The 19 F 19 F nuclear spin-spin coupling constants J FF for a set of eighteen compounds related structurally to 1,8-difluoronaphthalene were measured by 19 F NMR spectroscopy. The FF distances d FF in these compounds were determined by ab initio 3-21G* molecular orbital calculations. Consistent with the lone-pair overlap theory of the origins of through-space 19 F 19 F coupling, an exponential relationship is found between J FF and d FF (regression coefficient r 2 ) 0.991), and a linear relationship is found between J FF and the extent of the overlap interaction between the in-plane fluorine 2p lone-pair orbitals (regression coefficient r 2 ) 0.993). The magnitudes of these lone-pair interactions were estimated from molecular orbital energies obtained by ab initio 6-31G* calculations for a model consisting of a pair of HF molecules separated by various distances.

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The chloroplatinic acid or platinum(II) bromide-catalyzed reaction of arachno-6,8-C 2 B 7 H 13 with ethylene results in hydroboration to yield the single product 7-(C 2 H 5 )-arachno-6,8-C 2 B 7 H 12 . Analogous reactions with 1-pentene or styrene yield a mixture of both hydroboration, 7-R-arachno-6,8-C 2 B 7 H 12 , and dehydrogenative borylation, 7-(trans-R-CHdCH)-arachno-6,8-C 2 B 7 H 12 , products. On the other hand, the palladium(II) bromidecatalyzed reaction of arachno-6,8-C 2 B 7 H 13 with ethylene yields predominantly the dehydrogenative borylation product (7-(CH 2 dCH)-arachno-6,8-C 2 B 7 H 12 along with smaller amounts of 7-(C 2 H 5 )-arachno-6,8-C 2 B 7 H 12 . Palladium(II) bromide-catalyzed reactions with 1-pentene or styrene result in only dehydrogenative borylation to produce 7-(trans-R-CHdCH)-arachno-6,8-C 2 B 7 H 12 . The hydroboration and dehydrogenative borylation products observed in the platinum-and palladium-catalyzed reactions are related to those that have been observed in recently reported metal-catalyzed hydrosilations and catecholborane or pinacolborane hydroborations and are consistent with a reaction mechanism involving competitive hydride-migration/reductive-elimination and boryl-migration/β-hydride-elimination steps. Crystallographic and DFT computational studies of the alkenylcarbaboranes have also revealed unusual cage-bonding features that suggest π-bonding interactions of the B7 cage boron with its olefinic substituent.

Triphenylborane, BPh 3 , serves as a phosphine "sponge", scavenging free PMe 3 from alkane solutions of the 18ecomplex (PMe 3 ) 4 Ru(SiMe 3 )H to form sparingly soluble Ph 3 B-PMe 3 and the 16e -(PMe 3 ) 3 Ru(SiMe 3 )H. Under nitrogen atmosphere the 16e -(PMe 3 ) 3 Ru(SiMe 3 )H forms a dimeric N 2 adduct, [(PMe 3 ) 3 Ru(SiMe 3 )H] 2 N 2 . Both the 16ecomplex and its N 2 adduct exist in equilibrium with the 18esilene complex, (PMe 3 ) 3 Ru(CH 2 dSiMe 2 )H 2 . However, long reaction times in the presence of excess borane leads to removal of another phosphine ligand as Ph 3 B-PMe 3 and formation of a new zwitterionic complex, (η 6 -PhBPh 2 H)Ru(PMe 3 ) 2 (SiMe 3 ) (5), in which a molecule of borane has abstracted a ruthenium hydride ligand and also coordinates as an η 6 -arene. The merits and limitations of BPh 3 as a phosphine removal agent are discussed. Compound 5 has been characterized by single-crystal X-ray analysis and exhibits unusually long Ru-C arene bonds.