Syed A. A. Shah
Queen Mary University of London
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Featured researches published by Syed A. A. Shah.
Journal of The Chemical Society-dalton Transactions | 1996
Michael Lazell; Majid Motevalli; Syed A. A. Shah; Charlotte K. Simon; Alice C. Sullivan
Experimental conditions and combinations of reagents have been varied in reactions between [(Ph2SiOM′)2O](M′= Li or Na) and Group 4 metal halides MCl4, with the broad aim of assessing their affects on the formation of ring-expanded products. Lithium-7 NMR spectroscopy was used to monitor the reaction between [(Ph2SiOLi)2O] and MgCl2·2thf in thf (tetrahydrofuran) which gives a ring-expanded product. The reaction between [(Ph2SiONa)2O], prepared in situ from sodium metal and (Ph2SiOH)2O, and TiCl4 in a 3 : 1 molar ratio gave the sodium-bridged compound [Ti{O(SiPh2O)2}3{Na(py)}2]·py, py = pyridine, the first example of a six-membered titanasiloxane ring. Further reaction with LiI gave the lithium-bridged analogue. The analogous reaction with HfCl4 gave the ring-expanded compound [Hf{Ph2Si(OSiPh2O)2}2(py)2]·2C6H5Me, the first examples of eight-membered hafnasiloxane rings. Results of 7Li, 29Si, and 23Na NMR, IR, and single-crystal X-ray diffraction studies are reported.
Journal of Organometallic Chemistry | 1995
Isaac Abrahams; Majid Motevalli; Syed A. A. Shah; Alice C. Sullivan
Abstract The reaction between the lithium compound [{Ph 2 SiOLi} 2 O] and SnCl 4 gave the lithium-bridged chlorostannasiloxane [Cl 2 Sn{O(SiPh 2 O) 2 } 2 ]-μ-(Li(THF) 2 ) 2 ] ( 1 ) containing six-membered stannasiloxane rings. A similar reaction betwee the corresponding sodium compound [{Ph 2 SiONa} 2 O] and SnCl 4 surprisingly gave the stannasiloxane [THF 2 Sn{(OSiPh 2 ) 3 O} 2 ] (bd crystallised as the mono-toluene solvate) containing eight-membered stannasiloxane [ings. Compounds 1 and 2 were obtained in reactions in which the relative molar ratio of the lithium or sodium reagents to SnCl 4 was varied from 1:1 to 3:1. Compounds 1 and 2 were characterised by 1 H and 29 Si NMR spectroscopy, elemental analysis and single-crystal X-ray diffraction studies.
Journal of The Chemical Society, Chemical Communications | 1994
Majid Motevalli; Dipti Shah; Syed A. A. Shah; Alice C. Sullivan
The dilithium salt, [(Ph2SiOLi·THF)2O], reacts with MgCl2·2THF to give, on addition of pyridine, the unexpected lithium bridged spirocyclic magnesiasiloxane compound [(py)2Li]2-µ-Mg[{Ph2SiO}2O][{Ph2SiO}3O] which is the first example of a molecular magnesium siloxide compound to be characterised and also the first example of a spirocyclic metallasiloxane having rings with different degrees of oligomerisation.
Journal of The Chemical Society, Chemical Communications | 1993
Majid Motevalli; Mahesh Sanganee; Paul D. Savage; Syed A. A. Shah; Alice C. Sullivan
The chromium(II) compound [C[graphic ommitted])-µ-Na(thf)2}2]1 has been isolated and structurally characterised; in combination with trimethylaluminium, it is a precatalyst for the polymerisation of ethene to linear polyethylene.
Polyhedron | 1996
Majid Motevalli; Dipti Shah; Syed A. A. Shah; Alice C. Sullivan
Abstract The oxovanadium halides VOCl2·2Py (1), VOCl2·3Py (2) and VO2Cl·2Py (3) have been isolated as unexpected products from reactions between VCl4 and VOCl3, respectively, with [(Ph2SiOM′)2O] (M′Li or Na). Further reaction of compound 1 with [O(SiPh2OLi)2·2THF], however, gave the cyclosiloxyoxovanadium(IV) complex [VOO(SiPh2O)22-μ-(Li(THF)2)2]. The manner in which 1, 2 and 3 may be formed in these reactions is illustrated. The X-ray structure of 2 and structures of two crystallography distinct forms of 3 are presented.
Journal of Organometallic Chemistry | 1998
Isaac Abrahams; Michael Lazell; Majid Motevalli; Syed A. A. Shah; Alice C. Sullivan
Abstract We report on the isolation and molecular structure of [{O(Ph 2 SiONa) 2 } 4 ·(NaOH)·(H 2 O)·(7pyridine)]·(pyridine)·(toluene) from toluene/pyridine solutions of [O(Ph 2 SiONa) 2 ·Py] in air; a unique structural assembly, of three edge-shared Na 4 O 4 siloxane-bridged cubes, sharing one μ 6 -OH site, where one cube corner is occupied by a μ 3 -OH 2 group.
Journal of Organometallic Chemistry | 1996
Isaac Abrahams; Charlotte K. Simon; Majid Motevalli; Syed A. A. Shah; Alice C. Sullivan
Abstract The reactions between Cp 2 ZrCl 2 or Cp 2 ∗ ZrCl 2 with in situ generated Ph 2 Si(OLi) 2 gave unexpected dimeric cyclozirconasiloxane products incorporating LiOH within the chelate-bridging unit OSiPh 2 OLi(OH). The crystal structure of [Cp 2 ∗ ZrOSiPh 2 OLiOH] 2 is reported and the origin of the LiOH discussed.
Journal of The Chemical Society-dalton Transactions | 1997
Michael Lazell; Majid Motevalli; Syed A. A. Shah; Alice C. Sullivan
Treatment of MCl 5 (M = Nb or Ta) with 3 equivalents of dilithium tetraphenyldisiloxanediolate, [(Ph 2 SiOLi) 2 O], gave the lithium-bridged metallasiloxane complex, [M{O(SiPh 2 O) 2 } 3 ]-µ-[Li(L) 2 ] (M = Nb 1 or M = Ta 2; L = pyridine). The solid-state structure of compound 2 determined by single crystal X-ray diffraction is reported. Variable-temperature 7 Li NMR of 2 revealed two separate exchange processes which may account for the equilibration of non-equivalent silicon environments in 1 and 2. Preparative scale thermal decomposition of the solid samples with L = tetrahydrofuran (thf) gave crystalline LiNbO 3 and LiTaO 3 .
Journal of Fluorine Chemistry | 1998
Hendrik Dorn; Syed A. A. Shah; Mathias Noltemeyer; Hans-Georg Schmidt; Herbert W. Roesky
Abstract Treatment of [( η 5 -C 5 Me 5 ) 2 ZrF 2 ] with Me 3 SiOSO 2 R (R = CF 3 , C 6 H 4 - p -CH 3 ) yield both the monosubstituted [( η 5 -C 5 Me 5 ) 2 ZrF(OSO 2 R)] ( 1 , R = CF 3 ; 2 , R = C 6 H 4 - p -CH 3 ) and disubstituted [( η -C 5 Me 5 ) 2 Zr(OSO 2 R) 2 ] ( 3 , R = CF 3 ; 4 , R = C 6 H 4 - p -CH 3 ) sulfonate complexes, when using stoichiometric amounts of reagents. An X-ray diffraction study of 3 revealed that the trifluoromethanesulfonate ligands are covalently bound to zirconium. Compounds 1–4 along with [( η 5 -C 5 Me 5 ) 2 ZrF(OCOCF 3 )] (5) and [( η 5 -C 5 Me 5 ) 2 Zr(OCOCF 3 ) 2 ] (6) were investigated as catalysts for the polymerization of ethylene in combination with methylaluminoxane (MAO).
Organometallics | 1994
Majid Motevalli; Dipti Shah; Syed A. A. Shah; Alice C. Sullivan