Crystal structure of 1,2-vinylenbis(triphenylphosphonium) tetrabromoplumbate( II), [Ph3P-CH=CH-PPh3][PbBr4]

Abstract

Source of materialPbBr 2 and [Ph 3 P-CH=CH-PPh 3 ][Br 2 ] were both dissolved in aqueous HBr, the solutions were mixed and water was slowly evaporated. After several hours a fine crystalline yellow powder precipitated. For the preparation of single crystals 1.5 g of this product and 5 ml H2O were filled into a glass ampoule which was sealed and heated to 45 3 K. The ampoule was cooled with a rate of 10 K/min to ambient temperature. DiscussionLead atom is coordinated by four bromide ligands, in form of a trigonal ψ-bipyramide with one equatorial position occupied by the s 2 -pair. The axial Pb-Br bond lengths are 2.99 Ä, the equatorial lengths 2.70 Ä, Br(ax)-Pb-Br(eq) angles are in the range 95.53° to 99.42°, the bond angle between the two axial Br-atoms is 159.0°. The data agree with those observed in comparable bromoplumbates(II) [1]. The distorted ψ-bipyramide was so far not observed in the structure of lead bromides with organic cations. Cations and anions form waved layers, which are stacked along the α-axis in the order A,A,A. Bond distances and bond angles in the cation agree well with the data of Stang and Zhdankin [2], The compound was investigated with a differential scanning calorimeter. Between 153 Κ and 423 Κ no phase transition was detected.

Bromoplumbate mit kettenförmigen und isolierten Anionen: (Bzl4P)2[Pb3Br8], (Bzl4P)2[Pb3Br8(dmf)2], (Bzl4P)[PbBr3], (Bzl4P)2[PbBr4] und (Bzl4P)4[Pb2Br6][PbBr4]

“…Die Struktur des Bromoplumbatanions in 3 ist somit a Èhnlich der des C 2v -symmetrischen Anions in (Ph 3 P±CH=CH±PPh 3 )[PbBr 4 ] [9]. Die Bindungswinkel und Abstandsverha Èltnisse sind im Einklang mit einem Bindungskonzept, nach dem zueinander transsta È ndige Bindungen im Koordinationspolyeder um die Pb II -Zentralatome in der Summe gleiche Bindungsordnungen aufweisen, unabha Èngig davon, ob sich gleich lange Bindungen, eine ku È rzere und eine la È ngere oder eine kurze Bindung und eine Koordinationslu È cke gegenu È berstehen [3,10].…”

“…(Bzl 4 P) 2 [Pb 3 Br 8 ] (1 a): a = 907,93 (6), b = 1305,39 (9), c = 1367,04 (9), a = 91,929 (6), b = 104,527 (6), c = 103,589 (6), V = 1517,1(2)´10 6 pm 3 , Raumgruppe P1;…”