Strong agostic-type interactions in ruthenium benzylidene complexes containing 7-azaindole based scorpionate ligands

Abstract

. (2011). Strong agostic-type interactions in ruthenium benzylidene complexes containing 7-azaindole based scorpionate ligands. Dalton Transactions, 40 (4), 951-958.

Important Steric Effects Resulting from the Additional Substituent at Boron within Scorpionate Complexes Containing κ3‐NNH Coordination Modes

“…Unfortunately, this means that the one‐bond B–H coupling constant could not be determined from the boron‐coupled experiment. An increased linewidth of the boron signal is typical in complexes of this type and has previously been observed in other complexes containing aryl‐substituted ligands 4a,11c,11d. The 31 P{ 1 H} NMR spectra of 4 – 6 show singlet resonances between δ = 66.3 and 68.8 ppm.…”

“…We recently reported the benzylidene–ruthenium complexes [RuCl{κ 3 ‐ NNH ‐R(H)B(azaindolyl) 2 }{=C(H)Ph}(PCy 3 )] [R = azaindolyl ( 1 ), phenyl ( 2 )] and [RuCl{κ 3 ‐ NNH ‐HB(azaindolyl) 3 }{PCy 2 (C 6 H 9 )}(PCy 3 )] ( 3 ; Figure 4). 11c Within these complexes very strong interactions were observed between the ruthenium centre and the borohydride units, as confirmed by their spectroscopic and structural characterisation (Table 1). A comparison of these compounds and other literature examples revealed that such interactions are particularly strong in those cases in which the borohydride unit is located trans to a halide or similar π‐donor ligand 11c.…”

“…11c Within these complexes very strong interactions were observed between the ruthenium centre and the borohydride units, as confirmed by their spectroscopic and structural characterisation (Table 1). A comparison of these compounds and other literature examples revealed that such interactions are particularly strong in those cases in which the borohydride unit is located trans to a halide or similar π‐donor ligand 11c. This is in contrast to examples in which the borohydride unit is located trans to a strong σ‐donor such as hydride or alkyl groups.…”

“…Our recent investigations have focused on obtaining a better understanding of the factors that govern hydride migration. We have studied a range of ligand systems and prepared a number of derivative ligands4a,11c,11d based on the parent ligand Tai (Figure 1). 1 Replacing one of the azaindole rings with an aryl group appears to inhibit hydride migration in the resulting compounds as it has not been observed in any of the Ar Bai (Ar = phenyl, 2‐naphthyl, mesityl) derivatives.…”

Dehydrogenation processes via C–H activation within alkylphosphines

“…8). 23 The unusual rearrangement affording the complex [CpRu{(Z 3 -CH 2 C(CH 2 ) 3 CCH 2 PCy 2 (Z 2 -C 6 H 9 )] + (21) resulted from the addition of 1,6-heptadiyne to [CpRu(NCCH 3 ) 2 (PCy 3 )] + (19) through an intermediate allyl carbene 20. 24 In this system, the phosphonium ligand is coordinated to the metal centre through the CQC double bond at the a position of the phosphorus, which is not bound to the ruthenium (Fig.…”