Maravanji S. Balakrishna

New tetraphosphane ligands {(X2P)2NC6H4N(PX2)2} (X = Cl, F,OMe, OC6H4OMe-o): synthesis, derivatization, group 10 and 11 metal complexes and catalytic investigations. DFT calculations on intermolecular P...P interactions in halo-phosphines.

The reaction of p-phenylenediamine with excess PCl 3 in the presence of pyridine affords p-C 6H 4[N(PCl 2) 2] 2 ( 1) in good yield. Fluorination of 1 with SbF 3 produces p-C 6H 4[N(PF 2) 2] 2 ( 2). The aminotetra(phosphonites) p-C 6H 4[N{P(OC 6H 4OMe- o) 2} 2] 2 ( 3) and p-C 6H 4[N{P(OMe) 2} 2] 2 ( 4) have been prepared by reacting 1 with appropriate amount of 2-(methoxy)phenol or methanol, respectively, in the presence of triethylamine. The reactions of 3 and 4 with H 2O 2, elemental sulfur, or selenium afforded the tetrachalcogenides, p-C 6H 4[N{P(O)(OC 6H 4OMe- o) 2} 2] 2 ( 5), p-C 6H 4[N{P(S)(OMe) 2} 2] 2 ( 6), and p-C 6H 4[N{P(Se)(OMe) 2} 2] 2 ( 7) in good yield. Reactions of 3 with [M(COD)Cl 2] (M = Pd or Pt) (COD = cycloocta-1,5-diene) resulted in the formation of the chelate complexes, [M 2Cl 4- p-C 6H 4{N{P(OC 6H 4OMe- o) 2} 2} 2] ( 8, M = Pd and 9, M = Pt). The reactions of 3 with 4 equiv of CuX (X = Br and I) produce the tetranuclear complexes, [Cu 4(mu 2-X) 4(NCCH 3) 4- p-C 6H 4{N(P(OC 6H 4OMe- o) 2) 2} 2] ( 10, X = Br; 11, X = I). The molecular structures of 1- 3, 6, 7, and 9- 11 are confirmed by single-crystal X-ray diffraction studies. The weak intermolecular P...P interactions observed in 1 leads to the formation of a 2D sheetlike structure, which is also examined by DFT calculations. The catalytic activity of the Pd(II) 8 has been investigated in Suzuki-Miyaura cross-coupling reactions.

Weak Interactions between Trivalent Pnictogen Centers: Computational Analysis of Bonding in Dimers X3E ... EX3 (E = Pnictogen, X = Halogen)

The nature of weak interactions in dimers X(3)E...EX(3) (E = N-Bi, X = F-I) was investigated by wave function and density functional theory (DFT)-based methods. Out of the 20 systems studied, 10 are found to be bound at the CP-MP2 and LMP2 levels of theory. Detailed partition of the interaction energy into different components revealed that dispersion is the primary force holding the dimers together but there also exists an important ionic component whose contribution increases with increasing halogen size. As expected, standard density functionals fail to describe bonding in the studied systems. However, the performance of DFT methods can be easily improved via empirical dispersion correction though full agreement with high level ab initio results was not obtained. Total binding energies calculated at the SCS-MP2 and LCCSD(T) levels of theory yield an energy scale of 10-15 kJ mol(-1) which is comparable to a weak hydrogen bond and demonstrates that E...E interactions, and P...P interactions in particular, can be considered relevant for determining supramolecular structure in the solid state. In addition to high-level energy estimates, results from detailed bonding analysis showed that group 13 dimetallenes are structural analogues of the studied dimers, and as such contain a slipped pi-interaction which is antibonding in nature.

Ruthenium(II) chemistry of phosphorus-based ligands, Ph2PN(R)PPh2 (R=Me or Ph) and Ph2PN(Ph)P(E) Ph2 (E=S or Se). Solution thermochemical study of ligand substitution reactions in the Cp′RuCl(COD) (Cp′=Cp, Cp*; COD=cyclooctadiene) system

Abstract The enthalpies of reactions of Cp′RuCl(COD) (Cp′=Cp, Cp*; COD=cyclooctadiene) with bis(phosphino)amines of the type Ph 2 PN(R)PPh 2 (R=Me 1 or R=Ph 2 ) and the monochalcogen derivatives Ph 2 PN(Ph)P(E)Ph 2 (E=S 3 or Se 4 ) leading to the formation of Cp′RuCl(PNP) and Cp′RuCl{PNP(E)} complexes, respectively, have been measured by anaerobic solution calorimetry in THF at 30°C. These reactions are clean and quantitative. The synthesis and characterization of new organoruthenium complexes is reported. Comparisons with enthalpy data in this two related organoruthenium systems and other similar organometallic systems are also presented.

First examples of methylene insertion into the phosphorus(III)–nitrogen bond

Abstract The reaction of N-substituted phosphinous amides with paraformaldehyde leads to methylene insertion into the P–N bond, followed by the oxidation of phosphorus from P(III) to P(V) state. The product, Ph2P(O)CH2NHPh was characterised by a single-crystal X-ray diffraction study. The reaction not only depends on the acidic proton on the nitrogen, but also on the oxidation state of phosphorus and it is considered to proceed through Staudinger–Wittig pathway.

Water-soluble cyclodiphosphazanes: synthesis, gold(I) metal complexes and their in vitro antitumor studies

The newly synthesized water-soluble cyclodiphosphazane ligands and their gold(I) complexes inhibit HeLa cell proliferation by activating p53 protein and inducing apoptosis.

Bis(2-diphenylphosphinoxynaphthalen-1-yl)methane: transition metal chemistry, Suzuki cross-coupling reactions and homogeneous hydrogenation of olefins

Transition metal complexes of bis(2-diphenylphosphinoxynaphthalen-1-yl)methane (1) are described. Bis(phosphinite) 1 reacts with Group 6 metal carbonyls, [Rh(CO)2Cl]2, anhydrous NiCl2, [Pd(C3H5)Cl]2/AgBF4 and Pt(COD)I2 to give the corresponding 10-membered chelate complexes 2, 3 and 5-8. Reaction of 1 with [Rh(COD)Cl]2 in the presence of AgBF4 affords a cationic complex, [Rh(COD){Ph2P(-OC10H6)(mu-CH2)(C10H6O-)PPh2-kappaP,kappaP}]BF4 (4). Treatment of 1 with AuCl(SMe2) gives mononuclear chelate complex, [(AuCl){Ph2P(-OC10H6)(mu-CH2)(C10H6O-)PPh2-kappaP,kappaP}] (9) as well as a binuclear complex, [Au(Cl){mu-Ph2P(-OC10H6)(mu-CH2)(C10H6O-)PPh2-kappaP,kappaP}AuCl] (10) with ligand 1 exhibiting both chelating and bridged bidentate modes of coordination respectively. The molecular structures of 2, 6, 7, 9 and 10 are determined by X-ray studies. The mixture of Pd(OAc)2 and effectively catalyzes Suzuki cross-coupling reactions of a range of aryl halides with aryl boronic acid in MeOH at room temperature or at 60 degrees C, giving generally high yields even under low catalytic loads. The cationic rhodium(I) complex, [Rh(COD){Ph2P(-OC10H6)(mu-CH2)(C10H6O-)PPh2-kappaP,kappaP}]BF4 (4) catalyzes the hydrogenation of styrenes to afford the corresponding alkyl benzenes in THF at room temperature or at 70 degrees C with excellent turnover frequencies.

Resorcinol Based Acyclic Dimeric and Cyclic Di- and Tetrameric Cyclodiphosphazanes: Synthesis, Structural Studies, and Transition Metal Complexes

The condensation reaction of resorcinol with cis-[ClP(μ-N(t)Bu)(2)PN(H)(t)Bu] produced a difunctional derivative 1,3-C(6)H(4)[OP(μ-N(t)Bu)(2)PN(H)(t)Bu](2) (1), whereas the similar reaction with [ClP(μ-N(t)Bu)](2) resulted in the formation of a 1:1 mixture of dimeric and tetrameric species, [{P(μ-N(t)Bu)}(2){1,3-(O)(2)-C(6)H(4)}](2) (2a) and [{P(μ-N(t)Bu)}(2){1,3-(O)(2)-C(6)H(4)}](4) (2b), which were separated by repeated fractional crystallization and column chromatography. The reaction of dimer 2a with H(2)O(2) and selenium produces tetrachalcogenides [{(O)P(μ-N(t)Bu)}(2){1,3-(O)(2)-C(6)H(4)}](2) (3) and [{(Se)P(μ-N(t)Bu)}(2){1,3-(O)(2)-C(6)H(4)}](2) (4), respectively. The reaction between the dimer (2a) and [Pd(μ-Cl)(η(3)-C(3)H(5))](2) or AuCl(SMe(2)) yielded the corresponding tetranuclear complexes, [{((Cl)(η(3)-C(3)H(5))Pd)P(μ-N(t)Bu)}(2){1,3-(O)(2)-C(6)H(4)}](2) (5) and [{(ClAu)P(μ-N(t)Bu)}(2){1,3-(O)(2)-C(6)H(4)}](2) (6) in good yield. The complexes 5 and 6 are the rare examples of phosphorus macrocycles containing two or more exocyclic transition metal fragments. Treatment of 1 with copper halides in 1:1 molar ratio resulted in the formation of one-dimensional (1D) coordination polymers, [(CuX){1,3-C(6)H(4){OP(μ-N(t)Bu)(2)PN(H)(t)Bu}}(2)](n) (7, X = Cl; 8, X = Br; 9, X = I), which showed the helical structure in solid state because of intramolecular hydrogen bonding, whereas similar reactions of 1 with 4 equiv of copper halides also produced 1D-coordination polymers, [(Cu(2)X(2))(2){1,3-C(6)H(4){OP(μ-N(t)Bu)(2)PN(H)(t)Bu}(2)}](n) (10, X = Cl; 11, X = Br; 12, X = I), but containing Cu(2)X(2) rhomboids instead of CuX linkers. The crystal structures of 1, 2a, 2b, 4, 7-9, and 12 were established by X-ray diffraction studies.

Synthesis and X-ray crystal structure of a novel long chain acyclic phosphazene, N,N′-{dimethyl-bis(diphenylphosphiniminophosphorane)}ethylenediamine {(PhO)2P(O)NPN(CH3)CH2}2, obtained via a Staudinger reaction

The title compound was synthesized by the reaction of N , N ′-dimethyl- N , N ′-bis(diphenylphosphino)ethylenediamine with phosphoryl azide and characterized by mass spectrometry, microanalysis, and 31 P and 1 H NMR spectroscopy and the structure was confirmed by single crystal X-ray studies.

An Acyclic Dimer of Cyclodiphosphazane {tBuHN(tBuNP)2OCH2}2 Containing Alkoxo and Amido Functionalities: Synthesis, Derivatization, Bi- (PdII, RhI), and Tetranuclear (PdII, AuI, RhIAuI) Transition Metal Complexes

Acyclic bis(cyclodiphosphazane) [(t)BuHN((t)BuNP)(2)OCH(2)](2) (2) containing alkoxo and amido functionalities was synthesized by reacting cis-[(t)BuHN((t)BuNP)(2)Cl] (1) with ethylene glycol and upon further treatment with 4 equiv of elemental sulfur or selenium affords the corresponding tetrachalcogenides [(t)BuHN((t)BuNPE)(2)OCH(2)](2) (3, E = S; 4, E = Se) in quantitative yield. The reaction of 2 with 2 equiv of elemental sulfur results in the oxidation of only the amido-phosphorus atoms to form the di(sulfide) derivative [(t)BuHN(S)P(mu-(t)BuN)POCH(2)](2) (5). The reaction of 2 with 2 equiv of [PdCl(eta(3)-C(3)H(5))](2) afforded the tetrametallic complex [{Pd(eta(3)-allyl)Cl}(4){(t)BuHN((t)BuNP)(2)OCH(2)}(2)] (7) containing four independent [PdCl(2)(eta(3)-C(3)H(5))] moieties each coordinated to a phosphorus atom. In contrast, the reaction between [Pd(PEt(3))Cl(2)](2) and 2 leads to the addition of two metal atoms with the formation of [{Pd(PEt(3))Cl}(2){(t)BuHN((t)BuNP)(2)OCH(2)}(2)] (8), in which alternating phosphorus atoms of the bis(cyclodiphosphazane) are coordinated to palladium. Interestingly, the palladium(II) atom coordinated to the phosphorus atom bearing the t-butylamino substituent adopts a trans geometry, whereas that coordinated to the phosphorus atom connected to the -OCH(2)CH(2)O- linker prefers a cis conformation. The reaction between 2 and [Rh(COD)Cl](2) produces exclusively the bimetallic complex [{Rh(COD)Cl}(2){(t)BuHN((t)BuNP)(2)OCH(2)}(2)] (6) irrespective of the stoichiometry of the reactants and the reaction conditions. In complex 6, only the alkoxo-phosphorus atoms are coordinated. However, complex 6 upon treatment with AuCl(SMe(2)) in a 1:2 ratio gives the heterometallic tetrasubstituted complex [{Rh(COD)Cl}(2)(AuCl)(2){(t)BuHN((t)BuNP)(2)OCH(2)}(2)] (10). The reaction between 4 equiv of AuCl(SMe(2)) and 2 resulted in the formation of a tetrametallic gold complex [(AuCl)(4){(t)BuHN((t)BuNP)(2)OCH(2)}(2)] (9). The crystal structures of 2-4 and 7-10 are reported.

One-dimensional silver(I) coordination polymers containing cyclodiphosphazane, cis-{(o-MeOC6H4O)P(µ-NtBu)}2

The 1 : 1 reaction between the cyclodiphosphazane cis-{(o-MeOC6H4O)P(µ-NtBu)}2 (1) and AgOTf afforded one-dimensional AgI coordination polymer [Ag{µ-OTf-κO,κO}{µ-(o-MeOC6H4O)P(µ-NtBu)-κP,κP}2]∞ (2) containing bridging cyclodiphosphazane and trifluoromethanesulfonate (OTf) ligands. The 2 : 1 reaction of 1 and AgOTf leads to the formation of simple mononuclear complex [Ag{OTf-κO,κO}({(o-MeOC6H4O)P(µ-NtBu)-κP}2)2] (3) in quantitative yield. Reaction of 1 with AgCN produces a strain-free zig-zag coordination polymer [({(o-MeOC6H4O)P(µ-NtBu)-κP,κP}2)2Ag(NCAgCN)]∞ (4) irrespective of reaction stoichiometry and conditions. In complexes 3 and 4 cyclodiphosphazanes coordinate to AgI centers in a monodentate fashion. Single crystal structures were established for the AgI polymers 2 and 4.