Synthesis of Metallacycles with Reactive Metal‐Carbon σ Bonds

Abstract

to R = 0.046 We are grateful lo Dr. K. P e r m and Prof. H. GI i'on S<hncnng. Max-Planck-lnstitut fur Fe\tkiirperforschung Stuttgart. for the diffractometer measurements. Wc 'ire gratetul to Dipl.-Chem. J. C. Wuhrmunn for recording the "C-NMR spectrum. M R. ChurchiN. R. Mu.son. Adv. Organomet. Chem. 3. 93 (1967). and reference\ cited therein. Metallacycloalkane derivatives play a n important role in the activation of C H bonds12' and in transition-metal catalyzed reactions"'. Most of these heterocycles have so far only been obtained with various Group 8 metals'4'. A new general procedure now also permits the synthesis of metallacycloalkanes with other metals, such as those from Group 7 whose weak metal-carbon u bonds ensure that the products are highly reactive. Synthesis of Metallacycles withp-Hydrogen elimination is avoided by performing the reaction in such a way that simultaneous a , w attack of the difunctional alkylphosphane takes place on the metal (with elimination of CO and MgCIBr). The metallacycles (I) are surprisingly stable owing to the chelate effect; they can be sublimed in a high vacuum, melt above 110 " C (except (Ic)), and dissolve in all the common organic solvents. They were characterized by complete elemental analysis, IR, and mass spectra (Table 1). Further characterization of (fa) was by Xray crystal structure analysis1" (Fig. 1) and by its "C('H1-NMR spectrum CnD6, rel. to TMS: 6=18.1 (s; C-4), 31.0 (d, J = 15 Hz; C-3). 34.6 (d, J = 2 9 Hz; C-5).

Secondary Coordination Sphere Alkylation Promotes Cyclometalation

“…Crystals of 6 were grown from a saturated pentane solution at −35 °C and analyzed by scXRD (Scheme ). The solid-state structure confirmed that one of the allyl moieties on the tape ligand had been activated, presumably through a transient (and unobserved) [Fe]–H intermediate, possibly via β-(allyl)carbon atom attack, which has been previously documented; related five-membered ring-systems (−MPCH 2 CH 2 CH 2 −) have also been reported. − Promiscuity of the tape ligand is further showcased by halide abstraction from 3 , which gives the η 2 -alkene complex, 7  31 P­{ 1 H} NMR signatures at δ P = + 83.0 and −8.3 ppm ( 2 J P–P = 59.6 Hz), in addition to a connectivity map provided by X-ray crystallography, buttress this assignment (Scheme ). …”

Technetium and Rhenium

“…464 - 480 We know of no reports for technetium in this category. The chemistry of rhenium is both interesting and varied although it represents only a small part of this area which has seen rapid growth in the last few years.…”

“…477 Two series of metallo-alicyclic derivatives are obtained in the reaction of [Re{P(O)R 2 j(CO) 4 ]2~ with (CH 2 ) W (CH 2 OS(O) 2 CF 3 ) 2 (n = 1 or 2) 478 ' 479 or in the reaction of [ReBr(CO) 5 ] with Ph 2 P(CH 2 ) n MgBr (« = 3 or 4). 480 These five-and six-membered metallocycles engage in SO 2 and CO insertions, 290 ' 480 (see also Section 30.6.6). For the latter, assistance of Al 2 Br 6 is required which yields the adduct (91); hydrolysis of this intermediate gives the acyl product listed next to it in Table 14.…”