Reaction of Spiro[2.4]hepta-4,6-diene with Molybdenum(II) Indenyl Compounds: Effects of Substitution in the Indenyl Ligand

Abstract

The series of molybdenum indenyl compounds [(Ind 0 )Mo(CO) 2 (NCMe) 2 ] [BF 4 ] was prepared, and their reactivity toward spiro[2.4]hepta-4,6-diene was studied. It was observed that the spiro-[2.4]hepta-4,6-diene ring opening could be blocked through substitution in the indenyl ring. Hence, the 2-substituted compound [(η 5 -C 9 H 6 Me)Mo(CO) 2 (NCMe) 2 ][BF 4 ] and 1,3-disubstituted compound [(η 5 -C 9 H 5 t Bu 2 )Mo(CO) 2 (NCMe) 2 ][BF 4 ] do not produce the usual ansa-compounds but the compounds with η 4 -bonded spiro[2.4]hepta-4,6-diene [(Ind 0 )(η 4 -C 5 H 4 (CH 2 ) 2 )Mo(CO) 2 ][BF 4 ]. The use of 1-substituted compounds [(η 5 -C 9 H 6 R)Mo(CO) 2 (NCMe) 2 ][BF 4 ] (R = Ph, t Bu) or compounds with less sterically demanding substituents in the 1,3-positions [(η 5 -C 9 H 5 Ph 2 )Mo(CO) 2 (NCMe) 2 ]-[BF 4 ] does not block the ring-opening reaction. These compounds give ansa-molybdenocenes [(Ind 0 )(η 5 -C 5 H 4 CH 2 -η 1 -CH 2 )Mo(CO)][BF 4 ] in a manner similar to that for the unsubstituted analogue. The reaction products were characterized by NMR and IR spectroscopy. Structures of [(η 5 -C 9 H 5 Ph 2 )Mo(η 3 -C 3 H 5 )(CO) 2 ], [(η 5 -C 9 H 6 Ph)(η 5 -C 5 H 4 CH 2 -η 1 -CH 2 )Mo(CO)][BF 4 ], and [(η 5 -C 9 H 5 Ph 2 )(η 5 -C 5 H 4 CH 2 -η 1 -CH 2 )Mo(CO)][BF 4 ] were determined by single-crystal X-ray analysis.

Toward the Synthesis of Indenyl Molybdenum Compound [(η3-Ind)(η5-Cp)Mo(CO)2]: Modified Compounds and Structure of a Previously Unrecognized Intermediate

“…The starting indenyl complexes 1 and 2 were synthesized using literature procedures. 11,12 The complex 3 was prepared accordingly starting from Li(4,7-Me 2 C 9 H 5 ) and [(η 3 -C 3 H 5 )-Mo(CO) 2 (NCMe) 2 Cl]; see Scheme 1. The infrared spectrum of compound 3 shows two bands in the region of CO stretching at 1928 and 1844 cm −1 .…”

“…10 The study on the series of modified compounds has shown that the spiro [2.4]hepta-4,6-diene ring-opening can be in particular cases controlled through substitution in the indenyl ring. 11 The aim of this work is to extend the synthetic route giving compounds of the type [(η 3 -Ind′)(η 5 -Cp′)Mo(CO) 2 ]. This study includes the compounds bearing functional groups in the cyclopentadienyl ring and also the compounds with η 5carbaborane or κ 3 -scorpionate ligands coordinated instead of η 5 -Cp.…”

How big is a Cp? Cycloheptatrienyl zirconium complexes with bulky cyclopentadienyl and indenyl ligands

“…33,60 The second tertbutyl group in 1,3-di(tert-butyl)indene was introduced via the Grignard method, which significantly increased the yield of this step (51%) compared to literature reported routes via lithium organyls (18%). 62 These improvements are also reflected in the overall yield of our synthesis of 1,3-di(tert-butyl)indene (42%) when compared to the best literature procedure (11%). 64 In addition, we were interested in using cyclohexyl-substituted systems.…”

“…The syntheses of iso-propyl and tert-butyl substituted cyclopentadienyl ligands are well established in the literature. 20,33,59,60 In contrast, the syntheses of the related indenyl derivatives such as 1,3-di(iso-propyl)indene 61 and 1,3-di(tert-butyl)indene [62][63][64] have been rather tedious, involving multiple steps or low yields; only a few indenyl complexes with these ligands have been reported, although they exhibit interesting properties. 8,13,61,62,[64][65][66][67] Therefore, a better synthetic protocol would be desirable to provide reasonable quantities of these ligands and to facilitate the exploration of the corresponding coordination chemistry.…”

Stabilization of η3-indenyl compounds by sterically demanding N,N-chelating ligands in the molybdenum coordination sphere

“…33 An activation of coordinated ligand was also observed for complexes with h 4 -bonded spiro- {h 4 -C 5 H 4 (CH 2 ) 2 }Mo(CO) 2 ][BF 4 ] is unusually stable, while the indenyl analogue undergoes a spontaneous and very fast ringopening to [(h 5 -Ind)(h 5 -C 5 H 4 CH 2 -h 1 -CH 2 )Mo(CO)][ BF 4 ]. 34,35 The aim of this study is to bring a detail description of the coordination properties of [{(h 5 -4,7-Me 2 C 9 H 5 )Mo(CO) 2 (m-Cl)} 2 ] (2) in attempt to synthesize new h 3 -indenyl compounds structurally related with the well-known complexes bearing h 3 -allyl [(h 3 -C 3 H 5 )Mo(CO) 2 ( N,N L)Cl]. It will be shown that a steric congestion of the chelating ligand is critical for the stability of [(h 3 -4,7-Me 2 C 9 H 5 )Mo(CO) 2 ( N,N L)Cl] and could be used for the control of the indenyl ring slippage.…”