Oligomerization of Terminal Phosphinidene Complexes

Abstract

The thermolysis of a 7-phenyl-7-phosphanorbornadiene pentacarbonylchromium complex yields a mixture of the cyclic trimer and tetramer of [PhP-Cr(CO) 5 ]. In the presence of CuCl and W(CO) 6 at 60 °C, the decomposition of 7-R-7-phosphanorbornadiene pentacarbonyltungsten complexes affords the corresponding diphosphene σ,π complexes [RPdPR][W(CO) 5 ] 3 (R = Me, CH 2 CH 2 CO 2 Et, 2-thienyl, 2-N-methylpyrrolyl). The Me derivative has been characterized as its [4þ2] cycloadduct with 2,3-dimethylbutadiene. The three others have been characterized by X-ray crystal structure analysis, NMR, and UV, and the electronic structure of the thienyl derivative has been studied by DFT calculations.

Simple Access to Tungsten-Stabilized Disecondary Diphosphines

“…Both THF and CuCl are necessary to obtain a satisfactory yield of the diphosphine complex 2a , which is obtained as a 1:1 mixture of the meso and rac diastereomers that have been described in our previous paper . Since copper chloride favors the formation of diphosphene complexes and since bulky diphosphenes are known to be reducible to the corresponding diphosphines, it was tempting to suspect that the phosphinidene species only sluggishly inserts into the B–H bond at 60 °C (the insertion is normally performed at 110 °C) and prefers to dimerize to give the diphosphene, which is then cleanly reduced by the borane adduct. THF is absolutely necessary to perform the reaction depicted in eq .…”

“…The mechanism of the reduction of PP by BH 3 L probably involves a nucleophilic attack of the negative boron onto the double bond, which is favored by THF. The probable intermediacy of the phosphinidene dimer has been proven by replacing 1a by the preformed diphosphene complex 4 (eq ). …”

“…Silica gel (200–300 mesh) was used for the chromatographic separations. The 7-phosphanorbornadiene complexes 1a – d were prepared according to literature methods. ,, Commercially available reagents were used without further purification.…”

Low temperature isolation of a dinuclear silver complex of the cyclotetraphosphane [ClP(μ-PMes*)]2

“…7 Interestingly, despite the indisputable importance of phosphorus compounds as ligands in catalysis, 8 the coordination chemistry of homologous P 4 ring systems (cyclotetraphosphanes) has received much less attention. Examples include mainly P 4 R 4 systems (A, Scheme 1; R = organic substituent) which coordinate to transition metal fragments such as metal carbonyls, [9][10][11][12][13] metal halides 14 or phosphane substituted metal complexes. 15 The coordination chemistry of unsubstituted P n scaffolds, on the other hand, is more versatile; 16,17 in particular, there are numerous examples of coordination to P 4 , which can adopt either a tetrahedral (B1, B2), [18][19][20][21][22] bicyclic (C1, C2) [23][24][25][26] or rectangular/square planar structure (D1-D3) [27][28][29][30][31] in the complex (Scheme 1).…”