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The binuclear cyclometalates [Pt2Cl2{2-CMe2C6H4P(C6H4(2-iPr))2}2] (1a) and [Pt2Cl2{2-CMe2C6H3(4-OMe)P(C6H3(2-iPr)(4-OMe))2}2] (1b) react with CHCl2CHCl2 to give the corresponding mononuclear phosphine-alkene chelates [PtCl2{2-CH2═CMeC6H4P(C6H4(2-iPr))2}] (2a) and [PtCl2{2-CH2═CMeC6H3(4-OMe)P(C6H3(2-iPr)(4-OMe))2}] (2b). The product 2a can also be formed directly from [PtCl2(NCtBu)2] and La in CHCl2CHCl2 or by addition of SO2Cl2 to 1a. Addition of an excess of SO2Cl2 to 1b gave [PtCl2{2-CH2═CMeC6H3(4-OMe)P(C6H2(2-iPr)(4-OMe)(5-Cl))2}] (3b), a derivative of 2b featuring meta-chlorine substituents on the terminal P groups as a result of electrophilic aromatic substitution. A mechanism for the conversion of 1a,b to 2a,b is proposed involving an electrophilic alkyl C−H activation by a coordinatively unsaturated platinum(IV) species. The mechanism is supported by the isolation of the diplatinum(IV) cyclometalate [Pt2Cl2{2-CH2C6H3(4-OMe)P(C6H3(2-Me)(4-OMe))2}] as a mixture of syn and anti isomers 5b and 5b′. The crystal structures of 2a and 3b have been determined.

C 1-Symmetric phosphino/phosphonite ligands are prepared by the reactions of Ph 2P(CH 2) 2P(NMe 2) 2 with ( S)-1,1'-bi-2-naphthol (to give L A ) or ( S)-10,10'-bi-9-phenanthrol (to give L B ). Racemic 10,10'-bi-9-phenanthrol is synthesized in three steps from phenanthrene in 44% overall yield. The complexes [PdCl 2( L A,B )] ( 1a, b), [PtCl 2( L A,B )] ( 2a, b), [Rh(cod)( L A,B )]BF 4 ( 3a, b) and [Rh( L A,B ) 2]BF 4 ( 4a, b) are reported and the crystal structure of 1a has been determined. A (31)P NMR study shows that M, a 1:1 mixture of the monodentates, PMePh 2 and methyl monophosphonite L 1a (based on ( S)-1,1 '-bi-2-naphthol), reacts with 1 equiv of [Rh(cod) 2]BF 4 to give the heteroligand complex [Rh(cod)(PMePh 2)( L 1a )]BF 4 ( 5) and homoligand complexes [Rh(cod)(PMePh 2) 2]BF 4 ( 6) and [Rh(cod)( L 1a ) 2]BF 4 ( 7) in the ratio 2:1:1. The same mixture of 5- 7 is obtained upon mixing the isolated homoligand complexes 6 and 7 although the equilibrium is only established rapidly in the presence of an excess of PMePh 2. The predominant species 5 is a monodentate ligand complex analogue of the chelate 3a. When the mixture of 5- 7 is exposed to 5 atm H 2 for 1 h (the conditions used for catalyst preactivation in the asymmetric hydrogenation studies), the products are identified as the solvento species [Rh(PMePh 2)( L 1a )(S) 2]BF 4 ( 5'), [Rh(S) 2(PMePh 2) 2]BF 4 ( 6') and [Rh(S) 2( L 1a ) 2]BF 4 ( 7') and are formed in the same 2:1:1 ratio. The reaction of M with 0.5 equiv of [Rh(cod) 2]BF 4 gives exclusively the heteroligand complex cis-[Rh(PMePh 2) 2( L 1a ) 2]BF 4 ( 8), an analogue of 4a. The asymmetric hydrogenation of dehydroamino acid derivatives catalyzed by 3a, b is reported, and the enantioselectivities are compared with those obtained with (a) chelate catalysts derived from analogous diphosphonite ligands L 2a and L 2b , (b) catalysts based on methyl monophosphonites L 1a and L 1b , and (c) catalysts derived from mixture M. For the cinnamate and acrylate substrates studied, the catalysts derived from the phosphino/phosphonite bidentates L A,B generally give superior enantioselectivities to the analogous diphosphonites L 2a and L 2b ; these results are rationalized in terms of delta/lambda-chelate conformations and allosteric effects of the substrates. The rate of hydrogenation of acrylate substrate A with heterochelate 3a is significantly faster than with the homochelate analogues [Rh( L 2a )(cod)]BF 4 and [Rh(dppe)(cod)]BF 4. A synergic effect on the rate is also observed with the monodentate analogues: the rate of hydrogenation with the mixture containing predominantly heteroligand complex 5 is faster than with the monophosphine complex 6 or monophosphonite complex 7. Thus the hydrogenation catalysis carried out with M and [Rh(cod) 2]BF 4 is controlled by the dominant and most efficient heteroligand complex 5. In this study, the heterodiphos chelate 3a is shown to be more efficient and gives the opposite sense of optical induction to the heteromonophos analogue 5.

The hydroboration of phenyl vinyl sulfide with catecholborane (HBcat) and pinacolborane (HBpin) has been examined with a number of rhodium complexes, all of which proceed with excellent regiocontrol in favour of the branched product PhSCH(B(OR)2)CH3. The corresponding linear product can be obtained exclusively in reactions employing [Cp*IrCl2]2 and HBcat. Catalysed hydroborations of (E)-2-(p-toluenethio)styrene with HBcat using Rh(acac)(dppp) gave predominant formation of one product while reactions using HBpin afforded several products arising from a competing C–S bond cleavage (acac = acetylacetonato, dppp = 1,3-bis(diphenylphosphino)propane). Although reactions of phenyl vinyl sulfoxide were complicated by a competing deoxygenation reaction, hydroborations of phenyl vinyl sulfone using HBcat once again gave regioselective formation of either the branched or linear products, depending on the choice of catalyst used to effect this transformation. Catalysed hydroborations of phenyl vinyl sulfonate were less chemo- and regioselective, yielding hydrogenation and diboration products in addition to the two hydroboration product isomers. © 2007 Elsevier B.V. All rights reserved.

The first s-trans-1,3-diene complexes of a first-row transition metal have been prepared and characterized both in solution and in the solid state. The unexpected s-trans configuration was obtained from photolytic decarbonylation of Cp'Cr-(NO)(CO) 2 (Cp' = η 5 -C 5 H 5 and η 5 -C 5 Me 5 ) in the presence of conjugated dienes. Related η 2 -olefin and η 2 -2-alkyne complexes have also been prepared.

The first thermally stable chromium(III) η3-allyl complexes have been prepared. Oxidation of neutral cyclopentadienylchromium(II) dicarbonyl η3-allyl, η3-crotyl, and η3-cyclohexenyl complexes 1−3, ...

Thermally stable chromium(II) dicarbonyl complexes bearing substituted η3-allyl and η5-cyclopentadienyl ligands have been prepared via oxidative addition of the allyl bromide to tris(acetonitrile)t...

This study evaluates two groups of variables (economic and structural/locational) associated with US short- and long-run direct foreign investment (DFI) in the Caribbean over the 1983–1994 period. Separate generalized least square models for the Caribbean and Latin America were estimated to determine whether differences existed between the two regions as to the variables associated with the levels of DFI. This helped provide insights as to the strategies that should be maintained or introduced to give the Caribbean a competitive edge in attracting the limited amounts of US DFI likely to be available for investment in the Western hemisphere.

Condensation of 2-aminophenol with boronate ester derivatives of benzaldehyde afforded the corresponding boron-containing Schiff bases, 2-HOC6H4N=C(H)C6H4R (1a: R = 2-Bpin; 1b: R = 3-Bpin; 1c: R = 4-Bpin; pin = 1,2-O2C2Me4). Crystals of 1b were triclinic, space group P[Formula: see text], a = 11.9420(6), b = 13.0871(7), and c = 13.2720(7) Å, α = 70.983(1), β = 67.793(1), and γ = 78.380(1)°, Z = 2. Reaction of 2-aminophenol with 2-HC(O)C6H4B(OH)2 in EtOH, however, gave a macrocyclic dimer 2 with a OBOBO structural unit. The molecular structure of this dimer has been confirmed by an X-ray diffraction study. Crystals of 2 were monoclinic, space group P21/c, a = 10.0447(8), b = 21.0894(15), and c = 12.6214(9) Å, β = 105.301(2)°, Z = 4. Further reaction of these Schiff bases with manganese triacetate in toluene afforded 2-arylbenzoxazoles 3a–c via an oxidative cyclization pathway. The molecular structure of the 4-Bpin derivative (3c) was characterized by an X-ray diffraction study. Crystals of 3c were monoclinic, space group P21/n, a = 6.5392(3), b = 16.3330(8), and c = 16.1942(8) Å, β = 97.9620(10)°, Z = 4.Key words: boron heterocycles, Schiff bases, arylbenzoxazoles.

Addition of 3-H2NC6H4Bpin (pin = 1,2-O2C2Me4) to a series of aldehydes and 4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)acetophenone afforded the corresponding benzylideneamines in moderate to high yields. Hydroboration of these imines with catecholborane (HBcat, cat = 1,2-O2C6H4) at room temperature gives, upon aqueous workup, the corresponding borylamines. An X-ray diffraction study was carried out on imine 1h derived from 9-anthraldehyde and 3-H2NC6H4Bpin. Crystals of1h were triclinic, a = 9.6793(4) Å, b = 10.7397(4) Å, c = 11.5353(4) Å, α = 105.1890(10)o, β = 97.3030(10)o, γ = 102.1480(10)o, Z = 2 with space group P[Formula: see text] and crystals of N-[3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl]-4-methoxybenzylamine 2c were orthorhombic, a = 8.6612(4) Å, b = 10.3794(4) Å, c = 20.6033(9) Å, Z = 4 with space group P212121. Amines have been tested for their antifungal properties against Aspergillus niger and Aspergillus flavus.Key words: benzylamines, boronate esters, aminoboron, hydroboration, antifungal.

On-farm research (OFR) has increased in popularity in the U.S. in recent years due to heightened interest in sustainability issues, the likely decline in resources available for agricultural research, and increasing pressures for accountability and responsiveness to state and local needs. Information relating to OFR was obtained from 431 commercial Kansas farmers. Data were analyzed to determine the degree of OFR being implemented, and three models were estimated to identify which farmer/farm characteristics influenced its implementation. The results indicate that OFR is commonly implemented, and that several farm/farmer characteristics are related to the degree of OFR initiated. It is proposed that to maximize the return from externally initiated OFR, there would be merit in focusing attention on farms/farmers with those characteristics.

α-Thioboronate esters are obtained directly in high yield and selectivity from metal-catalyzed additions of B−X bonds (X = H, B) to thiocarbonyl compounds and vinyl sulfides.

Addition of 3-H2NC6H4Bpin (pin = 1,2-O2C2Me4) to a series of aldehydes and 4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)acetophenone afforded the corresponding benzylideneamines in moderate to hi...