Organometallic Molybdenum(V) Complexes with Promary Phosphane Ligands — Syntheses, Spectroscopic Properties, and Crystal Structures of [Cp′MoCl₄(PH₂R)] (R=2,4,6‐Prⁱ₃C₆H₂, Cyclohexyl, Cp′=C₅H₄Me)

Abstract

Various substituted cyclopentadienyl molybdenum(V) tetrachlorides are reduced on reaction with PH-functionallzed lithium phosphanides to give the corresponding cyclopentadienyl molybdenum(II1) dichloro which can then react with further lithium reagent, yielding terminal phosphanido. diphosphanyl, and diphosphene complexes [5]. We attempted to prevent the reduction of Mo(V) by employing a primary phosphane instead of the highly reducing lithium reagents for the introduction of a P-functionalized ligand.Here we report on the preparation, spectroscopic properties and molecular structures of the first organometallic molybdenum(V) complexes with primary phosphane ligands, [Cp'MoCI4(PH2R)] [Cp' = C5H4Me, R = 2,4,6-Pr!3C6H2 (l), Cy (211.

Half-sandwich molybdenum compounds with phosphine–alkylthiolate and phosphine–thioether ligands. Crystal structure of [CpMo(SCH2CH2PPh2)2][BPh4]

“…The EPR spectrum of compound 6 does not show coupling to the phosphorus atom (singlet at g = 1.954, aMo = 51.8 G). Previously reported phosphine adducts of alkyl-substituted cyclopentadienyl derivatives of Mo(V) display rather large phosphorus hyperfine constants (greater than 24 G), [29][30][31] thus indicating the possibility that the bifunctional ligand binds the metal in a monodentate fashion via the sulfur donor in compound 6. However, we find that the addition of the electronically similar PMePh2 ligand to CpMoCl4 affords an EPR spectrum which consists of a single resonance with no observable hyperfine coupling to the P nucleus.…”

“…Compound 1, which is obtained as a yellow precipitate from the reaction mixture, is insoluble in all common solvents and only slightly soluble in MeOH. A 31 P{ 1 H}-NMR spectrum in MeOH shows a single resonance at δ 85.1, indicating its diamagnetic nature.…”

“…The suspension was filtered and the yellow solid was dissolved in THF. 31 P{ 1 H}-NMR (THF, δ): 84.7 ppm.…”

A reinvestigation of compound CpMo(PMe3)2(CH3)2: alkylation by single electron transfer and radical addition?

“…Previous examples of triplet 16-electron halfsandwich Mo(IV) compounds are known, 16,[31][32][33] stronger donors such as phosphine ligands. 31,34,35 Compound Cp*Mo(CH 3 ) 4 is also a stable 15electron compound. 36 The lack of reversibility for the second oxidation of CpMo(PMe 3 ) 2 Cl 2 could indeed be ascribed to solvent co-ordination to the highly unsaturated…”

Different Approaches to Mid-Valent, Paramagnetic Half-Sandwich Complexes of the Heavier Group 6 Metals

“…On the other hand, the addition of basic phosphine ligands (even primary ones) to the more encumbered and less acidic Cp*MoCl 4 or to tungsten analogues leads to stable adducts. 19,[25][26][27][28] The reduction of Lewis acidic metal halide reagents by basic phosphine ligands is a known nuisance, which we have encountered time and again in other areas, such as the coordination chemistry of iron 29,30 and the organometallic chemistry of niobium. 31 Thus, in order to circumvent the phosphine-induced CpMoCl 4 decomposition, we decided to first reduce the CpMoCl 4 material to CpMoCl 2 , then add the desired phosphine, in two separate steps.…”