The bis-arylated phosphazene compounds [HN(PPh2NAr)2] (Ar = phenyl (HL1), 2,6-dimethylphenyl (HL2), 2,6-diisopropylphenyl (HL3)) and the imidodiphosphinate compound HN(PPh2O)2 (HL4) have been prepared via the Staudinger reaction. Treatment of the neutral compounds HL1, HL2, and HL3 with Ln(CH2SiMe3)3(THF)2 (Ln = Sc, Y, Lu) generated the solvent-free bis(alkyl) complexes L1Ln(CH2SiMe3)2 (Ln = Sc (1a), Y (1b), Lu (1c)), L2Sc(CH2SiMe3)2 (2a), L3Y(CH2SiMe3)2 (3b), and L3Lu(CH2SiMe3)2 (3c), respectively. The reaction between HL4 and Y(CH2SiMe3)3(THF)2 gave the rare zwitterionic complex 4b. Lithiation of the ligand HL1 by nBuLi followed by a metathesis reaction with Nd(BH4)3(THF)3 afforded the corresponding complex L1Nd(BH4)2(THF)2 (5). Complexes 1 upon incorporation of [Ph3C][B(C6F5)4] and AliBu3 led to ternary systems that initiated isoprene polymerization with high activities, among which complex 1a was the first example of a scandium catalytic precursor providing trans-1,4-selectivity (90.0%), while the lutetium analogue 1c had medium trans-1,4-selectivity (54.3%) and the yttrium complex 1b exhibited high cis-1,4-selectivity (76.3%). The ternary system based on the zwitterion 4b displayed the highest activity for the isoprene polymerization among these complexes and gave cis-1,4-regularity-enriched polyisoprene (70.6%). Highly stereospecific homopolymerizations of isoprene (trans-1,4-content: 97.0%) and butadiene (trans-1,4-content: 94.0%) were achieved by using the borohydrido complex 5 upon the activation of dibutylmagnesium. The copolymerization of isoprene and butadiene with 1a/[Ph3C][B(C6F5)4/AliBu3] gave randomly arranged trans-1,4-regulated polybutadiene and polyisoprene sequences. The kinetics study displayed competitive polymerization rates of r BD = 2.89 and r IP = 0.41. The thermal behaviors of the (co)polymers were investigated.

Alkylation of iridium 5,10,15,20-tetrakistolylporphyrinato carbonyl chloride, Ir(ttp)Cl(CO) (1), with 1°, 2° alkyl halides was achieved to give (ttp)Ir-alkyls in good yields under air and water compatible conditions by utilizing KOH as the cheap reducing agent. The reaction rate followed the order: RCl < RBr < RI (R = alkyl), and suggests an SN2 pathway by [Ir(I)(ttp)](-). Ir(ttp)-adamantyl was obtained under N2 when 1-bromoadamantane was utilized, which could only undergo bromine atom transfer pathway. Mechanistic investigations reveal a substrate dependent pathway of SN2 or halogen atom transfer.

No abstract

Alkylation of rhodium porphyrins was achieved in moderate to high yields in the presence of air and water. With this facile alkylation method, various alkyl Rh III (por) species, including those with tertiary alkyl, were synthesized. Mechanistic investigations suggest a parallel S N 2 via [Rh I (ttp)] − with halogen atom transfer pathway via [Rh II (ttp)] • . ■ INTRODUCTIONRhodium porphyrin alkyls ( Figure 1) play an important role in catalysis. They are precursors of [Rh II (por)] • (por = porphyrinato dianion) metalloradicals for carbon−hydrogen bond 1 and carbon−carbon single bond activation. 1d,2 Activation of these strong bonds has gained much current interest for more efficient utilization of hydrocarbons. 3 To the best of our knowledge, only primary and secondary alkyl Rh III (por) species have been reported so far. Tertiary alkyl Rh III (por) species remain unknown, which may be of great interest in investigating its role in catalysis. Hence, developing robust methods to access alkyl Rh III (por) species, especially tertiary alkyl Rh III (por) species, is important.The synthesis of rhodium porphyrin alkyls was first reported by Ogoshi in 1972 by the reaction between Rh III (oep)Cl (oep =2,3,7,8,12,13,17,18-octaethylporphyrinato dianion) and MeLi (Scheme 1a). 4 A more versatile method involves the reduction of Rh III (por)Cl by NaBH 4 to generate [Rh I (por)] − . [Rh I (por)] − then undergoes nucleophilic substitution with alkyl halides to give the corresponding rhodium porphyrin alkyls (Scheme 1b). 5 In 1986, Kadish and co-workers reported the Rh−C bond formation by the electrochemically generated monomeric species [Rh II (tpp)] • (tpp = 5,10,15,20-tetraphenylporphyrinato dianion) (Scheme 1c). 6 In 1990, Wayland discovered the formation of Rh−C bond by carbon−hydrogen bond activation of CH 4 and toluene to give Rh(por)Me and Rh(por)Bn (Scheme 1d). 1a,b The carbon−oxygen bond cleavage of methanol by Rh III (ttp)Cl (ttp =5,10,15,20-tetratolylporphyrinato dianion) in alkaline media was discovered to give a high yield of Rh III (ttp)Me and was reported by Chan in 2009 (Scheme 1e). 7 In 2010, Chan and co-workers found the formation of the Rh−C bonds by carbon−nitrogen bond activation (CNA) of amines (Scheme 1f). 8 This CNA method, further developed by the Dong group, tolerates air and water by utilizing ammonium salts as the alkylating agents (Scheme 1g). An S N 2-like reaction pathway involving a [Rh I (por)] − intermediate was proposed. 9 These reported methods are unlikely to prepare a tertiary alkyl Rh III (por) species due to the steric hindrance. Herein, we disclose a facile Figure 1. Structure of rhodium porphyrin alkyls. Scheme 1. Synthesis of Rhodium Porphyrin AlkylsArticle pubs.acs.org/Organometallics

No abstract

A series of group 9 metal tetra(ptolyl)porphyrin (M(ttp), M = Co(II), Rh(III), Ir(III)) complexes with axial phenyl substituents have been synthesized and characterized. An aryl bromide cleavage reaction of transition metal complexes was used to prepare the complexes from Co(ttp), Rh(ttp)Cl and Ir(ttp)COCl, respectively. Magnetic circular dichroism (MCD) spectroscopy and TDDFT calculations have been used to study trends in the optical spectra and electronic structures. The effect of introducing different parasubstituents on the phenyl substituents was examined. During fluorescence emission studies, phosphorescence was observed for the Ir(III) complexes in the near infrared (NIR) region.