Greg J. Spivak

Mechanistic and thermodynamic aspects of methylene transfer from CH2N2 to MHCl(CO)L2 (M=Ru, Os; L=tertiary phosphine): non-least motion behavior and extreme dependence on phosphine identity

Reaction of MHCl(CO)(PBut2Me)2 (M=Ru and Os) with CH2N2 was studied from -78 to 25°C, revealing first the formation of MHCl(CH2)(CO)(PBut2Me)2, where the carbene ligand CH2 occupies what was the open coordination site of MHCl(CO)(PBut2Me)2, which lies trans to the hydride. This intermediate then isomerizes to M(CH3)Cl(CO)(PBut2Me)2, below 25°C for each metal. The analogous reaction of MHCl(CO)(PPri3)2 with CH2N2 does indeed give MHCl(CH2)(CO)(PPri3)2, which then ‘decomposes’ unselectively; when M=Os, C2H4 and OsHCl(CO)(PPri3)2 are among the products. This extreme phosphine dependence is attributed to the H–MCH2 to M(CH3) isomerization requiring phosphine dissociation; the smaller PPri3 fails to dissociate at a rate competitive with alternative decomposition reactions.

Coordination, fluxionality and fragmentation in reactions of platinum cluster complexes with alkynes

Abstract The activated alkyne MeO 2 CCCCO 2 Me reacts at low temperature with the cluster complexes [Pt 3 ( μ -CO) 3 L 3 ], L=PCy 3 , and [Pt 6 ( μ -CO) 6 ( μ -dppm) 3 ], 4 , to give 1:1 complexes [Pt 3 (CO) 3 L 3 (MeO 2 CCCCO 2 Me)], L=PCy 3 , and [Pt 6 ( μ -CO) 6 ( μ -dppm) 3 (MeO 2 CCCCO 2 Me)], which undergo cluster fragmentation on warming to room temperature to yield the binuclear complexes [Pt 2 (CO) 2 L 2 ( μ -MeO 2 CCCCO 2 Me)] and [Pt 2 (CO) 2 ( μ -dppm)( μ -MeO 2 CCCCO 2 Me)], respectively.

The bicluster oxidative addition as a route to bicapped hexaplatinum clusters

Abstract The reaction of either the 84-electron cluster [Pt 6 (μ-CO) 6 (μ-dppm) 3 ] ( 1 ) or the 82-electron cluster [Pt 6 (CO) 6 (μ-dppm) 3 ] 2+ ( 2 ), dppm = Ph 2 PCH 2 PPh 2 , with SnX 3 − or Hg 2 X 2 gave the corresponding bicapped trigonal prismatic 86-electron clusters [Pt 6 ( μ 3 -SnX 3 ) 2 ( μ -CO) 6 ( μ -dppm) 3 ] ( 3 : X = F( 3a , Cl( 3b ), Br( 3e ) or [ Pt 6 (μ 3 - HgX ) 2 (μ- CO ) 6 (μ- dppm ) 3 ] 4 : X = Cl ( 4a ) , Br ( 4b ), l ( 4c ), respectively. The new clusters 3 and 4 have been characterized spectroscopically and 4c has also been characterized by X-ray diffraction. Crystals of 4c·CH 2 Cl 2 ·2Et 2 O are monoclinic, space group P 2 1 c , a=20.092(9), b=18.718(7), c=26.258(7) A , β=108.09(3)° V=9387(6) A 3 , Z =4. The molecular core in 4c is a Pt 6 trigonal prism with each triangular Pt 3 face capped by an Hgl fragment. The intertriangle PtPt bond distances (2.910(1)–2.948(1) A) are longer than the intratriangle PtPt distances (2.634(1)–2.687(1) A) and this is consistent with EHMO calculations. The reaction of 1 with Hg 2 X 2 to give 4 is termed a bicluster oxidative addition; according to predictions from EHMO calculations it should lead to stronger intertriangle PtPt bonding in 3 and 4 than in the precursor cluster 1 , but this is not suppored by structural data observed in 3c and 4c .

Pt3Ir cluster complexes: butterfly clusters with iridium at a wingtip

Abstract The new coordinatively unsaturated cluster [Pt 3 Ir(μ-CO) 3 (CO)(μ-dppm) 3 ] + and [Pt 3 Ir(μ-CO) 3 {P(OPh)} 3 (μ-dppm) 3 ] + are fluxional, butterfly clusters with iridium at a wingtip positions.

Evidence for long-range electronic effects in hexaplatinum clusters: the case of phosphite ligand addition and migration

Abstract The 84-electron cluster [Pt 6 ( μ 2 -CO) 6 ( μ 2 -dppm) 3 ] ( 1 ) (dppm = Ph 2 PCH 2 PPh 2 ) forms an adduct with the phosphite P(OCH 2 ) 3 CMe to give the 86-electron cluster [Pt 6 ( μ 2 -CO) 6 ( μ 2 -dppm) 3 (P(OCH 2 ) 3 CMe)] ( 2 ). The phosphite ligand in 2 is fluxional as shown by a variable temperature NMR study between 20 and −90°C. At low temperatures the spectra indicate a structure in which the phosphite is terminally bound to one platinum atom, while at temperatures above −70°C, the complex is fluxional with the phosphite migrating rapidly around a triangular face of the cluster. The selective formation of only a 1:1 complex, coupled with the predictions of EHMO theory, provides good evidence for long-range electronic effects across the hexaplatinum cluster.