Joan M. Holmes

NOVEL CYCLIC PENTACOORDINATE AND PSEUDOPENTACOORDINATE LEAD COMPOUNDS

Abstract The new bicyclic lead(II) phosphinate [(t-Bu)2PO2]2Pb (1) was synthesized by the reaction of p-tolyllead triacetate with di-t-butylphosphinic acid and water. An X-ray study showed that it had a pseudo-trigonal bipyramidal geometry (p-TBP) with a stereochemically active lone pair of electrons occupying an equatorial site. Infrared data ruled out the possible presence of a Pb[sbnd]H bond. A series of new monocyclic Pb(IV) compounds, [Et4N][(MeC6H3S2)PbPh2X] where X = Br (2), CI (3), and F (4), was synthesized from the addition reaction of tetraethylammonium halide to 2,2-diphenyl-1,3,2-toluene dithiolato plumbole(IV), (MeC6H3S2)PbPh2 (5). An X-ray study of 3 revealed a monocyclic anionic TBP geometry which was compared with related dithiolato cyclic structures formed earlier by lighter elements of Group IVA. The lead(II) compound 1 crystallizes in the monoclinic space group C2/c with a = 15.594(4) A, b = 16.889(3) A, c = 12.642(2) A, β = 136.85(1)°, and Z = 4. The lead(IV) compound 3 crystallizes i...

2-Phospha-Allylic Systems

Abstract Phosphamethincyanines prepared in 1964 by Dimroth and Hoffmann were among the first compounds with two-coordinate phosphorus. They are special cases of 2-phospha-allylic cations. Simple representatives of this type become available from the reaction of imidoyl chlorides with tris(trimethylsily1)phosphane.

NEW RING SYSTEMS OF ELEMENTS OF MAIN GROUPS IV AND V

Abstract The synthesis of [PhSn(O)O2CC6H11]6 represents the first example of tin(IV) in a drum-shaped molecule. The formation of the dimeric composition, [(MeSn(O)O2CC6H11)2(MeSn(O2CC6H11)3]2, appears to be an intermediate hydrolysis product on the way to the drum composition. The X-ray structure reveals an “unfolded” drum array. The distannoxane unit which is represented as the sides of the drum is found in additional new dimeric compositions, [(SCH2CH2O)2SnCl]2[H][Et4N], [((CN)2C2S2)2SnOH]2, and [BuSnCl2(OH) · H2O]2. These all have six-coordinated tin atoms which contrasts to the dimeric aryl distannoxanes recently isolated, [Ph2(Cl)SnOSnPh2(X)]2, X = OH, Cl, containing five-coordinated tin. Also isolated are the new ring containing, five-coordinated tin derivatives, [(SCH2CH2S)2Sn]2[SCH2CH2S][Et3NH]2 and [(SC(CN)C(CN)S)2SnMe][Et4N]. The former has two trigonal bipyramidal tin atoms while the latter composition has a square pyramidal geometry. Related ring systems of new five-coordinated derivatives of ...

SYNTHESIS AND MOLECULAR STRUCTURES OF FLUOROPHOSPHORANES, R3PF2, ISOELECTRONIC WITH ANIONIC FLUOROSILICATES

Abstract The new difluorophosphoranes Ph(o-Tol)2PF2 (1), Mes3PF2 (2), Ph(I-Np)2PF2 (3), (o-Tol)3PF2, (p-Tol3PF2, Ph(t-Bu)2PF2, and (Ph2PF2CH2 containing bulky substituents were prepared by the fluorination reaction of precursor organophosphines with dimethylaminosulfur trifluoride. They were characterized by 1H, 31P, and 19F NMR spectra. The molecular structures of 1–3 revealed trigonal bipyramidal geometries. Comparison of the structural data with that of isoelectronic anionic fluorosilicates along with the NMR data suggests the operation of a steric effect that increases bond lengths in the difluorophosphoranes 1–3 and in related anionic silicates. The data are discussed relative to enhanced reactivity observed for anionic silicates. 1 crystallizes in the monoclinic space group C2/c with a = 11.819(3) A, b = 10.163(2) A, c = 13.992(3) A, β = 99.14(2)°, and Z = 4.2 crystallizes in the monoclinic space group C2/c with a = 10.531(2) A, b = 12.667(2) A, c = 18.110(4) A, β = 104.21(2)°, and Z = 4. 3 crystall...

Cyclic Oxyphosphoranes with Six- and Seven-Membered Rings

Abstract X-ray and variable temperature NMR investigations of cyclic pentaaxyphosphoranes reveal a preference of six- and seven-membered rings for apical-equatorlal orientations of trigonal bipyramids. Saturated six-membered rings prefer a boat conformation. Apical-equatorial ring pseudorotations are more facile for five-membered rings, whereas ligand exchange via diequatorial ring placement is more facile for the larger rings. Application to enzymatic reactions of cyclic AMP is emphasized.

CHAIN STRUCTURES OF TRIMETHYLTIN ESTERS OF SALICYLIC ACID AND o-ANISIC ACID. TIN-119m MÖSSBAUER STUDY OF A SERIES OF TRIMETHYLTIN AND TRIPHENYLTIN CARBOXYLATES1

Abstract The synthesis, crystal structure, 119m Sn Mossbauer parameters, and infrared and NMR data are reported for the trimethyltin esters of o-anisic and salicylic acids, Me3SnO2CC6H4OMe-2 (1) and Me3SnO2CC6H4OH-2 (2), respectively. Mossbauer parameters for a series of triorganotin esters are determined on substances whose X-ray structures have been established. Both 1 and 2 possess chain polymer structures showing conformational differences related to the presence of hydrogen bonding in 2 and its absence in 1. The 199mSn Mossbauer quadrupole splitting parameter (QS) falls in the range 2.30-2.55 mm s−1 for triorganotin esters having a discrete geometry formed by intramolecular oxygen atom co-ordination, while for those having a chain formulation formed by intermolecular donor atom coordination a QS range of 3.59-3.74 mm s−1 is observed. Hydrogen-bonded members show a QS range of 2.97-3.47 mm s−1. The correlation of crystallographic and Mossbauer data reveals the importance of hydrogen bonding in account...

DISTORTION COORDINATE FOR NONRIGID FIVE-COORDINATED ANTIMONY. SYNTHESIS AND STRUCTURE OF OXYGEN- AND SULFUR-CONTAINING CYCLIC ORGANOSTIBORANES

Abstract The monocyclic stiboranes Ph3,Sb[S2,C2,(CN)2,] (1) and Ph3,Sb(O2,C6,H3-4-NO2) (3) were synthesized by the reaction of Ph3SbCl2, with the disodium salt of maleonitriledithiol and by the reaction of 4-nitrocatechol in the presence of Et3N, respectively. Reaction of p-tolylstibonic acid with pinacol gave the bicyclicstiborane (Me4,C2,O2)2Sb(C6,H4-p-Me) (2). Stiboranes 2 and 3 are new compounds. X-ray analysis revealed that 1 and 2 are trigonal bipyramidal while 3 is closer to a square-pyramidal structure. Molecules of 3 exist in the solid as weakly connected dimers, which accounts for its structural displacement toward the square pyramid. The distortion coordinate expressing solid-state nonrigidity is the Berry pseudorotational coordinate, the same as that found for pentacoordinated structures of other elements of main groups 4 (14) and 5 (15). However, lattice effects enter as a more important structural influence for some stiboranes. Stiborane I crystallizes in the monoclinic space group P21/c wit...

ANIONIC FIVE-COORDINATED CYCLIC ORGANOFLUOROSILICATES VARYING IN RING SIZE FROM FIVE- TO SEVEN-MEMBERED

Abstract Synthesis of the potassium crown ether complexes (K, 18-c-6) 3 and 4 of the anionic five-coordinated spirocyclic fluorosilicates from the precursor fluorosilanes has provided additional members of this new class of silicon compounds. Silicates 3 and 4 are monofluoro catecholate derivatives [(CH2) n SiF(O2C6H4)]−, containing the five-membered tetramethylene (n = 4) and six-membered pentamethylene (n = 5) ring system, respectively. X-ray analyses of these fluorosilicates are reported along with that of the previously synthesized related monocyclic anionic fluorosilicates [BiPhSiF3][K, 18-c-6] (1) and [BiBzSiF3][K, 18-c-6] (2). The first structural characterization of a pentacoordinated silicon compound containing a seven-membered ring is provided by 2. The study also yields the first structure of a fluorosilicate containing a six-membered ring (4). The geometries are all trigonal bipyramids. Silicates 2–4 have carbon-containing rings positioned diequatorially, whereas the trifluorosilicate 1, with ...

ISOLATION OF THE FIRST ANIONIC FIVE-COORDINATED SILICATES WITH SIX-AND SEVEN-MEMBERED OXYGEN-CONTAINING RINGS

Abstract Reaction of PhSi(OMe)3 with KOMe and naphthalenediol led to the first five-coordinated anionic silicate with an oxygen-containing six-membered ring, [(C10H6O2)2Si(C6H5)][K, 18-c-6] (1). Reaction of the tetracoordinate spirocyclic silane (C12H8O2)2Si with either KO-t-Bu or KF in the presence of 18-crown-6 led to the isolation of the first five-coordinated anionic silicates with seven-membered oxygen-containing rings, [(C12H8O2)2SiR][K, 18-c-6], R = O-t-Bu (2), F (3). 29Si NMR spectroscopy shows that the five-coordinated silicates 2 and 3 slowly disproportionate into four-coordinate silicon compounds and organic species lacking any silicon. Syntheses similar to that for 2 and 3 conducted with other ligands containing the isopropoxy group or use of Bu4N+F− in place of potassium 18-crown-4 imparts less stability to the system and leads directly to the formation of anionic organic products consisting of two biphenolate species hydrogen bonded to each other. In the case of [(C12H8O2)2H3][(n-Bu)4N] (5) ...

FIRST STRUCTURAL STUDY OF A THIOPHOSPHORANE CONTAINING A SIX-MEMBERED RING. PHOSPHORUS-SULFUR VS PHOSPHORUS-OXYGEN LIGAND PREFERENCES

Abstract Oxidative addition of phenanthrenequinone to the newly synthesized dithiaphosphorinane, (Xylyl-O)P-S(CH2)3S (1), results in a new thiophosphorane containing a sulfur-bonded six-membered ring. X-ray analysis on separate crystals reveals both a monoclinic and triclinic modification. This represents the first structural study of a six-membered ring containing thiophosphorane. The structure which is a trigonal bipyramid has the ring sulfur atoms located in apical-equatorial sites instead of the expected diequatorial arrangement. As a consequence, the more electronegative xylyloxy oxygen atom is relegated to an equatorial position. A slightly twisted boat conformation exists for the dithiaphosphorinane ring. IH NMR spectroscopy is consistent with the retention of the solid-state structure in solution which undergoes rapid intramolecular ligand exchange.