A. J. Welch

Theoretical comparison of the “slip” distortion and rotational barriers in comparable seven and twelve vertex carbaplatinaboranes

Abstract Extended Huckel molecular orbital calculations on the related closo-platinaboranes [(H3P)2Pt(B11H11)]2- and [(H3Pt2Pt(B6H6)]2- and the closo-carbaplatinaboranes [(H3P)2Pt(C2B9H11)] and [(H3P)2Pt(C2B4H6)] have suggested that the larger “slip” distortions in the pentagonal bipyramidal derivatives can be attributed in large measure to the different metal—ligand interactions which are induced by the different elevation angles of the substituents on the pentagonal faces of the ligands. Differences in bond lengths associated with the two classes of carbaplatinaboranes have been interpreted in terms of the different bonding capabilities of the two types of carbaborane ligands.

Synthesis of nido- and closo-diplatinacarborane complexes by direct insertion; crystal and molecular structures of closo-2,3-[(Et3P)2]2-1,2,3,6-CPt2CB5H7, nido-µ(4,8)-[(Me3P)2Pt]-8,8-[(Me3P)2]-7,8,10-CPtCB8H10 and nido-8,8-[(Me3)2]-7,8,10-CPtCB8H10.

Reaction of closo-2,4-C2B5H7 with [Pt(styrene)-(PEt3)2] affords closo-2,3-[(Et3P)2]2-1,2,3,6 -CPt2CB5H7, whereas [Pt(1,5-C8H12)(PMe3)2] and 1,6-C2B8H10 gives nido-µ(4,8)-[(Me3P)2]- 7,8,10-CPtCB8H10 which on treatment with activated charcoal affords, nido-8,8-[(Me3P)2]-7,8,10-CPtCB8H10; the structural identity of the complexes was established by X-ray crystallography.

Co-ordinatively unsaturated molybdenum and tungsten cyclopentadienyl complexes; molecular structures of [WCl(CF3C2CF3)2(η5-C5H5)] and [Mo(C4F6)2(C5H5)2]

Reaction of [MCl(CO)3(η5-C5H5)](M = Mo or W) with acetylenes affords the 16-electron species [MCl-(RC2R)2(η5-C5H5)]; structurally characterised by X-ray crystallography, and shown to react with donor ligands and with TlC5H5.

Synthesis of a boron analogue of co-ordinated cyclobutadiene; X-ray molecular structures of closo- and nido-L2PtC2B6H6R2

Reaction of closo-1,6-R2-1,6-C2B6H6(R = H or Me) with [Pt(trans-stilbene)L2](L = PEt3 or PMe3) affords closo-[L2PtC2B6H6R2] and nido-[L2PtC2B6H6R2]complexcomplexes which are structurally characterised by X-ray crystallography.

Formation of closo- and nido-metallocarboranes from closo-C2B9 and -C2B7 carborbranes; molecular structures of closo-1,1-(Me2PhP)2-2,4-Me2-1,2,4-PtC2B9H9 and nido-10,10-(Et3P)2-2,8-Me2-10,2,8-PtC2B7H7

Reaction of closo-1,6-Me2-1,6-C2B7H7 with [Pt(Et3P)3] affords nido-10,10-(Et3P)2-2,8-Me2-10,2,8-PtC2B7H7, a stereochemically non-rigid molecule; the structural identity of closo-1,1-(Me2PhP)2-2,4-Me2-1,2,4-PtC2B9H9 and the nido-metallocarborane are established by X-ray crystallography.