N,N-Diborylamines have emerged as promising reagents in organic synthesis; however, their efficient preparation and full synthetic utility have yet to be realized. To address both shortcomings, an effective catalyst for nitrile dihydroboration was sought. Heating CoCl 2 in the presence of PyEt PDI afforded the six-coordinate Co(II) salt, [( PyEt PDI)CoCl][Cl]. Upon adding 2 equiv of NaEt 3 BH, hydride transfer to one chelate imine functionality was observed, resulting in the formation of (κ 4 -N,N,N,N-PyEt IP CHMe N EtPy )Co. Single-crystal X-ray diffraction and density functional theory calculations revealed that this compound possesses a low-spin Co(II) ground state featuring antiferromagnetic coupling to a singly reduced imino(pyridine) moiety. Importantly, (κ 4 -N,N,N,N-PyEt IP CHMe N EtPy )Co was found to catalyze the dihydroboration of nitriles using HBPin with turnover frequencies of up to 380 h −1 at ambient temperature. Stoichiometric addition experiments revealed that HBPin adds across the Co−N amide bond to generate a hydride intermediate that can react with additional HBPin or nitriles. Computational evaluation of the reaction coordinate revealed that the B−H addition and nitrile insertion steps occur on the antiferromagnetically coupled triplet spin manifold. Interestingly, formation of the borylimine intermediate was found to occur following BPin transfer from the borylated chelate arm to regenerate (κ 4 -N,N,N,N-PyEt IP CHMe N EtPy )Co. Borylimine reduction is in turn facile and follows the same ligand-assisted borylation pathway. The independent hydroboration of alkyl and aryl imines was also demonstrated at 25 °C. With a series of N,N-diborylamines in hand, their addition to carboxylic acids allowed for the direct synthesis of amides at 120 °C, without the need for an exogenous coupling reagent.

The formally zero-valent Mn dimer [( Ph2PEt PDI)Mn] 2 has been synthesized upon reducing ( Ph2PEt PDI)MnCl 2 with excess Na/Hg. Single crystal X-ray diffraction analysis has revealed that [( Ph2PEt PDI)Mn] 2 possesses a κ 4 -PDI chelate about each Mn center, as well as η 2 -imine coordination across the dimer. The chelate metrical parameters suggest single electron PDI reduction and EPR spectroscopic analysis afforded a signal consistent with two weakly interacting S = 1 / 2 Mn centers. At ambient temperature in the absence of solvent, [( Ph2PEt PDI)Mn] 2 has been found to catalyze the hydrosilylation of aldehydes at loadings as low as 0.005 mol % (0.01 mol % relative to Mn) with a maximum turnover frequency of 9,900 min −1 (4,950 min −1 per Mn). Moreover, the [( Ph2PEt PDI)Mn] 2 -catalyzed dihydrosilylation of formates has been found to proceed with turnover frequencies of up to 330 min −1 (165 min −1 relative to Mn). These metrics are comparable to those described for the leading Mn catalyst for this transformation, the propylene-bridged variant ( Ph2PPr PDI)Mn; however, [( Ph2PEt PDI)Mn] 2 is more easily inhibited by donor functionalities. Carbonyl and carboxylate hydrosilylation is believed to proceed through a modified Ojima mechanism following dimer dissociation.

Heating (THF)2MnCl2 in the presence of the pyridine-substituted bis(imino)pyridine ligand, (PyEt)PDI, allowed preparation of the respective dihalide complex, ((PyEt)PDI)MnCl2. Reduction of this precursor using excess Na/Hg resulted in deprotonation of the chelate methyl groups to yield the bis(enamide)tris(pyridine)-supported product, (κ(5)-N,N,N,N,N-(PyEt)PDEA)Mn. This complex was characterized by single-crystal X-ray diffraction and found to possess an intermediate-spin (S = (3)/2) Mn(II) center by the Evans method and electron paramagnetic resonance spectroscopy. Furthermore, (κ(5)-N,N,N,N,N-(PyEt)PDEA)Mn was determined to be an effective precatalyst for the hydrosilylation of aldehydes and ketones, exhibiting turnover frequencies of up to 2475 min(-1) when employed under solvent-free conditions. This optimization allowed for isolation of the respective alcohols and, in two cases, the partially reacted silyl ethers, PhSiH(OR)2 [R = Cy and CH(Me)((n)Bu)]. The aldehyde hydrosilylation activity observed for (κ(5)-N,N,N,N,N-(PyEt)PDEA)Mn renders it one of the most efficient first-row transition metal catalysts for this transformation reported to date.

Introduction: The rates of atypia of undetermined significance (AUS) by fine-needle aspiration (FNA) and malignant outcomes have been estimated at < 7% and 5–15%, respectively. Initial AUS diagnosis is followed up clinically with serial ultrasounds, repeat FNA, molecular testing, or direct surgery. We investigated the incidence, follow-up modalities, and final outcomes of AUS in Newfoundland. Methods: All cases of AUS diagnosed at the Eastern Health Cytology Laboratory between 1 January 2010 and 31 December 2013 were identified. Electronic medical records were examined for follow-up modalities and final histologic diagnosis. The final outcomes were reported as benign, malignant, or undetermined. Results: Out of 3,285 thyroid FNAs, 181 (5.5%) were AUS. Fifty-seven (31.5%) had repeat FNA diagnosed as benign (38.6%), AUS (29.8%), or suspicious/malignant (8.8%). Eighty-four (46.4%) had surgery after the first AUS diagnosis, 39 (46.4%) of which were malignant. Twenty-four patients (13.3%) were followed up by serial ultrasound only, 2 (1.1%) by molecular testing, and 1 (0.6%) died of unrelated disease. Thirteen (7.2%) had no follow-up record. Our malignancy rate (MR) was 29.8%. Conclusion: The MR in our population was higher than the rate proposed by The Bethesda System for Reporting Thyroid Cytopathology. Repeat FNA can reduce the rate of unnecessary surgeries, but practice guidelines should consider individual and institutional circumstances. The ratio MR:ADR (AUS diagnostic rate) may be a better indicator of performance.

It was recently discovered that (Ph2PPrPDI)Mn (PDI = pyridine diimine) exists as a superposition of low-spin Mn­(II) that is supported by a PDI dianion and intermediate-spin Mn­(II) that is antiferromagnetically coupled to a triplet PDI dianion, a finding that encouraged the synthesis and electronic structure evaluation of late first row metal variants that feature the same chelate. The addition of Ph2PPrPDI to FeBr2 resulted in bromide dissociation and the formation of [(Ph2PPrPDI)­FeBr]­[Br]. Reduction of this precursor using excess sodium amalgam afforded (Ph2PPrPDI)­Fe, which possesses an Fe­(II) center that is supported by a dianionic PDI ligand. Similarly, reduction of a premixed solution of Ph2PPrPDI and CoCl2 yielded the cobalt analog, (Ph2PPrPDI)­Co. EPR spectroscopy and density functional theory calculations revealed that this compound features a high-spin Co­(I) center that is antiferromagnetically coupled to a PDI radical anion. The addition of Ph2PPrPDI to Ni­(COD)2 resulted in ligand displacement and the formation of (Ph2PPrPDI)­Ni, which was found to possess a pendent phosphine group. Single-crystal X-ray diffraction, CASSCF calculations, and EPR spectroscopy indicate that (Ph2PPrPDI)Ni is best described as having a Ni­(II)-PDI2– configuration. The electronic differences between these compounds are highlighted, and a computational analysis of Ph2PPrPDI denticity has revealed the thermodynamic penalties associated with phosphine dissociation from 5-coordinate (Ph2PPrPDI)­Mn, (Ph2PPrPDI)­Fe, and (Ph2PPrPDI)­Co.