The chemistry of cycloheptatrienyl complexes of molybdenum and tungsten: the synthesis and reactions of some vinylidene and alkynyl derivatives

Synthesis of the sterically crowded cycloheptatrienyl complexes [M(CO)(PPh3)2(η-C7H7)]+ (M=Mo or W): X-ray crystal structures of [W(CO)(PPh3)2(η-C7H7)][BF4] and [W(CO)2(PPh3)(η-C7H7)][BF4]·CH2Cl2

“…Inspection of the literature reveals that a similar mechanism is proposed for the reac- 6 ] in thf [12]. 4 ]. The material was too unstable to characterise fully but infrared spectroscopy in CH 2 Cl 2 revealed a single carbonyl band (m(CO)(CH 2 Cl 2 ) 1917 cm À1 ) shifted to high wavenumber by 6 cm À1 from that of the starting material [WI(CO)(PPh 3 )(g-C 7 H 7 )].…”

“…The contrasting behaviour of the Ru(PPh 3 ) 2 Cp and W(PPh 3 ) 2 (g-C 7 H 7 ) systems in this respect may be important in rationalising the relative stability of their complexes. 4 ] AE CH 2 Cl 2 (4) reveals that the additional PPh 3 ligand is accommodated in the structure by a series of modifications to the molecular geometry including an increase in the sum of the angles between the tripodal ligands, tilting of the cycloheptatrienyl ring and a small decrease in the experimental cone angle of the PPh 3 ligands. However, the most significant change appears to be an elongation of the W-PPh 3 bond lengths by approximately 0.05 Å .…”

“…The isoelectronic character of the 13-electron fragments Ru(g-C 5 R 5 ) and Mo(g-C 7 H 7 ) (C 7 H 7 = cycloheptatrienyl) has been well documented by ourselves [4] and others [5] and similarities in complex type and reactivity noted.…”

“…The experimental consequences of the effect of increasing ring size on the accommodation of sterically demanding tripodal ligands are nicely illustrated by a comparison of the known auxiliaries RuðPR 0 3 Þ 2 ðg-C 5 R 5 Þ and MoðPR 0 3 Þ 2 ðg-C 7 H 7 Þ. Accordingly, whilst the bis(triphenylphosphine) auxiliary Ru(PPh 3 ) 2 (g-C 5 R 5 ) is one of the cornerstones of the organometallic chemistry of ruthenium [7], the chemistry of bis(phosphine) cycloheptatrienyl systems MoðPR 0 3 Þ 2 -ðg-C 7 H 7 Þ is dominated by complexes of the chelate phosphine Ph 2 PCH 2 CH 2 PPh 2 (dppe) [4,8,9] or small cone angle P-donor ligands such as P(OMe) 3 [10]. This paper reports the syntheses of the sterically crowded complexes [M(CO)-(PPh 3 ) 2 (g-C 7 H 7 )] + (M = Mo or W), the first examples of derivatives of the bis(triphenylphosphine) auxiliary M(PPh 3 ) 2 (g-C 7 H 7 ), and explores the structural modifications required to accommodate the combination of sterically demanding ring and phosphine ligands in a halfsandwich complex.…”

“…Crystal data and refinement parameters for [W(CO)(PPh 3 ) 2 (g-C 7 H 7 )][BF 4 ] (3) and [W(CO) 2 (PPh 3 )(g-C 7 H 7 )][BF 4 ] AE CH 2 Cl 2(4) …”