Arnold J. Smith

The crystal structure of a µ-phenolato copper(II) dinuclear complex containing two chemically distinct metal co-ordination environments

The crystal structure of [L1Cu2(µ-Br)(µ-HCO2)]2[Cu2Br4](3) is reported, where HL1 is the Schiff base derived from the condensation of 2-aminomethylpyridine and 2-[(N-diethylaminoethyl-N-ethyl)aminomethyl]-4-bromo-6-formylphenol (1); the structure comprises a copper(II) dinuclear cation with phenolate, bromide, and formate bridges in which the metals have different co-ordination environments, and a copper(I) dinuclear dianion with bromide bridges.

Synthesis and characterisation of disubstituted di-µ-methylene-bis(η-pentamethylcyclopentadienyl)dirhodium(IV) complexes; X-ray structure of [{(C5Me5)Rh}2(µ-CH2)2(CO)2]2+

Reaction of either cis- or trans-[{(C5Me5)Rh}2(µ-CH2)2Me2] with HCl in pentane gave the trans-dichloro-complex [{(C5Me5)Rh}2(µ-CH2)2X2](4a; X = Cl), from which a variety of other complexes (4; X = Br, I, SCN, N3, CN, or NCO) were made by metathesis. Reaction of (4a; X = Cl) with neutral ligands (L) in the presence of non-co-ordinating anions gave first the monocations, [{(C5Me5)Rh}2(µ-CH2)2(L)Cl]+, and then the dications, [{(C5Me5)Rh}2(µ-CH2)2L2]2+(5; L = MeCN, CO, or H2O). The X-ray crystal structure of (5b; L = CO) shows the trans configuration predicted on the basis of the 1H n.m.r. spectra. Reaction of (5b) with methanol and base gave the bis(methoxycarbonyl) complex [{(C5Me5)Rh}2(µ-CH2)2(CO2Me)2]. cis Complexes [{(C5Me5)Rh}2(µ-CH2)2X]n+(X = O2CMe or O2CCF3, n= 1; X = pyridazine or Ph2PCH2PPh2, n= 2) were isolated and identified by their 1H n.m.r. spectra which showed the diastereotopic methylene protons as two resonances, only one of which was coupled to the rhodiums. The nitrate complex [{(C5Me5)Rh}2(µ-CH2)2(NO3)2] was found to exist as two isomers, one trans and the other cis with one bridging and one ionic nitrate, as shown by the n.m.r. spectra.

The selective reduction of benzene to cyclohexene mediated by platinum metal complexes: X-ray crystal structure of [(η5-C5Me5)Ir(η5-C6H6CH2NO2)][BF4]

The dicationic η6-benzene complexes [(CnMen)M(C6H6)]2+[M = Rh, n= 5 (2a); M = Ir, n= 5 (2b); M = Ru, n= 6 (2c)] are reduced by tetrahydroborate to the η5-cyclohexadienyl complexes [(CnMen)M(C6H7)]+(3) which are further reduced to the η4-cyclohexadiene complexes [(CnMen)M(C6H8)](4). Reaction of complexes (4) with acid gives cyclohexene with 100% selectivity; when the reaction is carried out with tetrafluoroboric acid in benzene, the initial benzene complexes (2) are regenerated. The overall reaction consists of addition of two hydrides followed by two protons to co-ordinated benzene, and a cycle catalytic in the platinum metal can be constructed. The efficiency of the overall reduction of benzene to cyclohexene decreases in the order Ir > Ru > Rh. The reaction is compared to the reduction of benzene to cyclohexane mediated by rhodium, iridium, and ruthenium trichloride hydrates and tetrahydroborate in ethanol. Other nucleophiles also attack the benzene ring in (2b): these include methyl-lithium (which gives two dimethylcyclohexadiene complexes from which isomeric dimethylcyclohexenes can be obtained with acid), methoxide (which gives the methoxycyclohexadienyl and, with an excess, two dimethoxycyclohexa-1,3-diene complexes), and nitromethane which in the presence of base gives the nitromethylcyclohexadienyl complex [(C5Me5)Ir(C6H6CH2NO2)][BF4](9). The single-crystal X-ray structure determination of (9) shows the C5Me5 and the C6 ring both to be η5-bonded, and the CH2NO2 substituent to, be in the exo position on the η5-cyclohexadienyl ring. Analysis of the high-field1H n.m.r. spectra of the complexes showed that exo attack on the C6 ring occurred with all the nucleophiles. In the presence of base, (9) reacted further with (2b) to give [{(C5Me5)Ir(C6H6)}2CHNO2]2+. These reactions show the versatility of the reduction procedure.

The reactions of the tri-µ-hydroxo-bis[η6-p-cymeneosmium(II)] cation with aldehydes and acids and the homogeneously catalysed oxidation of acetaldehyde and propionaldehyde with water. X-Ray structure of [(p-MeC6H4CHMe2)2Os2(µ-HCO2)(µ-OH)(µ-H)][PF6]

Reaction of [(p-MeC6H4CHMe2)2Os2Cl4] with sodium hydroxide in water gave the tri-µ-hydroxo cation [(p-MeC6H4CHMe2)2Os2(µ-OH)3]+, isolated as PF6(1a) or BPh4(1b) salts. Complex (1a) reacted with formaldehyde, acetaldehyde, or propionaldehyde to give the complexes [(p-MeC6H4CHMe2)2Os2(µ-RCO2)(µ-OH)(µ-H)][PF6][R = H (2a), Me (2b), Et (2c)], and with cinnamaldehyde, benzaldehyde, or pivaldehyde to give the complexes [(p-MeC6H4CHMe2)2Os2(µ-RCO2)(µ-OH)2][PF6][R =trans-PhCHCH (3a), Ph (3b), But(3c)]. Reaction of (1a) with carboxylic acids gave (3; R =trans-PhCHCH, Ph, Me, or H). Complex (1a) catalysed the oxidation of acetaldehyde and propionaldehyde by water to the corresponding carboxylic acids; hydrogen was also produced. This reaction was slower but more selective than the previously reported ruthenium-catalysed reaction. The complexes have been characterised by microanalysis and i.r. and 1H n.m.r. spectra. A single-crystal X-ray diffraction study on complex (2a) confirmed the proposed structure.

Polythiolated complexes. Part 2(1). Palladium(II) and platinum(II) derivatives of polyfluorophenylthiolates

SummaryThe preparation and characterization of the new thiolate complexes [M(SR)2(SEt2)2] (M=Pt, R=C6F5 orp-C6HF4) and [M(SR)2]n (M=Pd, R=C6F5,p-C6HF4 orp-C6H4F; M=Pt, R=p-C6H4F) is discussed. The tendency to form polymeric, rather than monomeric species, varies as follows: Pd>Pt; C6H4F>C6HF4> C6F5. [Pt(SC6F5)2(SEt2)2] has atrans square planar coordination.

The reactions of di-µ-methylene-bis(pentamethylcyclopentadienyl)-dirhodium(IV) complexes with benzylmagnesium chloride and with alkynylmagnesium chloride; X-ray structure of [(η5-C5Me5)Rh(CH2Ph)(µ-CH2)2Rh(η4-C5Me5CH2Ph)]

Reaction of trans-[(C5Me5)2Rh2(µ-CH2)2Cl2](1) with RCCMgCl gave trans-[(C5Me5)2Rh2(-µ-CH2)2(RC2)2](R = Ph or But). However attack on (1) by benzylmagnesium chloride occurred at one C5Me5 ring as well as at one rhodium to give [(η5-C5Me5)Rh(CH2Ph)(µ-CH2)2Rh(η4-C5Me5CH2Ph)](6). The structure of (6) has been deduced by n.m.r. spectroscopy and confirmed by a single-crystal X-ray structure determination which showed the two rhodiums [2.559(3)A apart] to be linked by two µ-methylene bridges. One rhodium (oxidation state formally +4) bears a σ-benzyl and an η5-C5Me5 ring; the other rhodium (formally +2) is η4-bound to C5Me5CH2Ph where the benzyl on the C5 ring is exo to the metal. Reaction of [(C5Me5)2Rh2(η-CH2)2(MeCN)2][PF6]2 with R′CCH gave a complex [(C5Me5)2Rh2(µ-CH2CHCR′CHCR′CH)]PF6(7)(R′=p-chlorophenyl); on the basis of the n.m.r. spectra it is proposed that the two rhodiums are linked by a σ,σ,η5-CH2CHCR′CHCR′CH bridge. The mode of formation of these complexes is discussed.

The cyclometallation of benzoic acid to give rhodium, iridium, and osmium C,O-benzoates. X-Ray structure determination of the dibenzoate [(C5Me5)Rh(OOCPh)2(H2O)]

The cyclometallated benzoate complexes [(C5Me5)[graphic omitted]H4)(Me2SO)][M = Rh (1a) or Ir (1b)] and [(p-MeC6H4CHMe2)O[graphic omitted]C6H4)(Me2SO)] were prepared by reaction of [(C5Me5)MMe2(Me2SO)] or [(p-MeC6H4CHMe2)OsMe(Cl)(Me2SO)] with benzoic acid or silver benzoate respectively. Methane was formed in these reactions. Complex (1b) was also prepared from [(C5Me5)IrCl2( Me2SO)] with silver benzoate. Complex (1a) reacted with water to give [{(C5Me5)Rh}2(µ-OH)3][OOCPh] and the dibenzoate hydrate [(C5Me5)Rh(OOCPh)2(H2O)](5a). Complex (5a) was also formed when (1a) was reacted with benzoic acid or when [(C5Me5)RhCl2(Me2SO)] reacted with two equivalents of silver benzoate. The structure of (5a) was determined by an X-ray study which showed two benzoates attached in a monodentate manner to the (C5Me5)Rh moiety; the rhodium also bore a co-ordinated water, which was also hydrogen-bonded to the two benzoate carbonyl oxygens. Both the rhodium and the iridium complexes (1a) and (1b), reacted with methyl iodide to give the cyclometallated methyl benzoate complexes [(C5Me5)[graphic omitted]H4}(I)]. They also underwent carbonylation to give phthalic anhydride and [(C5Me5)]Rh(CO)2 from (1a), and [(C5Me5)I[graphic omitted]H4)(CO)] from (1b). Mechanismsofthe various transformations are discussed.

The synthesis and structure determination of a novel η6-arenerhodium(III) complex, [(Me2SiC6H5)4Rh2H2], and the synthesis of [(Me2SiC6H5)4Ir2H2]

Abstract Reaction of Me 2 PhSiH (DMPS) with [(indenyl)Rh( 2 H 4 ) 2 ], [{CODRhCl}], or [{CODRh(OMe)} 2 ] in the presence of benzoyl peroxide, gave [(Me 2 SiC 6 H 5 ) 4 Rh 2 H 2 ], ( 1a ); reaction of [{CODIr(OMe)} 2 ] in the presence of benzoyl peroxide, gave [(Me 2 SiC 6 H 5 ) 4 Ir 2 H 2 ] ( 1b ) similarly. The X-ray structure of 1a showed the molecule to be a centrosymmetric dinuclear complex, each rhodium being η 6 -bonded to a phenyldimethylsilyl (RhC(phenyl) av. 2.33 A) which was in turn σ-bonded to the other rhodium through the silicon (RhSi 2.294(6) A). In addition each rhodium bore another σ-bonded PhMe 2 Si (RhSi 2.328(6) A) and a hydride ligand. The rhodiums were 4.48 A apart and not bonded. Complexes 1a and 1b were rather insoluble and inert..

Unsymmetric dicopper(II) complexes of dinucleating ligands bearing chemically distinct co-ordination environments

Dicopper(II) complexes of unsymmetrical dinucleating Schiff-base ligands bearing chemically distinct co-ordination sites have been prepared and their properties studied. The ligands were derived from the condensation of 4-bromo-2-formyl-6-(4-methylpiperazin-1-ylmethyl)phenol and 4-bromo-2-[(2-diethylaminoethyl)ethylaminomethyl]-6-formylphenol with 2-(aminomethyl)pyridine, 2-(2-aminoethyl)pyridine, and 2-(aminomethyl)-4-nitrophenol.

The cyclometallation of benzoic acid and the X-ray crystal structure of [C5Me5Ir(O2CC6H4)(Me2SO)]

The complexes [C5Me5M(C6H4CO2)(Me2SO)](1a, M = Rh; 1b, M = Ir), and [(p-cymene)Os(C6H4CO2)(Me2SO)], containing cyclometallated benzoic acid, have been prepared and characterised; carbonylation of (1a) yields phthalic anhydride.