis-[Pt{Ph2P(Se)NPPh2}2], have been determined. The PtSeP2N rings are puckered in both cases although there are some differences as a result of the formal charge upon the ligand and the cis/trans geometries. The cis neutral complex has shorter Pt–P and longer Pt–Se bonds than those of the trans protonated complex. Deprotonation of the ligand also results in a significant shortening of the P–N bond lengths.