Ring Expansion of Spirocyclic Cyclobutenylidene Ligands in Pentacarbonylchromium Complexes to Tetrahydroindene Derivatives

Abstract

Pentacarbonyl(pentamethylenevinylidene)chromium, [(CO),Cr=C=C(CH,),] (l), reacts with l-methylthio-l-propyne (2a) and N-( 1-propyny1)phenothiazine (2b) by regiospecific addition of the C=C bond of the alkyne to the C=C bond of the vinylidene ligand of 1. Initially, complexes with a spirocyclic cyclobutenylidene ligand are formed, [(CO) Previously, we described the synthesis of n-donor-substituted cyclobutenylidene complexes and cyclobutenones from pentacarbonyl(viny1idene) complexes of chromium and tungsten and electron-rich alkynes such as l-diethylamino-and l-ethoxy-l-pr~pyne [~~]. We now report on the preparation of pentacarbonylchromium complexes with a spirocyclic cyclobutenylidene ligand, the thermal rearrangement of the cyclobutenylidene ligands to substituted 4,5,6,7-tetrahydroindenes and the decomplexation of N-(2-methyl-4,5,6,7-tetrahydroindenyl)phenothiazine. Results and DiscussionThe starting pentamethylenevinylidene complex (l)IZ4] was generated by the reaction sequence shown in Scheme 1. Reduction of Cr (C0) At O"C, complex 1 rapidly reacts with l-methylthio-lpropyne (2a) in n-pentaneldichloromethane to give the 2-methyl-4,5,6,7-tetrahydroindenyl(methyl)thioether complex 4. Complex 4 is presumably formed by an initial regiospecific cycloaddition of the C=C bond of 2a to the C=C bond of 1 and subsequent ring expansion of the resulting 3-methylthio-substituted cyclobutenylidene complex 3 (vide infra) (Scheme 2). [2 + 21 cycloaddition of alkynes to the C=C bond of pentacarbonyl(viny1idene) complexes was also observed in the reactions of ynamines and alkoxypropynes with (C0)5M=C=CR2 (M = Cr, W R = alkyl,

Zwitterionic adducts from addition of imines to the α-carbon atom of pentacarbonyl(vinylidene)chromium and -tungsten complexes

“…Reduction of [Cr(CO) 6 ] with potassiumgraphite (C 9 K 2 ) laminate in THF at 0°C gave K 2 [Cr(CO) 5 ] [10]. Subsequent reaction with isobutyryl chloride afforded potassium pentacarbonyl(isobutyryl)chromate which was then transformed into 4 by reaction with trifluoroacetic acid anhydride in CH 2 Cl 2 at −78°C [11]. Complex 4 is unstable and rapidly decomposes in solution at room temperature.…”

“…3.6. Pentacarbonyl [4,5-dihydro-2-methylthiazole-N]tungsten (11) At −30°C 0.36 ml (0.23 mmol) of 2-methyl 4,5-dihydrothiazole (8a) is added to the highly concentrated solution of the alkyne complex [(CO) 5 W(H -C C -Ph)]. The solution is stirred and gradually warmed to r.t.…”

“…11: C 9 H 7 NO 5 SW, molecular mass (425.1), crystal size 0.28× 0.28× 0.28 mm 3 (obtained by recrystallization from pentane); crystal system monoclinic, space group P2 1 /c, a= 9.648 7 The measurements were performed at − 44°C (6), − 34°C (9a), −35°C (11) with a crystal mounted in a glass capillary on a Siemens P4 diffractometer (graphite monochromator, Mo -K a radiation, u= 0.71073 A , ). The structures were solved by Patterson methods (6, 9a) or by direct methods (11) using the SHELXTL PLUS (VMS) program package. The positions of the hydrogen atoms were calculated by assuming ideal geometry (d C-H = 0.96 A , ), and their coordinates were refined together with those of the attached C atoms as 'riding model'.…”

Aminolysis of 3-alkoxysubstituted cyclobutenylidene complexes. A novel convenient route to chiral 3-aminosubstituted cyclobutenylidene complexes

“…Elemental analyses: Heraeus CHN-O-RAPID. The vinylidene complexes 1a [10], 1b [1], 1c [9], the 3-ethoxy-cyclobut-2-en-1-ylidene complexes 3a [3], the alkyne 2 [13] and the amines (R)-5 [14] and (S)-7 [15] were prepared according to literature procedures. All other compounds were commercially available and were used without further purification.…”

A unusual bridging mode of vinylidene ligands in nonacarbonyl(vinylidene)dichromium complexes

“…For instance the reactions with ynamines and alkoxyacetylene afforded 3-amino-and 3-alkoxy-substituted cyclobutenylidene complexes, respectively [4 Á/6], those with alkynyl complexes gave bi-, tri-and tetra-nuclear complexes with bridging cyclobutenylidene ligands [7,8]. Monosubstituted pentacarbonyl(vinylidene)chromium complexes, [(CO) 5 Cr Ä/C Ä/ C(R)H], were also proposed as intermediates in the synthesis of 2-azetidin-1-ylidene complexes by reactions of imines and carbodiimides with pentacarbonyl[hydroxy-(methyl)carbene]chromium (R 0/H) [9], tetramethylammonium acetyl(pentacarbonyl)chromate toluene-4-sulfonyl chloride [10,11] and alkyne(pentacarbonyl)chromium complexes [12,13], respectively. In contrast, disubstituted vinylidene complexes add imines to the a-carbon atom of the vinylidene ligand to form zwitterionic adducts [14].…”