Abstract
By reacting [{Cp‴Fe(CO)2}2(µ,η1:1-P4)] (1) with in situ generated phosphenium ions [Ph2P][A] ([A]− = [OTf]− = [O3SCF3]−, [PF6]−), a mixture of two main products of the composition [{Cp‴Fe(CO)2}2(µ,η1:1-P5(C6H5)2)][PF6] (2a and 3a) could be identified by extensive 31P NMR spectroscopic studies at 193 K. Compound 3a was also characterized by X-ray diffraction analysis, showing the rarely observed bicyclo[2.1.0]pentaphosphapentane unit. At room temperature, the novel compound [{Cp‴Fe}(µ,η4:1-P5Ph2){Cp‴(CO)2Fe}][PF6] (4) is formed by decarbonylation. Reacting 1 with in situ generated diphenyl arsenium ions gives short-lived intermediates at 193 K which disproportionate at room temperature into tetraphenyldiarsine and [{Cp‴Fe(CO)2}4(µ4,η1:1:1:1-P8)][OTf]2 (5) containing a tetracyclo[3.3.0.02,7.03,6]octaphosphaoctane ligand.
Highlights
The activation of small molecules such as N2 or P4 with reactive transition metal fragments or main group reactants is one of the important aspects of modern chemistry.More energy-efficient reaction pathways leading, by higher atom economy, to compounds containing nitrogen or phosphorus seem more tangible with every new insight gained into the activation pathways [1,2,3,4,5]
Since the highest occupied molecular orbital (HOMO) in 1 is localized on the "wing tip" phosphorus atoms of the butterfly unit, we have investigated the reactivity towards Lewis-acidic transition metal fragments [9,10,11,12] or the coinage metal salts such as Cu(I), Ag(I) and
The results show that the attack of the phosphenium ion is exergonic, while the first decarbonylation of 3 is noticeably endergonic
Summary
The activation of small molecules such as N2 or P4 with reactive transition metal fragments or main group reactants is one of the important aspects of modern chemistry. The activation leads to a cage-like compound by insertion of a metal fragment as observed for example in [L2RhCl(η1:1-P4)] (L = PPh3, P(m-tol), P(p-tol), AsPh3) (I), the first reported polyphosphorus ligand complex (Scheme 1) [6]. A prominent example for main group electrophiles which have been used in the activation of P4 are phosphenium cations [R2P]+ (R = alkyl or aryl) which, in general, are too reactive to be isolated, but can be generated in situ by halogen abstraction from halogenophosphines with abstractors, such as, for instance GaCl3, silver or thallium salts in the presence of a suitable substrate to react with. The connectivity of the phosphorus cores of the two spin system could be determined by 31P-31P COSY NMR (homonuclear correlation spectroscopy) experiments and iterative simulations (Figure 2 and Supplementary Materials). HHyyddrrooggeenn aattoommss,, ssoollvveenntt mmoolleeccuulleess anndd ccoouunnteterrioinosnasrearoemiotmtedittfeodr mfoorremcloarreityc.laSreilteyc.teSdebleocnteddlebnognthds (lÅen)—gthFse4(-ÅP8)—2.2F7e546-P(58), 2F.2e735-P65(52),.2F4e638-(P55), 2F.e224-6P82(52).,2F58e27(-5P), F2e.215-P871(52.)3, 0F4e01(-5P), P25.3-P06402(.52)1,1P55(7-P),6P25.-2P17152(.179),1P6(57-)P, 7P52-.1P94126.(271)3, 4P(57-), PP422-P.231234.1(879),0P(72)-,PP322-P.168920.2(71),3P(62)-,PP622-P.217123.2(67)5,8P(72)-,PP132-.P287528.1(76)1,2P(73)-,PP832-.P146122.2(70)6,2P(37-)P, P462-.P270622.2(70)7, 1P(6-), PP782-P.27027.11(962),5P(78)-,PP742-P.11922.52(470),2P(74)-.P1 2.2402(7)
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