Organo-transition metal cluster complexes

Abstract

The number of c.v.e. donated by m 3 -alkenyl and m 4 -alkyne ligands has been examined using fragment molecular orbital (FMO) calculations on two representative clusters, Ru 3 (m 3 -H 2 NNH)(m 3 -CHCH 2 )(m-CO)(CO) 7 and Ru 4 (m 4 -HC 2 H)(CO) 12 . Results suggest donation of three and four electrons, respectively, the observed stability of these unsaturated clusters attributed to the large HOMO-LUMO gaps. 8 DFT calculations on the series of triosmium-fullerene complexes Os 3 (m 3 -Z 2 :Z 2 :Z 2 -C 60 )(CO) 8 L (L = CO, PMe 3 ) and their anions (À1 to À4) show that all three metal atoms are p-coordinated to the C 6 unit of the fullerene in the neutral, mono-and dianionic complexes, but consist of mixed s-p-coordination in the tri-and tetraanionic cases, affording [Os 3 (m 3 -Z 2 :Z 2 :Z 1 -C 60 )(CO) 8 L] 3À and [Os 3 (m 3 -Z 2 :Z 1 :Z 1 -C 60 )-(CO) 8 L] 4À . 9 Interstitial nickel and palladium atoms in icosahedral and pentagonal antiprismatic clusters with five-fold symmetry have been shown to be analogous to endohedral noble gas atoms in fullerenes. 10 The electronic structure and bonding of the omnicapped truncated tetrahedral Au 20 cluster has been examined, its large band gap (1.77 eV) rationalized, and its structure related to those of other M 20 complexes. 11 4 Structural studies A single-crystal neutron diffraction study of Co 4 (m 3 -H) 4 (Z 5 -C 5 Me 4 Et) 4 has revealed the presence of four face-capping hydride ligands. 12 5 High-nuclearity clusters 5.1 Homonuclear high-nuclearity clusters The dinitrido cluster tetraanion [Co 10 (m 6 -N) 2 (CO) 19 ] 4À can be chemically or electrochemically oxidized to give [Co 11 (m 6 -N) 2 (CO) 21 ] 3À (2) via three spectroscopicallyidentified intermediates. The 154 c.v.e. cluster contains a bent bioctahedral metal cage with 10 of the carbonyl ligands bridging Co-Co bonds and has four excess electrons; cyclic voltammetry indicates reversible loss of two electrons. 13 Reaction of Pd 10 (CO) 12 (PEt 3 ) 6 with Pd 2 (dba) 3 (dba = dibenzylideneacetone) or [Pd(NCMe) 4 ] 2+ affords Pd 52 (CO) 36 (PEt 3 ) 14 (ca. 5%) or Pd 66 (CO) 45 (PEt 3 ) 16 (13%), respectively. The clusters can be considered to be derived from a common Pd 38 core via condensation of Pd 7 caps and form mixed ccp/hcp layered structures. 14 [Pt 38 (CO) 44 ] 2À has been prepared in high yield by carbonylation (800 mmHg) of [PtCl 6 ] 2À salts in water; a similar carbonylation at 900 mmHg affords quantitative yields of [Pt 3n (CO) 6n ] 2À (n 4 6). 15 The double salt Ag 12 (C 2 ) 2 (O 2 CCF 3 ) 8 (2-pyzCONH 2 ) 3 (3) is prepared from a mixture of Ag 2 C 2 , RCO 2 Ag (R = CF 3 ) and AgBF 4 and contains a m 8 -Z 2 -C 2 unit embedded in an Ag 8 cage and a second m 6 -bound C 2 unit contained in an open arrangement of six silver atoms, one of which forms the common vertex of the infinite column structure. The triple salt Ag 20 (C 2 ) 4 (O 2 CC 2 F 5 ) 8 (2-pyzCOO) 4 -